Author name code: vandriel-gesztelyi
ADS astronomy entries on 2022-09-14
author:"van Driel-Gesztelyi, Lidia" OR author:"Gesztelyi, Lidia"
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Title: Stellar FIP effect from the empirical side
Authors: Seli, Bálint; Van Driel-Gesztelyi, Lidia; Baker, Deborah;
   Laming, J. Martin; Kovari, Zsolt; Oláh, Katalin; Kriskovics, Levente;
   Vida, Krisztián; Balázs, Lajos
Bibcode: 2022cosp...44.2585S
Altcode:
  The difference between the elemental abundances of the corona and the
  photosphere is an apparently common feature of stellar atmospheres. The
  abundance difference depends on the first ionization potential of the
  given element, so the phenomenon is known as the FIP effect. Here we
  explore the variation of the strength of the FIP effect for different
  types of stars, through the FIP bias parameter. Using a sample of 59
  main sequence and evolved stars with known coronal abundances from the
  literature, we look for macroscopic, measurable parameters that affect
  the stellar FIP bias, and also re-evaluate the simple dependence on
  the effective temperature.

Title: Investigating of the nature of magnetic oscillations associated
    with FIP effect
Authors: Murabito, Mariarita; Jafarzadeh, Shahin; Van Driel-Gesztelyi,
   Lidia; Ermolli, Ilaria; Baker, Deborah; Brooks, David; Long, David;
   Jess, David; Valori, Gherardo; Stangalini, Marco
Bibcode: 2022cosp...44.2591M
Altcode:
  Observations of the photosphere, chromosphere, and corona combined with
  magnetic field modeling of one of the biggest sunspots of the 24 solar
  cycle, revealed that regions of high FIP bias plasma in the corona
  were magnetically linked to the locations of the intrinsic magnetic
  oscillations in the solar chromosphere. In order to characterize
  the driver of the oscillations, we analyzed the relation between
  the spatial distribution of the magnetic wave power and the overall
  field geometry and plasma parameters obtained from the multi-height
  spectropolarimetric non-local thermodynamic equilibrium (NLTE)
  inversions. In correspondence with the locations where the magnetic
  wave energy is observed at chromospheric heights, we found evidence
  in support of locally excited acoustic waves that, after crossing the
  equipartition layer located close to the umbra-penumbra boundary at
  photospheric heights, are converted into magnetic-like waves. These
  results indicate a direct connection between sunspot chromospheric
  activity and observable changes in coronal plasma composition,
  demonstrating the power of high resolution, multi-height studies of the
  solar atmosphere that will become the gold standard in the era of DKIST.

Title: Understanding the Correlation between Solar Coronal Abundances
    and F10.7 Radio Emission
Authors: To, Andy S. H.; Baker, Deborah; Long, David; James, Alexander;
   Brooks, David; van Driel-Gesztelyi, Lidia; Valori, Gherardo; Bastian,
   Tim; Lomuscio, Samantha; Stansby, David
Bibcode: 2022cosp...44.2592T
Altcode:
  Solar corona plasma composition, derived from full-Sun spectra, and
  the F10.7 radio flux (2.8 GHz) have been shown to be highly correlated
  (r = 0.88) during the recent weak solar cycle. However, this correlation
  becomes nonlinear at times of increased solar magnetic activity. We used
  co-temporal, high spatial resolution, radio (JVLA), and EUV (Hinode/EIS)
  images of the Sun taken on the 3 and 7 April 2020 to understand the
  underlying causes of the non-linearity of the FIP bias-F10.7 solar
  index correlation. We then calculated differential emission measures
  from AIA images, and paired them with the observed FIP bias to predict
  the bremsstrahlung component of F10.7 radio emission. Results of this
  study provide constraints on the amplitude of composition variability
  related to solar cycle amplitude, and provide an alternative method
  to calculate coronal composition.

Title: What determines active region coronal plasma composition?
Authors: Mihailescu, Teodora; Baker, Deborah; Long, David; Green,
   Lucie; Brooks, David; van Driel-Gesztelyi, Lidia; To, Andy S. H.
Bibcode: 2022cosp...44.2580M
Altcode:
  The chemical composition of the solar corona is different from that
  of the solar photosphere, with the strongest variation being observed
  in active regions. Using spectral data from the Extreme Ultraviolet
  (EUV) Imaging Spectrometer (EIS) on Hinode, we present a survey of
  coronal elemental composition as expressed in the FIP bias in 28 active
  regions with a wide range of ages and magnetic flux contents, and at
  different stages in their evolution. We find no correlation between the
  FIP bias of an active region and its magnetic flux or age. However,
  there is a dependence of the FIP bias on the evolutionary stage of
  the active region. FIP bias shows an increasing trend with average
  magnetic flux density up to 200 G but this trend does not continue
  at higher values. In contrast to the single values typically used
  to characterize the FIP bias in a region, we find that the FIP bias
  distribution within active regions has a significant spread. The highest
  spread is observed in very dispersed active regions and active regions
  that have formed a filament channel along their main polarity inversion
  lines, which is an indicator of the wide range of physical processes
  that take place in these active regions. These findings indicate that,
  while some general trends can be observed, the processes influencing
  the composition of an active region are complex and specific to its
  evolution, history and magnetic configuration or environment. The
  spread of FIP bias values in active regions shows a broad match with
  that previously observed in situ in the slow solar wind.

Title: What have we learned about I-FIP Effect on the Sun from
    Hinode/EIS?
Authors: Baker, Deborah; van Driel-Gesztelyi, Lidia
Bibcode: 2022cosp...44.2572B
Altcode:
  Plasma composition in stellar coronae can differ from that of their
  photospheres, the cause of which is one of the open questions in
  astrophysics. Elements with a low first ionization potential (FIP)
  are observed to have either enhanced or depleted abundances relative
  to that of high FIP elements. The abundance pattern is known as the FIP
  effect or inverse FIP (I-FIP) effect, depending on whether the low FIP
  elements are over-/under- (FIP/I-FIP) abundant in coronae. Some stellar
  coronae are dominated by FIP effect plasma but cooler, more active stars
  are dominated by I-FIP effect plasma. Our local laboratory, the Sun,
  has a FIP effect dominated corona, however, short-lived I-FIP patches
  have occasionally been observed. Analysis of multiple cases of I-FIP
  effect revealed certain conditions in the magnetic field and flare
  heating to be necessary for the occurrence of I-FIP effect plasma on
  the Sun. An overview of what we have learned from sixteen years of
  spatially resolved spectroscopic observations from Hinode/EIS will be
  presented. We will demonstrate the power of combining spectroscopic,
  imaging, and magnetic field observations of our Sun to understand
  the physical processes on cooler stars which we only observe as point
  sources.

Title: Evolution of Plasma Composition in an Eruptive Flux Rope
Authors: Baker, Deborah; Demoulin, Pascal; Long, David; Janvier, Miho;
   Green, Lucie; Brooks, David; van Driel-Gesztelyi, Lidia; Mihailescu,
   Teodora; To, Andy S. H.; Yardley, Stephanie; Valori, Gherardo
Bibcode: 2022cosp...44.1361B
Altcode:
  Magnetic flux ropes are bundles of twisted magnetic field enveloping a
  central axis. They harbor free magnetic energy and can be progenitors
  of coronal mass ejections (CMEs). However, identifying flux ropes on
  the Sun can be challenging. One of the key coronal observables that
  has been shown to indicate the presence of a flux rope is a peculiar
  bright coronal structure called a sigmoid. In this work, we show Hinode
  EUV Imaging Spectrometer observations of sigmoidal active region (AR)
  10977. We analyze the coronal plasma composition in the AR and its
  evolution as a sigmoid (flux rope) forms and erupts as a CME. Plasma
  with photospheric composition was observed in coronal loops close to
  the main polarity inversion line during episodes of significant flux
  cancellation, suggestive of the injection of photospheric plasma into
  these loops driven by photospheric flux cancellation. Concurrently,
  the increasingly sheared core field contained plasma with coronal
  composition. As flux cancellation decreased and a sigmoid/flux
  rope formed, the plasma evolved to an intermediate composition in
  between photospheric and typical AR coronal compositions. Finally,
  the flux rope contained predominantly photospheric plasma during and
  after a failed eruption preceding the CME. Hence, plasma composition
  observations of AR 10977 strongly support models of flux rope formation
  by photospheric flux cancellation forcing magnetic reconnection first
  at the photospheric level then at the coronal level.

Title: What Determines Active Region Coronal Plasma Composition?
Authors: Mihailescu, Teodora; Baker, Deborah; Green, Lucie M.;
   van Driel-Gesztelyi, Lidia; Long, David M.; Brooks, David H.; To,
   Andy S. H.
Bibcode: 2022ApJ...933..245M
Altcode: 2022arXiv220505027M
  The chemical composition of the solar corona is different from that
  of the solar photosphere, with the strongest variation being observed
  in active regions (ARs). Using data from the Extreme Ultraviolet
  (EUV) Imaging Spectrometer (EIS) on Hinode, we present a survey of
  coronal elemental composition as expressed in the first ionization
  potential (FIP) bias in 28 ARs of different ages and magnetic flux
  content, which are at different stages in their evolution. We find
  no correlation between the FIP bias of an AR and its total unsigned
  magnetic flux or age. However, there is a weak dependence of FIP
  bias on the evolutionary stage, decreasing from 1.9 to 2.2 in ARs
  with spots to 1.5-1.6 in ARs that are at more advanced stages of
  the decay phase. FIP bias shows an increasing trend with average
  magnetic flux density up to 200 G, but this trend does not continue
  at higher values. The FIP bias distribution within ARs has a spread
  between 0.4 and 1. The largest spread is observed in very dispersed
  ARs. We attribute this to a range of physical processes taking place
  in these ARs, including processes associated with filament channel
  formation. These findings indicate that, while some general trends
  can be observed, the processes influencing the composition of an AR
  are complex and specific to its evolution, magnetic configuration,
  or environment. The spread of FIP bias values in ARs shows a broad
  match with that previously observed in situ in the slow solar wind.

Title: Detection of Stellar-like Abundance Anomalies in the Slow
    Solar Wind
Authors: Brooks, David H.; Baker, Deborah; van Driel-Gesztelyi, Lidia;
   Warren, Harry P.; Yardley, Stephanie L.
Bibcode: 2022ApJ...930L..10B
Altcode: 2022arXiv220409332B
  The elemental composition of the Sun's hot atmosphere, the corona,
  shows a distinctive pattern that is different from the underlying
  surface or photosphere. Elements that are easy to ionize in the
  chromosphere are enhanced in abundance in the corona compared to
  their photospheric values. A similar pattern of behavior is often
  observed in the slow-speed (&lt;500 km s<SUP>-1</SUP>) solar wind
  and in solar-like stellar coronae, while a reversed effect is seen
  in M dwarfs. Studies of the inverse effect have been hampered in the
  past because only unresolved (point-source) spectroscopic data were
  available for these stellar targets. Here we report the discovery of
  several inverse events observed in situ in the slow solar wind using
  particle-counting techniques. These very rare events all occur during
  periods of high solar activity that mimic conditions more widespread
  on M dwarfs. The detections allow a new way of connecting the slow
  wind to its solar source and are broadly consistent with theoretical
  models of abundance variations due to chromospheric fast-mode waves
  with amplitudes of 8-10 km s<SUP>-1</SUP>, sufficient to accelerate
  the solar wind. The results imply that M-dwarf winds are dominated
  by plasma depleted in easily ionized elements and lend credence to
  previous spectroscopic measurements.

Title: Extending the FIP bias sample to magnetically active
    stars. Challenging the FIP bias paradigm
Authors: Seli, B.; Oláh, K.; Kriskovics, L.; Kővári, Zs.; Vida,
   K.; Balázs, L. G.; Laming, J. M.; van Driel-Gesztelyi, L.; Baker, D.
Bibcode: 2022A&A...659A...3S
Altcode: 2021arXiv211114735S
  Context. The different elemental abundances of the photosphere and the
  corona are striking features of not only the Sun, but of other stars
  as well. This phenomenon is known as the first ionisation potential
  (FIP) effect, and its strength can be characterized by the FIP bias,
  the logarithmic abundance difference between low- and high-FIP elements
  in the corona, compared to the photosphere. The FIP bias was shown to
  depend on the surface temperature of the star. <BR /> Aims: We aim to
  extend the T<SUB>eff</SUB>−FIP bias relationship to a larger stellar
  sample and analyse the effect of other astrophysical parameters on
  the relation (e.g. surface gravity, age, activity indicators). <BR
  /> Methods: We compiled FIP bias and other parameters for 59 stars
  for which coronal composition is available, now including evolved
  stars. Using principal component analysis and linear discriminant
  analysis, we searched for correlations with other astrophysical
  parameters within the sample that may influence the stellar FIP
  bias. <BR /> Results: Adding stars to the T<SUB>eff</SUB>−FIP bias
  diagram unveiled new features in its structure. In addition to the
  previously known relationship, there appears to be a second branch:
  a parallel sequence about 0.5 dex above it. While the T<SUB>eff</SUB>
  remains the main determinant of the FIP bias, other parameters such as
  stellar activity indicators also have influence. We find three clusters
  in the FIP bias determinant parameter space. One distinct group is
  formed by the evolved stars. Two groups contain main sequence stars
  in continuation separated roughly by the sign change of the FIP-bias
  value. <BR /> Conclusions: The new branch of the T<SUB>eff</SUB>−FIP
  bias diagram contains stars with higher activity level, in terms of
  X-ray flux and rotational velocity. The Rossby number also seems
  to be important, indicating possible dependence on the type of
  dynamo operating in these stars influencing their FIP bias. The two
  main-sequence clusters run from the earliest spectral types of A-F with
  shallow convection zones through G-K-early-M stars with gradually deeper
  convection zones, and they end with the fully convective M dwarf stars,
  depicting the change of the dynamo type with the internal differences
  of the main sequence stars in connection with the FIP-bias values.

Title: Evolution of Plasma Composition in an Eruptive Flux Rope
Authors: Baker, D.; Green, L. M.; Brooks, D. H.; Démoulin, P.;
   van Driel-Gesztelyi, L.; Mihailescu, T.; To, A. S. H.; Long, D. M.;
   Yardley, S. L.; Janvier, M.; Valori, G.
Bibcode: 2022ApJ...924...17B
Altcode: 2021arXiv211011714B
  Magnetic flux ropes are bundles of twisted magnetic field enveloping a
  central axis. They harbor free magnetic energy and can be progenitors
  of coronal mass ejections (CMEs). However, identifying flux ropes on
  the Sun can be challenging. One of the key coronal observables that
  has been shown to indicate the presence of a flux rope is a peculiar
  bright coronal structure called a sigmoid. In this work, we show Hinode
  EUV Imaging Spectrometer observations of sigmoidal active region (AR)
  10977. We analyze the coronal plasma composition in the AR and its
  evolution as a sigmoid (flux rope) forms and erupts as a CME. Plasma
  with photospheric composition was observed in coronal loops close to
  the main polarity inversion line during episodes of significant flux
  cancellation, suggestive of the injection of photospheric plasma into
  these loops driven by photospheric flux cancellation. Concurrently,
  the increasingly sheared core field contained plasma with coronal
  composition. As flux cancellation decreased and a sigmoid/flux
  rope formed, the plasma evolved to an intermediate composition in
  between photospheric and typical AR coronal compositions. Finally,
  the flux rope contained predominantly photospheric plasma during and
  after a failed eruption preceding the CME. Hence, plasma composition
  observations of AR 10977 strongly support models of flux rope formation
  by photospheric flux cancellation forcing magnetic reconnection first
  at the photospheric level then at the coronal level.

Title: Editorial Appreciation
Authors: Arregui, Iñigo; Leibacher, John; Mandrini, Cristina H.;
   van Driel-Gesztelyi, Lidia; Wheatland, Michael S.
Bibcode: 2022SoPh..297...11A
Altcode:
  No abstract at ADS

Title: Investigating the origin of magnetic perturbations associated
    with the FIP Effect
Authors: Murabito, M.; Stangalini, M.; Baker, D.; Valori, G.; Jess,
   D. B.; Jafarzadeh, S.; Brooks, D. H.; Ermolli, I.; Giorgi, F.; Grant,
   S. D. T.; Long, D. M.; van Driel-Gesztelyi, L.
Bibcode: 2021A&A...656A..87M
Altcode: 2021arXiv210811164M
  Recently, magnetic oscillations were detected in the chromosphere
  of a large sunspot and found to be linked to the coronal locations
  where a first ionization potential (FIP) effect was observed. In
  an attempt to shed light on the possible excitation mechanisms
  of these localized waves, we further investigate the same data
  by focusing on the relation between the spatial distribution of
  the magnetic wave power and the overall field geometry and plasma
  parameters obtained from multi-height spectropolarimetric non-local
  thermodynamic equilibrium (NLTE) inversions of IBIS data. We find,
  in correspondence with the locations where the magnetic wave energy
  is observed at chromospheric heights, that the magnetic fields have
  smaller scale heights, meaning faster expansions of the field lines,
  which ultimately results in stronger vertical density stratification
  and wave steepening. In addition, the acoustic spectrum of the
  oscillations at the locations where magnetic perturbations are
  observed is broader than that observed at other locations, which
  suggests an additional forcing driver to the p-modes. Analysis of the
  photospheric oscillations in the sunspot surroundings also reveals
  a broader spectrum between the two opposite polarities of the active
  region (the leading spot and the trailing opposite polarity plage),
  and on the same side where magnetic perturbations are observed in
  the umbra. We suggest that strong photospheric perturbations between
  the two polarities are responsible for this broader spectrum of
  oscillations, with respect to the p-mode spectrum, resulting in locally
  excited acoustic waves that, after crossing the equipartition layer,
  located close to the umbra-penumbra boundary at photopheric heights,
  are converted into magnetic waves and steepen due to the strong
  density gradient. <P />Movie associated to Fig. 1 is available at <A
  href="https://www.aanda.org/10.1051/0004-6361/202141504/olm">https://www.aanda.org</A>

Title: Global Contributions of Active Regions to the Solar Wind
Authors: Stansby, David; Green, Lucie; van Driel-Gesztelyi, Lidia;
   Horbury, Timothy
Bibcode: 2021AGUFMSH24C..04S
Altcode:
  Both coronal holes and active regions are source regions of the solar
  wind. The distribution of these coronal structures across both space
  and time within the corona is well known, and is driven by photospheric
  magnetic flux evolution across the 11-year solar cycle. In turn these
  coronal structures drive variability in the solar wind throughout
  the heliosphere. To understand how important active regions are as
  solar wind sources, we have used photospheric magnetic field maps from
  the past four solar cycles to estimate what fraction of magnetic open
  solar flux is rooted in active regions, a proxy for the fraction of all
  solar wind originating in active regions. We found that the fractional
  contribution of active regions to the solar wind varies between 30%
  to 80% at any one time during solar maximum and is negligible at solar
  minimum, showing a strong correlation with sunspot number. While active
  regions are typically confined to latitudes ±30 in the corona, the
  solar wind they produce can reach latitudes up to ±60. These results
  quantify the importance of active regions in globally influencing the
  whole heliosphere, providing motivation for further studies of active
  regions as solar wind sources during Solar Cycle 25.

Title: Active Region Contributions to the Solar Wind over Multiple
    Solar Cycles
Authors: Stansby, David; Green, Lucie M.; van Driel-Gesztelyi, Lidia;
   Horbury, Timothy S.
Bibcode: 2021SoPh..296..116S
Altcode: 2021arXiv210404417S
  Both coronal holes and active regions are source regions of the solar
  wind. The distribution of these coronal structures across both space and
  time is well known, but it is unclear how much each source contributes
  to the solar wind. In this study we use photospheric magnetic field maps
  observed over the past four solar cycles to estimate what fraction
  of magnetic open solar flux is rooted in active regions, a proxy
  for the fraction of all solar wind originating in active regions. We
  find that the fractional contribution of active regions to the solar
  wind varies between 30% to 80% at any one time during solar maximum
  and is negligible at solar minimum, showing a strong correlation with
  sunspot number. While active regions are typically confined to latitudes
  ±30<SUP>∘</SUP> in the corona, the solar wind they produce can reach
  latitudes up to ±60<SUP>∘</SUP>. Their fractional contribution to
  the solar wind also correlates with coronal mass ejection rate, and
  is highly variable, changing by ±20% on monthly timescales within
  individual solar maxima. We speculate that these variations could
  be driven by coronal mass ejections causing reconfigurations of the
  coronal magnetic field on sub-monthly timescales.

Title: Graphical evidence for the solar coronal structure during the
Maunder minimum: comparative study of the total eclipse drawings in
    1706 and 1715
Authors: Hayakawa, Hisashi; Lockwood, Mike; Owens, Matthew J.; Sôma,
   Mitsuru; Besser, Bruno P.; van Driel-Gesztelyi, Lidia
Bibcode: 2021JSWSC..11....1H
Altcode:
  We discuss the significant implications of three eye-witness drawings
  of the total solar eclipse on 1706 May 12 in comparison with two on 1715
  May 3, for our understanding of space climate change. These events took
  place just after what has been termed the "deep Maunder Minimum" but
  fall within the "extended Maunder Minimum" being in an interval when the
  sunspot numbers start to recover. Maria Clara Eimmert's image in 1706
  is particularly important because she was both a highly accomplished
  astronomical observer and an excellent artist: it was thought lost and
  was only re-discovered in 2012. Being the earliest coronal drawings of
  observational value yet identified, these drawings corroborate verbal
  accounts a corona without significant streamers, seen at totality of
  this and another eclipse event in 1652 during the Maunder Minimum. The
  graphical evidence implies that the coronal solar magnetic field was
  not lost but significantly weakened and the lack of coronal structure
  means there was little discernable open flux (either polar or at lower
  latitudes) even during the recovery phase of the Maunder Minimum. These
  observations provide evidence for a different state of oscillation of
  the solar dynamo, and hence behaviour of the Sun, in comparison with
  that during normal solar cycle minima (when a streamer belt between
  two polar coronal holes is visible) or near normal sunspot maxima
  (when coronal structure is caused by coronal holes at all latitudes)
  even to observers without a telescope.

Title: Plasma Upflows Induced by Magnetic Reconnection Above an
    Eruptive Flux Rope
Authors: Baker, Deborah; Mihailescu, Teodora; Démoulin, Pascal;
   Green, Lucie M.; van Driel-Gesztelyi, Lidia; Valori, Gherardo; Brooks,
   David H.; Long, David M.; Janvier, Miho
Bibcode: 2021SoPh..296..103B
Altcode: 2021arXiv210616137B
  One of the major discoveries of Hinode's Extreme-ultraviolet
  Imaging Spectrometer (EIS) is the presence of upflows at the edges
  of active regions. As active regions are magnetically connected
  to the large-scale field of the corona, these upflows are a likely
  contributor to the global mass cycle in the corona. Here we examine
  the driving mechanism(s) of the very strong upflows with velocities
  in excess of 70 km s<SUP>−1</SUP>, known as blue-wing asymmetries,
  observed during the eruption of a flux rope in AR 10977 (eruptive flare
  SOL2007-12-07T04:50). We use Hinode/EIS spectroscopic observations
  combined with magnetic-field modeling to investigate the possible
  link between the magnetic topology of the active region and the strong
  upflows. A Potential Field Source Surface (PFSS) extrapolation of the
  large-scale field shows a quadrupolar configuration with a separator
  lying above the flux rope. Field lines formed by induced reconnection
  along the separator before and during the flux-rope eruption are
  spatially linked to the strongest blue-wing asymmetries in the upflow
  regions. The flows are driven by the pressure gradient created when
  the dense and hot arcade loops of the active region reconnect with
  the extended and tenuous loops overlying it. In view of the fact
  that separator reconnection is a specific form of the more general
  quasi-separatrix (QSL) reconnection, we conclude that the mechanism
  driving the strongest upflows is, in fact, the same as the one driving
  the persistent upflows of ≈10 - 20 km s<SUP>−1</SUP> observed in
  all active regions.

Title: The Evolution of Plasma Composition during a Solar Flare
Authors: To, Andy S. H.; Long, David M.; Baker, Deborah; Brooks, David
   H.; van Driel-Gesztelyi, Lidia; Laming, J. Martin; Valori, Gherardo
Bibcode: 2021ApJ...911...86T
Altcode: 2021arXiv210209985T
  We analyze the coronal elemental abundances during a small flare using
  Hinode/EIS observations. Compared to the preflare elemental abundances,
  we observed a strong increase in coronal abundance of Ca XIV 193.84
  Å, an emission line with low first ionization potential (FIP &lt;
  10 eV), as quantified by the ratio Ca/Ar during the flare. This is in
  contrast to the unchanged abundance ratio observed using Si X 258.38
  Å/S X 264.23 Å. We propose two different mechanisms to explain
  the different composition results. First, the small flare-induced
  heating could have ionized S, but not the noble gas Ar, so that the
  flare-driven Alfvén waves brought up Si, S, and Ca in tandem via
  the ponderomotive force which acts on ions. Second, the location of
  the flare in strong magnetic fields between two sunspots may suggest
  fractionation occurred in the low chromosphere, where the background
  gas is neutral H. In this region, high-FIP S could behave more like a
  low-FIP than a high-FIP element. The physical interpretations proposed
  generate new insights into the evolution of plasma abundances in the
  solar atmosphere during flaring, and suggests that current models must
  be updated to reflect dynamic rather than just static scenarios.

Title: Editorial Appreciation
Authors: Leibacher, John; Mandrini, Cristina H.; van Driel-Gesztelyi,
   Lidia; Wheatland, Michael S.
Bibcode: 2021SoPh..296...14L
Altcode:
  No abstract at ADS

Title: Alfvénic Perturbations in a Sunspot Chromosphere Linked to
    Fractionated Plasma in the Corona
Authors: Baker, Deborah; Stangalini, Marco; Valori, Gherardo; Brooks,
   David H.; To, Andy S. H.; van Driel-Gesztelyi, Lidia; Démoulin,
   Pascal; Stansby, David; Jess, David B.; Jafarzadeh, Shahin
Bibcode: 2021ApJ...907...16B
Altcode: 2020arXiv201204308B
  In this study, we investigate the spatial distribution of highly
  varying plasma composition around one of the largest sunspots of solar
  cycle 24. Observations of the photosphere, chromosphere, and corona
  are brought together with magnetic field modeling of the sunspot
  in order to probe the conditions that regulate the degree of plasma
  fractionation within loop populations of differing connectivities. We
  find that, in the coronal magnetic field above the sunspot umbra,
  the plasma has photospheric composition. Coronal loops rooted in the
  penumbra contain fractionated plasma, with the highest levels observed
  in the loops that connect within the active region. Tracing field
  lines from regions of fractionated plasma in the corona to locations
  of Alfvénic fluctuations detected in the chromosphere shows that they
  are magnetically linked. These results indicate a connection between
  sunspot chromospheric activity and observable changes in coronal
  plasma composition.

Title: Spectropolarimetric Insight into Plasma Sheet Dynamics of a
    Solar Flare
Authors: French, R.; Judge, P. G.; Matthews, S.; van Driel-Gesztelyi,
   L.; Long, D.
Bibcode: 2020AGUFMSH045..03F
Altcode:
  Magnetic reconnection is thought to lie at the heart of energy release
  in solar flares, but the process is not yet fully understood. We examine
  spectropolarimetric data from the CoMP coronagraph, acquired a few hours
  into the evolution of the September 10th 2017 X8.2-class flare. We
  find a striking and spatially coherent low polarisation structure,
  aligned with the hot plasma sheet observed in EUV. By elimination,
  we find the significant depolarisation to be a result of small-scale
  sub-pixel magnetic structure along the plasma sheet, consistent with
  theory of reconnection instabilities. This interpretation of ongoing
  reconnection is supported by further Hinode/EIS observations and AIA
  DEMs, from well beyond the impulsive phase of the flare. The plasma
  sheet remains visible in CoMP linear polarisation over a day into the
  flare's evolution, several hours after its last appearance in EUV. We
  conclude that polarisation measurements with new coronagraphs, such
  the DKIST CRYO-NIRSP instrument, will further enhance our understanding
  of magnetic reconnection during eruptive flares.

Title: A new trigger mechanism for coronal mass ejections. The role
    of confined flares and photospheric motions in the formation of hot
    flux ropes
Authors: James, A. W.; Green, L. M.; van Driel-Gesztelyi, L.;
   Valori, G.
Bibcode: 2020A&A...644A.137J
Altcode: 2020arXiv201011204J
  Context. Many previous studies have shown that the magnetic precursor of
  a coronal mass ejection (CME) takes the form of a magnetic flux rope,
  and a subset of them have become known as "hot flux ropes" due to
  their emission signatures in ∼10 MK plasma. <BR /> Aims: We seek to
  identify the processes by which these hot flux ropes form, with a view
  of developing our understanding of CMEs and thereby improving space
  weather forecasts. <BR /> Methods: Extreme-ultraviolet observations
  were used to identify five pre-eruptive hot flux ropes in the solar
  corona and study how they evolved. Confined flares were observed in the
  hours and days before each flux rope erupted, and these were used as
  indicators of episodic bursts of magnetic reconnection by which each
  flux rope formed. The evolution of the photospheric magnetic field
  was observed during each formation period to identify the process(es)
  that enabled magnetic reconnection to occur in the β &lt; 1 corona and
  form the flux ropes. <BR /> Results: The confined flares were found
  to be homologous events and suggest flux rope formation times that
  range from 18 hours to 5 days. Throughout these periods, fragments of
  photospheric magnetic flux were observed to orbit around each other
  in sunspots where the flux ropes had a footpoint. Active regions
  with right-handed (left-handed) twisted magnetic flux exhibited
  clockwise (anticlockwise) orbiting motions, and right-handed
  (left-handed) flux ropes formed. <BR /> Conclusions: We infer that
  the orbital motions of photospheric magnetic flux fragments about
  each other bring magnetic flux tubes together in the corona, enabling
  component reconnection that forms a magnetic flux rope above a flaring
  arcade. This represents a novel trigger mechanism for solar eruptions
  and should be considered when predicting solar magnetic activity. <P
  />Movies associated to Figs. 4, 8, 12, and 14 are available at <A
  href="https://www.aanda.org/10.1051/0004-6361/202038781/olm">https://www.aanda.org</A>

Title: The Solar Orbiter Science Activity Plan. Translating solar
    and heliospheric physics questions into action
Authors: Zouganelis, I.; De Groof, A.; Walsh, A. P.; Williams, D. R.;
   Müller, D.; St Cyr, O. C.; Auchère, F.; Berghmans, D.; Fludra,
   A.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic, M.;
   Owen, C. J.; Rodríguez-Pacheco, J.; Romoli, M.; Solanki, S. K.;
   Watson, C.; Sanchez, L.; Lefort, J.; Osuna, P.; Gilbert, H. R.;
   Nieves-Chinchilla, T.; Abbo, L.; Alexandrova, O.; Anastasiadis, A.;
   Andretta, V.; Antonucci, E.; Appourchaux, T.; Aran, A.; Arge, C. N.;
   Aulanier, G.; Baker, D.; Bale, S. D.; Battaglia, M.; Bellot Rubio,
   L.; Bemporad, A.; Berthomier, M.; Bocchialini, K.; Bonnin, X.; Brun,
   A. S.; Bruno, R.; Buchlin, E.; Büchner, J.; Bucik, R.; Carcaboso,
   F.; Carr, R.; Carrasco-Blázquez, I.; Cecconi, B.; Cernuda Cangas, I.;
   Chen, C. H. K.; Chitta, L. P.; Chust, T.; Dalmasse, K.; D'Amicis, R.;
   Da Deppo, V.; De Marco, R.; Dolei, S.; Dolla, L.; Dudok de Wit, T.;
   van Driel-Gesztelyi, L.; Eastwood, J. P.; Espinosa Lara, F.; Etesi,
   L.; Fedorov, A.; Félix-Redondo, F.; Fineschi, S.; Fleck, B.; Fontaine,
   D.; Fox, N. J.; Gandorfer, A.; Génot, V.; Georgoulis, M. K.; Gissot,
   S.; Giunta, A.; Gizon, L.; Gómez-Herrero, R.; Gontikakis, C.; Graham,
   G.; Green, L.; Grundy, T.; Haberreiter, M.; Harra, L. K.; Hassler,
   D. M.; Hirzberger, J.; Ho, G. C.; Hurford, G.; Innes, D.; Issautier,
   K.; James, A. W.; Janitzek, N.; Janvier, M.; Jeffrey, N.; Jenkins,
   J.; Khotyaintsev, Y.; Klein, K. -L.; Kontar, E. P.; Kontogiannis,
   I.; Krafft, C.; Krasnoselskikh, V.; Kretzschmar, M.; Labrosse, N.;
   Lagg, A.; Landini, F.; Lavraud, B.; Leon, I.; Lepri, S. T.; Lewis,
   G. R.; Liewer, P.; Linker, J.; Livi, S.; Long, D. M.; Louarn, P.;
   Malandraki, O.; Maloney, S.; Martinez-Pillet, V.; Martinovic, M.;
   Masson, A.; Matthews, S.; Matteini, L.; Meyer-Vernet, N.; Moraitis,
   K.; Morton, R. J.; Musset, S.; Nicolaou, G.; Nindos, A.; O'Brien,
   H.; Orozco Suarez, D.; Owens, M.; Pancrazzi, M.; Papaioannou, A.;
   Parenti, S.; Pariat, E.; Patsourakos, S.; Perrone, D.; Peter, H.;
   Pinto, R. F.; Plainaki, C.; Plettemeier, D.; Plunkett, S. P.; Raines,
   J. M.; Raouafi, N.; Reid, H.; Retino, A.; Rezeau, L.; Rochus, P.;
   Rodriguez, L.; Rodriguez-Garcia, L.; Roth, M.; Rouillard, A. P.;
   Sahraoui, F.; Sasso, C.; Schou, J.; Schühle, U.; Sorriso-Valvo, L.;
   Soucek, J.; Spadaro, D.; Stangalini, M.; Stansby, D.; Steller, M.;
   Strugarek, A.; Štverák, Š.; Susino, R.; Telloni, D.; Terasa, C.;
   Teriaca, L.; Toledo-Redondo, S.; del Toro Iniesta, J. C.; Tsiropoula,
   G.; Tsounis, A.; Tziotziou, K.; Valentini, F.; Vaivads, A.; Vecchio,
   A.; Velli, M.; Verbeeck, C.; Verdini, A.; Verscharen, D.; Vilmer, N.;
   Vourlidas, A.; Wicks, R.; Wimmer-Schweingruber, R. F.; Wiegelmann,
   T.; Young, P. R.; Zhukov, A. N.
Bibcode: 2020A&A...642A...3Z
Altcode: 2020arXiv200910772Z
  Solar Orbiter is the first space mission observing the solar plasma
  both in situ and remotely, from a close distance, in and out of the
  ecliptic. The ultimate goal is to understand how the Sun produces
  and controls the heliosphere, filling the Solar System and driving
  the planetary environments. With six remote-sensing and four in-situ
  instrument suites, the coordination and planning of the operations are
  essential to address the following four top-level science questions:
  (1) What drives the solar wind and where does the coronal magnetic field
  originate?; (2) How do solar transients drive heliospheric variability?;
  (3) How do solar eruptions produce energetic particle radiation that
  fills the heliosphere?; (4) How does the solar dynamo work and drive
  connections between the Sun and the heliosphere? Maximising the
  mission's science return requires considering the characteristics
  of each orbit, including the relative position of the spacecraft
  to Earth (affecting downlink rates), trajectory events (such
  as gravitational assist manoeuvres), and the phase of the solar
  activity cycle. Furthermore, since each orbit's science telemetry
  will be downloaded over the course of the following orbit, science
  operations must be planned at mission level, rather than at the level
  of individual orbits. It is important to explore the way in which those
  science questions are translated into an actual plan of observations
  that fits into the mission, thus ensuring that no opportunities are
  missed. First, the overarching goals are broken down into specific,
  answerable questions along with the required observations and the
  so-called Science Activity Plan (SAP) is developed to achieve this. The
  SAP groups objectives that require similar observations into Solar
  Orbiter Observing Plans, resulting in a strategic, top-level view of
  the optimal opportunities for science observations during the mission
  lifetime. This allows for all four mission goals to be addressed. In
  this paper, we introduce Solar Orbiter's SAP through a series of
  examples and the strategy being followed.

Title: The Solar Orbiter EUI instrument: The Extreme Ultraviolet
    Imager
Authors: Rochus, P.; Auchère, F.; Berghmans, D.; Harra, L.; Schmutz,
   W.; Schühle, U.; Addison, P.; Appourchaux, T.; Aznar Cuadrado,
   R.; Baker, D.; Barbay, J.; Bates, D.; BenMoussa, A.; Bergmann, M.;
   Beurthe, C.; Borgo, B.; Bonte, K.; Bouzit, M.; Bradley, L.; Büchel,
   V.; Buchlin, E.; Büchner, J.; Cabé, F.; Cadiergues, L.; Chaigneau,
   M.; Chares, B.; Choque Cortez, C.; Coker, P.; Condamin, M.; Coumar,
   S.; Curdt, W.; Cutler, J.; Davies, D.; Davison, G.; Defise, J. -M.;
   Del Zanna, G.; Delmotte, F.; Delouille, V.; Dolla, L.; Dumesnil, C.;
   Dürig, F.; Enge, R.; François, S.; Fourmond, J. -J.; Gillis, J. -M.;
   Giordanengo, B.; Gissot, S.; Green, L. M.; Guerreiro, N.; Guilbaud,
   A.; Gyo, M.; Haberreiter, M.; Hafiz, A.; Hailey, M.; Halain, J. -P.;
   Hansotte, J.; Hecquet, C.; Heerlein, K.; Hellin, M. -L.; Hemsley, S.;
   Hermans, A.; Hervier, V.; Hochedez, J. -F.; Houbrechts, Y.; Ihsan,
   K.; Jacques, L.; Jérôme, A.; Jones, J.; Kahle, M.; Kennedy, T.;
   Klaproth, M.; Kolleck, M.; Koller, S.; Kotsialos, E.; Kraaikamp, E.;
   Langer, P.; Lawrenson, A.; Le Clech', J. -C.; Lenaerts, C.; Liebecq,
   S.; Linder, D.; Long, D. M.; Mampaey, B.; Markiewicz-Innes, D.;
   Marquet, B.; Marsch, E.; Matthews, S.; Mazy, E.; Mazzoli, A.; Meining,
   S.; Meltchakov, E.; Mercier, R.; Meyer, S.; Monecke, M.; Monfort,
   F.; Morinaud, G.; Moron, F.; Mountney, L.; Müller, R.; Nicula, B.;
   Parenti, S.; Peter, H.; Pfiffner, D.; Philippon, A.; Phillips, I.;
   Plesseria, J. -Y.; Pylyser, E.; Rabecki, F.; Ravet-Krill, M. -F.;
   Rebellato, J.; Renotte, E.; Rodriguez, L.; Roose, S.; Rosin, J.;
   Rossi, L.; Roth, P.; Rouesnel, F.; Roulliay, M.; Rousseau, A.; Ruane,
   K.; Scanlan, J.; Schlatter, P.; Seaton, D. B.; Silliman, K.; Smit,
   S.; Smith, P. J.; Solanki, S. K.; Spescha, M.; Spencer, A.; Stegen,
   K.; Stockman, Y.; Szwec, N.; Tamiatto, C.; Tandy, J.; Teriaca, L.;
   Theobald, C.; Tychon, I.; van Driel-Gesztelyi, L.; Verbeeck, C.;
   Vial, J. -C.; Werner, S.; West, M. J.; Westwood, D.; Wiegelmann, T.;
   Willis, G.; Winter, B.; Zerr, A.; Zhang, X.; Zhukov, A. N.
Bibcode: 2020A&A...642A...8R
Altcode:
  Context. The Extreme Ultraviolet Imager (EUI) is part of the remote
  sensing instrument package of the ESA/NASA Solar Orbiter mission
  that will explore the inner heliosphere and observe the Sun from
  vantage points close to the Sun and out of the ecliptic. Solar Orbiter
  will advance the "connection science" between solar activity and the
  heliosphere. <BR /> Aims: With EUI we aim to improve our understanding
  of the structure and dynamics of the solar atmosphere, globally as well
  as at high resolution, and from high solar latitude perspectives. <BR />
  Methods: The EUI consists of three telescopes, the Full Sun Imager and
  two High Resolution Imagers, which are optimised to image in Lyman-α
  and EUV (17.4 nm, 30.4 nm) to provide a coverage from chromosphere
  up to corona. The EUI is designed to cope with the strong constraints
  imposed by the Solar Orbiter mission characteristics. Limited telemetry
  availability is compensated by state-of-the-art image compression,
  onboard image processing, and event selection. The imposed power
  limitations and potentially harsh radiation environment necessitate
  the use of novel CMOS sensors. As the unobstructed field of view of
  the telescopes needs to protrude through the spacecraft's heat shield,
  the apertures have been kept as small as possible, without compromising
  optical performance. This led to a systematic effort to optimise the
  throughput of every optical element and the reduction of noise levels
  in the sensor. <BR /> Results: In this paper we review the design
  of the two elements of the EUI instrument: the Optical Bench System
  and the Common Electronic Box. Particular attention is also given to
  the onboard software, the intended operations, the ground software,
  and the foreseen data products. <BR /> Conclusions: The EUI will
  bring unique science opportunities thanks to its specific design,
  its viewpoint, and to the planned synergies with the other Solar
  Orbiter instruments. In particular, we highlight science opportunities
  brought by the out-of-ecliptic vantage point of the solar poles,
  the high-resolution imaging of the high chromosphere and corona,
  and the connection to the outer corona as observed by coronagraphs.

Title: Dynamics of Late-stage Reconnection in the 2017 September 10
    Solar Flare
Authors: French, Ryan J.; Matthews, Sarah A.; van Driel-Gesztelyi,
   Lidia; Long, David M.; Judge, Philip G.
Bibcode: 2020ApJ...900..192F
Altcode: 2020arXiv200713377F
  In this multi-instrument paper, we search for evidence of sustained
  magnetic reconnection far beyond the impulsive phase of the X8.2-class
  solar flare on 2017 September 10. Using Hinode/EIS, CoMP, SDO/AIA,
  K-Cor, Hinode/XRT, RHESSI, and IRIS, we study the late-stage evolution
  of the flare dynamics and topology, comparing signatures of reconnection
  with those expected from the standard solar flare model. Examining
  previously unpublished EIS data, we present the evolution of nonthermal
  velocity and temperature within the famous plasma sheet structure,
  for the first four hours of the flare's duration. On even longer
  timescales, we use differential emission measures and polarization data
  to study the longevity of the flare's plasma sheet and cusp structure,
  discovering that the plasma sheet is still visible in observations
  of CoMP linear polarization on 2017 September 11, long after its last
  appearance in EUV. We deduce that magnetic reconnection of some form
  is still ongoing at this time—27 hr after flare onset.

Title: Spectropolarimetric Insight into Plasma Sheet Dynamics of a
    Solar Flare
Authors: French, R.; Judge, P.; Matthews, S.; van Driel-Gesztelyi,
   L.; Long, D.
Bibcode: 2020SPD....5121102F
Altcode:
  Magnetic reconnection is thought to lie at the heart of energy release
  in solar flares, but the process is not yet fully understood. We examine
  spectropolarimetric data from the CoMP coronagraph, acquired a few hours
  into the evolution of the September 10th 2017 X8.2-class flare. We
  find a striking and spatially coherent low polarisation structure,
  aligned with the hot plasma sheet observed in EUV. By elimination,
  we find the significant depolarisation to be a result of small-scale
  sub-pixel magnetic structure along the plasma sheet, consistent with
  theory of reconnection instabilities. This interpretation of ongoing
  reconnection is supported by further Hinode/EIS observations and AIA
  DEMs, from well beyond the impulsive phase of the flare. The plasma
  sheet remains visible in CoMP linear polarisation over a day into the
  flare's evolution, several hours after its last appearance in EUV. We
  conclude that polarisation measurements with new coronagraphs, such
  the DKIST CRYO-NIRSP instrument, will further enhance our understanding
  of magnetic reconnection during eruptive flares.

Title: Editorial: Solar Wind at the Dawn of the Parker Solar Probe
    and Solar Orbiter Era
Authors: Lapenta, Giovanni; Zhukov, Andrei; van Driel-Gesztelyi, Lidia
Bibcode: 2020SoPh..295..103L
Altcode:
  Solar Wind 15 brought together almost 250 experts from all continents
  of the world to discuss the current trends and future perspectives
  of the research on the Sun and its solar wind. The present article
  collection recaptures some of the highlights of their contributions.

Title: Can Subphotospheric Magnetic Reconnection Change the Elemental
    Composition in the Solar Corona?
Authors: Baker, Deborah; van Driel-Gesztelyi, Lidia; Brooks, David H.;
   Démoulin, Pascal; Valori, Gherardo; Long, David M.; Laming, J. Martin;
   To, Andy S. H.; James, Alexander W.
Bibcode: 2020ApJ...894...35B
Altcode: 2020arXiv200303325B
  Within the coronae of stars, abundances of those elements with low
  first ionization potential (FIP) often differ from their photospheric
  values. The coronae of the Sun and solar-type stars mostly show
  enhancements of low-FIP elements (the FIP effect) while more active
  stars such as M dwarfs have coronae generally characterized by the
  inverse-FIP effect (I-FIP). Here we observe patches of I-FIP effect
  solar plasma in AR 12673, a highly complex βγδ active region. We
  argue that the umbrae of coalescing sunspots, and more specifically
  strong light bridges within the umbrae, are preferential locations for
  observing I-FIP effect plasma. Furthermore, the magnetic complexity
  of the active region and major episodes of fast flux emergence also
  lead to repetitive and intense flares. The induced evaporation of
  the chromospheric plasma in flare ribbons crossing umbrae enables
  the observation of four localized patches of I-FIP effect plasma in
  the corona of AR 12673. These observations can be interpreted in the
  context of the ponderomotive force fractionation model which predicts
  that plasma with I-FIP effect composition is created by the refraction
  of waves coming from below the chromosphere. We propose that the waves
  generating the I-FIP effect plasma in solar active regions are generated
  by subphotospheric reconnection of coalescing flux systems. Although
  we only glimpse signatures of I-FIP effect fractionation produced by
  this interaction in patches on the Sun, on highly active M stars it
  may be the dominant process.

Title: Editorial Appreciation
Authors: Leibacher, John; Mandrini, Cristina H.; van Driel-Gesztelyi,
   Lidia; Wheatland, Michael S.
Bibcode: 2020SoPh..295....9L
Altcode:
  No abstract at ADS

Title: Spectropolarimetric Insight into Plasma Sheet Dynamics of a
    Solar Flare
Authors: French, Ryan J.; Judge, Philip G.; Matthews, Sarah A.;
   van Driel-Gesztelyi, Lidia
Bibcode: 2019ApJ...887L..34F
Altcode: 2019arXiv191112666F
  We examine spectropolarimetric data from the Coronal Multi-channel
  Polarimeter (CoMP) instrument, acquired during the evolution of the 2017
  September 10 X8.2 solar flare on the western solar limb. CoMP captured
  linearly polarized light from two emission lines of Fe XIII at 1074.7
  and 1079.8 nm, from 1.03 to 1.5 solar radii. We focus here on the hot
  plasma sheet lying above the bright flare loops and beneath the ejected
  coronal mass ejection. The polarization has a striking and coherent
  spatial structure, with unexpectedly small polarization aligned with
  the plasma sheet. By elimination, we find that small-scale magnetic
  field structure is needed to cause such significant depolarization,
  and suggest that plasmoid formation during reconnection (associated
  with the tearing-mode instability) creates magnetic structure on scales
  below instrument resolution of 6 Mm. We conclude that polarization
  measurements with new coronagraphs, such as the upcoming Daniel
  K. Inouye Solar Telescope, will further enhance our understanding of
  magnetic reconnection and development of turbulence in the solar corona.

Title: Understanding the Plasma and Magnetic Field Evolution of a
    Filament Using Observations and Nonlinear Force-free Field Modeling
Authors: Yardley, Stephanie L.; Savcheva, Antonia; Green, Lucie M.;
   van Driel-Gesztelyi, Lidia; Long, David; Williams, David R.; Mackay,
   Duncan H.
Bibcode: 2019ApJ...887..240Y
Altcode: 2019arXiv191101314Y
  We present observations and magnetic field models of an intermediate
  filament present on the Sun in 2012 August, associated with a polarity
  inversion line that extends from AR 11541 in the east into the quiet
  Sun at its western end. A combination of Solar Dynamics Observatory
  (SDO)/Atmospheric Imaging Assembly, SDO/Helioseismic and Magnetic
  Imager (HMI), and Global Oscillation Network Group Hα data allow
  us to analyze the structure and evolution of the filament from 2012
  August 4 23:00 UT to 2012 August 6 08:00 UT when the filament was in
  equilibrium. By applying the flux rope insertion method, nonlinear
  force-free field models of the filament are constructed using SDO/HMI
  line-of-sight magnetograms as the boundary condition at the two times
  given above. Guided by observed filament barbs, both modeled flux ropes
  are split into three sections each with a different value of axial flux
  to represent the nonuniform photospheric field distribution. The flux
  in the eastern section of the rope increases by 4 × 10<SUP>20</SUP>
  Mx between the two models, which is in good agreement with the amount
  of flux canceled along the internal PIL of AR 11541, calculated to be
  3.2 × 10<SUP>20</SUP> Mx. This suggests that flux cancellation builds
  flux into the filament’s magnetic structure. Additionally, the number
  of field line dips increases between the two models in the locations
  where flux cancellation, the formation of new filament threads, and
  growth of the filament is observed. This suggests that flux cancellation
  associated with magnetic reconnection forms concave-up magnetic field
  that lifts plasma into the filament. During this time, the free magnetic
  energy in the models increases by 0.2 × 10<SUP>31</SUP> ergs.

Title: Polarized radiative transfer, rotation measure fluctuations,
    and large-scale magnetic fields
Authors: On, Alvina Y. L.; Chan, Jennifer Y. H.; Wu, Kinwah; Saxton,
   Curtis J.; van Driel-Gesztelyi, Lidia
Bibcode: 2019MNRAS.490.1697O
Altcode: 2019arXiv190906703O; 2019MNRAS.tmp.2320O
  Faraday rotation measure (RM) at radio wavelengths is commonly
  used to diagnose large-scale magnetic fields. It is argued that
  the length-scales on which magnetic fields vary in large-scale
  diffuse astrophysical media can be inferred from correlations in the
  observed RM. RM is a variable which can be derived from the polarized
  radiative transfer equations in restrictive conditions. This paper
  assesses the usage of rotation measure fluctuation (RMF) analyses for
  magnetic field diagnostics in the framework of polarized radiative
  transfer. We use models of various magnetic field configurations and
  electron density distributions to show how density fluctuations could
  affect the correlation length of the magnetic fields inferred from the
  conventional RMF analyses. We caution against interpretations of RMF
  analyses when a characteristic density is ill defined, e.g. in cases
  of lognormal-distributed and fractal-like density structures. As the
  spatial correlations are generally not the same in the line-of-sight
  longitudinal direction and the sky plane direction, one also needs to
  clarify the context of RMF when inferring from observational data. In
  complex situations, a covariant polarized radiative transfer calculation
  is essential to capture all aspects of radiative and transport
  processes, which would otherwise ambiguate the interpretations of
  magnetism in galaxy clusters and larger scale cosmological structures.

Title: Flaring Activity of Proxima Centauri from TESS Observations:
    Quasiperiodic Oscillations during Flare Decay and Inferences on the
    Habitability of Proxima b
Authors: Vida, Krisztián; Oláh, Katalin; Kővári, Zsolt; van
   Driel-Gesztelyi, Lidia; Moór, Attila; Pál, András
Bibcode: 2019ApJ...884..160V
Altcode: 2019arXiv190712580V
  We analyze the light curve of the M5.5 dwarf Proxima Centauri obtained
  by the Transiting Exoplanet Survey Satellite (TESS) in Sectors 11 and
  12. In the ≈50 day long light curve we identified and analyzed 72
  flare events. The flare rate was 1.49 events per day; in total, 7.2%
  of the observing time was classified as flaring. The estimated flare
  energies were on the order of 10<SUP>30</SUP>-10<SUP>32</SUP> erg in
  the TESS passband (≈4.8× higher in bolometric energies, but on the
  same order of magnitude). Most of the eruptions appeared in groups. Two
  events showed quasiperiodic oscillations during their decay phase with
  a timescale of a few hours, which could be caused by quasiperiodic
  motions of the emitting plasma or oscillatory reconnection. From the
  cumulative flare frequency distribution we estimate that superflares
  with energy output of 10<SUP>33</SUP> erg are expected to occur three
  times per year, while magnitude larger events (with 10<SUP>34</SUP> erg)
  can occur every second year. This reduces the chances of habitability
  of Proxima Cen b, although earlier numerical models did not rule out
  the existence of liquid water on the planetary surface. We did not
  find any obvious signs of planetary transit in the light curve.

Title: Spectroscopic Signatures of Plasma-Sheet Dynamics in a
    Solar Flare
Authors: French, Ryan J.; Matthews, Sarah A.; van Driel-Gesztelyi,
   Lidia; Long, David M.
Bibcode: 2019shin.confE.186F
Altcode:
  According to the standard eruptive flare model, energy is released
  in a current sheet formed in the wake of an erupting flux rope. The
  current sheet itself is theoretically predicted to be 10m wide,
  thus representing a significant challenge for current observational
  techniques. However, a handful of observations have reported enhanced
  emission from the region surrounding the current sheet, often referred
  to as the plasma-sheet. Since this region must respond to processes
  occurring in the current sheet itself, the study of its properties
  offers the possibility to indirectly probe conditions in the current
  sheet related to the reconnection process. Recent observations
  (Warren al., (2018), Li et al., 2018) have demonstrated the presence
  of enhanced nonthermal velocities in the current sheet observed in the
  10th September 2017 X8.2 class flare, consistent with the presence of
  turbulence and possible tearing mode instability. In this study, we
  combine observations from the Extreme-ultraviolet Imaging Spectrometer
  (EIS) and Atmospheric Imaging Assembly (AIA) to explore the relationship
  between the Alfven speed calculated for different plasma beta regimes,
  observed non-thermal velocity measurements, and the evolution of the
  plasma-sheet to test for the presence of the plasmoid instability.

Title: Transient Inverse-FIP Plasma Composition Evolution within a
    Solar Flare
Authors: Baker, Deborah; van Driel-Gesztelyi, Lidia; Brooks, David
   H.; Valori, Gherardo; James, Alexander W.; Laming, J. Martin; Long,
   David M.; Démoulin, Pascal; Green, Lucie M.; Matthews, Sarah A.;
   Oláh, Katalin; Kővári, Zsolt
Bibcode: 2019ApJ...875...35B
Altcode: 2019arXiv190206948B
  Understanding elemental abundance variations in the solar corona
  provides an insight into how matter and energy flow from the
  chromosphere into the heliosphere. Observed variations depend on the
  first ionization potential (FIP) of the main elements of the Sun’s
  atmosphere. High-FIP elements (&gt;10 eV) maintain photospheric
  abundances in the corona, whereas low-FIP elements have enhanced
  abundances. Conversely, inverse FIP (IFIP) refers to the enhancement of
  high-FIP or depletion of low-FIP elements. We use spatially resolved
  spectroscopic observations, specifically the Ar XIV/Ca XIV intensity
  ratio, from Hinode’s Extreme-ultraviolet Imaging Spectrometer to
  investigate the distribution and evolution of plasma composition
  within two confined flares in a newly emerging, highly sheared
  active region. During the decay phase of the first flare, patches
  above the flare ribbons evolve from the FIP to the IFIP effect, while
  the flaring loop tops show a stronger FIP effect. The patch and loop
  compositions then evolve toward the preflare basal state. We propose
  an explanation of how flaring in strands of highly sheared emerging
  magnetic fields can lead to flare-modulated IFIP plasma composition
  over coalescing umbrae which are crossed by flare ribbons. Subsurface
  reconnection between the coalescing umbrae leads to the depletion of
  low-FIP elements as a result of an increased wave flux from below. This
  material is evaporated when the flare ribbons cross the umbrae. Our
  results are consistent with the ponderomotive fractionation model for
  the creation of IFIP-biased plasma.

Title: Modeling the Effect of Mass-draining on Prominence Eruptions
Authors: Jenkins, Jack M.; Hopwood, Matthew; Démoulin, Pascal; Valori,
   Gherardo; Aulanier, Guillaume; Long, David M.; van Driel-Gesztelyi,
   Lidia
Bibcode: 2019ApJ...873...49J
Altcode: 2019arXiv190110970J
  Quiescent solar prominences are observed within the solar atmosphere
  for up to several solar rotations. Their eruption is commonly preceded
  by a slow increase in height that can last from hours to days. This
  increase in the prominence height is believed to be due to their host
  magnetic flux rope transitioning through a series of neighboring
  quasi-equilibria before the main loss of equilibrium that drives
  the eruption. Recent work suggests that the removal of prominence
  mass from a stable, quiescent flux rope is one possible cause for
  this change in height. However, these conclusions are drawn from
  observations and are subject to interpretation. Here, we present a
  simple model to quantify the effect of “mass-draining” during the
  pre-eruptive height evolution of a solar flux rope. The flux rope is
  modeled as a line current suspended within a background potential
  magnetic field. We first show that the inclusion of mass, up to
  10<SUP>12</SUP> kg, can modify the height at which the line current
  experiences loss of equilibrium by up to 14%. Next, we show that
  the rapid removal of mass prior to the loss of equilibrium can allow
  the height of the flux rope to increase sharply and without an upper
  bound as it approaches its loss-of-equilibrium point. This indicates
  that the critical height for the loss of equilibrium can occur at a
  range of heights depending explicitly on the amount and evolution of
  mass within the flux rope. Finally, we demonstrate that for the same
  amount of drained mass, the effect on the height of the flux rope is
  up to two orders of magnitude larger for quiescent prominences than
  for active region prominences.

Title: The quest for stellar coronal mass ejections in late-type
    stars. I. Investigating Balmer-line asymmetries of single stars in
    Virtual Observatory data
Authors: Vida, Krisztián; Leitzinger, Martin; Kriskovics, Levente;
   Seli, Bálint; Odert, Petra; Kovács, Orsolya Eszter; Korhonen, Heidi;
   van Driel-Gesztelyi, Lidia
Bibcode: 2019A&A...623A..49V
Altcode: 2019arXiv190104229V
  Context. Flares and coronal mass ejections (CMEs) can have deleterious
  effects on their surroundings: they can erode or completely destroy
  atmospheres of orbiting planets over time and also have high importance
  in stellar evolution. Most of the CME detections in the literature
  are single events found serendipitously sparse for statistical
  investigation. <BR /> Aims: We aimed to gather a large amount of
  spectral data of M-dwarfs to drastically increase the number of known
  events to make statistical analysis possible in order to study the
  properties of potential stellar CMEs. <BR /> Methods: Using archival
  spectral data we investigated asymmetric features of Balmer-lines,
  which could indicate the Doppler-signature of ejected material. <BR
  /> Results: Of more than 5500 spectra we find 478 that have line
  asymmetries - including nine larger events, in terms of velocity and
  mass - on 25 objects, with 1.2-19.6 events per day on objects with
  line asymmetries. Most events are connected with enhanced peaks of
  Balmer-lines, indicating that these are connected to flares similar
  to solar events. In most cases the detected speed does not reach
  surface escape velocity: the typical observed maximum velocities are
  on the order of 100-300 km s<SUP>-1</SUP>, while the typical masses
  of the ejecta were on the order of 10<SUP>15</SUP>-10<SUP>18</SUP>
  g. Statistical analysis of the events suggests that these events are
  more frequent on cooler stars with stronger chromospheric activity. <BR
  /> Conclusions: If the detected events correspond to CMEs, the
  detected maximum velocities are lower than those observed on the Sun,
  while event rates were somewhat lower than we could expect from the
  solar case. If the velocities are not distorted significantly due to
  a projection effect, these findings may support the idea that most of
  the coronal mass ejections could be suppressed by a strong magnetic
  field. Alternatively, it is possible that we can observe only an early
  low-coronal phase of the events before being accelerated at higher
  altitudes. Our findings could indicate that later-type, active dwarfs
  could be a safer environment for exoplanetary systems CME-wise than
  previously thought, and atmosphere loss due to radiation effects would
  play a stronger role in exoplanetary atmosphere evolution than CMEs.

Title: Editorial Appreciation
Authors: Leibacher, John; Mandrini, Cristina H.; van Driel-Gesztelyi,
   Lidia; Wheatland, Michael S.
Bibcode: 2019SoPh..294....3L
Altcode:
  We are pleased to acknowledge, with sincere thanks, the following
  colleagues who supported the community by reviewing articles for Solar
  Physics during 2018.

Title: An Observationally Constrained Model of a Flux Rope that
    Formed in the Solar Corona
Authors: James, Alexander W.; Valori, Gherardo; Green, Lucie M.; Liu,
   Yang; Cheung, Mark C. M.; Guo, Yang; van Driel-Gesztelyi, Lidia
Bibcode: 2018csc..confE...9J
Altcode:
  Coronal mass ejections (CMEs) are large-scale eruptions of plasma
  from the coronae of stars, and it is important to study the plasma
  processes involved in their initiation. This first requires us to
  understand the pre-eruptive configuration of CMEs. To this end, we used
  extreme-ultraviolet (EUV) observations from SDO/AIA to conclude that a
  magnetic flux rope formed high-up in the solar corona above NOAA Active
  Region 11504 before it erupted on 2012 June 14. Then, we used data from
  SDO/HMI and our knowledge of the EUV observations to model the coronal
  magnetic field of the active region one hour prior to eruption using a
  nonlinear force-free field extrapolation. The extrapolation revealed
  a flux rope that matches the EUV observations remarkably well, with
  its axis 120 Mm above the photosphere. The erupting structure was not
  observed to kink, but the decay index near the apex of the axis of
  the extrapolated flux rope is comparable to typical critical values
  required for the onset of the torus instability. Therefore, we suggest
  that the torus instability drove the eruption of the flux rope.

Title: Understanding the Role of Mass-Unloading in a Filament Eruption
Authors: Jenkins, Jack; Long, David; van Driel-Gesztelyi, Lidia;
   Carlyle, Jack; Hopwood, Matthew
Bibcode: 2018csc..confE..17J
Altcode:
  We combine observations of a partial filament eruption on 11
  December 2011 with a simple line-current model to demonstrate
  that including mass is an important next step for understanding
  solar eruptions. Observations from the Solar Terrestrial Relations
  Observatory-Behind (STEREO-B) and the Solar Dynamics Observatory (SDO)
  spacecraft were used to remove line-of-sight projection effects in
  filament motion and correlate the effect of plasma dynamics with
  the evolution of the filament height. The two viewpoints enable
  the amount of mass drained to be estimated, and an investigation of
  the subsequent radial expansion and eruption of the filament. We use
  these observational measurements to constrain a line-current model and
  quantitatively demonstrate the important role that the presence and
  draining of mass has in the lead-up to solar eruptions. Specifically,
  we show that the balance of magnetic and gravitational forces acting
  on the line-current is increasingly sensitive to mass perturbations
  as it approaches its loss-of-equilibrium. Finally, we conclude that
  the eruption of the observed filament was restrained until 70% of the
  mass had drained from the structure.

Title: The Role of Flux Cancellation in Eruptions from Bipolar ARs
Authors: Yardley, S. L.; Green, L. M.; van Driel-Gesztelyi, L.;
   Williams, D. R.; Mackay, D. H.
Bibcode: 2018ApJ...866....8Y
Altcode: 2018arXiv180810635Y
  The physical processes or trigger mechanisms that lead to the eruption
  of coronal mass ejections (CMEs), the largest eruptive phenomenon in the
  heliosphere, are still undetermined. Low-altitude magnetic reconnection
  associated with flux cancellation appears to play an important role in
  CME occurrence as it can form an eruptive configuration and reduce the
  magnetic flux that contributes to the overlying, stabilizing field. We
  conduct the first comprehensive study of 20 small bipolar ARs (ARs)
  in order to probe the role of flux cancellation as an eruption trigger
  mechanism. We categorize eruptions from the bipolar regions into three
  types related to location, and find that the type of eruption produced
  depends on the evolutionary stage of the AR. In addition, we find that
  ARs that form eruptive structures by flux cancellation (low-altitude
  reconnection) had, on average, lower flux cancellation rates than the AR
  sample as a whole. Therefore, while flux cancellation plays a key role,
  by itself it is insufficient for the production of an eruption. The
  results provide supporting evidence that although flux cancellation
  in a sheared arcade may be able to build an eruptive configuration,
  a successful eruption depends upon the removal of sufficient overlying
  and stabilizing field. Convergence of the bipole polarities also appears
  to be present in regions that produce an eruption. These findings have
  important implications for understanding the physical processes that
  occur on our Sun in relation to CMEs and for space weather forecasting.

Title: Sequential Eruptions Triggered by Flux Emergence: Observations
    and Modeling
Authors: Dacie, S.; Török, T.; Démoulin, P.; Linton, M. G.; Downs,
   C.; van Driel-Gesztelyi, L.; Long, D. M.; Leake, J. E.
Bibcode: 2018ApJ...862..117D
Altcode: 2018arXiv180700020D
  We describe and analyze observations by the Solar Dynamics Observatory
  of the emergence of a small, bipolar active region within an area of
  unipolar magnetic flux that was surrounded by a circular, quiescent
  filament. Within only 8 hours from the start of the emergence, a
  partial splitting of the filament and two consecutive coronal mass
  ejections took place. We argue that all three dynamic events occurred
  as a result of particular magnetic-reconnection episodes between
  the emerging bipole and the pre-existing coronal magnetic field. To
  substantiate our interpretation, we consider 3D magnetohydrodynamic
  simulations that model the emergence of magnetic flux in the vicinity of
  a large-scale coronal flux rope. The simulations qualitatively reproduce
  most of the reconnection episodes suggested by the observations, as
  well as the filament splitting, the first eruption, and the formation
  of sheared/twisted fields that may have played a role in the second
  eruption. Our results suggest that the position of emerging flux with
  respect to the background magnetic configuration is a crucial factor for
  the resulting evolution, while previous results suggest that parameters
  such as the orientation or the amount of emerging flux are important
  as well. This poses a challenge for predicting the onset of eruptions
  that are triggered by flux emergence, and calls for a detailed survey
  of the relevant parameter space by means of numerical simulations.

Title: Solar Cycle Observations of the Neon Abundance in the
    Sun-as-a-star
Authors: Brooks, David H.; Baker, Deborah; van Driel-Gesztelyi, Lidia;
   Warren, Harry P.
Bibcode: 2018ApJ...861...42B
Altcode: 2018arXiv180507032B
  Properties of the Sun’s interior can be determined accurately
  from helioseismological measurements of solar oscillations. These
  measurements, however, are in conflict with photospheric elemental
  abundances derived using 3D hydrodynamic models of the solar
  atmosphere. This divergence of theory and helioseismology is known as
  the “solar modeling problem.” One possible solution is that the
  photospheric neon abundance, which is deduced indirectly by combining
  the coronal Ne/O ratio with the photospheric O abundance, is larger
  than generally accepted. There is some support for this idea from
  observations of cool stars. The Ne/O abundance ratio has also been
  found to vary with the solar cycle in the slowest solar wind streams
  and coronal streamers, and the variation from solar maximum to minimum
  in streamers (∼0.1-0.25) is large enough to potentially bring some
  of the solar models into agreement with the seismic data. Here we use
  daily sampled observations from the EUV Variability Experiment on the
  Solar Dynamics Observatory taken in 2010-2014, to investigate whether
  the coronal Ne/O abundance ratio shows a variation with the solar cycle
  when the Sun is viewed as a star. We find only a weak dependence on,
  and moderate anti-correlation with, the solar cycle with the ratio
  measured around 0.2-0.3 MK falling from 0.17 at solar minimum to
  0.11 at solar maximum. The effect is amplified at higher temperatures
  (0.3-0.6 MK) with a stronger anti-correlation and the ratio falling
  from 0.16 at solar minimum to 0.08 at solar maximum. The values we
  find at solar minimum are too low to solve the solar modeling problem.

Title: Understanding the Role of Mass-Unloading in a Filament Eruption
Authors: Jenkins, Jack Michael; Long, David; van Driel-Gesztelyi,
   Lidia; Carlyle, Jack
Bibcode: 2018tess.conf10907J
Altcode:
  Solar filaments are persistent features on the solar surface,
  lasting from days to months before either successfully erupting into
  the heliosphere as part of a CME, or collapsing and returning the
  suspended plasma to the chromosphere. To date, the consensus has
  been that the plasma comprising the filament plays no significant
  role in the global evolution of the host flux rope. As a result,
  little effort has been made to quantify the impact that mass has on
  the evolution of magnetic structures in the solar atmosphere. Here we
  present observations and analysis that suggest that the inclusion of
  mass is an important next step to fully understand solar eruptions. A
  partial filament eruption that occurred on 11 December 2011 was
  observed by both the Solar Terrestrial Relations Observatory-Behind
  (STEREO-B) and the Solar Dynamics Observatory (SDO) spacecraft. The
  combination of multiple perspectives from different locations within
  the heliosphere allowed the removal of line-of-sight projection
  effects, and the correlation of plasma dynamics to the evolution in
  filament height. Our results show that 70\% of the measurable filament
  mass drained shortly \textit{prior} to a change in the height--time
  expansion profile of the remaining filament material from a shallow
  to steeper exponential. A proxy was then formulated to test whether
  the observed mass-unloading was responsible for this observed change
  in behaviour. This proxy is defined as the ratio between the upward
  force supplied to the host flux rope due to this mass-unloading and
  the restraining force caused by the tension of the overlying magnetic
  field. A ratio range of between 1.8 and 4.1 was found, indicating that
  the upward force as a result of the the mass-unloading dominated the
  evolution. We conclude that the unloading of filament mass from the
  host flux rope was likely responsible for the accelerated expansion.

Title: Václav Bumba (1925 - 2018)
Authors: Kotrč, Pavel; Heinzel, Petr; Sobotka, Michal; Ambrož,
   Pavel; van Driel-Gesztelyi, Lidia
Bibcode: 2018SoPh..293...40K
Altcode:
  No abstract at ADS

Title: An Observationally Constrained Model of a Flux Rope that
    Formed in the Solar Corona
Authors: James, Alexander W.; Valori, Gherardo; Green, Lucie M.; Liu,
   Yang; Cheung, Mark C. M.; Guo, Yang; van Driel-Gesztelyi, Lidia
Bibcode: 2018ApJ...855L..16J
Altcode: 2018arXiv180207965J
  Coronal mass ejections (CMEs) are large-scale eruptions of plasma
  from the coronae of stars. Understanding the plasma processes involved
  in CME initiation has applications for space weather forecasting and
  laboratory plasma experiments. James et al. used extreme-ultraviolet
  (EUV) observations to conclude that a magnetic flux rope formed in
  the solar corona above NOAA Active Region 11504 before it erupted on
  2012 June 14 (SOL2012-06-14). In this work, we use data from the Solar
  Dynamics Observatory (SDO) to model the coronal magnetic field of the
  active region one hour prior to eruption using a nonlinear force-free
  field extrapolation, and find a flux rope reaching a maximum height
  of 150 Mm above the photosphere. Estimations of the average twist of
  the strongly asymmetric extrapolated flux rope are between 1.35 and
  1.88 turns, depending on the choice of axis, although the erupting
  structure was not observed to kink. The decay index near the apex
  of the axis of the extrapolated flux rope is comparable to typical
  critical values required for the onset of the torus instability,
  so we suggest that the torus instability drove the eruption.

Title: Coronal Elemental Abundances in Solar Emerging Flux Regions
Authors: Baker, Deborah; Brooks, David H.; van Driel-Gesztelyi,
   Lidia; James, Alexander W.; Démoulin, Pascal; Long, David M.; Warren,
   Harry P.; Williams, David R.
Bibcode: 2018ApJ...856...71B
Altcode: 2018arXiv180108424B
  The chemical composition of solar and stellar atmospheres differs from
  the composition of their photospheres. Abundances of elements with low
  first ionization potential (FIP) are enhanced in the corona relative
  to high-FIP elements with respect to the photosphere. This is known as
  the FIP effect and it is important for understanding the flow of mass
  and energy through solar and stellar atmospheres. We used spectroscopic
  observations from the Extreme-ultraviolet Imaging Spectrometer on board
  the Hinode observatory to investigate the spatial distribution and
  temporal evolution of coronal plasma composition within solar emerging
  flux regions inside a coronal hole. Plasma evolved to values exceeding
  those of the quiet-Sun corona during the emergence/early-decay phase
  at a similar rate for two orders of magnitude in magnetic flux, a rate
  comparable to that observed in large active regions (ARs) containing
  an order of magnitude more flux. During the late-decay phase, the rate
  of change was significantly faster than what is observed in large,
  decaying ARs. Our results suggest that the rate of increase during the
  emergence/early-decay phase is linked to the fractionation mechanism
  that leads to the FIP effect, whereas the rate of decrease during
  the later decay phase depends on the rate of reconnection with the
  surrounding magnetic field and its plasma composition.

Title: Editorial Appreciation
Authors: Leibacher, John; Mandrini, Cristina H.; van Driel-Gesztelyi,
   Lidia; Wheatland, Michael S.
Bibcode: 2018SoPh..293...14L
Altcode:
  No abstract at ADS

Title: Understanding the Role of Mass-Unloading in a Filament Eruption
Authors: Jenkins, J. M.; Long, D. M.; van Driel-Gesztelyi, L.;
   Carlyle, J.
Bibcode: 2018SoPh..293....7J
Altcode: 2017arXiv171102565J
  We describe a partial filament eruption on 11 December 2011 that
  demonstrates that the inclusion of mass is an important next step for
  understanding solar eruptions. Observations from the Solar Terrestrial
  Relations Observatory-Behind (STEREO-B) and the Solar Dynamics
  Observatory (SDO) spacecraft were used to remove line-of-sight
  projection effects in filament motion and correlate the effect
  of plasma dynamics with the evolution of the filament height. Flux
  cancellation and nearby flux emergence are shown to have played a role
  in increasing the height of the filament prior to eruption. The two
  viewpoints allow the quantitative estimation of a large mass-unloading,
  the subsequent radial expansion, and the eruption of the filament to be
  investigated. A 1.8 to 4.1 lower-limit ratio between gravitational and
  magnetic-tension forces was found. We therefore conclude that following
  the loss-of-equilibrium of the flux-rope, the radial expansion of
  the flux-rope was restrained by the filamentary material until 70%
  of the mass had evacuated the structure through mass-unloading.

Title: The Life Cycle of Active Region Magnetic Fields
Authors: Cheung, M. C. M.; van Driel-Gesztelyi, L.; Martínez Pillet,
   V.; Thompson, M. J.
Bibcode: 2018smf..book..317C
Altcode:
  No abstract at ADS

Title: Non-thermal distributions and energy transport in the solar
    flares
Authors: Matthews, Sarah; del Zanna, Guilio; Calcines, Ariadna;
   Mason, Helen; Mathioudakis, Mihalis; Culhane, Len; Harra, Louise;
   van Driel-Gesztelyi, Lidia; Green, Lucie; Long, David; Baker, Deb;
   Valori, Gherardo
Bibcode: 2017arXiv171200773M
Altcode:
  Determining the energy transport mechanisms in flares remains a central
  goal in solar flares physics that is still not adequately answered
  by the 'standard flare model'. In particular, the relative roles of
  particles and/or waves as transport mechanisms, the contributions of low
  energy protons and ions to the overall flare budget, and the limits of
  low energy non-thermal electron distribution are questions that still
  cannot be adequately reconciled with current instrumentation. In this
  'White Paper' submitted in response to the call for inputs to the Next
  Generation Solar Physics Mission review process initiated by JAXA,
  NASA and ESA in 2016, we outline the open questions in this area and
  possible instrumentation that could provide the required observations
  to help answer these and other flare-related questions.

Title: Editorial: Last Print Issue of Solar Physics
Authors: Leibacher, John; Mandrini, Cristina H.; van Driel-Gesztelyi,
   Lidia; Wheatland, Michael S.
Bibcode: 2017SoPh..292..196L
Altcode:
  No abstract at ADS

Title: Field distribution of magnetograms from simulations of active
    region formation
Authors: Dacie, S.; van Driel-Gesztelyi, L.; Démoulin, P.; Linton,
   M. G.; Leake, J. E.; MacTaggart, D.; Cheung, M. C. M.
Bibcode: 2017A&A...606A..34D
Altcode:
  Context. The evolution of the photospheric magnetic field distributions
  (probability densities) has previously been derived for a set of active
  regions. Photospheric field distributions are a consequence of physical
  processes that are difficult to determine from observations alone. <BR
  /> Aims: We analyse simulated magnetograms from numerical simulations,
  which model the emergence and decay of active regions. These simulations
  have different experimental set-ups and include different physical
  processes, allowing us to investigate the relative importance of
  convection, magnetic buoyancy, magnetic twist, and braiding for flux
  emergence. <BR /> Methods: We specifically studied the photospheric
  field distributions (probability densities found with a kernel density
  estimation analysis) and compared the results with those found from
  observations. <BR /> Results: Simulations including convection most
  accurately reproduce the observed evolution of the photospheric field
  distributions during active region evolution. <BR /> Conclusions: This
  indicates that convection may play an important role during the decay
  phase and also during the formation of active regions, particularly
  for low flux density values.

Title: The Life Cycle of Active Region Magnetic Fields
Authors: Cheung, M. C. M.; van Driel-Gesztelyi, L.; Martínez Pillet,
   V.; Thompson, M. J.
Bibcode: 2017SSRv..210..317C
Altcode: 2016SSRv..tmp...46C
  We present a contemporary view of how solar active region
  magnetic fields are understood to be generated, transported and
  dispersed. Empirical trends of active region properties that guide model
  development are discussed. Physical principles considered important
  for active region evolution are introduced and advances in modeling
  are reviewed.

Title: The 2015 St Patrick's Day Storm: Origins
Authors: Carlyle, Jack; van Driel-Gesztelyi, Lidia; Zuccarello,
   Francesco; James, Alexander; Williams, David
Bibcode: 2017SPD....4840402C
Altcode:
  The magnetic storm experienced at Earth on St. Patrick's Day 2015 had
  been the strongest of cycle 24 (at that time) with a measured DST of
  -223 nT, though it was not expected to cause much of a disturbance. In
  this work we study the solar source region of several peculiar
  eruptions, leading to the formation and destruction of various
  structures, in the week leading up to the storm, and determine the
  true sequence of events. The evolution of the magnetic flux at the
  solar surface is examined in order to place suspected flux-ropes
  into context, and the evolution of the magnetic connectivities
  is described alongside a PFSS model of the surrounding region. The
  balance between positive and negative flux directly before two key
  eruptions is investigated in detail, in order to ascertain whether
  particular trigger mechanisms are feasible explanations. As well as
  these magnetic investigations, the column density of plasma involved
  is calculated from extreme ultraviolet images, and this is used to
  estimate the total mass of one filament, as well as select other
  features relevant to the eruptions. This information is then used to
  comment on the energy budgets and requirements of several processes in
  order to best understand the underlying drivers of this event.Previous
  studies on the St. Patrick's Day Storm are also incorporated into this
  work, and an attempt is made to reconcile the disparate conclusions
  drawn by the scientific community as to why this storm was not only
  so effective, but also a major forecasting failure.

Title: A Solar cycle correlation of coronal element abundances in
    Sun-as-a-star observations
Authors: Brooks, David H.; Baker, Deborah; van Driel-Gesztelyi, Lidia;
   Warren, Harry P.
Bibcode: 2017NatCo...8..183B
Altcode: 2018arXiv180200563B
  The elemental composition in the coronae of low-activity solar-like
  stars appears to be related to fundamental stellar properties such as
  rotation, surface gravity, and spectral type. Here we use full-Sun
  observations from the Solar Dynamics Observatory, to show that when
  the Sun is observed as a star, the variation of coronal composition
  is highly correlated with a proxy for solar activity, the F10.7 cm
  radio flux, and therefore with the solar cycle phase. Similar cyclic
  variations should therefore be detectable spectroscopically in X-ray
  observations of solar analogs. The plasma composition in full-disk
  observations of the Sun is related to the evolution of coronal magnetic
  field activity. Our observations therefore introduce an uncertainty
  into the nature of any relationship between coronal composition and
  fixed stellar properties. The results highlight the importance of
  systematic full-cycle observations for understanding the elemental
  composition of solar-like stellar coronae.

Title: A study of the long term evolution in active region upflows
Authors: Harra, Louise K.; Ugarte-Urra, Ignacio; De Rosa, Marc;
   Mandrini, Cristina; van Driel-Gesztelyi, Lidia; Baker, Deborah;
   Culhane, J. Leonard; Démoulin, Pascal
Bibcode: 2017PASJ...69...47H
Altcode:
  Since their discovery, upflows at the edges of active regions have
  attracted a lot of interest, primarily as they could potentially
  contribute to the slow solar wind. One aspect that has not been studied
  yet is how the long term evolution of active regions impacts the
  upflows. In this work, we analyze one active region that survives three
  solar rotations. We track how the flows change with time. We use local
  and global modeling of the decaying active region to determine how the
  age of the active region will impact the extent of the open magnetic
  fields, and then how some of the upflows could become outflows. We
  finish with a discussion of how these results, set in a broader context,
  can be further developed with the Solar Orbiter mission.

Title: On-Disc Observations of Flux Rope Formation Prior to Its
    Eruption
Authors: James, A. W.; Green, L. M.; Palmerio, E.; Valori, G.; Reid,
   H. A. S.; Baker, D.; Brooks, D. H.; van Driel-Gesztelyi, L.; Kilpua,
   E. K. J.
Bibcode: 2017SoPh..292...71J
Altcode: 2017arXiv170310837J
  Coronal mass ejections (CMEs) are one of the primary manifestations of
  solar activity and can drive severe space weather effects. Therefore,
  it is vital to work towards being able to predict their
  occurrence. However, many aspects of CME formation and eruption
  remain unclear, including whether magnetic flux ropes are present
  before the onset of eruption and the key mechanisms that cause CMEs
  to occur. In this work, the pre-eruptive coronal configuration of
  an active region that produced an interplanetary CME with a clear
  magnetic flux rope structure at 1 AU is studied. A forward-S sigmoid
  appears in extreme-ultraviolet (EUV) data two hours before the onset
  of the eruption (SOL2012-06-14), which is interpreted as a signature
  of a right-handed flux rope that formed prior to the eruption. Flare
  ribbons and EUV dimmings are used to infer the locations of the flux
  rope footpoints. These locations, together with observations of the
  global magnetic flux distribution, indicate that an interaction between
  newly emerged magnetic flux and pre-existing sunspot field in the days
  prior to the eruption may have enabled the coronal flux rope to form
  via tether-cutting-like reconnection. Composition analysis suggests
  that the flux rope had a coronal plasma composition, supporting our
  interpretation that the flux rope formed via magnetic reconnection in
  the corona. Once formed, the flux rope remained stable for two hours
  before erupting as a CME.

Title: Editorial Appreciation
Authors: Leibacher, John; Mandrini, Cristina H.; van Driel-Gesztelyi,
   Lidia; Wheatland, Michael S.
Bibcode: 2017SoPh..292...19L
Altcode:
  We are pleased to acknowledge, with sincere thanks, the following
  referees who supported the community by refereeing articles for Solar
  Physics during 2016.

Title: Evolution of the magnetic field distribution of active regions
Authors: Dacie, S.; Démoulin, P.; van Driel-Gesztelyi, L.; Long,
   D. M.; Baker, D.; Janvier, M.; Yardley, S. L.; Pérez-Suárez, D.
Bibcode: 2016A&A...596A..69D
Altcode: 2016arXiv160903723D
  <BR /> Aims: Although the temporal evolution of active regions (ARs)
  is relatively well understood, the processes involved continue to be
  the subject of investigation. We study how the magnetic field of a
  series of ARs evolves with time to better characterise how ARs emerge
  and disperse. <BR /> Methods: We examined the temporal variation in
  the magnetic field distribution of 37 emerging ARs. A kernel density
  estimation plot of the field distribution was created on a log-log
  scale for each AR at each time step. We found that the central portion
  of the distribution is typically linear, and its slope was used to
  characterise the evolution of the magnetic field. <BR /> Results:
  The slopes were seen to evolve with time, becoming less steep as the
  fragmented emerging flux coalesces. The slopes reached a maximum value
  of -1.5 just before the time of maximum flux before becoming steeper
  during the decay phase towards the quiet-Sun value of -3. This behaviour
  differs significantly from a classical diffusion model, which produces
  a slope of -1. These results suggest that simple classical diffusion
  is not responsible for the observed changes in field distribution, but
  that other processes play a significant role in flux dispersion. <BR />
  Conclusions: We propose that the steep negative slope seen during the
  late-decay phase is due to magnetic flux reprocessing by (super)granular
  convective cells.

Title: Editorial: 50 Years of Solar Physics
Authors: Charbonneau, Paul; Leibacher, John; Mandrini, Cristina;
   van Driel-Gesztelyi, Lidia; Wheatland, Michael S.
Bibcode: 2016SoPh..291.3461C
Altcode: 2016SoPh..tmp..189C
  No abstract at ADS

Title: Preface to Topical Issue: Waves in the Solar Corona: From
    Microphysics to Macrophysics
Authors: Nakariakov, V. M.; Pascoe, D. J.; Sych, R.; van
   Driel-Gesztelyi, L.
Bibcode: 2016SoPh..291.3139N
Altcode: 2016SoPh..tmp..187N
  No abstract at ADS

Title: Flux Cancellation and the Evolution of the Eruptive Filament
    of 2011 June 7
Authors: Yardley, S. L.; Green, L. M.; Williams, D. R.; van
   Driel-Gesztelyi, L.; Valori, G.; Dacie, S.
Bibcode: 2016ApJ...827..151Y
Altcode: 2016arXiv160608264Y
  We investigate whether flux cancellation is responsible for the
  formation of a very massive filament resulting in the spectacular
  eruption on 2011 June 7. We analyze and quantify the amount of flux
  cancellation that occurs in NOAA AR 11226 and its two neighboring active
  regions (ARs 11227 &amp; 11233) using line-of-sight magnetograms from
  the Heliospheric Magnetic Imager. During a 3.6 day period building
  up to the eruption of the filament, 1.7 × 10<SUP>21</SUP> Mx, 21%
  of AR 11226's maximum magnetic flux, was canceled along the polarity
  inversion line (PIL) where the filament formed. If the flux cancellation
  continued at the same rate up until the eruption then up to 2.8 ×
  10<SUP>21</SUP> Mx (34% of the AR flux) may have been built into the
  magnetic configuration that contains the filament plasma. The large flux
  cancellation rate is due to an unusual motion of the positive-polarity
  sunspot, which splits, with the largest section moving rapidly toward
  the PIL. This motion compresses the negative polarity and leads to
  the formation of an orphan penumbra where one end of the filament is
  rooted. Dense plasma threads above the orphan penumbra build into the
  filament, extending its length, and presumably injecting material into
  it. We conclude that the exceptionally strong flux cancellation in
  AR 11226 played a significant role in the formation of its unusually
  massive filament. In addition, the presence and coherent evolution of
  bald patches in the vector magnetic field along the PIL suggest that
  the magnetic field configuration supporting the filament material is
  that of a flux rope.

Title: An Investigation of the Sources of Earth-directed Solar Wind
    during Carrington Rotation 2053
Authors: Fazakerley, A. N.; Harra, L. K.; van Driel-Gesztelyi, L.
Bibcode: 2016ApJ...823..145F
Altcode:
  In this work we analyze multiple sources of solar wind through a full
  Carrington Rotation (CR 2053) by analyzing the solar data through
  spectroscopic observations of the plasma upflow regions and the in
  situ data of the wind itself. Following earlier authors, we link solar
  and in situ observations by a combination of ballistic backmapping
  and potential-field source-surface modeling. We find three sources
  of fast solar wind that are low-latitude coronal holes. The coronal
  holes do not produce a steady fast wind, but rather a wind with
  rapid fluctuations. The coronal spectroscopic data from Hinode’s
  Extreme Ultraviolet Imaging Spectrometer show a mixture of upflow
  and downflow regions highlighting the complexity of the coronal
  hole, with the upflows being dominant. There is a mix of open and
  multi-scale closed magnetic fields in this region whose (interchange)
  reconnections are consistent with the up- and downflows they generate
  being viewed through an optically thin corona, and with the strahl
  directions and freeze-in temperatures found in in situ data. At the
  boundary of slow and fast wind streams there are three short periods
  of enhanced-velocity solar wind, which we term intermediate based on
  their in situ characteristics. These are related to active regions that
  are located beside coronal holes. The active regions have different
  magnetic configurations, from bipolar through tripolar to quadrupolar,
  and we discuss the mechanisms to produce this intermediate wind, and
  the important role that the open field of coronal holes adjacent to
  closed-field active regions plays in the process.

Title: Photospheric Vector Magnetic Field Evolution of NOAA Active
    Region 11504 and the Ensuing CME
Authors: James, Alexander; Green, Lucie; Valori, Gherardo; van
   Driel-Gesztelyi, Lidia; Baker, Deborah; Brooks, David; Palmerio, Erika
Bibcode: 2016SPD....4730305J
Altcode:
  Coronal mass ejections (CMEs) are eruptions of billions of tonnes of
  plasma from the Sun that drive the most severe space weather effects
  we observe. In order to be able to produce forecasts of space weather
  with lead times of the order of days, accurate predictions of the
  occurrence of CMEs must be developed. The eruptive active-region
  studied in this work (NOAA 11504) is complex, featuring fragmentation
  of penumbral magnetic field in the days prior to eruption, as well as
  rotation of the leading sunspot. SDO/HMI vector photospheric magnetic
  field measurements are utilised alongside SDO/AIA multi-wavelength
  extreme ultra-violet (EUV) observations to study the dynamics of the
  photospheric and coronal structures, as well as Hinode/EIS spectroscopic
  measurements, including elemental composition data. The EUV data show
  flare ribbons as well as coronal dimmings, which are used to infer
  the orientation of the erupting flux rope. This flux rope orientation
  is then compared to in situ measurements of the flux rope. The vector
  magnetic field data is used to determine the possible contributions
  the field fragmentation and sunspot rotation may have made to the
  formation of the flux rope and the triggering of the CME.

Title: Division E Commission 10: Solar Activity
Authors: Schrijver, Carolus J.; Fletcher, Lyndsay; van Driel-Gesztelyi,
   Lidia; Asai, Ayumi; Cally, Paul S.; Charbonneau, Paul; Gibson, Sarah
   E.; Gomez, Daniel; Hasan, Siraj S.; Veronig, Astrid M.; Yan, Yihua
Bibcode: 2016IAUTA..29..245S
Altcode: 2015arXiv151003348S
  After more than half a century of community support related to the
  science of ``solar activity'', IAU's Commission 10 was formally
  discontinued in 2015, to be succeeded by C.E2 with the same area
  of responsibility. On this occasion, we look back at the growth of
  the scientific disciplines involved around the world over almost a
  full century. Solar activity and fields of research looking into the
  related physics of the heliosphere continue to be vibrant and growing,
  with currently over 2,000 refereed publications appearing per year from
  over 4,000 unique authors, publishing in dozens of distinct journals
  and meeting in dozens of workshops and conferences each year. The
  size of the rapidly growing community and of the observational and
  computational data volumes, along with the multitude of connections
  into other branches of astrophysics, pose significant challenges;
  aspects of these challenges are beginning to be addressed through,
  among others, the development of new systems of literature reviews,
  machine-searchable archives for data and publications, and virtual
  observatories. As customary in these reports, we highlight some
  of the research topics that have seen particular interest over the
  most recent triennium, specifically active-region magnetic fields,
  coronal thermal structure, coronal seismology, flares and eruptions,
  and the variability of solar activity on long time scales. We close
  with a collection of developments, discoveries, and surprises that
  illustrate the range and dynamics of the discipline.

Title: Editorial Appreciation
Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia
Bibcode: 2016SoPh..291..337L
Altcode: 2016SoPh..tmp...10L
  No abstract at ADS

Title: Erratum to: The Magnetic Helicity Budget of a CME-Prolific
    Active Region
Authors: Green, L. M.; López Fuentes, M.; Mandrini, C. H.; Démoulin,
   P.; van Driel-Gesztelyi, L.; Culhane, J. L.
Bibcode: 2016SoPh..291..335G
Altcode: 2015SoPh..tmp..179G
  No abstract at ADS

Title: Preface
Authors: Fletcher, L.; Heinzel, P.; van Driel-Gesztelyi, L.; Mandrini,
   C. H.; Fárník, F.
Bibcode: 2015SoPh..290.3379F
Altcode: 2015SoPh..tmp..168F
  No abstract at ADS

Title: Preface: Probing the Sun Inside and Out
Authors: Harra, Louise; Baker, Deborah; Howe, Rachel; Leibacher,
   John; van Driel-Gesztelyi, Lidia
Bibcode: 2015SoPh..290.3091H
Altcode: 2015SoPh..tmp..167H
  No abstract at ADS

Title: Persistent Near-Surface Flow Structures from Local
    Helioseismology
Authors: Howe, Rachel; Komm, R. W.; Baker, D.; Harra, L.; van
   Driel-Gesztelyi, L.; Bogart, R. S.
Bibcode: 2015SoPh..290.3137H
Altcode: 2015arXiv150706525H; 2015SoPh..tmp..115H
  Near-surface flows measured by the ring-diagram technique of local
  helioseismology show structures that persist over multiple rotations. We
  examine these phenomena using data from the Global Oscillation Network
  Group (GONG) and the Helioseismic and Magnetic Imager (HMI) and show
  that a correlation analysis of the structures can be used to estimate
  the rotation rate as a function of latitude, giving a result consistent
  with the near-surface rate from global helioseismology and slightly
  slower than that obtained from a similar analysis of the surface
  magnetic field strength. At latitudes of 60<SUP>∘</SUP> and above,
  the HMI flow data reveal a strong signature of a two-sided zonal flow
  structure. This signature may be related to recent reports of "giant
  cells" in solar convection.

Title: A Study of the Coronal Non-thermal Velocity in Polar Regions
    During the Rise from Solar Minimum to Solar Maximum in Cycle 24
Authors: Harra, L.; Baker, D.; Edwards, S. J.; Hara, H.; Howe, R.;
   van Driel-Gesztelyi, L.
Bibcode: 2015SoPh..290.3203H
Altcode: 2015SoPh..tmp....8H
  We explore the changes in coronal non-thermal velocity (V<SUB>nt</SUB>)
  measurements at the poles from solar minimum to solar maximum using
  Hinode EUV Imaging Spectrometer data. We find that although the
  intensity in the corona at the poles does tend to increase with
  the cycle, there are no significant changes in the V<SUB>nt</SUB>
  values. The locations of enhanced V<SUB>nt</SUB> values measured do not
  always have a counterpart in intensity, and they are sometimes located
  in weak emission regions. Unipolar magnetic streams, created through
  diffusion of the following polarity of the decaying active regions,
  slowly progress towards the poles. These streams are expected to
  be related to magnetic nulls as locations that indicate an increased
  likelihood for magnetic reconnection to occur. Through global potential
  field source-surface modelling, we determine how the number of nulls
  varied during the cycle and find that those that lie at &lt; 1.1
  solar radii vary significantly. We search for a correlation between
  the variation of the magnetic nulls and the V<SUB>nt</SUB> values,
  as it may be expected that with an increasing number of nulls, the
  V<SUB>nt</SUB> values in the corona increase as well. There is no
  correlation with the V<SUB>nt</SUB> values, however. This indicates
  that the magnetic structures that create the enhanced V<SUB>nt</SUB>
  behaviour are small-scale features and hence not easily measurable at
  the poles. Because they do not change during the solar cycle, they are
  likely to be created by a local dynamo. The variation of the upper
  range of V<SUB>nt</SUB> is reduced, which highlights that strongly
  dynamic behaviour is reduced as the solar maximum approaches. This
  is likely to be due to the reduced area of the polar coronal hole,
  which allows fewer opportunities for reconnection to occur between
  open and closed magnetic fields.

Title: Source of a Prominent Poleward Surge During Solar Cycle 24
Authors: Yeates, A. R.; Baker, D.; van Driel-Gesztelyi, L.
Bibcode: 2015SoPh..290.3189Y
Altcode: 2015SoPh..tmp...18Y; 2015arXiv150204854Y
  As an observational case study, we consider the origin of a prominent
  poleward surge of leading polarity, visible in the magnetic butterfly
  diagram during Solar Cycle 24. A new technique is developed for
  assimilating individual regions of strong magnetic flux into a
  surface-flux transport model. By isolating the contribution of each
  of these regions, the model shows the surge to originate primarily in
  a single high-latitude activity group consisting of a bipolar active
  region present in Carrington Rotations 2104 - 05 (November 2010 -
  January 2011) and a multipolar active region in Rotations 2107 - 08
  (February - April 2011). This group had a strong axial dipole moment
  opposed to Joy's law. On the other hand, the modelling suggests that
  the transient influence of this group on the butterfly diagram will
  not be matched by a large long-term contribution to the polar field
  because it is located at high latitude. This is in accordance with
  previous flux-transport models.

Title: Evolution of Active Regions
Authors: van Driel-Gesztelyi, Lidia; Green, Lucie May
Bibcode: 2015LRSP...12....1V
Altcode:
  The evolution of active regions (AR) from their emergence through
  their long decay process is of fundamental importance in solar
  physics. Since large-scale flux is generated by the deep-seated
  dynamo, the observed characteristics of flux emergence and that of the
  subsequent decay provide vital clues as well as boundary conditions
  for dynamo models. Throughout their evolution, ARs are centres of
  magnetic activity, with the level and type of activity phenomena being
  dependent on the evolutionary stage of the AR. As new flux emerges
  into a pre-existing magnetic environment, its evolution leads to
  re-configuration of small-and large-scale magnetic connectivities. The
  decay process of ARs spreads the once-concentrated magnetic flux over
  an ever-increasing area. Though most of the flux disappears through
  small-scale cancellation processes, it is the remnant of large-scale AR
  fields that is able to reverse the polarity of the poles and build up
  new polar fields. In this Living Review the emphasis is put on what
  we have learned from observations, which is put in the context of
  modelling and simulation efforts when interpreting them. For another,
  modelling-focused Living Review on the sub-surface evolution and
  emergence of magnetic flux see Fan (2009). In this first version we
  focus on the evolution of dominantly bipolar ARs.

Title: Parallel Evolution of Quasi-separatrix Layers and Active
    Region Upflows
Authors: Mandrini, C. H.; Baker, D.; Démoulin, P.; Cristiani, G. D.;
   van Driel-Gesztelyi, L.; Vargas Domínguez, S.; Nuevo, F. A.; Vásquez,
   A. M.; Pick, M.
Bibcode: 2015ApJ...809...73M
Altcode: 2015arXiv150701264M
  Persistent plasma upflows were observed with Hinode’s EUV
  Imaging Spectrometer (EIS) at the edges of active region (AR)
  10978 as it crossed the solar disk. We analyze the evolution of
  the photospheric magnetic and velocity fields of the AR, model
  its coronal magnetic field, and compute the location of magnetic
  null-points and quasi-sepratrix layers (QSLs) searching for the origin
  of EIS upflows. Magnetic reconnection at the computed null points
  cannot explain all of the observed EIS upflow regions. However, EIS
  upflows and QSLs are found to evolve in parallel, both temporarily
  and spatially. Sections of two sets of QSLs, called outer and
  inner, are found associated to EIS upflow streams having different
  characteristics. The reconnection process in the outer QSLs is forced
  by a large-scale photospheric flow pattern, which is present in the AR
  for several days. We propose a scenario in which upflows are observed,
  provided that a large enough asymmetry in plasma pressure exists
  between the pre-reconnection loops and lasts as long as a photospheric
  forcing is at work. A similar mechanism operates in the inner QSLs; in
  this case, it is forced by the emergence and evolution of the bipoles
  between the two main AR polarities. Our findings provide strong support
  for the results from previous individual case studies investigating the
  role of magnetic reconnection at QSLs as the origin of the upflowing
  plasma. Furthermore, we propose that persistent reconnection along
  QSLs does not only drive the EIS upflows, but is also responsible for
  the continuous metric radio noise-storm observed in AR 10978 along
  its disk transit by the Nançay Radio Heliograph.

Title: Active region plasma outflows as sources of slow/intermediate
    solar wind
Authors: van Driel-Gesztelyi, Lidia M.
Bibcode: 2015IAUGA..2257850V
Altcode:
  L. van Driel-Gesztelyi (1,2,3), D. Baker (1), P. Démoulin (2),
  Culhane, J.L. (1), M.L. DeRosa (4) C.H. Mandrini (5,6), D.H. Brooks
  (7), A.N. Fazakerley (1), L.K. Harra (1), L. Zhao (7), T.H. Zurbuchen
  (7), F.A. Nuevo (5,6), A.M. Vásquez (5,6), G.D. Cristiani (5,6)
  M. Pick (2)1) UCL/MSSL, UK, (2) Paris Observatory, LESIA, CNRS,
  France, (3) Konkoly Observatory, Hungary, (4) Lockheed Martin Solar and
  Astrophysics Laboratory, USA, (5) IAFE, CONICET-UBA, Argentina (6) FCEN,
  UBA, Argentina (7) Dept. of Atmospheric, Oceanic and Earth Sciences,
  Univ. of Michigan, USAWe analyse plasma upflows of tens of km/s from the
  edges of solar active regions discovered by Hinode/EIS and investigate
  whether or not they become outflows, i.e. find their way into the solar
  wind. We analyse two magnetic configurations: bipolar and quadrupolar
  and find that the active region plasma may be directly channeled
  into the solar wind via interchange reconnection at a high-altitude
  null point above the active region especially when active regions are
  located besides coronal holes or in a more complex way via multiple
  reconnections even from under a closed helmet streamer. We relate the
  solar observations to in-situ slow/intermediate solar wind streams.

Title: Division II: Commission 10: Solar Activity
Authors: van Driel-Gesztelyi, Lidia; Scrijver, Karel J.; Klimchuk,
   James A.; Charbonneau, Paul; Fletcher, Lyndsay; Hasan, S. Sirajul;
   Hudson, Hugh S.; Kusano, Kanya; Mandrini, Cristina H.; Peter, Hardi;
   Vršnak, Bojan; Yan, Yihua
Bibcode: 2015IAUTB..28..106V
Altcode:
  The Business Meeting of Commission 10 was held as part of the Business
  Meeting of Division II (Sun and Heliosphere), chaired by Valentin
  Martínez-Pillet, the President of the Division. The President of
  Commission 10 (C10; Solar activity), Lidia van Driel-Gesztelyi, took
  the chair for the business meeting of C10. She summarised the activities
  of C10 over the triennium and the election of the incoming OC.

Title: Interaction between CME and surrounding magnetic fields
    producing multiple flaring sites
Authors: van Driel-Gesztelyi, Lidia M.
Bibcode: 2015IAUGA..2257826V
Altcode:
  L. van Driel-Gesztelyi (1,2,3), D. Baker (1), T. Török (4), E. Pariat
  (2), L.M. Green (1),D.R. Williams (1), J. Carlyle (1,5) G. Valori
  (1, 2), P. Démoulin (2), B. Kliem (1,7,8),D. Long (1), S.A. Matthews
  (1), J.-M. Malherbe (2)(1) UCL/MSSL, UK, (2) Paris Observatory, LESIA,
  CNRS, France, (3) Konkoly Observatory, Hungary, (4) Predictive Science,
  Dan Diego, USA, (5) Max Planck Inst., Göttingen, Germany, (6) INAF,
  Obs. Roma, Italy, (7) Potsdam Univ., Germany, (8) Yunnan Observatories,
  Kunming, ChinaAnalyzing Solar Dynamics Observatory (SDO) observations
  of the spectacular Coronal Mass Ejection eruption on 7 June 2011,
  we present evidence of coronal magnetic reconnection between the
  expanding magnetic structure of the CME and the magnetic fields of an
  adjacent active region (AR). The onset of reconnection first became
  apparent in the SDO/AIA images when filament plasma, originally
  contained within the erupting flux rope, was re-directed towards
  remote areas in the neighboring AR, tracing the change of large-scale
  magnetic connectivity. The observations are presented jointly with
  a topological analysis of the pre-eruption magnetic configuration,
  and a data-constrained numerical simulation of the three-AR complex,
  demonstrating the formation/intensification of current sheets along
  a pre-existing hyperbolic flux tube (HFT) at the interface between
  the CME and the neighboring AR, where a secondary flare ribbon was
  created. Reconnection across this current sheet resulted in the
  formation of new magnetic connections between the erupting magnetic
  structure and a neighboring AR about 200 Mm from the eruption site,
  in strong qualitative agreement with the observations. In addition,
  the CME temporarily created unusually dense plasma conditions around a
  reconnection region at high coronal altitudes, enabling us to observe
  emission resulting from it. We argue that this exceptional observation
  of a coronal brightening was directly observable at SDO/AIA wavelengths
  owing to the presence of down-flowing cool and dense (estimated to be
  of the order of 10<SUP>10 </SUP>cm<SUP>-3</SUP>) filament plasma in
  the vicinity of the reconnection region.

Title: FIP Bias Evolution in a Decaying Active Region
Authors: Baker, D.; Brooks, D. H.; Démoulin, P.; Yardley, S. L.;
   van Driel-Gesztelyi, L.; Long, D. M.; Green, L. M.
Bibcode: 2015ApJ...802..104B
Altcode: 2015arXiv150107397B
  Solar coronal plasma composition is typically characterized by
  first ionization potential (FIP) bias. Using spectra obtained by
  Hinode’s EUV Imaging Spectrometer instrument, we present a series
  of large-scale, spatially resolved composition maps of active region
  (AR)11389. The composition maps show how FIP bias evolves within the
  decaying AR during the period 2012 January 4-6. Globally, FIP bias
  decreases throughout the AR. We analyzed areas of significant plasma
  composition changes within the decaying AR and found that small-scale
  evolution in the photospheric magnetic field is closely linked to the
  FIP bias evolution observed in the corona. During the AR’s decay
  phase, small bipoles emerging within supergranular cells reconnect
  with the pre-existing AR field, creating a pathway along which
  photospheric and coronal plasmas can mix. The mixing timescales are
  shorter than those of plasma enrichment processes. Eruptive activity
  also results in shifting the FIP bias closer to photospheric in the
  affected areas. Finally, the FIP bias still remains dominantly coronal
  only in a part of the AR’s high-flux density core. We conclude that
  in the decay phase of an AR’s lifetime, the FIP bias is becoming
  increasingly modulated by episodes of small-scale flux emergence,
  i.e., decreasing the AR’s overall FIP bias. Our results show that
  magnetic field evolution plays an important role in compositional
  changes during AR development, revealing a more complex relationship
  than expected from previous well-known Skylab results showing that
  FIP bias increases almost linearly with age in young ARs.

Title: JD3 - 3D Views of the Cycling Sun in Stellar Context: Overview
Authors: van Driel-Gesztelyi, Lidia; Schrijver, Carolus J.
Bibcode: 2015HiA....16...81V
Altcode:
  We summarise the motivations and main results of the joint discussion
  ``3D Views of the Cycling Sun in Stellar Context'', and give credit
  to contributed talks and poster presentations, as due to the limited
  number of pages, this proceedings could only include contributions
  from the keynote speakers.

Title: Editorial Appreciation
Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia
Bibcode: 2015SoPh..290..657L
Altcode: 2015SoPh..tmp...24L
  No abstract at ADS

Title: Time Evolution of Force-Free Parameter and Free Magnetic
    Energy in Active Region NOAA 10365
Authors: Valori, G.; Romano, P.; Malanushenko, A.; Ermolli, I.;
   Giorgi, F.; Steed, K.; van Driel-Gesztelyi, L.; Zuccarello, F.;
   Malherbe, J. -M.
Bibcode: 2015SoPh..290..491V
Altcode:
  We describe the variation of the accumulated coronal helicity derived
  from the magnetic helicity flux through the photosphere in active region
  (AR) NOAA 10365, where several large flares and coronal mass ejections
  (CMEs) occurred. We used SOHO/MDI full-disk line-of-sight magnetograms
  to measure the helicity flux, and the integral of GOES X-ray flux as a
  proxy of the coronal energy variations due to flares or CMEs. Using the
  linear force-free field model, we transformed the accumulated helicity
  flux into a time sequence of the force-free parameter α accounting for
  flares or CMEs via the proxy derived from GOES observations. This method
  can be used to derive the value of α at different times during the
  AR evolution, and is a partial alternative to the commonly used match
  of field lines with EUV loops. By combining the accumulated helicity
  obtained from the observations with the linear force-free theory, we
  describe the main phases of the emergence process of the AR, and relate
  them temporally with the occurrence of flares or CMEs. Additionally,
  a comparison with the loop-matching method of fixing alpha at each time
  independently shows that the proposed method may be helpful in avoiding
  unrealistic or undetermined values of alpha that may originate from
  an insufficient quality of the image used to identify coronal loops
  at a given time. For the relative intensity of the considered events,
  the linear force-free field theory implies that there is a direct
  correlation between the released energy on the one hand and the product
  of the coronal helicity with the variation of α due to the event on
  the other. Therefore, the higher the value of the accumulated coronal
  helicity, the smaller the force-free parameter variation required to
  produce the same decrease in the free energy during the CMEs.

Title: Solar Cycle Indices from the Photosphere to the Corona:
    Measurements and Underlying Physics
Authors: Ermolli, Ilaria; Shibasaki, Kiyoto; Tlatov, Andrey; van
   Driel-Gesztelyi, Lidia
Bibcode: 2015sac..book..105E
Altcode:
  No abstract at ADS

Title: New Eyes Looking at Solar Activity: Challenges for Theory
    and Simulations - Placing It into Context
Authors: Pohjolainen, S.; Karlický, M.; van Driel-Gesztelyi, L.;
   Mandrini, C. H.
Bibcode: 2015SoPh..290....1P
Altcode: 2014SoPh..tmp..190P
  Solar Cycle 24 has opened a new era in solar radio physics as we now
  have instruments that can probe solar processes from submillimeter to
  kilometer waves. New and upgraded instruments provide data that enable
  studies of both energetic particles and thermal plasma, enhancing
  our knowledge of solar eruptions and acceleration and propagation
  of particles, through the solar chromosphere and corona and into
  the interplanetary space. In this Topical Issue we highlight the new
  observational capabilities and discuss the theoretical issues connected
  to solar radio emission and interplanetary radio physics.

Title: Magnetic Helicity, Tilt, and Twist
Authors: Pevtsov, Alexei A.; Berger, Mitchell A.; Nindos, Alexander;
   Norton, Aimee A.; van Driel-Gesztelyi, Lidia
Bibcode: 2015sac..book..285P
Altcode:
  No abstract at ADS

Title: Solar Cycle Indices from the Photosphere to the Corona:
    Measurements and Underlying Physics
Authors: Ermolli, Ilaria; Shibasaki, Kiyoto; Tlatov, Andrey; van
   Driel-Gesztelyi, Lidia
Bibcode: 2014SSRv..186..105E
Altcode: 2017arXiv170507054E; 2014SSRv..tmp...48E
  A variety of indices have been proposed in order to represent the
  many different observables modulated by the solar cycle. Most of these
  indices are highly correlated with each other owing to their intrinsic
  link with the solar magnetism and the dominant eleven year cycle,
  but their variations may differ in fine details, as well as on short-
  and long-term trends. In this paper we present an overview of the
  indices that are often employed to describe the many features of the
  solar cycle, moving from the ones referring to direct observations
  of the inner solar atmosphere, the photosphere and chromosphere, to
  those deriving from measurements of the transition region and solar
  corona. For each index, we summarize existing measurements and typical
  use, and for those that quantify physical observables, we describe
  the underlying physics.

Title: Magnetic Helicity, Tilt, and Twist
Authors: Pevtsov, Alexei A.; Berger, Mitchell A.; Nindos, Alexander;
   Norton, Aimee A.; van Driel-Gesztelyi, Lidia
Bibcode: 2014SSRv..186..285P
Altcode:
  Since its introduction to astro- and solar physics, the concept of
  helicity has proven to be useful in providing critical insights into
  physics of various processes from astrophysical dynamos, to magnetic
  reconnection and eruptive phenomena. Signature of helicity was also
  detected in many solar features, including orientation of solar active
  regions, or Joy's law. Here we provide a summary of both solar phenomena
  and consider mutual relationship and its importance for the evolution
  of solar magnetic fields.

Title: How Can Active Region Plasma Escape into the Solar Wind from
    Below a Closed Helmet Streamer?
Authors: Mandrini, C. H.; Nuevo, F. A.; Vásquez, A. M.; Démoulin,
   P.; van Driel-Gesztelyi, L.; Baker, D.; Culhane, J. L.; Cristiani,
   G. D.; Pick, M.
Bibcode: 2014SoPh..289.4151M
Altcode: 2014arXiv1409.7369M; 2014SoPh..tmp..115M
  Recent studies show that active-region (AR) upflowing plasma,
  observed by the EUV-Imaging Spectrometer (EIS) onboard Hinode, can
  gain access to open-field lines and be released into the solar wind
  (SW) via magnetic-interchange reconnection at magnetic null-points in
  pseudo-streamer configurations. When only one bipolar AR is present
  on the Sun and is fully covered by the separatrix of a streamer, such
  as AR 10978 in December 2007, it seems unlikely that the upflowing AR
  plasma can find its way into the slow SW. However, signatures of plasma
  with AR composition have been found at 1 AU by Culhane et al. (Solar
  Phys.289, 3799, 2014) that apparently originated west of AR 10978. We
  present a detailed topology analysis of AR 10978 and the surrounding
  large-scale corona based on a potential-field source-surface (PFSS)
  model. Our study shows that it is possible for the AR plasma to move
  around the streamer separatrix and be released into the SW via magnetic
  reconnection, which occurs in at least two main steps. We analyse data
  from the Nançay Radioheliograph (NRH) in a search for evidence of the
  chain of magnetic reconnections that we propose. We find a noise storm
  above the AR and several varying sources at 150.9 MHz. Their locations
  suggest that they might be associated with particles accelerated during
  the first-step reconnection process at a null point well outside of
  the AR. We find no evidence of the second reconnection step in the
  radio data, however. Our results demonstrate that even when it appears
  highly improbable for the AR plasma to reach the SW, indirect channels
  involving a sequence of reconnections can make it possible.

Title: Extreme-ultraviolet Observations of Global Coronal Wave
    Rotation
Authors: Attrill, G. D. R.; Long, D. M.; Green, L. M.; Harra, L. K.;
   van Driel-Gesztelyi, L.
Bibcode: 2014ApJ...796...55A
Altcode:
  We present evidence of global coronal wave rotation in EUV data from
  SOHO/EIT, STEREO/EUVI, and SDO/AIA. The sense of rotation is found
  to be consistent with the helicity of the source region (clockwise
  for positive helicity, anticlockwise for negative helicity), with the
  source regions hosting sigmoidal structures. We also study two coronal
  wave events observed by SDO/AIA where no clear rotation (or sigmoid)
  is observed. The selected events show supporting evidence that they
  all originate with flux rope eruptions. We make comparisons across
  this set of observations (both with and without clear sigmoidal
  structures). On examining the magnetic configuration of the source
  regions, we find that the nonrotation events possess a quadrupolar
  magnetic configuration. The coronal waves that do show a rotation
  originate from bipolar source regions.

Title: Tracking Solar Active Region Outflow Plasma from Its Source
    to the Near-Earth Environment
Authors: Culhane, J. L.; Brooks, D. H.; van Driel-Gesztelyi, L.;
   Démoulin, P.; Baker, D.; DeRosa, M. L.; Mandrini, C. H.; Zhao, L.;
   Zurbuchen, T. H.
Bibcode: 2014SoPh..289.3799C
Altcode: 2014SoPh..tmp...90C; 2014arXiv1405.2949C
  Seeking to establish whether active-region upflow material contributes
  to the slow solar wind, we examine in detail the plasma upflows from
  Active Region (AR) 10978, which crossed the Sun's disc in the interval 8
  to 16 December 2007 during Carrington rotation (CR) 2064. In previous
  work, using data from the Hinode/EUV Imaging Spectrometer, upflow
  velocity evolution was extensively studied as the region crossed the
  disc, while a linear force-free-field magnetic extrapolation was used
  to confirm aspects of the velocity evolution and to establish the
  presence of quasi-separatrix layers at the upflow source areas. The
  plasma properties, temperature, density, and first ionisation potential
  bias [FIP-bias] were measured with the spectrometer during the disc
  passage of the active region. Global potential-field source-surface
  (PFSS) models showed that AR 10978 was completely covered by the
  closed field of a helmet streamer that is part of the streamer
  belt. Therefore it is not clear how any of the upflowing AR-associated
  plasma could reach the source surface at 2.5 R<SUB>⊙</SUB> and
  contribute to the slow solar wind. However, a detailed examination of
  solar-wind in-situ data obtained by the Advanced Composition Explorer
  (ACE) spacecraft at the L<SUB>1</SUB> point shows that increases in
  O<SUP>7+</SUP>/O<SUP>6+</SUP>, C<SUP>6+</SUP>/C<SUP>5+</SUP>, and Fe/O -
  a FIP-bias proxy - are present before the heliospheric current-sheet
  crossing. These increases, along with an accompanying reduction in
  proton velocity and an increase in density are characteristic of
  both AR and slow-solar-wind plasma. Finally, we describe a two-step
  reconnection process by which some of the upflowing plasma from the
  AR might reach the heliosphere.

Title: The evolution of writhe in kink-unstable flux ropes and
    erupting filaments
Authors: Török, T.; Kliem, B.; Berger, M. A.; Linton, M. G.;
   Démoulin, P.; van Driel-Gesztelyi, L.
Bibcode: 2014PPCF...56f4012T
Altcode: 2014arXiv1403.1565T
  The helical kink instability of a twisted magnetic flux tube has been
  suggested as a trigger mechanism for solar filament eruptions and
  coronal mass ejections (CMEs). In order to investigate if estimations
  of the pre-emptive twist can be obtained from observations of writhe
  in such events, we quantitatively analyze the conversion of twist into
  writhe in the course of the instability, using numerical simulations. We
  consider the line tied, cylindrically symmetric Gold-Hoyle flux rope
  model and measure the writhe using the formulae by Berger and Prior
  which express the quantity as a single integral in space. We find that
  the amount of twist converted into writhe does not simply scale with
  the initial flux rope twist, but depends mainly on the growth rates
  of the instability eigenmodes of higher longitudinal order than the
  basic mode. The saturation levels of the writhe, as well as the shapes
  of the kinked flux ropes, are very similar for considerable ranges of
  initial flux rope twists, which essentially precludes estimations of
  pre-eruptive twist from measurements of writhe. However, our simulations
  suggest an upper twist limit of ∼6π for the majority of filaments
  prior to their eruption.

Title: Coronal Magnetic Reconnection Driven by CME Expansion—the
    2011 June 7 Event
Authors: van Driel-Gesztelyi, L.; Baker, D.; Török, T.; Pariat, E.;
   Green, L. M.; Williams, D. R.; Carlyle, J.; Valori, G.; Démoulin,
   P.; Kliem, B.; Long, D. M.; Matthews, S. A.; Malherbe, J. -M.
Bibcode: 2014ApJ...788...85V
Altcode: 2014arXiv1406.3153V
  Coronal mass ejections (CMEs) erupt and expand in a magnetically
  structured solar corona. Various indirect observational pieces of
  evidence have shown that the magnetic field of CMEs reconnects with
  surrounding magnetic fields, forming, e.g., dimming regions distant
  from the CME source regions. Analyzing Solar Dynamics Observatory
  (SDO) observations of the eruption from AR 11226 on 2011 June 7, we
  present the first direct evidence of coronal magnetic reconnection
  between the fields of two adjacent active regions during a CME. The
  observations are presented jointly with a data-constrained numerical
  simulation, demonstrating the formation/intensification of current
  sheets along a hyperbolic flux tube at the interface between the CME
  and the neighboring AR 11227. Reconnection resulted in the formation of
  new magnetic connections between the erupting magnetic structure from
  AR 11226 and the neighboring active region AR 11227 about 200 Mm from
  the eruption site. The onset of reconnection first becomes apparent
  in the SDO/AIA images when filament plasma, originally contained
  within the erupting flux rope, is redirected toward remote areas in
  AR 11227, tracing the change of large-scale magnetic connectivity. The
  location of the coronal reconnection region becomes bright and directly
  observable at SDO/AIA wavelengths, owing to the presence of down-flowing
  cool, dense (10<SUP>10</SUP> cm<SUP>-3</SUP>) filament plasma in its
  vicinity. The high-density plasma around the reconnection region is
  heated to coronal temperatures, presumably by slow-mode shocks and
  Coulomb collisions. These results provide the first direct observational
  evidence that CMEs reconnect with surrounding magnetic structures,
  leading to a large-scale reconfiguration of the coronal magnetic field.

Title: Editorial Appreciation
Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia
Bibcode: 2014SoPh..289.1455L
Altcode: 2014SoPh..tmp....6L
  No abstract at ADS

Title: Investigating the Dynamics and Density Evolution of Returning
    Plasma Blobs from the 2011 June 7 Eruption
Authors: Carlyle, Jack; Williams, David R.; van Driel-Gesztelyi,
   Lidia; Innes, Davina; Hillier, Andrew; Matthews, Sarah
Bibcode: 2014ApJ...782...87C
Altcode: 2014arXiv1401.4824C
  This work examines in-falling matter following an enormous coronal mass
  ejection on 2011 June 7. The material formed discrete concentrations,
  or blobs, in the corona and fell back to the surface, appearing as dark
  clouds against the bright corona. In this work we examined the density
  and dynamic evolution of these blobs in order to formally assess the
  intriguing morphology displayed throughout their descent. The blobs
  were studied in five wavelengths (94, 131, 171, 193, and 211 Å)
  using the Solar Dynamics Observatory Atmospheric Imaging Assembly,
  comparing background emission to attenuated emission as a function
  of wavelength to calculate column densities across the descent of
  four separate blobs. We found the material to have a column density of
  hydrogen of approximately 2 × 10<SUP>19</SUP> cm<SUP>-2</SUP>, which is
  comparable with typical pre-eruption filament column densities. Repeated
  splitting of the returning material is seen in a manner consistent
  with the Rayleigh-Taylor instability. Furthermore, the observed
  distribution of density and its evolution is also a signature of this
  instability. By approximating the three-dimensional geometry (with data
  from STEREO-A), volumetric densities were found to be approximately 2
  × 10<SUP>-14</SUP> g cm<SUP>-3</SUP>, and this, along with observed
  dominant length scales of the instability, was used to infer a magnetic
  field of the order 1 G associated with the descending blobs.

Title: Density evolution of in-falling prominence material from the
    7th June 2011 CME
Authors: Carlyle, Jack; Williams, David; van Driel-Gesztelyi, Lidia;
   Innes, Davina
Bibcode: 2014IAUS..300..401C
Altcode:
  This work investigates the density of in-falling prominence material
  following the 7 <SUP>th</SUP> June 2011 eruption. Both the evolution
  and the distribution of the density is analysed in five discreet
  ``blobs'' of material. The density appears to be remarkably uniform,
  both spatially within the blobs, and temporally over the course of the
  descent of each, although a slight concentration of material towards
  the leading edge is noted in some cases. Online material is available
  at bit.ly/jackblob

Title: Spectroscopic measurements of EUV ejecta in a CME: a
    high-blueshift trailing thread
Authors: Williams, David; Baker, Deborah; van Driel-Gesztelyi, Lidia;
   Green, Lucie
Bibcode: 2014IAUS..300..464W
Altcode:
  The mass of erupting prominence material can be inferred from the
  obscuration of emission behind this mass of cool plasma thanks to
  the rapid cadence of SDO/AIA images in the short EUV wavelength range
  (Carlyle et al. 2013, these proceedings). In comparing this approach
  with spectral observations from Hinode/EIS, to monitor contributions
  from emission seen around the erupting prominence material, we have
  found an intriguing component of blue-shifted emission, trailing
  the erupting prominence, with Doppler shifts on the order of 350 km
  s<SUP>-1</SUP> in bright lines of both He ii and Fe xii.

Title: FIP bias in a sigmoidal active region
Authors: Baker, D.; Brooks, D. H.; Démoulin, P.; van Driel-Gesztelyi,
   Lidia; Green, L. M.; Steed, K.; Carlyle, J.
Bibcode: 2014IAUS..300..222B
Altcode:
  We investigate first ionization potential (FIP) bias levels in
  an anemone active region (AR) - coronal hole (CH) complex using an
  abundance map derived from Hinode/EIS spectra. The detailed, spatially
  resolved abundance map has a large field of view covering 359'' ×
  485''. Plasma with high FIP bias, or coronal abundances, is concentrated
  at the footpoints of the AR loops whereas the surrounding CH has a low
  FIP bias, ~1, i.e. photospheric abundances. A channel of low FIP bias
  is located along the AR's main polarity inversion line containing a
  filament where ongoing flux cancellation is observed, indicating a
  bald patch magnetic topology characteristic of a sigmoid/flux rope
  configuration.

Title: Active region upflow plasma: its relation to small activity
    and the solar wind
Authors: Mandrini, Cristina H.; Culhane, J. Leonard; Cristiani,
   Germán; Vásquez, Alberto; Van Driel-Gesztelyi, Lidia; Baker, Deborah;
   Pick, Monique; Demoulin, Pascal; Nuevo, Federico
Bibcode: 2014cosp...40E1979M
Altcode:
  Recent studies show that active region (AR) upflowing plasma,
  observed by the Hinode EUV Imaging Spectrometer (EIS), can gain
  access to open field lines and be released into the solar wind via
  magnetic interchange reconnection occurring below the source surface
  at magnetic null-points in pseudo-streamer configurations. When only
  one simple bipolar AR is present on the Sun and it is fully covered by
  the separatrix of a streamer, like AR 10978 on December 2007, it seems
  unlikely that the upflowing AR plasma could find its way into the slow
  solar wind. However, signatures of plasma with AR composition at 1 AU
  that appears to originate from the West of AR 10978 were recently found
  by Culhane and coworkers. We present a detailed topology analysis of
  AR 10978 based on a linear force-free magnetic field model at the AR
  scale, combined with a global PFSS model. This allows us, on one hand,
  to explain the variations observed in the upflows to the West of the
  AR as the result of magnetic reconnection at quasi-separatrix layers
  (QSLs). While at a global scale, we show that reconnection, occurring
  in at least two main steps, first at QSLs and later at a high-altitude
  coronal null-point, allows the AR plasma to get around the topological
  obstacle of the streamer separatrix and be released into the solar wind.

Title: Magnetic reconnection driven by filament eruption in the 7
    June 2011 event
Authors: van Driel-Gesztelyi, L.; Baker, D.; Török, T.; Pariat, E.;
   Green, L. M.; Williams, D. R.; Carlyle, J.; Valori, G.; Démoulin,
   P.; Matthews, S. A.; Kliem, B.; Malherbe, J. -M.
Bibcode: 2014IAUS..300..502V
Altcode:
  During an unusually massive filament eruption on 7 June 2011,
  SDO/AIA imaged for the first time significant EUV emission around a
  magnetic reconnection region in the solar corona. The reconnection
  occurred between magnetic fields of the laterally expanding CME
  and a neighbouring active region. A pre-existing quasi-separatrix
  layer was activated in the process. This scenario is supported by
  data-constrained numerical simulations of the eruption. Observations
  show that dense cool filament plasma was re-directed and heated in
  situ, producing coronal-temperature emission around the reconnection
  region. These results provide the first direct observational evidence,
  supported by MHD simulations and magnetic modelling, that a large-scale
  re-configuration of the coronal magnetic field takes place during
  solar eruptions via the process of magnetic reconnection.

Title: Initiation of Coronal Mass Ejections by Sunspot Rotation
Authors: Valori, G.; Török, T.; Temmer, M.; Veronig, A. M.; van
   Driel-Gesztelyi, L.; Vršnak, B.
Bibcode: 2014IAUS..300..201V
Altcode:
  We report observations of a filament eruption, two-ribbon flare, and
  coronal mass ejection (CME) that occurred in Active Region NOAA 10898
  on 6 July 2006. The filament was located South of a strong sunspot that
  dominated the region. In the evolution leading up to the eruption, and
  for some time after it, a counter-clockwise rotation of the sunspot of
  about 30 degrees was observed. We suggest that the rotation triggered
  the eruption by progressively expanding the magnetic field above the
  filament. To test this scenario, we study the effect of twisting
  the initially potential field overlying a pre-existing flux rope,
  using three-dimensional zero-β MHD simulations. We consider a magnetic
  configuration whose photospheric flux distribution and coronal structure
  is guided by the observations and a potential field extrapolation. We
  find that the twisting leads to the expansion of the overlying field. As
  a consequence of the progressively reduced magnetic tension, the flux
  rope quasi-statically adapts to the changed environmental field, rising
  slowly. Once the tension is sufficiently reduced, a distinct second
  phase of evolution occurs where the flux rope enters an unstable regime
  characterized by a strong acceleration. Our simulation thus suggests
  a new mechanism for the triggering of eruptions in the vicinity of
  rotating sunspots.

Title: Magnetic Polarity Streams and Subsurface Flows
Authors: Howe, R.; Baker, D.; Harra, L.; van Driel-Gesztelyi, L.;
   Komm, R.; Hill, F.; González Hernández, I.
Bibcode: 2013ASPC..478..291H
Altcode:
  An important feature of the solar cycle is the transport of unbalanced
  magnetic flux from active regions towards the poles, which eventually
  results in polarity reversal. This transport takes the form of distinct
  “polarity streams” that are visible in the magnetic butterfly
  diagram. We compare the poleward migration rate estimated from such
  streams to that derived from the subsurface meridional flows measured
  in helioseismic data from the GONG network since 2001, and find that
  the results are in reasonable agreement.

Title: Plasma Composition in a Sigmoidal Anemone Active Region
Authors: Baker, D.; Brooks, D. H.; Démoulin, P.; van Driel-Gesztelyi,
   L.; Green, L. M.; Steed, K.; Carlyle, J.
Bibcode: 2013ApJ...778...69B
Altcode: 2013arXiv1310.0999B
  Using spectra obtained by the EUV Imaging Spectrometer (EIS) instrument
  onboard Hinode, we present a detailed spatially resolved abundance map
  of an active region (AR)-coronal hole (CH) complex that covers an area
  of 359'' × 485''. The abundance map provides first ionization potential
  (FIP) bias levels in various coronal structures within the large EIS
  field of view. Overall, FIP bias in the small, relatively young AR
  is 2-3. This modest FIP bias is a consequence of the age of the AR,
  its weak heating, and its partial reconnection with the surrounding
  CH. Plasma with a coronal composition is concentrated at AR loop
  footpoints, close to where fractionation is believed to take place in
  the chromosphere. In the AR, we found a moderate positive correlation
  of FIP bias with nonthermal velocity and magnetic flux density, both
  of which are also strongest at the AR loop footpoints. Pathways of
  slightly enhanced FIP bias are traced along some of the loops connecting
  opposite polarities within the AR. We interpret the traces of enhanced
  FIP bias along these loops to be the beginning of fractionated plasma
  mixing in the loops. Low FIP bias in a sigmoidal channel above the
  AR's main polarity inversion line, where ongoing flux cancellation is
  taking place, provides new evidence of a bald patch magnetic topology
  of a sigmoid/flux rope configuration.

Title: Initiation of Coronal Mass Ejections by Sunspot Rotation
Authors: Török, T.; Temmer, M.; Valori, G.; Veronig, A. M.; van
   Driel-Gesztelyi, L.; Vršnak, B.
Bibcode: 2013SoPh..286..453T
Altcode: 2014arXiv1401.2922T
  We study a filament eruption, two-ribbon flare, and coronal mass
  ejection (CME) that occurred in NOAA Active Region 10898 on 6 July
  2006. The filament was located South of a strong sunspot that dominated
  the region. In the evolution leading up to the eruption, and for some
  time after it, a counter-clockwise rotation of the sunspot of about
  30 degrees was observed. We suggest that the rotation triggered the
  eruption by progressively expanding the magnetic field above the
  filament. To test this scenario, we study the effect of twisting
  the initially potential field overlying a pre-existing flux-rope,
  using three-dimensional zero-β MHD simulations. We first consider
  a relatively simple and symmetric system, and then study a more
  complex and asymmetric magnetic configuration, whose photospheric-flux
  distribution and coronal structure are guided by the observations and a
  potential field extrapolation. In both cases, we find that the twisting
  leads to the expansion of the overlying field. As a consequence of the
  progressively reduced magnetic tension, the flux-rope quasi-statically
  adapts to the changed environmental field, rising slowly. Once the
  tension is sufficiently reduced, a distinct second phase of evolution
  occurs where the flux-rope enters an unstable regime characterised by
  a strong acceleration. Our simulations thus suggest a new mechanism
  for the triggering of eruptions in the vicinity of rotating sunspots.

Title: Observations and Modelling of the Inner Heliosphere: Preface
    and Tribute to the Late Dr. Andy Breen
Authors: Bisi, M. M.; Harrison, R. A.; Lugaz, N.; van Driel-Gesztelyi,
   L.; Mandrini, C. H.
Bibcode: 2013SoPh..285....1B
Altcode:
  No abstract at ADS

Title: Are subsurface flows and coronal holes related?
Authors: Komm, R.; Howe, R.; González Hernández, I.; Harra, L.;
   Baker, D.; van Driel-Gesztelyi, L.
Bibcode: 2013JPhCS.440a2022K
Altcode:
  We study synoptic maps of solar subsurface flows covering six Carrington
  rotations (2050 to 2055). The subsurface flows are determined with
  a ring-diagram analysis of GONG high-resolution Doppler data. We
  identify the locations of coronal holes in synoptic maps of EUV images
  at 195Å from the EIT instrument and determine the characteristics
  of associated subsurface flows. We study two long-lived coronal holes
  that are present during this epoch. We find that large-scale patterns
  are present in the subsurface flows but appear to be unrelated to
  these coronal holes. The horizontal subsurface flows associated with
  the two long-lived coronal holes are weakly divergent (upflows) with
  small cyclonic vorticity. These flows are thus similar to subsurface
  flows of quiet regions with regard to the vertical flows and similar
  to flows of active regions with regard to vorticity.

Title: Can we detect local helioseismic parameter shifts in coronal
    holes?
Authors: Howe, R.; Haber, D. A.; Bogart, R. S.; Zharkov, S.; Baker,
   D.; Harra, L.; van Driel-Gesztelyi, L.
Bibcode: 2013JPhCS.440a2019H
Altcode:
  Changes in helioseismic mode parameters in active regions and across
  the solar disk are well documented, but local magnetic activity
  and geometric effects may not account for all of the scatter seen
  in the results. We use results from the Helioseismic and Magnetic
  Imager ring-diagram pipeline for Carrington rotation 2113 to look for
  differences in mode amplitude and frequency between coronal holes and
  other quiet-Sun regions. While we do not find a systematic difference,
  the results do suggest that the correlation between magnetic activity
  index and mode parameters shows less scatter in coronal hole regions
  than in general quiet Sun.

Title: Subsurface flows associated with non-Joy oriented active
regions: a case study
Authors: González Hernández, Irene; Komm, Rudolf; van
   Driel-Gesztelyi, Lidia; Baker, Deborah; Harra, Louise; Howe, Rachel
Bibcode: 2013JPhCS.440a2050G
Altcode:
  Non-Joy oriented active regions (ARs) are a challenge for solar magnetic
  field modelers. Although significant deviations from Joy's law are
  relatively rare for simple bipolar ARs, understanding the causes of
  their particularity could be critical for the big picture of the solar
  dynamo. We explore the possibility of the sub-surface local dynamics
  being responsible for the significant rotation of these ARs. We apply
  the ring-diagram technique, a local helioseismology method, to infer
  the flows under and surrounding a non-Joy oriented AR and present the
  results of a case study in this paper.

Title: Preface
Authors: Gopalswamy, N.; Nieves-Chinchilla, T.; Hidalgo, M.; Zhang,
   J.; Riley, P.; van Driel-Gesztelyi, L.; Mandrini, C. H.
Bibcode: 2013SoPh..284....1G
Altcode: 2013arXiv1304.0085G
  This Topical Issue of Solar Physics, devoted to the study of flux-rope
  structure in coronal mass ejections (CMEs), is based on two Coordinated
  Data Analysis Workshops (CDAWs) held in 2010 (20 - 23 September in Dan
  Diego, California, USA) and 2011 (September 5-9 in Alcala, Spain). The
  primary purpose of the CDAWs was to address the question: Do all CMEs
  have flux rope structure? There are 18 papers om this topical issue,
  including this preface.

Title: On the response of the solar atmosphere to small-scale magnetic
    flux emergence
Authors: Vargas Dominguez, Santiago; van Driel-Gesztelyi, Lidia
Bibcode: 2013EGUGA..15..925V
Altcode:
  In this work we analyze data from the Hinode spacecraft targeting
  an emerging magnetic flux region. We focus on small-scale events
  identified by distinctive dark features in CaII H chromospheric
  filtergrams. Energy release at low chromospheric heights is detected
  to be boosted by the disappearance of the dark features after they
  reached their maximum size. The observed phenomena are explained as
  evidencing elementary flux emergence into the solar atmosphere. We
  are thus detecting granular-scale arch filament systems, that emerge
  and interact with pre-existing fields. The results give new insights
  on the resistive flux emergence scenario driving the configuration
  and evolution of solar active regions. We compare the results with
  emergence of individual magnetic loops seen in quiet sun regions.

Title: The 3D Geometry of Active Region Upflows Deduced from Their
    Limb-to-Limb Evolution
Authors: Démoulin, P.; Baker, D.; Mandrini, C. H.; van
   Driel-Gesztelyi, L.
Bibcode: 2013SoPh..283..341D
Altcode: 2012arXiv1211.5962D
  We analyze the evolution of coronal plasma upflows from the edges of
  AR 10978, which has the best limb-to-limb data coverage with Hinode's
  EUV Imaging Spectrometer (EIS). We find that the observed evolution is
  largely due to the solar rotation progressively changing the viewpoint
  of nearly stationary flows. From the systematic changes in the upflow
  regions as a function of distance from disc center, we deduce their
  3D geometrical properties as inclination and angular spread in three
  coronal lines (Si VII, Fe XII, and Fe XV). In agreement with magnetic
  extrapolations, we find that the flows are thin, fan-like structures
  rooted in quasi separatrix layers (QSLs). The fans are tilted away
  from the AR center. The highest plasma velocities in these three
  spectral lines have similar magnitudes and their heights increase with
  temperature. The spatial location and extent of the upflow regions
  in the Si VII, Fe XII, and Fe XV lines are different owing to i)
  temperature stratification and ii) line of sight integration of the
  spectral profiles with significantly different backgrounds. We conclude
  that we sample the same flows at different temperatures. Further,
  we find that the evolution of line widths during the disc passage is
  compatible with a broad range of velocities in the flows. Everything
  considered, our results are compatible with the AR upflows originating
  from reconnections along QSLs between over-pressure AR loops and
  neighboring under-pressure loops. The flows are driven along magnetic
  field lines by a pressure gradient in a stratified atmosphere. Our
  interpretation of the above results is that, at any given time, we
  observe the superposition of flows created by successive reconnections,
  leading to a broad velocity distribution.

Title: Editorial Appreciation
Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia
Bibcode: 2013SoPh..283....1L
Altcode:
  No abstract at ADS

Title: Mass Estimates of Rapidly Moving Prominence Material from
    High-cadence EUV Images
Authors: Williams, David R.; Baker, Deborah; van Driel-Gesztelyi, Lidia
Bibcode: 2013ApJ...764..165W
Altcode: 2013arXiv1301.4271W
  We present a new method for determining the column density of erupting
  filament material using state-of-the-art multi-wavelength imaging
  data. Much of the prior work on filament/prominence structure can
  be divided between studies that use a polychromatic approach with
  targeted campaign observations and those that use synoptic observations,
  frequently in only one or two wavelengths. The superior time resolution,
  sensitivity, and near-synchronicity of data from the Solar Dynamics
  Observatory's Advanced Imaging Assembly allow us to combine these
  two techniques using photoionization continuum opacity to determine
  the spatial distribution of hydrogen in filament material. We apply
  the combined techniques to SDO/AIA observations of a filament that
  erupted during the spectacular coronal mass ejection on 2011 June 7. The
  resulting "polychromatic opacity imaging" method offers a powerful way
  to track partially ionized gas as it erupts through the solar atmosphere
  on a regular basis, without the need for coordinated observations,
  thereby readily offering regular, realistic mass-distribution estimates
  for models of these erupting structures.

Title: Tracking Solar Active Region Outflow Plasma from its Source
    to the near-Earth Environment
Authors: Culhane, J. L.; Brooks, D.; Zurbuchen, T.; van
   Driel-Gesztelyi, L.; Fazakerley, A. N.; DeRosa, M. L.
Bibcode: 2012AGUFMSH53A2255C
Altcode:
  In a recent study of persistent active region outflow from AR 10978 in
  the period 10 - 15, December, 2007, Brooks and Warren (2011), using the
  Hinode EUV Imaging Spectrometer (EIS) instrument showed the presence
  of a strong low-FIP element enhancement in the outflowing plasma that
  was replicated three days later in the in-situ solar wind measurements
  made by the ACE/SWICS instrument. In the present work, we examine the
  outflowing plasma properties (Te, Ne, v, abundances) as a function
  of time in greater detail as AR 10978 passes the Earth-Sun line. The
  structure of the magnetic field above the two outflow regions - E and
  W of the AR, is also examined. Following an assessment of the relevant
  magnetic structures between Sun and Earth, the properties of the solar
  wind plasma arriving at ACE approximately three days later are measured
  and compared with those of the outflowing AR plasma. The relationship
  of these measurements to the in-situ magnetic field observed by the
  ACE magnetometer is also studied. Finally the role of persistent AR
  outflows in contributing to the slow solar wind is assessed.

Title: Preface
Authors: Fleck, Bernhard; Heber, Bernd; Vourlidas, Angelos; van
   Driel-Gesztelyi, Lidia; Mandrini, Cristina H.; Leibacher, John
Bibcode: 2012SoPh..281....1F
Altcode: 2012SoPh..tmp..223F
  No abstract at ADS

Title: Magnetic Topology of Active Regions and Coronal Holes:
    Implications for Coronal Outflows and the Solar Wind
Authors: van Driel-Gesztelyi, L.; Culhane, J. L.; Baker, D.; Démoulin,
   P.; Mandrini, C. H.; DeRosa, M. L.; Rouillard, A. P.; Opitz, A.;
   Stenborg, G.; Vourlidas, A.; Brooks, D. H.
Bibcode: 2012SoPh..281..237V
Altcode: 2012SoPh..tmp..228V
  During 2 - 18 January 2008 a pair of low-latitude opposite-polarity
  coronal holes (CHs) were observed on the Sun with two active regions
  (ARs) and the heliospheric plasma sheet located between them. We use
  the Hinode/EUV Imaging Spectrometer (EIS) to locate AR-related outflows
  and measure their velocities. Solar-Terrestrial Relations Observatory
  (STEREO) imaging is also employed, as are the Advanced Composition
  Explorer (ACE) in-situ observations, to assess the resulting impacts on
  the solar wind (SW) properties. Magnetic-field extrapolations of the two
  ARs confirm that AR plasma outflows observed with EIS are co-spatial
  with quasi-separatrix layer locations, including the separatrix of a
  null point. Global potential-field source-surface modeling indicates
  that field lines in the vicinity of the null point extend up to the
  source surface, enabling a part of the EIS plasma upflows access
  to the SW. We find that similar upflow properties are also observed
  within closed-field regions that do not reach the source surface. We
  conclude that some of plasma upflows observed with EIS remain confined
  along closed coronal loops, but that a fraction of the plasma may be
  released into the slow SW. This suggests that ARs bordering coronal
  holes can contribute to the slow SW. Analyzing the in-situ data, we
  propose that the type of slow SW present depends on whether the AR is
  fully or partially enclosed by an overlying streamer.

Title: Preface
Authors: Nakariakov, V. M.; Georgoulis, M. K.; Poedts, S.; van
   Driel-Gesztelyi, L.; Mandrini, C. H.; Leibacher, J.
Bibcode: 2012SoPh..280..295N
Altcode: 2012SoPh..tmp..226N
  No abstract at ADS

Title: Identifying the Main Driver of Active Region Outflows
Authors: Baker, D.; van Driel-Gesztelyi, L.; Mandrini, C. H.;
   Démoulin, P.; Murray, M. J.
Bibcode: 2012ASPC..454..425B
Altcode:
  Hinode's EUV Imaging Spectrometer (EIS) has discovered ubiquitous
  outflows of a few to 50 km s<SUP>-1</SUP> from active regions (ARs). The
  characteristics of these outflows are very curious in that they are
  most prominent at the AR boundary and appear over monopolar magnetic
  areas. They are linked to strong non-thermal line broadening and
  are stronger in hotter EUV lines. The outflows persist for at least
  several days. Whereas red-shifted down flows observed in AR closed
  loops are well understood, to date there is no general consensus
  for the mechanism(s) driving blue-shifted AR-related outflows. We
  use Hinode EIS and X-Ray Telescope observations of AR 10942 coupled
  with magnetic modeling to demonstrate for the first time that the
  outflows originate from specific locations of the magnetic topology
  where field lines display strong gradients of magnetic connectivity,
  namely quasi-separatrix layers (QSLs), or in the limit of infinitely
  thin QSLs, separatrices. The strongest AR outflows were found to be
  in the vicinity of QSL sections located over areas of strong magnetic
  field. We argue that magnetic reconnection at QSLs, separating closed
  field lines of the AR and either large-scale externally connected or
  ‘open’ field lines, is a viable mechanism for driving AR outflows
  which are potentially sources of the slow solar wind. In fact, magnetic
  reconnection along QSLs (including separatricies) is the first theory
  to explain the most puzzling characteristics of the outflows, namely
  their occurrence over monopolar areas at the periphery of ARs and
  their longevity.

Title: Does Magnetic Helicity Affect Active Region Evolution and
    Energetics?
Authors: Wallace, A. J.; Green, L. M.; Mandrini, C. H.; Démoulin,
   P.; van Driel-Gesztelyi, L.; Matthews, S. A.
Bibcode: 2012ASPC..454..281W
Altcode:
  The purpose of this investigation is to determine whether there is a
  difference between the evolution of an active region with additional new
  flux emergence if the new flux has either the same or the opposite sign
  of magnetic helicity from the active region. Of these two scenarios, the
  one that produces the most energetics is still a topic for debate. We
  present a study of two active regions following the emergence of a
  bipole, one with the same and one with the opposite sign of helicity
  from the active region. We discover that while there is less flaring
  in the mixed helicity active region the EUV flux normalised to the
  magnetic field is three times higher than that of the same helicity
  active region. We propose that reconnection is more likely to occur
  between opposite helicity structures and thus, the energy can never
  build up to the levels required for flaring.

Title: The Slow Solar Wind: From Formation on the Sun to the Earth
Authors: Harra, L. K.; Fazakerley, A. N.; van Driel-Gesztelyi, L.
Bibcode: 2012ASPC..454..421H
Altcode:
  Hinode has discovered a potential source of slow solar wind at the
  edges of active regions with the X-ray Telescope (XRT) and EUV Imaging
  spectrometer (EIS) on board Hinode e.g. Sakao et al. (2007), Harra
  et al. (2008), Doschek et al. (2008). These upflows are long-lasting
  and exist at the edges of most active regions. In this conference
  paper we first discuss the onset of the upflows. This is related to
  newly emerged magnetic flux into an active region. Next we discuss
  whether the flows that we see on the surface of the Sun actually are
  transported to the Earth in the slow solar wind. To do this we looked at
  a number of different examples over a Carrington rotation and tracked
  the response in the solar wind as measured by the ACE spacecraft at
  L1. We found that there is a significant enhancement of the in situ
  solar wind speed for active regions located close to a coronal hole.

Title: Parallels among the ``music scores'' of solar cycles, space
    weather and Earth's climate
Authors: Kolláth, Zoltán; Oláh, Katalin; van Driel-Gesztelyi, Lidia
Bibcode: 2012IAUS..286..423K
Altcode:
  Solar variability and its effects on the physical variability of our
  (space) environment produces complex signals. In the indicators of
  solar activity at least four independent cyclic components can be
  identified, all of them with temporal variations in their timescales. <P
  />Time-frequency distributions (see Kolláth &amp; Oláh 2009) are
  perfect tools to disclose the ``music scores'' in these complex time
  series. Special features in the time-frequency distributions, like
  frequency splitting, or modulations on different timescales provide
  clues, which can reveal similar trends among different indices like
  sunspot numbers, interplanetary magnetic field strength in the Earth's
  neighborhood and climate data. <P />On the pseudo-Wigner Distribution
  (PWD) the frequency splitting of all the three main components (the
  Gleissberg and Schwabe cycles, and an ~5.5 year signal originating from
  cycle asymmetry, i.e. the Waldmeier effect) can be identified as a
  ``bubble'' shaped structure after 1950. The same frequency splitting
  feature can also be found in the heliospheric magnetic field data and
  the microwave radio flux.

Title: Modulated stellar and solar cycles: parallels and differences
Authors: Oláh, K.; van Driel-Gesztelyi, L.; Strassmeier, K. G.
Bibcode: 2012IAUS..286..279O
Altcode:
  We present examples of activity cycle timescales on different types
  of stars from lowmass dwarfs to more massive giants, with wide-ranging
  rotation rates, and compare the observed cyclicities to the irradiance
  based solar cycle and its modulations. Using annual spectral solar
  irradiance in wavelength bands typical for stellar observations
  reconstructed by Shapiro et al. (2011), a direct comparison can be
  made between cycle timescales and amplitudes derived for the Sun and
  the stars. We show that cycles on multiple timescales, known to be
  present in solar activity, also show up on stars when the dataset is
  long enough to allow recognition. The cycle lengths are not fixed,
  but evolve - gradually during some periods but there are also changes
  on short timescales. In case the activity is dominated by spots,
  i.e., by cooler surface features, the star is redder when fainter,
  whereas other type of activity make the stars bluer when the activity
  is higher. We found the Sun to be a member of the former group, based
  on reconstructed spectral irradiance data by Shapiro et al. (2011).

Title: Magnetic topology, coronal outflows, and the solar wind
Authors: Mandrini, Cristina H.; Culhane, J. Leonard; Vourlidas,
   Angelos; Demoulin, Pascal; Stenborg, Guillermo; Opitz, Andrea;
   Rouillard, Alexis; Van Driel-Gesztelyi, Lidia; Baker, Deborah; DeRosa,
   Marc; Brooks, David
Bibcode: 2012cosp...39.1173M
Altcode: 2012cosp.meet.1173M
  During 2-18 January 2008 a pair of low-latitude opposite polarity
  coronal holes were observed on the Sun flanked by two ARs with
  the heliospheric plasma sheet between them. Hinode/EUV Imaging
  Telescope (EIS) is used to locate AR-related outflows and measure their
  velocities. The Advanced Composition Explorer (ACE) in-situ observations
  are employed to assess the resulting impacts on the interplanetary solar
  wind (SW). Magnetic field extrapolations of the two ARs confirm that AR
  plasma outflows observed with EIS are co-spatial with quasi-separatrix
  layer locations, including the separatrix of a null point. Global
  potential field source-surface modeling indicates that field lines
  in the vicinity of the null point extend up to the source-surface,
  enabling a part of the EIS plasma upflows access to the SW. Similar
  upflow magnitude is also observed within closed field regions. Though
  part of the plasma upflows observed with EIS remain confined along
  closed coronal loops, a subset of them are indeed able to make their
  imprint in the slow SW, making ARs bordering coronal holes a slow
  SW contributor.

Title: CME-related changes in line-of-sight magnetic field strength
    in dimming regions observed by Hinode on 14 December 2006
Authors: Pedram, Ehsan; Matthews, Sarah A.; Van Driel-Gesztelyi, Lidia
Bibcode: 2012cosp...39.1479P
Altcode: 2012cosp.meet.1479P
  No abstract at ADS

Title: Are subsurface flows and coronal holes related?
Authors: Komm, Rudolf W.; Howe, R.; González Hernández, I.; Harra,
   L.; Baker, D.; van Driel-Gesztelyi, L.
Bibcode: 2012shin.confE.120K
Altcode:
  We study subsurface flows measured with a ring-diagram analysis of GONG
  high-resolution Doppler data. In previous studies, we have focused on
  the relationship between active regions and subsurface flows associated
  with them. Synoptic subsurface flow maps show also large-scale patterns
  that are not obviously associated with active regions. It is unknown
  whether these flow patterns correlate with any large-scale magnetic
  features. Here, we explore whether there is a relationship between
  subsurface flows and coronal features. We analyze synoptic maps of
  subsurface flows covering 18 Carrington rotations during the years
  2006 and 2007 (CR 2038-2055). Long-lived coronal holes are present
  during this epoch at low latitudes, which are accessible by ring-diagram
  analysis of GONG data. We compare subsurface flow maps with EIT synoptic
  maps of EUV images at 195A (http://sun.stanford.edu/synop/EIT/) and
  will present the latest results.

Title: The Creation of Outflowing Plasma in the Corona at Emerging
Flux Regions: Comparing Observations and Simulations
Authors: Harra, L. K.; Archontis, V.; Pedram, E.; Hood, A. W.; Shelton,
   D. L.; van Driel-Gesztelyi, L.
Bibcode: 2012SoPh..278...47H
Altcode:
  In this paper we analyse the flux emergence that occurred in the
  following polarity area of an active region on 1 - 2 December
  2006. Observations have revealed the existence of fast outflows
  at the edge of the emerging flux region. We have performed 3-D
  numerical simulations to study the mechanisms responsible for these
  flows. The results indicate that these outflows are reconnection jets
  or pressure-driven outflows, depending on the relative orientation
  of the magnetic fields in contact (i.e. the emerging flux and the
  active region's field which is favourable for reconnection on the
  west side and nearly parallel with the pre-existing field on the east
  side of the emerging flux). In the observations, the flows are larger
  on the west side until late in the flux emergence, when the reverse
  is true. The simulations show that the flows are faster on the west
  side, but do not show the east flows increasing with time. There is an
  asymmetry in the expansion of the emerging flux region, which is also
  seen in the observations. The west side of the emerging flux region
  expands faster into the corona than the other side. In the simulations,
  efficient magnetic reconnection occurs on the west side, with new loops
  being created containing strong downflows that are clearly seen in the
  observations. On the other side, the simulations show strong compression
  as the dominant mechanism for the generation of flows. There is evidence
  of these flows in the observations, but the flows are stronger than
  the simulations predict at the later stages. There could be additional
  small-angle reconnection that adds to the flows from the compression,
  as well as reconnection occurring in larger loops that lie across the
  whole active region.

Title: Nonlinear Force-Free Extrapolation of Emerging Flux with a
    Global Twist and Serpentine Fine Structures
Authors: Valori, G.; Green, L. M.; Démoulin, P.; Vargas Domínguez,
   S.; van Driel-Gesztelyi, L.; Wallace, A.; Baker, D.; Fuhrmann, M.
Bibcode: 2012SoPh..278...73V
Altcode:
  We study the flux emergence process in NOAA active region 11024, between
  29 June and 7 July 2009, by means of multi-wavelength observations
  and nonlinear force-free extrapolation. The main aim is to extend
  previous investigations by combining, as much as possible, high spatial
  resolution observations to test our present understanding of small-scale
  (undulatory) flux emergence, whilst putting these small-scale events
  in the context of the global evolution of the active region. The
  combination of these techniques allows us to follow the whole process,
  from the first appearance of the bipolar axial field on the east limb,
  until the buoyancy instability could set in and raise the main body
  of the twisted flux tube through the photosphere, forming magnetic
  tongues and signatures of serpentine field, until the simplification
  of the magnetic structure into a main bipole by the time the active
  region reaches the west limb. At the crucial time of the main emergence
  phase high spatial resolution spectropolarimetric measurements of the
  photospheric field are employed to reconstruct the three-dimensional
  structure of the nonlinear force-free coronal field, which is then
  used to test the current understanding of flux emergence processes. In
  particular, knowledge of the coronal connectivity confirms the identity
  of the magnetic tongues as seen in their photospheric signatures,
  and it exemplifies how the twisted flux, which is emerging on small
  scales in the form of a sea-serpent, is subsequently rearranged by
  reconnection into the large-scale field of the active region. In
  this way, the multi-wavelength observations combined with a nonlinear
  force-free extrapolation provide a coherent picture of the emergence
  process of small-scale magnetic bipoles, which subsequently reconnect
  to form a large-scale structure in the corona.

Title: Preface
Authors: Green, L. M.; Sakurai, T.; van Driel-Gesztelyi, L.
Bibcode: 2012SoPh..278....1G
Altcode:
  No abstract at ADS

Title: Granular-Scale Elementary Flux Emergence Episodes in a Solar
    Active Region
Authors: Vargas Domínguez, S.; van Driel-Gesztelyi, L.; Bellot Rubio,
   L. R.
Bibcode: 2012SoPh..278...99V
Altcode: 2012SoPh..tmp..259F; 2012arXiv1203.6428V
  We analyse data from Hinode spacecraft taken over two 54-minute periods
  during the emergence of AR 11024. We focus on small-scale portions
  within the observed solar active region and discover the appearance of
  very distinctive small-scale and short-lived dark features in Ca II H
  chromospheric filtergrams and Stokes I images. The features appear in
  regions with close-to-zero longitudinal magnetic field, and are observed
  to increase in length before they eventually disappear. Energy release
  in the low chromospheric line is detected while the dark features
  are fading. Three complete series of these events are detected with
  remarkably similar properties, i.e. lifetime of ≈ 12 min, maximum
  length and area of 2 - 4 Mm and 1.6 - 4 Mm<SUP>2</SUP>, respectively,
  and all with associated brightenings. In time series of magnetograms a
  diverging bipolar configuration is observed accompanying the appearance
  of the dark features and the brightenings. The observed phenomena
  are explained as evidencing elementary flux emergence in the solar
  atmosphere, i.e. small-scale arch filament systems rising up from the
  photosphere to the lower chromosphere with a length scale of a few
  solar granules. Brightenings are explained as being the signatures of
  chromospheric heating triggered by reconnection of the rising loops
  (once they have reached chromospheric heights) with pre-existing
  magnetic fields, as well as being due to reconnection/cancellation
  events in U-loop segments of emerging serpentine fields. The
  characteristic length scale, area and lifetime of these elementary
  flux emergence events agree well with those of the serpentine field
  observed in emerging active regions. We study the temporal evolution
  and dynamics of the events and compare them with the emergence of
  magnetic loops detected in quiet Sun regions and serpentine flux
  emergence signatures in active regions. The physical processes of
  the emergence of granular-scale magnetic loops seem to be the same
  in the quiet Sun and active regions. The difference is the reduced
  chromospheric emission in the quiet Sun attributed to the fact that
  loops are emerging in a region of lower ambient magnetic field density,
  making interactions and reconnection less likely to occur. Incorporating
  the novel features of granular-scale flux emergence presented in this
  study, we advance the scenario for serpentine flux emergence.

Title: On Signatures of Twisted Magnetic Flux Tube Emergence
Authors: Vargas Domínguez, S.; MacTaggart, D.; Green, L.; van
   Driel-Gesztelyi, L.; Hood, A. W.
Bibcode: 2012SoPh..278...33V
Altcode: 2011arXiv1105.0758V
  Recent studies of NOAA active region 10953, by Okamoto et
  al. (Astrophys. J. Lett.673, 215, 2008; Astrophys. J.697, 913, 2009),
  have interpreted photospheric observations of changing widths of the
  polarities and reversal of the horizontal magnetic field component as
  signatures of the emergence of a twisted flux tube within the active
  region and along its internal polarity inversion line (PIL). A filament
  is observed along the PIL and the active region is assumed to have an
  arcade structure. To investigate this scenario, MacTaggart and Hood
  (Astrophys. J. Lett.716, 219, 2010) constructed a dynamic flux emergence
  model of a twisted cylinder emerging into an overlying arcade. The
  photospheric signatures observed by Okamoto et al. (2008, 2009) are
  present in the model although their underlying physical mechanisms
  differ. The model also produces two additional signatures that can be
  verified by the observations. The first is an increase in the unsigned
  magnetic flux in the photosphere at either side of the PIL. The second
  is the behaviour of characteristic photospheric flow profiles associated
  with twisted flux tube emergence. We look for these two signatures in
  AR 10953 and find negative results for the emergence of a twisted flux
  tube along the PIL. Instead, we interpret the photospheric behaviour
  along the PIL to be indicative of photospheric magnetic cancellation
  driven by flows from the dominant sunspot. Although we argue against
  flux emergence within this particular region, the work demonstrates
  the important relationship between theory and observations for the
  successful discovery and interpretation of signatures of flux emergence.

Title: Division II: Sun and Heliosphere
Authors: Martínez Pillet, Valentín; Klimchuk, James A.; Melrose,
   Donald B.; Cauzzi, Gianna; van Driel-Gesztelyi, Lidia; Gopalswamy,
   Natchimuthuk; Kosovichev, Alexander; Mann, Ingrid; Schrijver,
   Carolus J.
Bibcode: 2012IAUTA..28...61M
Altcode: 2012IAUTA..28...61P
  The solar activity cycle entered a prolonged quiet phase that started
  in 2008 and ended in 2010. This minimum lasted for a year longer
  than expected and all activity proxies, as measured from Earth and
  from Space, reached minimum values never observed before (de Toma,
  2012). The number of spotless days from 2006 to 2009 totals 800, the
  largest ever recorded in modern times. Solar irradiance was at historic
  minimums. The interplanetary magnetic field was measured at values as
  low as 2.9 nT and the cosmic rays were observed at records-high. While
  rumors spread that the Sun could be entering a grand minimum quiet
  phase (such as the Maunder minimum of the XVII century), activity
  took over in 2010 and we are now well into Solar Cycle 24 (albeit,
  probably, a low intensity cycle), approaching towards a maximum due
  by mid 2013. In addition to bringing us the possibility to observe
  a quiet state of the Sun and of the Heliosphere that was previously
  not recorded with modern instruments, the Sun has also shown us how
  little we know about the dynamo mechanism that drives its activity as
  all solar cycle predictions failed to see this extended minimum coming.

Title: Commission 10: Solar Activity
Authors: van Driel-Gesztelyi, Lidia; Schrijver, Carolus J.; Klimchuk,
   James A.; Charbonneau, Paul; Fletcher, Lyndsay; Hasan, S. Sirajul;
   Hudson, Hugh S.; Kusano, Kanya; Mandrini, Cristina H.; Peter, Hardi;
   Vršnak, Bojan; Yan, Yihua
Bibcode: 2012IAUTA..28...69V
Altcode:
  Commission 10 of the International Astronomical Union has more than
  650 members who study a wide range of activity phenomena produced by
  our nearest star, the Sun. Solar activity is intrinsically related
  to solar magnetic fields and encompasses events from the smallest
  energy releases (nano- or even picoflares) to the largest eruptions
  in the Solar System, coronal mass ejections (CMEs), which propagate
  into the Heliosphere reaching the Earth and beyond. Solar activity is
  manifested in the appearance of sunspot groups or active regions, which
  are the principal sources of activity phenomena from the emergence of
  their magnetic flux through their dispersion and decay. The period
  2008-2009 saw an unanticipated extended solar cycle minimum and
  unprecedentedly weak polar-cap and heliospheric field. Associated with
  that was the 2009 historical maximum in galactic cosmic rays flux since
  measurements begun in the middle of the 20th Century. Since then Cycle
  24 has re-started solar activity producing some spectacular eruptions
  observed with a fleet of spacecraft and ground-based facilities. In
  the last triennium major advances in our knowledge and understanding
  of solar activity were due to continuing success of space missions as
  SOHO, Hinode, RHESSI and the twin STEREO spacecraft, further enriched
  by the breathtaking images of the solar atmosphere produced by the
  Solar Dynamic Observatory (SDO) launched on 11 February 2010 in the
  framework of NASA's Living with a Star program. In August 2012, at the
  time of the IAU General Assembly in Beijing when the mandate of this
  Commission ends, we will be in the unique position to have for the
  first time a full 3-D view of the Sun and solar activity phenomena
  provided by the twin STEREO missions about 120 degrees behind and
  ahead of Earth and other spacecraft around the Earth and ground-based
  observatories. These new observational insights are continuously
  posing new questions, inspiring and advancing theoretical analysis
  and modelling, improving our understanding of the physics underlying
  magnetic activity phenomena. Commission 10 reports on a vigorously
  evolving field of research produced by a large community. The number
  of refereed publications containing `Sun', `heliosphere', or a synonym
  in their abstracts continued the steady growth seen over the preceding
  decades, reaching about 2000 in the years 2008-2010, with a total of
  close to 4000 unique authors. This report, however, has its limitations
  and it is inherently incomplete, as it was prepared jointly by the
  members of the Organising Committee of Commission 10 (see the names
  of the primary contributors to the sections indicated in parentheses)
  reflecting their fields of expertise and interest. Nevertheless, we
  believe that it is a representative sample of significant new results
  obtained during the last triennium in the field of solar activity.

Title: Editorial Appreciation
Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia
Bibcode: 2012SoPh..276....1L
Altcode:
  No abstract at ADS

Title: Forecasting a CME by Spectroscopic Precursor?
Authors: Baker, D.; van Driel-Gesztelyi, L.; Green, L. M.
Bibcode: 2012SoPh..276..219B
Altcode:
  Multi-temperature plasma flows resulting from the interaction between
  a mature active region (AR) inside an equatorial coronal hole (CH) are
  investigated. Outflow velocities observed by Hinode EIS ranged from a
  few to 13 km s<SUP>−1</SUP> for three days at the AR's eastern and
  western edges. However, on the fourth day, velocities intensified up to
  20 km s<SUP>−1</SUP> at the AR's western footpoint about six hours
  prior to a CME. 3D MHD numerical simulations of the observed magnetic
  configuration of the AR-CH complex showed that the expansion of the
  mature AR's loops drives persistent outflows along the neighboring CH
  field (Murray et al. in Solar Phys.261, 253, 2010). Based on these
  simulations, intensification of outflows observed pre-eruption on
  the AR's western side where same-polarity AR and CH field interface,
  is interpreted to be the result of the expansion of a sigmoidal
  AR, in particular, a flux rope containing a filament that provides
  stronger compression of the neighboring CH field on this side of the
  AR. Intensification of outflows in the AR is proposed as a new type
  of CME precursor.

Title: Preface
Authors: Marqué, C.; Nindos, A.; van Driel-Gesztelyi, L.; Mandrini,
   C. H.
Bibcode: 2012esrs.book....1M
Altcode:
  No abstract at ADS

Title: The Sun-Earth Connection near Solar Minimum: Placing it
    into Context
Authors: Bisi, Mario M.; Thompson, Barbara J.; Emery, Barbara A.;
   Gibson, Sarah E.; Leibacher, John; van Driel-Gesztelyi, Lidia
Bibcode: 2011SoPh..274....1B
Altcode:
  No abstract at ADS

Title: Preface
Authors: Marqué, C.; Nindos, A.; van Driel-Gesztelyi, L.; Mandrini,
   C. H.
Bibcode: 2011SoPh..273..307M
Altcode: 2011SoPh..tmp..385M
  No abstract at ADS

Title: Coronal Jets, Magnetic Topologies, and the Production of
    Interplanetary Electron Streams
Authors: Li, C.; Matthews, S. A.; van Driel-Gesztelyi, L.; Sun, J.;
   Owen, C. J.
Bibcode: 2011ApJ...735...43L
Altcode: 2013arXiv1305.5602L
  We investigate the acceleration source of the impulsive solar
  energetic particle (SEP) events on 2007 January 24. Combining the in
  situ electron measurements and remote-sensing solar observations, as
  well as the calculated magnetic fields obtained from a potential-field
  source-surface model, we demonstrate that the jets associated with
  the hard X-ray flares and type-III radio bursts, rather than the
  slow and partial coronal mass ejections, are closely related to the
  production of interplanetary electron streams. The jets, originated
  from the well-connected active region (AR 10939) whose magnetic
  polarity structure favors the eruption, are observed to be forming
  in a coronal site, extending to a few solar radii, and having a good
  temporal correlation with the electron solar release. The open-field
  lines near the jet site are rooted in a negative polarity, along which
  energetic particles escape from the flaring AR to the near-Earth space,
  consistent with the in situ electron pitch angle distribution. The
  analysis enables us to propose a coronal magnetic topology relating
  the impulsive SEP events to their solar source.

Title: Twisted Flux Tube Emergence Evidenced in Longitudinal
Magnetograms: Magnetic Tongues
Authors: Luoni, M. L.; Démoulin, P.; Mandrini, C. H.; van
   Driel-Gesztelyi, L.
Bibcode: 2011SoPh..270...45L
Altcode: 2011SoPh..tmp...66L
  Bipolar active regions (ARs) are thought to be formed by twisted flux
  tubes, as the presence of such twist is theoretically required for a
  cohesive rise through the whole convective zone. We use longitudinal
  magnetograms to demonstrate that a clear signature of a global magnetic
  twist is present, particularly, during the emergence phase when the AR
  is forming in a much weaker pre-existing magnetic field environment. The
  twist is characterised by the presence of elongated polarities, called
  "magnetic tongues", which originate from the azimuthal magnetic field
  component. The tongues first extend in size before retracting when the
  maximum magnetic flux is reached. This implies an apparent rotation of
  the magnetic bipole. Using a simple half-torus model of an emerging
  twisted flux tube having a uniform twist profile, we derive how the
  direction of the polarity inversion line and the elongation of the
  tongues depend on the global twist in the flux rope. Using a sample of
  40 ARs, we verify that the helicity sign, determined from the magnetic
  polarity distribution pattern, is consistent with the sign derived from
  the photospheric helicity flux computed from magnetogram time series,
  as well as from other proxies such as sheared coronal loops, sigmoids,
  flare ribbons and/or the associated magnetic cloud observed in situ
  at 1 AU. The evolution of the tongues observed in emerging ARs is
  also closely similar to the evolution found in recent MHD numerical
  simulations. We also found that the elongation of the tongue formed
  by the leading magnetic polarity is significantly larger than that of
  the following polarity. This newly discovered asymmetry is consistent
  with an asymmetric Ω-loop emergence, trailing the solar rotation,
  which was proposed earlier to explain other asymmetries in bipolar ARs.

Title: Pulsed Flows Along a Cusp Structure Observed with SDO/AIA
Authors: Thompson, Barbara; Démoulin, P.; Mandrini, C.; Mays, M.;
   Ofman, L.; Van Driel-Gesztelyi, L.; Viall, N.
Bibcode: 2011SPD....42.2117T
Altcode: 2011BAAS..43S.2117T
  We present observations of a cusp-shaped structure that formed after
  a flare and coronal mass ejection on 14 February 2011. Throughout
  the evolution of the cusp structure, blob features up to a few Mm in
  size were observed flowing along the legs and stalk of the cusp at
  projected speeds ranging from 50 to 150 km/sec. Around two dozen blob
  features, on order of 1 - 3 minutes apart, were tracked in multiple
  AIA EUV wavelengths. The blobs flowed outward (away from the Sun)
  along the cusp stalk, and most of the observed speeds were either
  constant or decelerating. We attempt to reconstruct the 3-D magnetic
  field of the evolving structure, discuss the possible drivers of the
  flows (including pulsed reconnection and tearing mode instability),
  and compare the observations to studies of pulsed reconnection and
  blob flows in the solar wind and the Earth's magnetosphere.

Title: Editorial Appreciation
Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia
Bibcode: 2011SoPh..269....1L
Altcode: 2011SoPh..tmp...21L
  No abstract at ADS

Title: Pre-Flare Flows in the Corona
Authors: Wallace, A. J.; Harra, L. K.; van Driel-Gesztelyi, L.; Green,
   L. M.; Matthews, S. A.
Bibcode: 2010SoPh..267..361W
Altcode: 2010SoPh..tmp..223W; 2010SoPh..tmp..199W
  Solar flares take place in regions of strong magnetic fields and
  are generally accepted to be the result of a resistive instability
  leading to magnetic reconnection. When new flux emerges into a
  pre-existing active region it can act as a flare and coronal mass
  ejection trigger. In this study we observed active region 10955 after
  the emergence of small-scale additional flux at the magnetic inversion
  line. We found that flaring began when additional positive flux levels
  exceeded 1.38×10<SUP>20</SUP> Mx (maxwell), approximately 7 h after
  the initial flux emergence. We focussed on the pre-flare activity of
  one B-class flare that occurred on the following day. The earliest
  indication of activity was a rise in the non-thermal velocity one
  hour before the flare. 40 min before flaring began, brightenings and
  pre-flare flows were observed along two loop systems in the corona,
  involving the new flux and the pre-existing active region loops. We
  discuss the possibility that reconnection between the new flux
  and pre-existing loops before the flare drives the flows by either
  generating slow mode magnetoacoustic waves or a pressure gradient
  between the newly reconnected loops. The subsequent B-class flare
  originated from fast reconnection of the same loop systems as the
  pre-flare flows.

Title: Temporal evolution and spatial variation of the solar wind
    from multi-spacecraft measurements
Authors: Opitz, A.; Wurz, P.; Fedorov, A.; Sauvaud, J.; Luhmann, J. G.;
   Riley, P.; Szego, K.; Russell, C. T.; Galvin, A. B.; Rouillard, A. P.;
   Vourlidas, A.; van Driel-Gesztelyi, L.
Bibcode: 2010AGUFMSH33C..07O
Altcode:
  We study the temporal evolution and the spatial variation of the solar
  wind on different scales. The analyzed multi-spacecraft (STEREO, VEX,
  SOHO, MEX, and other spacecraft) measurements were obtained between 2007
  and 2010 during solar minimum in the inner heliosphere. We derived
  the temporal and spatial variability of the different solar wind
  parameters (proton bulk velocity, electron core density, etc). These
  results support prediction of the solar wind parameters for different
  heliospheric positions and help to derive its validity range. In order
  to explain occasional deviations from the nominal solar wind evolution
  we use imaging data and modeling results.

Title: Solar Physics Memoir Series Reinstituted
Authors: Cliver, Ed; van Driel-Gesztelyi, Lidia
Bibcode: 2010SoPh..267..233C
Altcode: 2010SoPh..tmp..194C
  No abstract at ADS

Title: Observational and numerical study of the 25 July 2004 event
Authors: Soenen, A.; Jacobs, C.; Poedts, S.; van Driel-Gesztelyi,
   L.; Torok, T.; Lapenta, G.
Bibcode: 2010AGUFMSH23B1843S
Altcode:
  We study the 25 July 2004 event. By analyzing SOHO EIT images we
  establish a basic understanding of the large-scale interaction going
  on during this event. Magnetic reconnection between the expanding
  CME and the Southern hemispheric active regions (AR) will connect the
  leading polarities of the two ARs, lead to brightening in the ARs and
  transport CME field line foot points to distant ARs (observable as
  dimming at the foot points).We reproduce the large scale interactions
  during this event using three-dimensional magneto-hydrodynamic (MHD)
  simulations. We superimpose a magnetic source region that resembles
  the SOHO MDI images on a basic wind model. By emerging new flux at the
  centre of this region we initiate a Coronal Mass Ejection (CME). We
  monitor the evolution of this CME and study its interaction with the
  source region.

Title: Preface
Authors: Bisi, M. M.; Breen, A. R.; van Driel-Gesztelyi, L.; Mandrini,
   C. H.
Bibcode: 2010SoPh..265....1B
Altcode: 2010SoPh..tmp..143B
  No abstract at ADS

Title: Revealing the Fine Structure of Coronal Dimmings and Associated
    Flows with Hinode/EIS. Implications for Understanding the Source
    Regions of Sustained Outflow Following CMEs
Authors: Attrill, G. D. R.; Harra, L. K.; van Driel-Gesztelyi, L.;
   Wills-Davey, M. J.
Bibcode: 2010SoPh..264..119A
Altcode: 2010SoPh..tmp...80A
  We study two CME events on 13 and 14 December 2006 that were associated
  with large-scale dimmings. We study the eruptions from pre-event on
  11 December through the recovery on 15 December, using a combination
  of Hinode/EIS, SOHO/EIT, SOHO/MDI, and MLSO Hα data. The GOES
  X-class flares obscured the core dimmings, but secondary dimmings
  developed remote from the active region (AR) in both events. The
  secondary dimmings are found to be formed by a removal of bright
  coronal material from loops in the plage region to the East of the
  AR. Using Hinode/EIS data, we find that the outflows associated with
  the coronal-dimming regions are highly structured. The concentrated
  outflows are located at the footpoints of coronal loops (which exist
  before, and are re-established after, the eruptions), and these are
  correlated with regions of positive magnetic elements. Comparative
  study of the Hinode/EIS and SOHO/EIT data shows that the reduction in
  outflow velocity is consistent with the recovery in intensity of the
  studied regions. We find that concentrated downflows develop during the
  recovery phase of the dimmings and are also correlated with the same
  positive magnetic elements that were previously related to outflows.

Title: Division II: Sun and Heliosphere
Authors: Melrose, Donald B.; Martinez Pillet, Valentin; Webb, David
   F.; Bougeret, Jean-Louis; Klimchuk, James A.; Kosovichev, Alexander;
   van Driel-Gesztelyi, Lidia; von Steiger, Rudolf
Bibcode: 2010IAUTB..27..146M
Altcode:
  This report is on activities of the Division at the General Assembly
  in Rio de Janeiro. Summaries of scientific activities over the past
  triennium have been published in Transactions A, see Melrose et
  al. (2008), Klimchuk et al. (2008), Martinez Pillet et al. (2008) and
  Bougeret et al. (2008). The business meeting of the three Commissions
  were incorporated into the business meeting of the Division. This
  report is based in part on minutes of the business meeting, provided
  by the Secretary of the Division, Lidia van Driel-Gesztelyi, and it
  also includes reports provided by the Presidents of the Commissions
  (C10, C12, C49) and of the Working Groups (WGs) in the Division.

Title: Solar Observation Target Identification Convention for use
    in Solar Physics
Authors: Leibacher, John; Sakurai, Takashi; Schrijver, Carolus J.;
   van Driel-Gesztelyi, Lidia
Bibcode: 2010SoPh..263....1L
Altcode: 2010SoPh..263....1.; 2010SoPh..tmp...71.
  We strongly encourage the use of a standardized target identification
  to be included in pub- lications on solar events. The primary purpose
  is to enable the automated identification of publications on the same
  event, or on other related events, in the on-line literature by search
  engines such as the Astrophysics Data System (ADS). The convention does
  not aim to categorize or classify events, but is limited specifically
  to the identification of regions in space and intervals in time within
  which events occur.

Title: Editorial Appreciation
Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia
Bibcode: 2010SoPh..262....1L
Altcode: 2010SoPh..tmp...18L
  No abstract at ADS

Title: Outflows at the Edges of an Active Region in a Coronal Hole:
    A Signature of Active Region Expansion?
Authors: Murray, M. J.; Baker, D.; van Driel-Gesztelyi, L.; Sun, J.
Bibcode: 2010SoPh..261..253M
Altcode: 2009arXiv0912.1246M
  Outflows of plasma at the edges of active regions surrounded by quiet
  Sun are now a common observation with the Hinode satellite. While there
  is observational evidence to suggest that the outflows are originating
  in the magnetic field surrounding the active regions, there is no
  conclusive evidence that reveals how they are driven. Motivated
  by observations of outflows at the periphery of a mature active
  region embedded in a coronal hole, we have used a three-dimensional
  simulation to emulate the active region's development in order to
  investigate the origin and driver of these outflows. We find that
  outflows are accelerated from a site in the coronal hole magnetic
  field immediately surrounding the active region and are channelled
  along the coronal hole field as they rise through the atmosphere. The
  plasma is accelerated simply as a result of the active region
  expanding horizontally as it develops. Many of the characteristics
  of the outflows generated in the simulation are consistent with
  those of observed outflows: velocities up to 45 km s<SUP>−1</SUP>,
  properties akin to the coronal hole, proximity to the active region's
  draining loops, expansion with height, and projection over monopolar
  photospheric magnetic concentrations. Although the horizontal expansion
  occurs as a consequence of the active region's development in the
  simulation, expansion is also a general feature of established active
  regions. Hence, it is entirely possible and plausible that the expansion
  acceleration mechanism displayed in the simulation is occurring in
  active regions on the Sun and, in addition to reconnection, is driving
  the outflows observed at their edges.

Title: EIT/Coronal waves and coronal dimming: a holistic approach
Authors: van Driel-Gesztelyi, Lidia
Bibcode: 2010cosp...38.1793V
Altcode: 2010cosp.meet.1793V
  If EIT waves were simple, they would not be such interesting and
  divisive a subject. I will argue that one of the main reasons for the
  persistent elusiveness of their interpretation is that they are due to
  a composite of causes, which include MHD waves, compression of coronal
  plasma by the expanding CME as well as magnetic reconnection between the
  CME and surrounding magnetic structures. There is not one single cause
  which on itself could explain all the observed characteristics. I will
  show that magnetic reconnection between the CME and other magnetic
  structures is responsible for some of the transient brightenings
  which show up along the diffuse bright EIT wave front, as evidenced by
  long-lived (¿ 1 h) dimming regions which form in their wake. CME-driven
  dynamic reconnection provides a natural explanation for the formation
  of widespread secondary dimming regions, indicating that large portions
  of the Sun become constituents of the CME. This implies that the extent
  of the secondary dimming matches the final angular width of the CME,
  as observed. I will review observations and MHD simulations supporting
  the composite nature of the causes of EIT waves, and will argue in
  favour of a holistic approach, which will not diminish their interest,
  but rather bring us closer to understanding them.

Title: Magnetic reconnection along QSLs -a major driver of active
    region outflows
Authors: Baker, Deborah; van Driel-Gesztelyi, Lidia; Mandrini,
   Cristina H.; Demoulin, Pascal
Bibcode: 2010cosp...38.2926B
Altcode: 2010cosp.meet.2926B
  The relationship between quasi-separatrix layers (QSLs), or in the limit
  of infinitely thin QSLs, separatrices, and various activity phenomena
  has been explored in many different solar magnetic configurations
  across all scales in recent years. In the absence of magnetic nulls,
  fast reconnec-tion along QSLs, which are specific locations in the
  magnetic topology where field lines display strong gradients of
  magnetic connectivity, was identified as the main physical process
  at the origin of flares. Recently, it was shown that fast (tens of
  km/s) persistent hot plasma upflows in active regions (ARs) can also
  be linked to locations of QSLs. It is likely that these upflows that
  occur at the edges of ARs over unipolar magnetic field concentrations
  are accelerated by magnetic reconnection along QSLs. We will show
  multi-temperature spectral scan observations from Hinode's EIS combined
  with magnetic modeling of QSLs in two ARs observed on 20-21 February
  2007 and 11 January 2008. The latter AR is observed and modeled when
  it is in the vicinity of the solar central meridian where there are no
  projection effects, thereby eliminating ambiguity linking the origin
  of multi-temperature observations of AR upflows to QSLs. We use the
  Potential Source Surface Model to look for open field lines in the
  vicinity of upflows and QSL locations in order to demonstrate whether
  these upflows become outflows and can contribute to the solar wind.

Title: Interacting active regions and coronal holes: implications
    for coronal outflows and solar wind structure
Authors: Culhane, J. Leonard; Baker, Deborah; Rouillard, Alexis;
   van Driel-Gesztelyi, Lidia
Bibcode: 2010cosp...38.1863C
Altcode: 2010cosp.meet.1863C
  When active regions are adjacent to coronal holes a variety of magnetic
  field interactions can result. These may include the interchange
  reconnection between the closed active region (AR) fields and the
  open field of the coronal hole (CH), leading to fast and significant
  evolution of coronal hole boundaries. Outcomes may include variability
  of -or changes in, active region-associated hot plasma outflows seen
  with Hinode/EIS and the modulation of the solar wind flows on open
  field lines. Depending on their relative positions on the Sun, the
  AR-CH interactions may have their signatures embedded in co-rotating
  interaction regions (CIRs) or rarefaction regions. During two intervals
  -8/11 January, 2008 and 7/9 December, 2008, we have made observations
  with Hinode of two oppositely configured situations on the Sun. For
  8/11 January, the coronal hole leads the active region while for
  7/9 December the order is reversed. The Hinode EIS instrument is
  used to locate outflows and measure their velocities while the XRT
  is used to image the source regions, including the variable nature
  of the outflows. SOHO EIT imaging is used to follow the longer-term
  evolution of the coronal hole boundaries while MDI is used to observe
  changes in the magnetic field. STEREO imaging and in-situ data are also
  employed -as are ACE observations, to assess the resulting impacts on
  interplanetary solar wind structures. The contrasting behaviour that
  results from magnetic interactions in the two different configurations
  is described and assessed.

Title: Coronal magnetic topology and the solar source of beam-like
    electron events
Authors: Li, Chuan; van Driel-Gesztelyi, Lidia; Matthews, Sarah A.;
   Sun, Jian; Mandrini, Cristina H.; Owen, Christopher
Bibcode: 2010cosp...38.2986L
Altcode: 2010cosp.meet.2986L
  More and more evidence indicates a strong correlation between impulsive
  solar energetic particle (SEP) events and the magnetic reconnections in
  the vicinity of flaring active regions (ARs). However, it is still not
  clear how they are related to each other. We present the investigation
  of the AR 10939, which produced two B-class flares, accompanied by
  narrow coronal mass ejections (CMEs)and successive beam-like electron
  events on 24 January 2007. Using in situ electron observations from
  ACE/EPAM and WIND/3DP, and imaging data from Hinode/EIS, RHESSI,
  and TRACE, coupled with magnetic modeling, we could establish the
  correlations of the coronal magnetic topologies, jet activities,
  and the accelerations of impulsive electrons.

Title: Characteristics of the Nonthermal Velocity Signature Observed
    in the Impulsive Phase of the 2007 May 19 Flare
Authors: Hara, H.; Watanabe, T.; Bone, L. A.; Culhane, J. L.; van
   Driel-Gesztelyi, L.; Young, P. R.
Bibcode: 2009ASPC..415..459H
Altcode:
  The Hinode EUV Imaging Spectrometer (EIS) observed a long duration
  flare with a weak impulsive phase that appears to conform to the
  standard two-ribbon flare reconnection model. EIS scanned the flare
  site during the impulsive phase and observed Fe XXIII and Fe XXIV line
  emission that closely followed the flare hard X-ray emission while the
  line profiles showed significant non-thermal broadening. We suggest
  that a shock originating at the reconnection site which sweeps up and
  heats the coronal plasma can account for our observations.

Title: Intensification of Plasma Upflows in an Active Region---Coronal
Hole Complex: A CME Precursor
Authors: Baker, D.; van Driel-Gesztelyi, L.; Murray, M. J.; Green,
   L. M.; Török, T.; Sun, J.
Bibcode: 2009ASPC..415...75B
Altcode:
  We investigate the plasma flows resulting from the interaction between
  a mature active region (AR) and a surrounding equatorial coronal hole
  (CH) observed by Hinode's EIS and XRT from 15 to 18 October 2007. For 3
  days, EIS velocity maps showed upflows at the AR's eastern and western
  edges that were consistently between 5 and 10 km s<SUP>-1</SUP>, whereas
  downflows of up to 30 km s<SUP>-1</SUP> were seen in AR loops. However,
  on 18 October, velocity profiles of hotter coronal lines revealed
  intensification in upflow velocities of up to 18 km s<SUP>-1</SUP>
  at the AR's western footpoints 4.5 hours prior to a CME. We compare
  the AR's plasma flows with 2.5D MHD numerical simulations of the
  magnetic configuration, which show that expansion of the mature AR's
  loops drives upflows along the neighboring CH field. Further, the
  intensification of upflows observed on the AR's western side prior to
  a CME is interpreted to be the result of the expansion of a flux rope
  containing a filament further compressing the neighboring CH field.

Title: Solar Physics Publication Ethics Policies
Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia
Bibcode: 2009SoPh..260....1L
Altcode:
  No abstract at ADS

Title: Magnetic Reconnection along Quasi-separatrix Layers as a
    Driver of Ubiquitous Active Region Outflows
Authors: Baker, D.; van Driel-Gesztelyi, L.; Mandrini, C. H.;
   Démoulin, P.; Murray, M. J.
Bibcode: 2009ApJ...705..926B
Altcode: 2009arXiv0909.4738B
  Hinode's EUV Imaging Spectrometer (EIS) has discovered ubiquitous
  outflows of a few to 50 km s<SUP>-1</SUP> from active regions
  (ARs). These outflows are most prominent at the AR boundary and
  appear over monopolar magnetic areas. They are linked to strong
  non-thermal line broadening and are stronger in hotter EUV lines. The
  outflows persist for at least several days. Using Hinode EIS and X-Ray
  Telescope observations of AR 10942 coupled with magnetic modeling,
  we demonstrate that the outflows originate from specific locations
  of the magnetic topology where field lines display strong gradients
  of magnetic connectivity, namely quasi-separatrix layers (QSLs),
  or in the limit of infinitely thin QSLs, separatrices. We found the
  strongest AR outflows to be in the vicinity of QSL sections located over
  areas of strong magnetic field. We argue that magnetic reconnection at
  QSLs separating closed field lines of the AR and either large-scale
  externally connected or "open" field lines is a viable mechanism for
  driving AR outflows which are likely sources of the slow solar wind.

Title: Signatures of interchange reconnection: STEREO, ACE and Hinode
    observations combined
Authors: Baker, D.; Rouillard, A. P.; van Driel-Gesztelyi, L.;
   Démoulin, P.; Harra, L. K.; Lavraud, B.; Davies, J. A.; Opitz, A.;
   Luhmann, J. G.; Sauvaud, J. -A.; Galvin, A. B.
Bibcode: 2009AnGeo..27.3883B
Altcode: 2009arXiv0909.5624B
  Combining STEREO, ACE and Hinode observations has presented an
  opportunity to follow a filament eruption and coronal mass ejection
  (CME) on 17 October 2007 from an active region (AR) inside a coronal
  hole (CH) into the heliosphere. This particular combination of
  "open" and closed magnetic topologies provides an ideal scenario for
  interchange reconnection to take place. With Hinode and STEREO data
  we were able to identify the emergence time and type of structure
  seen in the in-situ data four days later. On the 21st, ACE observed
  in-situ the passage of an ICME with "open" magnetic topology. The
  magnetic field configuration of the source, a mature AR located
  inside an equatorial CH, has important implications for the solar and
  interplanetary signatures of the eruption. We interpret the formation of
  an "anemone" structure of the erupting AR and the passage in-situ of the
  ICME being disconnected at one leg, as manifested by uni-directional
  suprathermal electron flux in the ICME, to be a direct result of
  interchange reconnection between closed loops of the CME originating
  from the AR and "open" field lines of the surrounding CH.

Title: Formation, Interaction and Merger of an Active Region and a
    Quiescent Filament Prior to Their Eruption on 19 May 2007
Authors: Bone, L. A.; van Driel-Gesztelyi, L.; Culhane, J. L.;
   Aulanier, G.; Liewer, P.
Bibcode: 2009SoPh..259...31B
Altcode:
  We report observations of the formation of two filaments - one
  active and one quiescent, and their subsequent interactions prior to
  eruption. The active region filament appeared on 17 May 2007, followed
  by the quiescent filament about 24 hours later. In the 26 hour interval
  preceding the eruption, which occurred at around 12:50 UT on 19 May
  2007, we see the two filaments attempting to merge and filament material
  is repeatedly heated suggesting magnetic reconnection. The filament
  structure is observed to become increasingly dynamic preceding the
  eruption with two small hard X-ray sources seen close to the active
  part of the filament at around 01:38 UT on 19 May 2007 during one of
  the activity episodes. The final eruption on 19 May at about 12:51 UT
  involves a complex CME structure, a flare and a coronal wave. A magnetic
  cloud is observed near Earth by the STEREO-B and WIND spacecraft about
  2.7 days later. Here we describe the behaviour of the two filaments
  in the period prior to the eruption and assess the nature of their
  dynamic interactions.

Title: Preface
Authors: Christian, Eric R.; Kaiser, Michael L.; Kucera, Therese A.;
   St. Cyr, O. C.; van Driel-Gesztelyi, Lidia; Mandrini, Cristina H.
Bibcode: 2009SoPh..256....1C
Altcode:
  No abstract at ADS

Title: Stereoscopic Analysis of the 19 May 2007 Erupting Filament
Authors: Liewer, P. C.; De Jong, E. M.; Hall, J. R.; Howard, R. A.;
   Thompson, W. T.; Culhane, J. L.; Bone, L.; van Driel-Gesztelyi, L.
Bibcode: 2009SoPh..256...57L
Altcode: 2009arXiv0904.1055L
  A filament eruption, accompanied by a B9.5 flare, coronal dimming,
  and an EUV wave, was observed by the Solar TERrestrial Relations
  Observatory (STEREO) on 19 May 2007, beginning at about 13:00 UT. Here,
  we use observations from the SECCHI/EUVI telescopes and other solar
  observations to analyze the behavior and geometry of the filament before
  and during the eruption. At this time, STEREO A and B were separated by
  about 8.5°, sufficient to determine the three-dimensional structure
  of the filament using stereoscopy. The filament could be followed in
  SECCHI/EUVI 304 Å stereoscopic data from about 12 hours before to about
  2 hours after the eruption, allowing us to determine the 3D trajectory
  of the erupting filament. From the 3D reconstructions of the filament
  and the chromospheric ribbons in the early stage of the eruption,
  simultaneous heating of both the rising filamentary material and the
  chromosphere directly below is observed, consistent with an eruption
  resulting from magnetic reconnection below the filament. Comparisons
  of the filament during eruption in 304 Å and Hα show that when it
  becomes emissive in He II, it tends to disappear in Hα , indicating
  that the disappearance probably results from heating or motion, not
  loss, of filamentary material.

Title: Magnetic reconnection and energy release on the Sun and
    solar-like stars
Authors: van Driel-Gesztelyi, Lidia
Bibcode: 2009IAUS..259..191V
Altcode:
  Magnetic reconnection is thought to play an important role in liberating
  free energy stored in stressed magnetic fields. The consequences vary
  from undetectable nanoflares to huge flares, which have signatures
  over a wide wavelength range, depending on e.g. magnetic topology,
  free energy content, total flux, and magnetic flux density of the
  structures involved. Events of small energy release, which are thought
  to be the most numerous, are one of the key factors in the existence
  of a hot corona in the Sun and solar-like stars. The majority of large
  flares are ejective, i.e. involve the expulsion of large quantities of
  mass and magnetic field from the star. Since magnetic reconnection
  requires small length-scales, which are well below the spatial
  resolution limits of even the solar observations, we cannot directly
  observe magnetic reconnection happening. However, there is a plethora
  of indirect evidences from X-rays to radio observations of magnetic
  reconnection. I discuss key observational signatures of flares on the
  Sun and solar-paradigm stellar flares and describe models emphasizing
  synergy between observations and theory.

Title: Magnetic Flux Emergence, Activity, Eruptions and Magnetic
Clouds: Following Magnetic Field from the Sun to the Heliosphere
Authors: van Driel-Gesztelyi, L.; Culhane, J. L.
Bibcode: 2009SSRv..144..351V
Altcode: 2008SSRv..tmp..185V
  We present an overview of how the principal physical properties of
  magnetic flux which emerges from the toroidal fields in the tachocline
  through the turbulent convection zone to the solar surface are linked
  to solar activity events, emphasizing the effects of magnetic field
  evolution and interaction with other magnetic structures on the
  latter. We compare the results of different approaches using various
  magnetic observables to evaluate the probability of flare and coronal
  mass ejection (CME) activity and forecast eruptive activity on the
  short term (i.e. days). Then, after a brief overview of the observed
  properties of CMEs and their theoretical models, we discuss the
  ejecta properties and describe some typical magnetic and composition
  characteristics of magnetic clouds (MCs) and interplanetary CMEs
  (ICMEs). We review some individual examples to clarify the link between
  eruptions from the Sun and the properties of the resulting ejecta. The
  importance of a synthetic approach to solar and interplanetary magnetic
  fields and activity is emphasized.

Title: The link between CME-associated dimmings and interplanetary
    magnetic clouds
Authors: Mandrini, Cristina H.; Nakwacki, María S.; Attrill, Gemma;
   van Driel-Gesztelyi, Lidia; Dasso, Sergio; Démoulin, Pascal
Bibcode: 2009IAUS..257..265M
Altcode:
  Coronal dimmings often develop in the vicinity of erupting magnetic
  configurations. It has been suggested that they mark the location of
  the footpoints of ejected flux ropes and, thus, their magnetic flux can
  be used as a proxy for the ejected flux. If so, this quantity can be
  compared to the flux in the associated interplanetary magnetic cloud
  (MC) to find clues about the origin of the ejected flux rope. In the
  context of this interpretation, we present several events for which
  we have done a comparative solar-interplanetary analysis. We combine
  SOHO/Extreme Ultraviolet Imaging Telescope (EIT) data and Michelson
  Doppler Imager (MDI) magnetic maps to identify and measure the flux
  in the dimmed regions. We model the associated MCs and compute their
  magnetic flux using in situ observations. We find that the magnetic
  fluxes in the dimmings and MCs are compatible in some events; though
  this is not the case for large-scale and intense eruptions that occur in
  regions that are not isolated from others. We conclude that, in these
  particular cases, a fraction of the dimmed regions can be formed by
  reconnection between the erupting field and the surrounding magnetic
  structures, via a stepping process that can also explain other CME
  associated events.

Title: Editorial Appreciation
Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia
Bibcode: 2009SoPh..255....1L
Altcode:
  No abstract at ADS

Title: Division II: Sun and Heliosphere
Authors: Melrose, Donald B.; Martínez Pillet, Valentin; Webb, David
   F.; van Driel-Gesztelyi, Lidia; Bougeret, Jean-Louis; Klimchuk,
   James A.; Kosovichev, Alexander; von Steiger, Rudolf
Bibcode: 2009IAUTA..27...73M
Altcode:
  Division II of the IAU provides a forum for astronomers and
  astrophysicists studying a wide range of phenomena related to the
  structure, radiation and activity of the Sun, and its interaction with
  the Earth and the rest of the solar system. Division II encompasses
  three Commissions, 10, 12 and 49, and four Working Groups.

Title: Commission 10: Solar Activity
Authors: Klimchuk, James A.; van Driel-Gesztelyi, Lidia; Schrijver,
   Carolus J.; Melrose, Donald B.; Fletcher, Lyndsay; Gopalswamy,
   Natchimuthuk; Harrison, Richard A.; Mandrini, Cristina H.; Peter,
   Hardi; Tsuneta, Saku; Vršnak, Bojan; Wang, Jing-Xiu
Bibcode: 2009IAUTA..27...79K
Altcode: 2008arXiv0809.1444K
  Commission 10 deals with solar activity in all of its forms,
  ranging from the smallest nanoflares to the largest coronal mass
  ejections. This report reviews scientific progress over the roughly
  two-year period ending in the middle of 2008. This has been an exciting
  time in solar physics, highlighted by the launches of the Hinode and
  STEREO missions late in 2006. The report is reasonably comprehensive,
  though it is far from exhaustive. Limited space prevents the inclusion
  of many significant results. The report is divided into the following
  sections: Photosphere and chromosphere; Transition region; Corona and
  coronal heating; Coronal jets; flares; Coronal mass ejection initiation;
  Global coronal waves and shocks; Coronal dimming; The link between low
  coronal CME signatures and magnetic clouds; Coronal mass ejections in
  the heliosphere; and Coronal mass ejections and space weather. Primary
  authorship is indicated at the beginning of each section.

Title: Simulations of emerging flux in a coronal hole: oscillatory
    reconnection
Authors: Murray, M. J.; van Driel-Gesztelyi, L.; Baker, D.
Bibcode: 2009A&A...494..329M
Altcode:
  Context: Observations and simulations show that reconnection will
  take place when a flux tube emerges into a coronal hole, which is
  characterised by magnetic fieldlines “open” towards interplanetary
  space. Although the mechanism by which reconnection is initiated has
  been thoroughly studied, the long-term evolution of this reconnecting
  magnetic system remains unreported. <BR />Aims: We aim to understand
  the long-term evolution of the reconnecting flux tube and coronal
  hole system and, in particular, to ascertain whether it can reach an
  equilibrium state in which all reconnection has ceased. By determining
  the evolution in this particular scenario, we aim to be able to
  select a subset from the broad spectrum of reconnecting systems,
  which will undergo the same progression to equilibrium. <BR />Methods:
  Using a 2.5-dimensional numerical magnetohydrodynamic (MHD) code, we
  evolve a simple stratified atmospheric domain, which is endowed with a
  vertical magnetic field, representing the interior of a coronal hole,
  and a horizontal buoyant flux tube that is placed near the bottom
  of the domain. To investigate the long-term evolution of the system,
  we continue to study the domain long after the flux tube has emerged
  and reconnection has commenced between the magnetic fields of the
  flux tube and coronal hole. <BR />Results: We find that a series of
  reconnection reversals (or oscillatory reconnection) takes place,
  whereby reconnection occurs in distinct bursts and the inflow and
  outflow magnetic fields of one burst of reconnection become the
  outflow and inflow fields in the following burst of reconnection,
  respectively. During each burst of reconnection the gas pressure in the
  bounded outflow regions increases above the level of that in the inflow
  regions and, eventually, gives rise to a reconnection reversal. In
  consecutive bursts of reconnection, the contrast in the gas pressure
  across the boundaries of the inflow and outflow regions decreases and,
  over time, the system settles towards equilibrium. Once the equilibrium
  state is reached, all reconnection ceases. This is the first reported
  instance of oscillatory reconnection initiated in a self-consistent
  manner, and the signatures of the mechanism compare favourably with
  observations of select flux emergence events and with solar and stellar
  flares. <BR />Conclusions: Across the broader spectrum of reconnecting
  systems, oscillatory reconnection will only occur if the outflow regions
  are quasi-bounded during each burst of reconnection. The swaying outflow
  jet and periodic heating signatures of oscillatory reconnection are
  exceedingly similar to those exhibited by MHD modes and, in many
  observations, distinction between the two mechanisms may be impossible.

Title: Magnetic Flux Emergence, Activity, Eruptions and Magnetic
Clouds: Following Magnetic Field from the Sun to the Heliosphere
Authors: van Driel-Gesztelyi, L.; Culhane, J. L.
Bibcode: 2009odsm.book..351V
Altcode:
  We present an overview of how the principal physical properties of
  magnetic flux which emerges from the toroidal fields in the tachocline
  through the turbulent convection zone to the solar surface are linked
  to solar activity events, emphasizing the effects of magnetic field
  evolution and interaction with other magnetic structures on the
  latter. We compare the results of different approaches using various
  magnetic observables to evaluate the probability of flare and coronal
  mass ejection (CME) activity and forecast eruptive activity on the
  short term (i.e. days). Then, after a brief overview of the observed
  properties of CMEs and their theoretical models, we discuss the
  ejecta properties and describe some typical magnetic and composition
  characteristics of magnetic clouds (MCs) and interplanetary CMEs
  (ICMEs). We review some individual examples to clarify the link between
  eruptions from the Sun and the properties of the resulting ejecta. The
  importance of a synthetic approach to solar and interplanetary magnetic
  fields and activity is emphasized.

Title: Flux Rope Eruption From the Sun to the Earth: What do Reversals
    in the Azimuthal Magnetic Field Gradient Tell us About the Evolution
    of the Magnetic Structure?
Authors: Steed, K.; Owen, C. J.; Harra, L. K.; Green, L. M.; Dasso,
   S.; Walsh, A. P.; Démoulin, P.; van Driel-Gesztelyi, L.
Bibcode: 2008AGUFMSH23B1638S
Altcode:
  Using ACE in situ data we identify and describe an interplanetary
  magnetic cloud (MC) observed near Earth on 13 April 2006. We also use
  multi-instrument and multi-wavelength observations from SOHO, TRACE and
  ground-based solar observatories to determine the solar source of this
  magnetic cloud. A launch window for the MC between 9 and 11 April 2006
  was estimated from the propagation time of the ejecta observed near
  Earth. A number of large active regions were present on the Sun during
  this period, which were initially considered to be the most likely
  candidate source regions of the MC. However, it was determined that
  the solar source of the MC was a small, spotless active region observed
  in the Northern Hemisphere. Following an eruption from this region on
  11 April 2006, the ACE spacecraft detected, 59 h later, the passage of
  the MC, preceded by the arrival of a weak, forward fast shock. The link
  between the eruption in this active region and the interplanetary MC is
  supported by several pieces of evidence, including the location of the
  solar source near to the disk centre and to the east of the central
  meridian (in agreement with the spacecraft trajectory through the
  western leg of the magnetic cloud), the propagation time of the ejecta,
  the agreement between the amount of flux in the magnetic cloud and in
  the active region, and the agreement between the signs of helicity of
  the magnetic cloud and the active region (which differs from the sign
  of helicity of each of the other active regions on the Sun at this
  time). In addition, the active region is located on the boundary of
  a coronal hole, and a high speed solar wind stream originating from
  this region is observed near Earth shortly after the passage of the
  magnetic cloud. This event highlights the complexities associated
  with locating the solar source of an ICME observed near Earth, and
  serves to emphasise that it is the combination of a number of physical
  characteristics and signatures that is important for successfully
  tying together the Earth-end and the Sun-end of an event. Further
  investigation of this MC has revealed some sub-structure towards its
  centre, observed as a small scale reversal of the azimuthal magnetic
  field of the MC, similar to that reported by Dasso et al., 2007. We
  explore several possible explanations for this signature, including
  the occurrence of multiple flux ropes and/or warping of the magnetic
  cloud. We also consider whether magnetic reconnection plays a role in
  creating the geometry that would explain these observations.

Title: Preface
Authors: Klein, Karl-Ludwig; Pohjolainen, Silja; van Driel-Gesztelyi,
   Lidia
Bibcode: 2008SoPh..253....1K
Altcode: 2008SoPh..tmp..191K
  No abstract at ADS

Title: The Recovery of CME-Related Dimmings and the ICME's Enduring
    Magnetic Connection to the Sun
Authors: Attrill, G. D. R.; van Driel-Gesztelyi, L.; Démoulin, P.;
   Zhukov, A. N.; Steed, K.; Harra, L. K.; Mandrini, C. H.; Linker, J.
Bibcode: 2008SoPh..252..349A
Altcode: 2008SoPh..tmp..158A
  It is generally accepted that transient coronal holes (TCHs, dimmings)
  correspond to the magnetic footpoints of CMEs that remain rooted in
  the Sun as the CME expands out into the interplanetary space. However,
  the observation that the average intensity of the 12 May 1997 dimmings
  recover to their pre-eruption intensity in SOHO/EIT data within 48
  hours, whilst suprathermal unidirectional electron heat fluxes are
  observed at 1 AU in the related ICME more than 70 hours after the
  eruption, leads us to question why and how the dimmings disappear
  whilst the magnetic connectivity is maintained. We also examine two
  other CME-related dimming events: 13 May 2005 and 6 July 2006. We study
  the morphology of the dimmings and how they recover. We find that, far
  from exhibiting a uniform intensity, dimmings observed in SOHO/EIT data
  have a deep central core and a more shallow extended dimming area. The
  dimmings recover not only by shrinking of their outer boundaries but
  also by internal brightenings. We quantitatively demonstrate that the
  model developed by Fisk and Schwadron (Astrophys. J.560, 425, 2001)
  of interchange reconnections between "open" magnetic field and small
  coronal loops is a strong candidate for the mechanism facilitating the
  recovery of the dimmings. This process disperses the concentration of
  "open" magnetic field (forming the dimming) out into the surrounding
  quiet Sun, thus recovering the intensity of the dimmings whilst still
  maintaining the magnetic connectivity to the Sun.

Title: Why are CMEs large-scale coronal events: nature or nurture?
Authors: van Driel-Gesztelyi, L.; Attrill, G. D. R.; Démoulin, P.;
   Mandrini, C. H.; Harra, L. K.
Bibcode: 2008AnGeo..26.3077V
Altcode:
  The apparent contradiction between small-scale source regions of,
  and large-scale coronal response to, coronal mass ejections (CMEs)
  has been a long-standing puzzle. For some, CMEs are considered to
  be inherently large-scale events eruptions in which a number of flux
  systems participate in an unspecified manner, while others consider
  magnetic reconnection in special global topologies to be responsible
  for the large-scale response of the lower corona to CME events. Some
  of these ideas may indeed be correct in specific cases. However,
  what is the key element which makes CMEs large-scale? Observations
  show that the extent of the coronal disturbance matches the angular
  width of the CME an important clue, which does not feature strongly
  in any of the above suggestions. We review observational evidence
  for the large-scale nature of CME source regions and find them
  lacking. Then we compare different ideas regarding how CMEs evolve
  to become large-scale. The large-scale magnetic topology plays an
  important role in this process. There is amounting evidence, however,
  that the key process is magnetic reconnection between the CME and other
  magnetic structures. We outline a CME evolution model, which is able
  to account for all the key observational signatures of large-scale
  CMEs and presents a clear picture how large portions of the Sun become
  constituents of the CME. In this model reconnection is driven by the
  expansion of the CME core resulting from an over-pressure relative to
  the pressure in the CME's surroundings. This implies that the extent of
  the lower coronal signatures match the final angular width of the CME.

Title: Locating the solar source of 13 April 2006 magnetic cloud
Authors: Steed, K.; Owen, C. J.; Harra, L. K.; Green, L. M.; Dasso,
   S.; Walsh, A. P.; Démoulin, P.; van Driel-Gesztelyi, L.
Bibcode: 2008AnGeo..26.3159S
Altcode:
  Using Advanced Composition Explorer (ACE) in situ data we identify and
  describe an interplanetary magnetic cloud (MC) observed near Earth
  on 13 April 2006. We also use multi-instrument and multi-wavelength
  observations from the Solar and Heliospheric Observatory (SOHO), the
  Transition Region and Coronal Explorer (TRACE) and ground-based solar
  observatories to determine the solar source of this magnetic cloud. A
  launch window for the MC between 9 and 11 April 2006 was estimated from
  the propagation time of the ejecta observed near Earth. A number of
  large active regions (ARs) were present on the Sun during this period,
  which were initially considered to be the most likely candidate source
  regions of the MC. However, it was determined that the solar source
  of the MC was a small, spotless active region observed in the Northern
  Hemisphere. Following an eruption from this region on 11 April 2006, the
  ACE spacecraft detected, 59 h later, the passage of the MC, preceded by
  the arrival of a weak, forward fast shock. The link between the eruption
  in this active region and the interplanetary MC is supported by several
  pieces of evidence, including the location of the solar source near to
  the disk centre and to the east of the central meridian (in agreement
  with the spacecraft trajectory through the western leg of the magnetic
  cloud), the propagation time of the ejecta, the agreement between
  the amount of flux in the magnetic cloud and in the active region,
  and the agreement between the signs of helicity of the magnetic cloud
  and the active region (which differs from the sign of helicity of each
  of the other active regions on the Sun at this time). In addition,
  the active region is located on the boundary of a coronal hole, and a
  high speed solar wind stream originating from this region is observed
  near Earth shortly after the passage of the magnetic cloud.

Title: Multi-scale reconnections in a complex CME
Authors: van Driel-Gesztelyi, L.; Goff, C. P.; Démoulin, P.; Culhane,
   J. L.; Matthews, S. A.; Harra, L. K.; Mandrini, C. H.; Klein, K. -L.;
   Kurokawa, H.
Bibcode: 2008AdSpR..42..858V
Altcode:
  A series of three flares of GOES class M, M and C, and a CME were
  observed on 20 January 2004 occurring in close succession in NOAA
  10540. Types II, III, and N radio bursts were associated. We use
  the combined observations from TRACE, EIT, Hα images from Kwasan
  Observatory, MDI magnetograms, GOES, and radio observations from
  Culgoora and Wind/ WAVES to understand the complex development of this
  event. We reach three main conclusions. First, we link the first two
  impulsive flares to tether-cutting reconnections and the launch of
  the CME. This complex observation shows that impulsive quadrupolar
  flares can be eruptive. Second, we relate the last of the flares, an
  LDE, to the relaxation phase following forced reconnections between
  the erupting flux rope and neighbouring magnetic field lines, when
  reconnection reverses and restores some of the pre-eruption magnetic
  connectivities. Finally, we show that reconnection with the magnetic
  structure of a previous CME launched about 8 h earlier injects electrons
  into open field lines having a local dip and apex (located at about six
  solar radii height). This is observed as an N-burst at decametre radio
  wavelengths. The dipped shape of these field lines is due to large-scale
  magnetic reconnection between expanding magnetic loops and open field
  lines of a neighbouring streamer. This particular situation explains
  why this is the first N-burst ever observed at long radio wavelengths.

Title: Study of the Physical Properties of Coronal ``Waves'' and
    Associated Dimmings
Authors: Attrill, G. D. R.; Harra, L. K.; van Driel-Gesztelyi, L.;
   Williams, D.; Alexeev, I. V.
Bibcode: 2008ASPC..397..126A
Altcode:
  We present results from our study run by Hinode, designed to obtain
  information on the physical properties of the diffuse bright fronts
  known as ``EIT coronal waves'' and their associated dimmings. We
  analyse data obtained during a frustrated eruption event on 5th May
  2007. The event produces a bright front as well as deep and shallow
  dimmings. We show that the dimmings of this frustrated eruption
  show similar physical properties to those observed in textbook ``EIT
  coronal wave'' events. The Hinode/EIS data show that both the deep
  and shallow dimmings associated with this frustrated eruption show
  blue-shifted velocities. It is therefore consistent that, like the
  deep core dimmings, the widespread shallow dimmings observed with many
  textbook coronal ``wave'' events may also be due to plasma outflows.

Title: Long Duration Thermal Hard X-ray Sources Observed in Two
    Eruptive Flares
Authors: Bone, L. A.; Culhane, J. L.; van Driel-Gesztelyi, L.; Hara, H.
Bibcode: 2008ASPC..397..160B
Altcode:
  We present observations of two eruptive flares on 17 of December
  2006 (C1.9) and 19 of May 2007 (B9.7) which had good coverage with
  both Hinode and RHESSI. In these flares we see a long lived, gradual
  thermal hard X-ray source of low emission measure and, relative to
  the loops observed with GOES and XRT, high temperature. The lack of a
  non-thermal hard X-ray component and impulsive behaviour is inconsistent
  with electron beam driven chromospheric evaporation.

Title: Hinode EIS and XRT Observations of Hot Jets in Coronal Holes -
    Does the Plasma Escape?
Authors: Baker, D.; van Driel-Gesztelyi, L.; Kamio, S.; Culhane,
   J. L.; Harra, L. K.; Sun, J.; Young, P. R.; Matthews, S. A.
Bibcode: 2008ASPC..397...23B
Altcode:
  X-ray jets have been detected in the extreme ultraviolet (EUV) and
  soft X-ray observations of Hinode's EIS and XRT instruments. Both
  instruments were used to observe the jets in polar and on-disk coronal
  holes (CHs). Here, we present a multi-wavelength study of an X-ray
  jet and its associated bright point found in an equatorial CH on 19
  June 2007. Light curves (LCs) in 22 different emission lines were
  compared to that of Hinode/XRT. As we found in a previous study of
  two polar X-ray jets, this jet shows a post-jet increase in its EUV
  LCs. The post-jet enhancement appears cooler than the jet. We suggest
  this feature arises because the hot plasma of the jet, having failed to
  reach escape speeds, cools and falls back along the near vertical paths
  expected to be created by reconnection with open field lines of CHs. In
  addition to the increase in post-jet EUV intensity, we found tentative
  evidence of impact heating possibly caused by the fall-back of plasma.

Title: Twist, Writhe and Rotation of Magnetic Flux Ropes in Filament
    Eruptions and Coronal Mass Ejections
Authors: Török, T.; Berger, M. A.; Kliem, B.; Démoulin, P.; Linton,
   M.; van Driel-Gesztelyi, L.
Bibcode: 2008ESPM...12.3.54T
Altcode:
  We present the first quantitative analysis of the conversion of twist
  into writhe in the course of ideal MHD instabilities in erupting coronal
  magnetic flux ropes. For our analysis, we consider numerical simulations
  of two instabilities which have been suggested as trigger and initial
  driving mechanisms in filament eruptions and coronal mass ejections,
  namely the helical kink instability and the torus instability. We
  use two different coronal flux rope models as initial conditions
  in the simulations, namely the cylindrical Gold-Hoyle equilibrium
  and the toroidal Titov-Demoulin equilibrium. <P />For each model, we
  perform a series of simulations with different amounts of initial flux
  rope twist. In order to study both confined and ejective eruptions,
  we additionally use different initial potential fields overlying
  the flux rope in the simulations of the Titov-Demoulin model. <P
  />In all simulations, we measure the writhe of the flux rope and the
  corresponding rotation of its axis in vertical projection by making use
  of recently developed expressions which permit us to calculate writhe as
  a single integral in space. We discuss the implications of our results
  for filament eruptions, coronal mass ejections and magnetic clouds.

Title: Outflows at the Edges of Active Regions: Contribution to
    Solar Wind Formation?
Authors: Harra, L. K.; Sakao, T.; Mandrini, C. H.; Hara, H.; Imada,
   S.; Young, P. R.; van Driel-Gesztelyi, L.; Baker, D.
Bibcode: 2008ApJ...676L.147H
Altcode:
  The formation of the slow solar wind has been debated for many years. In
  this Letter we show evidence of persistent outflow at the edges of
  an active region as measured by the EUV Imaging Spectrometer on board
  Hinode. The Doppler velocity ranged between 20 and 50 km s<SUP>-1</SUP>
  and was consistent with a steady flow seen in the X-Ray Telescope. The
  latter showed steady, pulsing outflowing material and some transverse
  motions of the loops. We analyze the magnetic field around the active
  region and produce a coronal magnetic field model. We determine from
  the latter that the outflow speeds adjusted for line-of-sight effects
  can reach over 100 km s<SUP>-1</SUP>. We can interpret this outflow as
  expansion of loops that lie over the active region, which may either
  reconnect with neighboring large-scale loops or are likely to open to
  the interplanetary space. This material constitutes at least part of
  the slow solar wind.

Title: Erratum: "Outflows at the Edges of Active Regions: Contribution
    to Solar Wind Formation?" (ApJ, 676, L147 [2008])
Authors: Harra, L. K.; Sakao, T.; Mandrini, C. H.; Hara, H.; Imada,
   S.; Young, P. R.; van Driel-Gesztelyi, L.; Baker, D.
Bibcode: 2008ApJ...677L.159H
Altcode:
  No abstract at ADS

Title: CME-related dimmings as a signature of interplanetary magnetic
    cloud footpoints
Authors: Mandrini, Cristina H.; Soledad Nakwacki, Ms Maria; Attrill,
   Gemma; van Driel-Gesztelyi, Lidia; Dasso, Sergio; Demoulin, Pascal
Bibcode: 2008cosp...37.1900M
Altcode: 2008cosp.meet.1900M
  Coronal dimmings are often present on both sides of erupting magnetic
  configurations. It has been suggested that dimmings mark the location
  of the footpoints of ejected flux ropes and, thus, their magnetic
  flux can be used as a proxy for the flux involved in the ejection. If
  so, this quantity can be compared to the flux in the associated
  interplanetary magnetic cloud to find clues about the origin of the
  ejected flux rope. In the context of this physical interpretation,
  we analyse several events, flares and coronal mass ejections (CMEs),
  for which we can find their interplanetary counterpart. We combine
  SOHO/Extreme Ultraviolet Imaging Telescope data and Michelson Doppler
  Imager magnetic maps to identify and measure the flux in the dimming
  regions. We model the associated clouds and compute their magnetic
  flux using in situ observations. We find that the magnetic fluxes of
  the dimmings and magnetic clouds are compatible in some cases; though
  this is not the case for large-scale events and eruptions that occur
  in regions that are not isolated from other flux concentrations. We
  conclude that the interpretation of dimmings requires a deeper analysis
  of the global magnetic field configuration, since at least a fraction
  of the dimmed regions could be formed by reconnection between the
  erupting field and the surrounding magnetic structures.

Title: Interaction between emerging flux and coronal hole -
    observations and simulations
Authors: van Driel-Gesztelyi, Lidia; Baker, Deborah; Murray, Michelle;
   Demoulin, Pascal; Attrill, Gemma; Matthews, Sarah A.; Mandrini,
   Cristina H.; Toeroek, Tibor
Bibcode: 2008cosp...37.3288V
Altcode: 2008cosp.meet.3288V
  Flux emergence in the vicinity of or inside a coronal hole (CH) is
  expected to induce magnetic reconnection between the closed emerging
  and open CH magnetic field lines, resulting in an evolution of the
  CH as formerly closed field lines become topologically open, while at
  the same time, open field lines close down. Through two case studies
  we show observational signatures of this (interchange) reconnection
  process and discuss its implications. First, using SOHO EIT and MDI
  data, we study a small active region (AR10869) emerging in the close
  vicinity of a low-latitude coronal hole in April 2006. The interfacing
  magnetic polarities between the AR and the CH were opposite, favourable
  for magnetic reconnection. We indeed observe the coupled formation of
  bright closed loops between the CH and the AR and coronal dimming on
  the far side of the AR, which we interpret as evidence of interchange
  reconnection. This process effectively modifies the CH boundary
  (making it retreat), while simultaneously displacing open field lines
  to the far side of the AR. In order to study this process in detail,
  we perform 2.5D MHD simulations, which qualitatively reproduce important
  aspects of the observations. We expect to find upflows of plasma at the
  location where previously closed field lines are opening up as well as
  on the reconnecting side, but since we had no spectroscopic data for
  this event, we can not verify this. Therefore we analyze Hinode/EIS
  line-of-sight velocity maps of another low-latitude CH with a small AR
  in its midst observed on 18 Oct. 2007. We find that while closed loops
  of the bipole are dominated by downflows in the Fe XII, Fe XIII and
  Fe XV lines, the strongest coronal plasma upflows are indeed located
  around and particularly at the "far side" of the bipolar AR, i.e. having
  the same polarity as the dominant polarity of the CH. The emerging
  biplole and the series of interchange reconnections it induces create
  a significant additional plasma upflow in the CH, thus we identify
  this outflow must contribute to the acceleration of the fast solar wind.

Title: Editorial Appreciation
Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia
Bibcode: 2008SoPh..247....1L
Altcode: 2008SoPh..tmp....5L
  No abstract at ADS

Title: Breaking or maintaining magnetic connection of CMEs to the
    Sun - solar vs. interplanetary signatures tested
Authors: van Driel-Gesztelyi, Lidia; Attrill, Gemma; Demoulin, Pascal;
   Mandrini, Cristina H.; Harra, Louise K.
Bibcode: 2008cosp...37.3287V
Altcode: 2008cosp.meet.3287V
  Though their relationship is complex, the presence of suprathermal
  unior bi-directional electron streams in ICMEs are treated as
  signatures of magnetic field lines with one or both ends being
  connected to the Sun, respectively, while their absence is
  interpreted as disconnection. However, do we have any reliable
  signature in the solar corona distinguishing between maintained
  connection and disconnection? We test two solar signatures against
  interplanetary suprathermal electron signatures in order to establish
  their relevance. We test the hypothesis that the recovery of Transient
  Coronal Holes (TCHs, dimming regions corresponding to the footpoints of
  CMEs) is a signature of magnetic disconnection from the Sun. Through
  three case studies we quantitatively demonstrate that magnetic
  reconnections between field lines of the expanded CME magnetic field
  and small coronal loops can act to disperse the concentration of
  CME footpoints (forming the dimming region) out into the surrounding
  quiet Sun, thus recovering the intensity of the dimming region whilst
  still maintaining the magnetic connectivity to the Sun. This analysis
  provides evidence that the recovery of coronal dimming regions can,
  in fact, be simply reconciled with maintained magnetic connectivity
  to the Sun. However, disconnection can occur when open field lines are
  involved in reconnection with CMEs. We show through two well-observed
  case studies that magnetic reconnection between the expanding CME and
  a nearby coronal hole (CH) is indeed able to disconnect one leg of
  the expanding CME magnetic structure, as indicated by uni-directional
  electron streams in their respective ICMEs. Therefore we suggest that
  brightenings (signatures of reconnection) appearing along a coronal
  hole boundary in the wake of a CME can be treated as a signature of
  (at least partial) disconnection of one of the CME legs from the Sun.

Title: Flare and Erupting Filament of 19th May, 2007 - Sources of
    a Magnetic Cloud Observed by Stereo
Authors: Culhane, J. Leonard; Bone, Laura; Hara, Hirohisa; Farrugia,
   Charles; Galvin, Antoinette; van Driel-Gesztelyi, Lidia; Popecki,
   Mark; Luhmann, Janet G.; Veronig, Astrid
Bibcode: 2008cosp...37..609C
Altcode: 2008cosp.meet..609C
  A GOES Class B9.5 flare was observed on the Sun starting 19-May-2007
  at 12:51 UT. Data obtained by the Hinode, TRACE, RHESSI, STEREO and
  SOHO spacecraft will be discussed. The evolution and eventual eruption
  of a related Halpha filament were monitored by patrol observations at
  Kanzelhoehe. These observations and associated detection of EUV-emitting
  filament material will also be presented. The flare energetics and
  the possible role of the flare in the filament eruption will be
  examined. Finally the relationship of the magnetic configuration
  of the solar eruption along with the temperature and composition of
  erupting material will be assessed in relation to the properties of
  a magnetic cloud later detected by STEREO in-situ instruments near
  Earth on 22-May-2007.

Title: What kinking filament eruptions tell us about the physical
    nature of transient coronal sigmoids ?
Authors: van Driel-Gesztelyi, Lidia; Green, Lucie M.; Kliem, Bernhard;
   Toeroek, Tibor; Attrill, Gemma
Bibcode: 2008cosp...37.3289V
Altcode: 2008cosp.meet.3289V
  Soft X-ray images of the Sun have shown that some active regions contain
  loops, or collections of loops, which appear forward or reverse 'S'
  in shape. These features have been termed sigmoids. These structures
  are of interest because their presence in an active region has been
  linked to eruptive activity and the sense of sigmoid orientation is
  taken to indicate the sense of shear and twist (or helicity) in the
  magnetic field. Differing models have been put forward in order to
  explain the physical nature of sigmoids and the role they play in an
  eruption. We use multiwavelength observations (Yohkoh/SXT, TRACE,
  SOHO/EIT and MDI, H-alpha) to investigate how transient sigmoids
  are formed. We also investigate filament eruptions from these active
  regions, which show a clear sign of rotation of their apex. We find
  that for positive (negative) helicity the filament apex rotates
  clockwise (counterclockwise), consistent with the flux rope taking on
  a reverse (forward) S shape, which is opposite to that observed for
  the sigmoid. These observations put constraints on sigmoid models,
  excluding some of them. We conclude that transient sigmoids are
  associated with the formation of current sheets and heating along
  field lines under a dynamic flux rope.

Title: Transient Coronal Sigmoids and Rotating Erupting Flux Ropes
Authors: Green, L. M.; Kliem, B.; Török, T.; van Driel-Gesztelyi,
   L.; Attrill, G. D. R.
Bibcode: 2007SoPh..246..365G
Altcode:
  To determine the relationship between transient coronal (soft X-ray
  or EUV) sigmoids and erupting flux ropes, we analyse four events
  in which a transient sigmoid could be associated with a filament
  whose apex rotates upon eruption and two further events in which
  the two phenomena were spatially but not temporally coincident. We
  find the helicity sign of the erupting field and the direction of
  filament rotation to be consistent with the conversion of twist
  into writhe under the ideal MHD constraint of helicity conservation,
  thus supporting our assumption of flux rope topology for the rising
  filament. For positive (negative) helicity the filament apex rotates
  clockwise (counterclockwise), consistent with the flux rope taking on
  a reverse (forward) S shape, which is opposite to that observed for
  the sigmoid. This result is incompatible with two models for sigmoid
  formation: one identifying sigmoids with upward arching kink-unstable
  flux ropes and one identifying sigmoids with a current layer between
  two oppositely sheared arcades. We find instead that the observations
  agree well with the model by Titov and Démoulin (Astron. Astrophys.351,
  707, 1999), which identifies transient sigmoids with steepened current
  layers below rising flux ropes.

Title: Hinode EUV Study of Jets in the Sun's South Polar Corona
Authors: Culhane, Len; Harra, Louise K.; Baker, Deborah; van
   Driel-Gesztelyi, Lidia; Sun, Jian; Doschek, George A.; Brooks, David
   H.; Lundquist, Loraine L.; Kamio, Suguru; Young, Peter R.; Hansteen,
   Viggo H.
Bibcode: 2007PASJ...59S.751C
Altcode:
  A number of coronal bright points and associated plasma jet features
  were seen in an observation of the South polar coronal hole during
  2007 January. The 40" wide slot was used at the focus of the Hinode
  EUV Imaging Spectrometer to provide spectral images for two of these
  events. Light curves are plotted for a number of emission lines that
  include He II 256Å (0.079MK) and cover the temperature interval from
  0.4MK to 5.0MK. Jet speed measurements indicate values less than the
  escape velocity. The light curves show a post-jet enhancement in a
  number of the cooler coronal lines indicating that after a few minutes
  cooling, the plasma fell back to its original acceleration site. This
  behavior has not been previously observed by e.g., the Yohkoh Soft
  X-ray Telescope due to the comparatively high temperature cut-off
  in its response. The observations are consistent with the existing
  models that involve magnetic reconnection between emerging flux and the
  ambient open field lines in the polar coronal hole. However we do not
  have sufficient coverage of lines from lower temperature ion species
  to register the Hα-emitting surge material that is associated with
  some of these models.

Title: Optical flares from the faint mid-dM star 2MASS
    J00453912+4140395
Authors: Kovári, Zs.; Vilardell, F.; Ribas, I.; Vida, K.; van
   Driel-Gesztelyi, L.; Jordi, C.; Oláh, K.
Bibcode: 2007AN....328..904K
Altcode: 2007arXiv0711.0742K
  We present B and V light curves of a large stellar flare obtained
  with the Wide Field Camera at the Isaac Newton 2.5-m telescope (La
  Palma). The source object is a faint (m_V=21.38) foreground star in
  the field of the Andromeda galaxy, with its most probable spectral
  type being dM4. We provide an estimate of the total flare energy in
  the optical range and find it to be of the order of 10<SUP>35</SUP>
  erg. The cooling phase of the large flare shows three additional
  weak flare-like events, which we interpret as results of a triggering
  mechanism also observed on the Sun during large coronal mass ejections.

Title: Editors' note
Authors: Forgács-Dajka, E.; Ballai, I.; van Driel-Gesztelyi, L.
Bibcode: 2007AN....328..725F
Altcode:
  No abstract at ADS

Title: Evidence for interchange reconnection between a coronal hole
    and an adjacent emerging flux region
Authors: Baker, D.; van Driel-Gesztelyi, L.; Attrill, G. D. R.
Bibcode: 2007AN....328..773B
Altcode:
  Coronal holes are regions of dominantly monopolar magnetic field on the
  Sun where the field is considered to be `open' towards interplanetary
  space. Magnetic bipoles emerging in proximity to a coronal hole
  boundary naturally interact with this surrounding "open" magnetic
  field. In the case of oppositely aligned polarities between the active
  region and the coronal hole, we expect interchange reconnection to
  take place, driven by the coronal expansion of the emerging bipole as
  well as occasional eruptive events. Using SOHO/EIT and SOHO/MDI data,
  we present observational evidence of such interchange reconnection
  by studying AR 10869 which emerged close to a coronal hole. We find
  closed loops forming between the active region and the coronal hole
  leading to the retreat of the hole. At the same time, on the far side
  of the active region, we see dimming of the corona which we interpret
  as a signature of field line `opening' there, as a consequence of a
  topological displacement of the `open' field lines of the coronal hole.

Title: Coronal ``wave'': A signature of the mechanism making CMEs
    large-scale in the low corona?
Authors: Attrill, G. D. R.; Harra, L. K.; van Driel-Gesztelyi, L.;
   Démoulin, P.; Wülser, J. -P.
Bibcode: 2007AN....328..760A
Altcode:
  We analyse one of the first coronal waves observed by STEREO/EUVI
  associated with a source region just behind the limb, NOAA 10940. We
  apply the coronal ``wave'' model proposed by Attrill et al. (2007) to
  explain the evolution of the observed bright fronts, thereby arguing
  that the bright fronts and dimmings are due to magnetic reconnections
  between the expanding CME core and surrounding magnetic structures. We
  offer a discussion showing that this model provides a mechanism via
  which CMEs, expanding from a small source region can naturally become
  large-scale in the low corona.

Title: How Does Large Flaring Activity from the Same Active Region
    Produce Oppositely Directed Magnetic Clouds?
Authors: Harra, Louise K.; Crooker, Nancy U.; Mandrini, Cristina H.;
   van Driel-Gesztelyi, Lidia; Dasso, Sergio; Wang, Jingxiu; Elliott,
   Heather; Attrill, Gemma; Jackson, Bernard V.; Bisi, Mario M.
Bibcode: 2007SoPh..244...95H
Altcode:
  We describe the interplanetary coronal mass ejections (ICMEs) that
  occurred as a result of a series of solar flares and eruptions from
  4 to 8 November 2004. Two ICMEs/magnetic clouds occurring from these
  events had opposite magnetic orientations. This was despite the fact
  that the major flares related to these events occurred within the same
  active region that maintained the same magnetic configuration. The solar
  events include a wide array of activities: flares, trans-equatorial
  coronal loop disappearance and reformation, trans-equatorial filament
  eruption, and coronal hole interaction. The first major ICME/magnetic
  cloud was predominantly related to the active region 10696 eruption. The
  second major ICME/magnetic cloud was found to be consistent with the
  magnetic orientation of an erupting trans-equatorial filament or else
  a rotation of 160° of a flux rope in the active region. We discuss
  these possibilities and emphasize the importance of understanding the
  magnetic evolution of the solar source region before we can begin to
  predict geoeffective events with any accuracy.

Title: CME Propagation Characteristics from Radio Observations
Authors: Pohjolainen, S.; van Driel-Gesztelyi, L.; Culhane, J. L.;
   Manoharan, P. K.; Elliott, H. A.
Bibcode: 2007SoPh..244..167P
Altcode: 2007arXiv0711.3168P
  We explore the relationship among three coronal mass ejections (CMEs),
  observed on 28 October 2003, 7 November 2004, and 20 January 2005,
  the type II burst-associated shock waves in the corona and solar wind,
  as well as the arrival of their related shock waves and magnetic clouds
  at 1 AU. Using six different coronal/interplanetary density models,
  we calculate the speeds of shocks from the frequency drifts observed
  in metric and decametric radio wave data. We compare these speeds
  with the velocity of the CMEs as observed in the plane-of-the-sky
  white-light observations and calculated with a cone model for the 7
  November 2004 event. We then follow the propagation of the ejecta using
  Interplanetary Scintillation measurements, which were available for the
  7 November 2004 and 20 January 2005 events. Finally, we calculate the
  travel time of the interplanetary shocks between the Sun and Earth and
  discuss the velocities obtained from the different data. This study
  highlights the difficulties in making velocity estimates that cover
  the full CME propagation time.

Title: Are CME-Related Dimmings Always a Simple Signature of
    Interplanetary Magnetic Cloud Footpoints?
Authors: Mandrini, C. H.; Nakwacki, M. S.; Attrill, G.; van
   Driel-Gesztelyi, L.; Démoulin, P.; Dasso, S.; Elliott, H.
Bibcode: 2007SoPh..244...25M
Altcode:
  Coronal dimmings are often present on both sides of erupting magnetic
  configurations. It has been suggested that dimmings mark the location
  of the footpoints of ejected flux ropes and, thus, their magnetic
  flux can be used as a proxy for the flux involved in the ejection. If
  so, this quantity can be compared to the flux in the associated
  interplanetary magnetic cloud to find clues about the origin of the
  ejected flux rope. In the context of this physical interpretation,
  we analyze the event, flare, and coronal mass ejection (CME) that
  occurred in active region 10486 on 28 October 2003. The CME on this
  day is associated with large-scale dimmings, located on either side of
  the main flaring region. We combine SOHO/Extreme Ultraviolet Imaging
  Telescope data and Michelson Doppler Imager magnetic maps to identify
  and measure the flux in the dimming regions. We model the associated
  cloud and compute its magnetic flux using in situ observations from
  the Magnetometer Instrument and the Solar Wind Electron Proton Alpha
  Monitor aboard the Advance Composition Explorer. We find that the
  magnetic fluxes of the dimmings and magnetic cloud are incompatible, in
  contrast to what has been found in previous studies. We conclude that,
  in certain cases, especially in large-scale events and eruptions that
  occur in regions that are not isolated from other flux concentrations,
  the interpretation of dimmings requires a deeper analysis of the global
  magnetic configuration, since at least a fraction of the dimmed regions
  is formed by reconnection between the erupting field and the surrounding
  magnetic structures.

Title: Hinode Euv Study Of Jets In The Sun’s South Polar Corona
Authors: Culhane, J. L.; Brooks, D. H.; Doschek, G. A.; Harra, L. K.;
   van Driel-Gesztelyi, L.; Baker, D.; Lundquist, L. L.; Hansteen, V. H.;
   Kamio, S.
Bibcode: 2007AAS...210.7201C
Altcode: 2007BAAS...39..178C
  Using the Hinode EUV Imaging Spectrometer coronal jets were observed
  on 20-JAN-2007 over a range of emission lines and corresponding plasma
  temperatures using the 40 arc sec wide slot images. In this preliminary
  analysis, jet plasma temperature and emissivity have been estimated
  while, based on assumptions about the jet morphology, electron density
  estimates are given and jet velocity measured. The evolution of the
  jets will be followed in a number of different EUV emission lines and
  jet energy input as a function of time will be assessed with reference
  to the magnetic field topologies involved.

Title: Coronal "wave": Magnetic Footprint Of A Cme?
Authors: Attrill, Gemma; Harra, L. K.; van Driel-Gesztelyi, L.;
   Demoulin, P.; Wuelser, J.
Bibcode: 2007AAS...210.2921A
Altcode: 2007BAAS...39..141A
  We propose a new mechanism for the generation of "EUV coronal
  waves". This work is based on new analysis of data from SOHO/EIT,
  SOHO/MDI &amp; STEREO/EUVI. Although first observed in 1997, the
  interpretation of coronal waves as flare-induced or CME-driven remains
  a debated topic. We investigate the properties of two "classical"
  SOHO/EIT coronal waves in detail. The source regions of the associated
  CMEs possess opposite helicities &amp; the coronal waves display
  rotations in opposite senses. We observe deep dimmings near the
  flare site &amp; also widespread diffuse dimming, accompanying the
  expansion of the EIT wave. We report a new property of these EIT
  waves, namely, that they display dual brightenings: persistent ones
  at the outermost edge of the core dimming regions &amp; simultaneously
  diffuse brightenings constituting the leading edge of the coronal wave,
  surrounding the expanding diffuse dimmings. We show that such behaviour
  is consistent with a diffuse EIT wave being the magnetic footprint of
  a CME. We propose a new mechanism where driven magnetic reconnections
  between the skirt of the expanding CME &amp; quiet-Sun magnetic loops
  generate the observed bright diffuse front. The dual brightenings &amp;
  widespread diffuse dimming are identified as innate characteristics
  of this process. In addition we present some of the first analysis
  of a STEREO/EUVI limb coronal wave. We show how the evolution of the
  diffuse bright front &amp; dimmings can be understood in terms of the
  model described above. We show that an apparently stationary part of
  the bright front can be understood in terms of magnetic interchange
  reconnections between the expanding CME &amp; the "open" magnetic
  field of a low-latitude coronal hole. We use both the SOHO/EIT &amp;
  STEREO/EUVI events to demonstrate that through successive reconnections,
  this new model provides a natural mechanism via which CMEs can become
  large-scale in the lower corona.

Title: Commission 10: Solar Activity
Authors: Melrose, Donald B.; Klimchuk, James A.; Benz, A. O.; Craig,
   I. J. D.; Gopalswamy, N.; Harrison, R. A.; Kozlovsky, B. Z.; Poletto,
   G.; Schrijver, K. J.; van Driel-Gesztelyi, L.; Wang, J. -X.
Bibcode: 2007IAUTA..26...75M
Altcode:
  Commission 10 aims at the study of various forms of solar activity,
  including networks, plages, pores, spots, fibrils, surges, jets,
  filaments/prominences, coronal loops, flares, coronal mass ejections
  (CMEs), solar cycle, microflares, nanoflares, coronal heating etc.,
  which are all manifestation of the interplay of magnetic fields and
  solar plasma. Increasingly important is the study of solar activities
  as sources of various disturbances in the interplanetary space
  and near-Earth "space weather".Over the past three years a major
  component of research on the active Sun has involved data from the
  RHESSI spacecraft. This review starts with an update on current and
  planned solar observations from spacecraft. The discussion of solar
  flares gives emphasis to new results from RHESSI, along with updates on
  other aspects of flares. Recent progress on two theoretical concepts,
  magnetic reconnection and magnetic helicity is then summarized, followed
  by discussions of coronal loops and heating, the magnetic carpet
  and filaments. The final topic discussed is coronal mass ejections
  and space weather.The discussions on each topic is relatively brief,
  and intended as an outline to put the extensive list of references
  in context.The review was prepared jointly by the members of the
  Organizing Committee, and the names of the primary contributors to
  the various sections are indicated in parentheses.

Title: A Multiple Flare Scenario where the Classic Long-Duration
    Flare Was Not the Source of a CME
Authors: Goff, C. P.; van Driel-Gesztelyi, L.; Démoulin, P.; Culhane,
   J. L.; Matthews, S. A.; Harra, L. K.; Mandrini, C. H.; Klein, K. L.;
   Kurokawa, H.
Bibcode: 2007SoPh..240..283G
Altcode:
  A series of flares (GOES class M, M and C) and a CME were observed in
  close succession on 20 January 2004 in NOAA 10540. Radio observations,
  which took the form of types II, III and N bursts, were associated with
  these events. We use the combined observations from TRACE, EIT, Hα
  images from Kwasan, MDI magnetograms and GOES to understand the complex
  development of this event. Contrary to a standard interpretation,
  we conclude that the first two impulsive flares are part of the CME
  launch process while the following long-duration event flare represents
  simply the recovery phase. Observations show that the flare ribbons
  not only separate but also shift along the magnetic inversion line
  so that magnetic reconnection progresses stepwise to neighboring flux
  tubes. We conclude that "tether cutting" reconnection in the sheared
  arcade progressively transforms it to a twisted flux tube, which
  becomes unstable, leading to a CME. We interpret the third flare,
  a long-duration event, as a combination of the classical two-ribbon
  flare with the relaxation process following forced reconnection between
  the expanding CME structure and neighboring magnetic fields.

Title: Decametric N Burst: A Consequence of the Interaction of Two
    Coronal Mass Ejections
Authors: Démoulin, P.; Klein, K. -L.; Goff, C. P.; van
   Driel-Gesztelyi, L.; Culhane, J. L.; Mandrini, C. H.; Matthews, S. A.;
   Harra, L. K.
Bibcode: 2007SoPh..240..301D
Altcode:
  Radio emissions of electron beams in the solar corona and interplanetary
  space are tracers of the underlying magnetic configuration and of
  its evolution. We analyse radio observations from the Culgoora and
  WIND/WAVES spectrographs, in combination with SOHO/LASCO and SOHO/MDI
  data, to understand the origin of a type N burst originating from NOAA
  AR 10540 on January 20, 2004, and its relationship with type II and
  type III emissions. All bursts are related to the flares and the CME
  analysed in a previous paper (Goff et al., 2007). A very unusual feature
  of this event was a decametric type N burst, where a type III-like
  burst, drifting towards low frequencies (negative drift), changes drift
  first to positive, then again to negative. At metre wavelengths, i.e.,
  heliocentric distances ≲1.5R<SUB>⊙</SUB>, these bursts are ascribed
  to electron beams bouncing in a closed loop. Neither U nor N bursts are
  expected at decametric wavelengths because closed quasi-static loops
  are not thought to extend to distances ≫1.5R<SUB>⊙</SUB>. We take
  the opportunity of the good multi-instrument coverage of this event to
  analyse the origin of type N bursts in the high corona. Reconnection
  of the expanding ejecta with the magnetic structure of a previous CME,
  launched about 8 hours earlier, injects electrons in the same manner as
  with type III bursts but into open field lines having a local dip and
  apex. The latter shape was created by magnetic reconnection between
  the expanding CME and neighbouring (open) streamer field lines. This
  particular flux tube shape in the high corona, between 5R<SUB>⊙</SUB>
  and 10R<SUB>⊙</SUB>, explains the observed type N burst. Since the
  required magnetic configuration is only a transient phenomenon formed
  by reconnection, severe timing and topological constraints are present
  to form the observed decametric N burst. They are therefore expected
  to be rare features.

Title: Coronal ``Wave'': Magnetic Footprint of a Coronal Mass
    Ejection?
Authors: Attrill, Gemma D. R.; Harra, Louise K.; van Driel-Gesztelyi,
   Lidia; Démoulin, Pascal
Bibcode: 2007ApJ...656L.101A
Altcode:
  We investigate the properties of two ``classical'' EUV Imaging Telescope
  (EIT) coronal waves. The two source regions of the associated coronal
  mass ejections (CMEs) possess opposite helicities, and the coronal waves
  display rotations in opposite senses. We observe deep core dimmings
  near the flare site and also widespread diffuse dimming, accompanying
  the expansion of the EIT wave. We also report a new property of these
  EIT waves, namely, that they display dual brightenings: persistent ones
  at the outermost edge of the core dimming regions and simultaneously
  diffuse brightenings constituting the leading edge of the coronal wave,
  surrounding the expanding diffuse dimmings. We show that such behavior
  is consistent with a diffuse EIT wave being the magnetic footprint of
  a CME. We propose a new mechanism where driven magnetic reconnections
  between the skirt of the expanding CME magnetic field and quiet-Sun
  magnetic loops generate the observed bright diffuse front. The dual
  brightenings and the widespread diffuse dimming are identified as
  innate characteristics of this process.

Title: From The Photosphere to the Interplanetary Medium: The Magnetic
    Helicity Sign from Observations
Authors: Luoni, M. L.; Mandrini, C. H.; Dasso, S.; Démoulin, P.;
   Van Driel-Gesztelyi, L.
Bibcode: 2007BAAA...50...43L
Altcode:
  The helicity sign of the solar magnetic field exhibits a hemispheric
  preference. On a certain statistical base, it is negative (positive)
  in the northern (southern) hemisphere. In this work we study a set of
  active regions, observed from 1997 to 2001, for which we can determine
  the magnetic helicity sign from the evolution of their polarities during
  flux emergence. We confirm this sign analyzing the coronal field of
  the studied regions. Then, we combine this analysis with ``in situ''
  observations of the magnetic clouds associated with the coronal mass
  ejections that occurred in those regions. Finally, we find that the
  helicity sign predicted by the distribution of the photospheric flux
  agrees with the one observed at coronal and interplanetary level.

Title: Study of CME transit speeds for the event of 07-NOV-2004
Authors: Culhane, J. L.; Pohjolainen, S.; van Driel-Gesztelyi, L.;
   Manoharan, P. K.; Elliott, H. A.
Bibcode: 2007AdSpR..40.1807C
Altcode:
  Several methods for CME speed estimation are discussed. These include
  velocity derivation based on the frequency drifts observed in metric
  and decametric radio wave data using a range of coronal density
  models. Coronagraph height-time plots allow measurement of plane-of-sky
  and expansion speeds. These in turn can enable propagation speeds to
  be derived from a range of empirical relations. Simple geometric e.g.,
  cone, models can provide propagation velocity estimates for suitable
  halo or partial halo events. Interplanetary scintillation observations
  allow speed estimates at large distances from the Sun detecting in
  particular the deceleration of the faster CMEs. Related interplanetary
  shocks and the arrival times and speeds of the associated magnetic
  clouds at Earth can also be considered. We discuss the application of
  some of these methods to the transit to Earth of a complex CME that
  originated earlier than 16:54 U.T. on 07-NOV-2004. The difficulties
  in making velocity estimates from radio observations, particularly
  under disturbed coronal conditions, are highlighted.

Title: Using the Evolution of Coronal Dimming Regions to Probe the
    Global Magnetic Field Topology
Authors: Attrill, G.; Nakwacki, M. S.; Harra, L. K.; Van
   Driel-Gesztelyi, L.; Mandrini, C. H.; Dasso, S.; Wang, J.
Bibcode: 2006SoPh..238..117A
Altcode: 2006SoPh..tmp...31A
  We demonstrate that study of the evolving magnetic nature of coronal
  dimming regions can be used to probe the large-scale magnetic structure
  involved in the eruption of a coronal mass ejection (CME). We analyse
  the intensity evolution of coronal dimming regions using 195 Å data
  from the Extreme ultraviolet Imaging Telescope (EIT) on board the Solar
  and Heliospheric Observatory (SOHO). We measure the magnetic flux, using
  data from the SOHO/Michelson Doppler Imager (MDI), in the regions that
  seem most likely to be related to plasma removal. Then, we compare these
  magnetic flux measurements to the flux in the associated magnetic cloud
  (MC). Here, we present our analysis of the well-studied event on 12
  May 1997 that took place just after solar minimum in a simple magnetic
  configuration. We present a synthesis of results already published and
  propose that driven "interchange reconnection" between the expanding
  CME structure with ``open'' field lines of the northern coronal hole
  region led to the asymmetric temporal and spatial evolution of the
  two main dimming regions, associated with this event. As a result of
  this reconnection process, we find the southern-most dimming region
  to be the principal foot-point of the MC. The magnetic flux from this
  dimming region and that of the MC are found to be in close agreement
  within the same order of magnitude, 10<SUP>21</SUP> Mx.

Title: Build-up of a CME and its Interaction with Large-Scale
    Magnetic Structures
Authors: van Driel-Gesztelyi, L.; Goff, C. P.; Demoulin, P.; Culhane,
   J. L.; Klein, K. L.; Mandrini, C. H.; Matthews, S. A.; Harra, K. L.;
   Kurokawa, H.
Bibcode: 2006IAUJD...3E..86V
Altcode:
  Introduction: A series of flares (GOES class M, M and C) and a
  CME were observed on 20-JAN-2004 occurring in close succession in
  NOAA 10540. Types II, III and a N radio bursts were associated. We
  investigate the link between the flares (two impulsive flares followed
  by an LDE) and the CME as well as the origin of the rare decametric
  N-burst. Methods: We use the combined observations from TRACE, SOHO/EIT,
  H-alpha images from Kwasan Observatory, SOHO/MDI magnetograms, GOES
  and radio observations from Culgoora and Wind/WAVES as well as magnetic
  modelling to understand the complex development of this event. Results:
  We link the first two impulsive flares to tether-cutting reconnections
  and the launch of the CME, while the last of the flares, an LDE,
  to the relaxation phase following forced reconnections between the
  erupting flux rope and neighbouring magnetic field lines. We show
  that reconnection with the magnetic structure of a previous CME,
  launched about 8 hours earlier, injects electrons into open field
  lines having a local dip and apex of about 6 solar radii height. The
  dipped shape of these field lines was due to large-scale magnetic
  reconnection between expanding magnetic loops and open field lines of a
  neighbouring streamer. This particular situation explains the observed
  decametric N burst. Discussion: This complex observation shows that
  impulsive quadrupolar flares can be eruptive, while an LDE may remain
  a confined event. We find that reconnection forced by the expanding CME
  structure is followed by a relaxation phase, when reconnection reverses
  and restores some of the pre-eruption magnetic connectivities. The
  observed decametric N-burst was caused by the interaction of two CMEs
  and reconnection of their expanding magnetic field with neighbouring
  streamer field lines - a very particular interplay, which explains
  why N-bursts are so rare.

Title: Magnetic Fields and Large-Scale SXR and EUV Coronal Structures
Authors: van Driel-Gesztelyi, Lidia
Bibcode: 2006IAUS..233..205V
Altcode:
  An overview is presented of large-scale coronal structures as observed
  in soft X-rays (SXR) and extreme ultraviolet (EUV) wavelengths in
  the context of their magnetic properties. These structures include
  large-scale interconnecting and trans-equatorial loops, coronal
  streamers, coronal holes, filaments and filament channels. Since the
  general appearance of the corona and its structures change with evolving
  underlying fields, evolutionary trends and solar cycle dependence of
  these coronal structures are discussed as well.

Title: Editorial Appreciation
Authors: Engvold, Oddbjørn; Harvey, Jack; Leibacher, John; Sakurai,
   Takashi; Švestka, Zdeněk; van Driel-Gesztelyi, Lidia; Solar Physics
   editors
Bibcode: 2006SoPh..233....1E
Altcode:
  No abstract at ADS

Title: Combined analysis of the 15-16 May, 1997, magnetic cloud and
    of its solar source region
Authors: Nakwacki, M. S.; Atrill, G.; Dasso, S.; Mandrini, C. H.;
   van Driel-Gesztelyi, L.; Harra, L.; Wang, J.
Bibcode: 2006BAAA...49...46N
Altcode:
  In this work we analise the structure of the magnetic cloud (MC)
  observed by Wind between 15-16 May 1997, and the related solar
  event, a long duration C1.3 flare which ocurred on 12 May 1997. This
  event presented two dark regions in EUV (dimmings) with asymmetric
  evolution. The magnetic structure of the MC was modeled using three
  cylindrical helicoidal models, considering the asymmetry between its
  front and its final part. We calculate the magnetic flux in the dimmings
  and their evolution, and the flux through the surface perpendicular to
  the cloud axis and to the azimuthal direction. Finally, we compare the
  total flux of both, MC and dimmings, and propose a topological model
  for the solar event. FULL TEXT IN SPANISH

Title: A combined analysis of the magnetic cloud on 15-16 May 1997
    and its solar source region
Authors: Nakwacki, M. S.; Attrill, G.; Dasso, S.; Mandrini, C. H.;
   van Driel-Gesztelyi, L.; Harra, L. K.; Wang, J.
Bibcode: 2006cosp...36.2479N
Altcode: 2006cosp.meet.2479N
  Coronal Mass Ejections CMEs are the most important short-lived agents
  that transport magnetic flux from the Sun to the interplanetary medium
  Thus detailed studies of the solar sources of CMEs and the associated
  magnetic clouds MCs are an important key to understand and constrain
  solar and interplanetary models We analyze the magnetic structure of the
  MC observed on 15-16 May 1997 by the spacecraft Wind and its associated
  solar event a C1 3 long duration event that occurred on 12 May 1997 in
  AR8038 Two main dimming regions that exhibit an asymmetric temporal
  and spatial evolution were observed in association with this event
  We compute the magnetic flux in the dimmings and follow its evolution
  using magnetograms from the Michelson Doppler Imager SoHO MDI The MC
  structure is inferred using three different helical cylindrical models
  with a significantly different radial twist distribution We also take
  into account the asymmetry observed between the front and the rear
  part of the cloud We fit the free parameters of each model comparing
  models with in situ observations Then we estimate the flux across the
  surface perpendicular to the axis of the cylinder and the flux across
  the surface formed by this axis and the cloud radial direction Finally
  we compare the MC total flux with that corresponding to both observed
  dimmings By combining our interplanetary measurements and the dimmings
  flux evolution we propose a topological model for the 12 May eruptive
  event We discuss the constrains set by solar observations on

Title: Multi-scale reconnections in a complex CME
Authors: van Driel-Gesztelyi, L.; Goff, C.; Demoulin, P.; Culhane,
   J. L.; Matthews, S. A.; Harra, L. K.; Mandrini, C. H.; Klein, K. L.;
   Kurokawa, H.
Bibcode: 2006cosp...36.2371V
Altcode: 2006cosp.meet.2371V
  A series of flares GOES class M M and C and a CME were observed on
  20-JAN-2004 occurring in close succession in NOAA 10540 Types II III
  and an N radio bursts were associated We use the combined observations
  from TRACE EIT H-alpha images from Kwasan Observatory MDI magnetograms
  GOES and radio observations from Culgoora and Wind WAVES to understand
  the complex development of this event We link the first two impulsive
  flares to tether-cutting reconnections and the launch of the CME while
  the last of the flares an LDE to the relaxation phase following forced
  reconnections between the erupting flux rope and neighbouring magnetic
  field lines We show that reconnection with the magnetic structure of
  a previous CME launched about 8 hours earlier injects electrons into
  open field lines having a local dip and apex of about 6 solar radii
  height The dipped shape of these field lines was due to large-scale
  magnetic reconnection between expanding magnetic loops and open field
  lines of a neighbouring streamer This particular situation explains
  the observed decametric N burst and why N-bursts are so rare

Title: Sun-to-earth propagation speeds for three CMEs
Authors: Culhane, L.; Pohjolainen, S.; van Driel-Gesztelyi, L.;
   Elliott, H.
Bibcode: 2006cosp...36.2544C
Altcode: 2006cosp.meet.2544C
  Several methods for CME speed estimation are discussed for events
  that occurred on 28-OCT-2003 7-NOV-2004 and 20-JAN-2005 These include
  velocity derivation based on the frequency drifts observed in metric
  and decametric radio wave data using a range of coronal density models
  These estimated speeds are compared with plane of the sky values and
  with estimates made from the application of a cone model The related
  interplanetary shocks and the arrival times of the associated magnetic
  clouds at Earth are also considered The range of speeds and Sun-Earth
  transit times obtained from these studies is assessed The difficulties
  in making velocity estimates from radio observations particularly
  under disturbed coronal conditions will be highlighted

Title: The MOSES spectral imager for KuaFu-A
Authors: Harra, L. K.; van Driel-Gesztelyi, L.; Cole, R.; Sun, J.;
   Winter, B.; Hancock, B.
Bibcode: 2006cosp...36.3670H
Altcode: 2006cosp.meet.3670H
  We will describe the instrument design for a spectral imager on the
  KuaFu mission KuaFu s science goals are aimed at understanding space
  weather with a spacecraft located at L1 and 2 spacecraft in a polar
  orbit around the Earth The spectral imager will provide crucial
  information on the source region of coronal mass ejections It will
  achieve this by measuring the Doppler velocities and intensity over
  the field of view of the solar activity zone which is geoeffective
  This allows us to determine whether activity on the Sun does actually
  releases material into the interplanetary medium BEFORE we observe
  it in coronagraphs We will summarise the instrument design and the
  scientific drivers for it

Title: Tracing magnetic helicity from the solar corona to the
    interplanetary space
Authors: Luoni, M. L.; Mandrini, C. H.; Dasso, Sergio; van
   Driel-Gesztelyi, L.; Démoulin, P.
Bibcode: 2005JASTP..67.1734L
Altcode: 2005JATP...67.1734L
  On October 14, 1995, a C1.6 long duration event (LDE) started in active
  region (AR) NOAA 7912 at approximately 5:00 UT and lasted for about
  15 h. On October 18, 1995, the Solar Wind Experiment and the Magnetic
  Field Instrument (MFI) on board the Wind spacecraft registered a
  magnetic cloud (MC) at 1 AU, which was followed by a strong geomagnetic
  storm. We identify the solar source of this phenomenon as AR 7912. We
  use magnetograms obtained by the Imaging Vector Magnetograph at Mees
  Solar Observatory, as boundary conditions to the linear force-free
  model of the coronal field, and, we determine the model in which the
  field lines best fit the loops observed by the Soft X-ray Telescope on
  board Yohkoh. The computations are done before and after the ejection
  accompanying the LDE. We deduce the loss of magnetic helicity from AR
  7912. We also estimate the magnetic helicity of the MC from in situ
  observations and force-free models. We find the same sign of magnetic
  helicity in the MC and in its solar source. Furthermore, the helicity
  values turn out to be quite similar considering the large errors that
  could be present. Our results are a first step towards a quantitative
  confirmation of the link between solar and interplanetary phenomena
  through the study of magnetic helicity.

Title: Erupting Flux Rope, Rising X-Ray Source and a Slow CME on 16
    April 2002
Authors: Goff, C. P.; van Driel-Gesztelyi, L.; Harra, L. K.; Matthews,
   S. A.; Mandrini, C. H.
Bibcode: 2005ESASP.600E..46G
Altcode: 2005ESPM...11...46G; 2005dysu.confE..46G
  No abstract at ADS

Title: Relating Near-Earth Observations of AN Interplanetary Coronal
    Mass Ejection to the Conditions at its Site of Origin in the Solar
    Corona
Authors: Fazakerley, A. N.; Harra, L. K.; Culhane, J. L.; van
   Driel-Gesztelyi, L.; Lucek, E.; Matthews, S. A.; Owen, C. J.; Mazelle,
   C.; Balogh, A.; Réme, H.
Bibcode: 2005ESASP.600E..47F
Altcode: 2005dysu.confE..47F; 2005ESPM...11...47F
  No abstract at ADS

Title: Quantitative Link Between Solar Ejecta and Interplanetary
Magnetic Clouds: Magnetic Helicity
Authors: Mandrini, C. H.; Dasso, S.; Luoni, M. L.; Pohjolainen, S.;
   Démoulin, P.; van Driel-Gesztelyi, L.
Bibcode: 2005ESASP.596E..29M
Altcode: 2005ccmf.confE..29M
  No abstract at ADS

Title: Linking Coronal to Heliospheric Magnetic Helicity: A New
    Model-Independent Technique to Compute Helicity in Magnetic Clouds
Authors: Dasso, Sergio; Mandrini, Cristina H.; Luoni, Maria L.;
   Gulisano, Adriana M.; Nakwacki, Maria S.; Pohjolainen, Silja; van
   Driel-Gesztelyi, Lidia; Démoulin, Pascal
Bibcode: 2005ESASP.592..605D
Altcode: 2005soho...16E.117D; 2005ESASP.592E.117D
  No abstract at ADS

Title: Flows in the solar atmosphere due to the eruptions on the
    15th July, 2002
Authors: Harra, L. K.; Démoulin, P.; Mandrini, C. H.; Matthews,
   S. A.; van Driel-Gesztelyi, L.; Culhane, J. L.; Fletcher, L.
Bibcode: 2005A&A...438.1099H
Altcode:
  Which kind of flows are present during flares? Are they compatible
  with the present understanding of energy release and which model
  best describes the observations? We analyze successive flare events
  in order to answer these questions. The flares were observed in the
  magnetically complex NOAA active region (AR) 10030 on 15 July 2002. One
  of them is of GOES X-class. The description of these flares and how
  they relate to the break-out model is presented in Gary &amp; Moore
  (2004). The Coronal Diagnostic Spectrometer on board SOHO observed
  this active region for around 14 h. The observed emission lines
  provided data from the transition region to the corona with a field
  of view covering more than half of the active region. In this paper
  we analyse the spatially resolved flows seen in the atmosphere from
  the preflare to the flare stages. We find evidence for evaporation
  occurring before the impulsive phase. During the main phase, the
  ongoing magnetic reconnection is demonstrated by upflows located at
  the edges of the flare loops (while downflows are found in the flare
  loops themselves). We also report the impact of a filament eruption
  on the atmosphere, with flows up to 300 km s<SUP>-1</SUP> observed at
  transition-region temperatures in regions well away from the location
  of the pre-eruptive filament. Our results are consistent with the
  predictions of the break out model before the impulsive phase of the
  flare; while, as the flare progresses, the directions of the flows are
  consistent with flare models invoking evaporation followed by cooling
  and downward plasma motions in the flare loops.

Title: Eruption of a Kink-unstable Filament in NOAA Active Region
    10696
Authors: Williams, David R.; Török, Tibor; Démoulin, Pascal;
   van Driel-Gesztelyi, Lidia; Kliem, Bernhard
Bibcode: 2005ApJ...628L.163W
Altcode: 2005astro.ph..7661W
  We present rapid-cadence Transition Region and Coronal Explorer (TRACE)
  observations that show evidence of a filament eruption from NOAA active
  region 10696, accompanied by an X2.5 flare, on 2004 November 10. The
  eruptive filament, which manifests as a fast coronal mass ejection
  some minutes later, rises as a kinking structure with an apparently
  exponential growth of height within TRACE's field of view. We compare
  the characteristics of this filament eruption with MHD numerical
  simulations of a kink-unstable magnetic flux rope, finding excellent
  qualitative agreement. We suggest that while tether weakening by
  breakout-like quadrupolar reconnection may be the release mechanism
  for the previously confined flux rope, the driver of the expansion is
  most likely the MHD helical kink instability.

Title: Relating near-Earth observations of an interplanetary coronal
    mass ejection to the conditions at its site of origin in the solar
    corona
Authors: Fazakerley, A. N.; Harra, L. K.; Culhane, J. L.; van
   Driel-Gesztelyi, L.; Lucek, E.; Matthews, S. A.; Owen, C. J.; Mazelle,
   C.; Balogh, A.; Rème, H.
Bibcode: 2005GeoRL..3213105F
Altcode:
  A halo coronal mass ejection (CME) was detected on January 20, 2004. We
  use solar remote sensing data (SOHO, Culgoora) and near-Earth in situ
  data (Cluster) to identify the CME source event and show that it was a
  long duration flare in which a magnetic flux rope was ejected, carrying
  overlying coronal arcade material along with it. We demonstrate that
  signatures of both the arcade material and the flux rope material are
  clearly identifiable in the Cluster and ACE data, indicating that the
  magnetic field orientations changed little as the material traveled
  to the Earth, and that the methods we used to infer coronal magnetic
  field configurations are effective.

Title: Editorial
Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia
Bibcode: 2005SoPh..229....3L
Altcode:
  No abstract at ADS

Title: A slow coronal mass ejection with rising X-ray source
Authors: Goff, C. P.; van Driel-Gesztelyi, L.; Harra, L. K.; Matthews,
   S. A.; Mandrini, C. H.
Bibcode: 2005A&A...434..761G
Altcode:
  An eruptive event, which occurred on 16th April 2002, is
  discussed. Using images from the Transition Region and Coronal Explorer
  (TRACE) at 195 Å, we observe a lifting flux rope which gives rise
  to a slow coronal mass ejection (CME). There are supporting velocity
  observations from the Coronal Diagnostic Spectrometer (CDS) on the Solar
  and Heliospheric Observatory (SOHO), which illustrate the helical nature
  of the structure. Additionally a rising coronal hard X-ray source,
  which is observed with the Reuven Ramaty High Energy Solar Spectroscopic
  Imager (RHESSI), is shown to follow the flux rope with a speed of ~60
  km s<SUP>-1</SUP>. It is also sampled by the CDS slit, although it has
  no signature in the Fe XIX band. Following the passage of this source,
  there is evidence from the CDS for down-flowing (cooling) material
  along newly reconnected loops through Doppler velocity observations,
  combined with magnetic field modeling. Later, a slow CME is observed
  with the Large Angle and Spectroscopic Coronagraph (LASCO). We combine
  a height-time profile of the flux rope at lower altitudes with the slow
  CME. The rising flux rope speeds up by a factor of 1.7 at the start
  of the impulsive energy release and goes through further acceleration
  before reaching 1.5 solar radii. These observations support classical
  CME scenarios in which the eruption of a filament precedes flaring
  activity. Cusped flare loops are observed following the erupting
  flux rope and their altitude increases with time. In addition we
  find RHESSI sources both below and above the probable location of the
  reconnection region.

Title: Interplanetary flux rope ejected from an X-ray bright
    point. The smallest magnetic cloud source-region ever observed
Authors: Mandrini, C. H.; Pohjolainen, S.; Dasso, S.; Green, L. M.;
   Démoulin, P.; van Driel-Gesztelyi, L.; Copperwheat, C.; Foley, C.
Bibcode: 2005A&A...434..725M
Altcode:
  Using multi-instrument and multi-wavelength observations (SOHO/MDI and
  EIT, TRACE and Yohkoh/SXT), as well as computing the coronal magnetic
  field of a tiny bipole combined with modelling of Wind in situ data,
  we provide evidences for the smallest event ever observed which links
  a sigmoid eruption to an interplanetary magnetic cloud (MC). The
  tiny bipole, which was observed very close to the solar disc centre,
  had a factor one hundred less flux than a classical active region
  (AR). In the corona it had a sigmoidal structure, observed mainly
  in EUV, and we found a very high level of non-potentiality in the
  modelled magnetic field, 10 times higher than we have ever found in
  any AR. From May 11, 1998, and until its disappearance, the sigmoid
  underwent three intense impulsive events. The largest of these events
  had extended EUV dimmings and a cusp. The Wind spacecraft detected 4.5
  days later one of the smallest MC ever identified (about a factor one
  hundred times less magnetic flux in the axial component than that of an
  average MC). The link between this last eruption and the interplanetary
  magnetic cloud is supported by several pieces of evidence: good timing,
  same coronal loop and MC orientation, same magnetic field direction
  and magnetic helicity sign in the coronal loops and in the MC. We
  further quantify this link by estimating the magnetic flux (measured
  in the dimming regions and in the MC) and the magnetic helicity (pre-
  to post-event change in the solar corona and helicity content of the
  MC). Within the uncertainties, both magnetic fluxes and helicities
  are in reasonable agreement, which brings further evidences of their
  link. These observations show that the ejections of tiny magnetic flux
  ropes are indeed possible and put new constraints on CME models.

Title: Relationship between X-ray and ultraviolet emission of flares
    from dMe stars observed by XMM-Newton
Authors: Mitra-Kraev, U.; Harra, L. K.; Güdel, M.; Audard, M.;
   Branduardi-Raymont, G.; Kay, H. R. M.; Mewe, R.; Raassen, A. J. J.;
   van Driel-Gesztelyi, L.
Bibcode: 2005A&A...431..679M
Altcode: 2004astro.ph.10592M
  We present simultaneous ultraviolet and X-ray observations of
  the dMe-type flaring stars <ASTROBJ>AT Mic</ASTROBJ>, <ASTROBJ>AU
  Mic</ASTROBJ>, <ASTROBJ>EV Lac</ASTROBJ>, <ASTROBJ>UV Cet</ASTROBJ>
  and <ASTROBJ>YZ CMi</ASTROBJ> obtained with the XMM-Newton
  observatory. During 40 h of simultaneous observation we identify
  13 flares which occurred in both wave bands. For the first time,
  a correlation between X-ray and ultraviolet flux for stellar flares
  has been observed. We find power-law relationships between these two
  wavelength bands for the flare luminosity increase, as well as for
  flare energies, with power-law exponents between 1 and 2. We also
  observe a correlation between the ultraviolet flare energy and the
  X-ray luminosity increase, which is in agreement with the Neupert
  effect and demonstrates that chromospheric evaporation is taking place.

Title: Coronal Mass Ejections and Magnetic Helicity
Authors: Van Driel-Gesztelyi, L.
Bibcode: 2005ASSL..320...57V
Altcode: 2005smp..conf...57V
  No abstract at ADS

Title: The smallest source region of an interplanetary magnetic cloud:
    A mini-sigmoid
Authors: Mandrini, C. H.; Pohjolainen, S.; Dasso, S.; Green, L. M.;
   Démoulin, P.; van Driel-Gesztelyi, L.; Foley, C.; Copperwheat, C.
Bibcode: 2005AdSpR..36.1579M
Altcode:
  We provide evidence for the smallest sigmoid eruption - CME -
  interplanetary magnetic cloud event ever observed by combining
  multi-wavelength remote sensing and in situ observations, as well as
  computing the coronal and interplanetary magnetic fields. The tiny
  bipole had 100 times less flux than an average active region (AR). It
  had a sigmoidal structure in the corona and we detected a very high
  level of twist in its magnetic field. On 11 May 1998, at about 8 UT, the
  sigmoid underwent eruption evidenced by expanding elongated EUV loops,
  dimmings and formation of a cusp. The Wind spacecraft, 4.5 days later,
  detected one of the smallest magnetic clouds (MC) ever identified
  (100 times less magnetic flux than an average MC). The link between
  the EUV bright point eruption and the interplanetary MC is supported by
  several pieces of evidence: timing, same coronal loop and MC orientation
  relative to the ecliptic, same magnetic field direction and magnetic
  helicity sign in the coronal loops and in the MC, comparable magnetic
  flux measured in the dimming regions and in the interplanetary MC and,
  most importantly, the pre- to post-event change of magnetic helicity
  in the solar corona is found to be comparable to the helicity content
  of the cloud.

Title: Source Regions of Coronal Mass Ejections
Authors: Schmieder, Brigitte; van Driel-Gesztelyi, L.
Bibcode: 2005IAUS..226..149S
Altcode:
  The majority of flare activity arises in active regions which
  contain sunspots, while CME activity can also originate from decaying
  active regions and even so-called quiet solar regions which contain a
  filament. Two classes of CME, namely flare-related CME events and CMEs
  associated with filament eruption are well reflected in the evolution
  of active regions, flare related CMEs mainly occur in young active
  regions containing sunspots and as the magnetic flux of active region
  is getting dispersed, the filament-eruption related CMEs will become
  dominant. This is confirmed by statistical analyses.&lt;/p&gt;All the
  CMEs are, nevertheless, caused by loss of equilibrium of the magnetic
  structure. With observational examples we show that the association
  of CME, flare and filament eruption depends on the characteristics
  of the source regions: (i) the strength of the magnetic field, the
  amount of possible free energy storage, (ii) the small- and large-scale
  magnetic topology of the source region as well as its evolution (new
  flux emergence, photospheric motions, canceling flux), and (iii) the
  mass loading of the configuration (effect of gravity). These examples
  are discussed in the framework of theoretical models.

Title: Linking Coronal to Interplanetary Magnetic Helicity
Authors: Luoni, M. L.; Dasso, S.; Mandrini, C. H.; Van Driel-Gesztelyi,
   L.; Démoulin, P.
Bibcode: 2005ASSL..320..243L
Altcode: 2005smp..conf..243L
  No abstract at ADS

Title: Solar and Interplanetary Magnetic Helicity Balance of Active
    Regions
Authors: Mandrini, Cristina H.; Démoulin, Pascal; van Driel-Gesztelyi,
   Lidia; Dasso, Sergio; Green, Lucinda M.; López Fuentes, Marcelo
Bibcode: 2005HiA....13..122M
Altcode:
  No abstract at ADS

Title: Relating magnetic field strengths to hard X-ray emission in
    solar flares
Authors: Goff, C. P.; Matthews, S. A.; van Driel-Gesztelyi, L.; Harra,
   L. K.
Bibcode: 2004A&A...423..363G
Altcode:
  The observation of hard X-ray (HXR) emission in solar flares provides
  important diagnostic information about the acceleration and subsequent
  transport of energetic electrons in the flare process. However,
  while hard X-rays are thought to be emitted from the flare footpoints
  through thick-target bremsstrahlung interactions, the details of the
  transport of accelerated electrons through the solar atmosphere still
  remains unclear. <P />Trapping of the electrons is one particular
  effect that is expected to occur as a result of the convergence of the
  magnetic field between the corona and the chromosphere. In this case
  the brightness of the HXR footpoints should be related to the strength
  of the magnetic field present and we would expect greater precipitation
  and higher HXR intensities at the footpoints with lower magnetic field
  strength. This relationship has been observed to hold in many flares
  (see \citealt{Sakaothesis}) but interestingly the opposite relationship,
  where the stronger HXR source is found at the stronger magnetic field
  region, has also been observed in an event studied by \citet{Asai}. <P
  />Using Data from Yohkoh's Hard X-Ray Telescope (HXT) and SOHO's
  Michelson Doppler Imager (MDI) we have studied the magnetic field
  strengths at the footpoints of a sample of 32 flares and have compared
  them to the hard X-ray brightness to determine whether the expected
  ratios are seen. We find that contrary to the expected relationship
  the brighter HXR footpoint is found in the region of stronger magnetic
  field in approximately one third of our sample of events. We discuss
  the implications of these results in terms of the transport mechanisms.

Title: Intensity variations in EIT shutterless mode: Waves or flows?
Authors: De Groof, A.; Berghmans, D.; van Driel-Gesztelyi, L.;
   Poedts, S.
Bibcode: 2004A&A...415.1141D
Altcode:
  On 11 July 2001 an EIT shutterless campaign was conducted which provided
  120 high-cadence (68 s) 304 Å images of the north eastern quarter of
  the Sun. The most interesting feature seen in the data is an off-limb
  half loop structure along which systematic intensity variations are
  seen which appear to propagate from the top of the loop towards its
  footpoint. We investigate the underlying cause of these propagating
  disturbances, i.e. whether they are caused by waves or by plasma
  flows. First we identify 7 blobs with the highest intensities and
  follow them along the loop. By means of a location-time plot, bulk
  velocities can be measured at several locations along the loop. The
  velocity curve found this way is then compared with characteristic
  wave speeds and with the free-fall speed in order to deduce the nature
  of the intensity variations. Additional information on density and
  temperature is derived by measuring the relative intensity enhancements
  and comparing the EIT 304 Å sequence with Big Bear data and 171 Å
  data (TRACE/EIT). The combination of all these constraints gives us an
  insight on the nature and origin of these intensity variations. The
  idea of slow magneto-acoustic waves is rejected, and we find several
  arguments supporting that these intensity variations are due to
  flowing/falling plasma blobs.

Title: Magnetic Helicity Budget of Solar-Active Regions from the
    Photosphere to Magnetic Clouds
Authors: Mandrini, C. H.; Démoulin, P.; van Driel-Gesztelyi, L.;
   van Driel-Gesztelyi, L.; van Driel-Gesztelyi, L.; van Driel-Gesztelyi,
   L. L. M.; López Fuentes, M. C.
Bibcode: 2004Ap&SS.290..319M
Altcode:
  We have analyzed the long-term evolution of two active regions (ARs)
  from their emergence through their decay using observations from several
  instruments on board SoHO (MDI, EIT and LASCO) and Yohkoh/SXT. We
  have computed the evolution of the relative coronal magnetic helicity
  combining data from MDI and SXT with a linear force-free model of
  the coronal magnetic field. Next, we have computed the injection of
  helicity by surface differential rotation using MDI magnetic maps. To
  estimate the depletion of helicity we have counted all the CMEs of which
  these ARs have been the source, and we have evaluated their magnetic
  helicity assuming a one to one correspondence with magnetic clouds
  with an average helicity contain. When these three values (variation
  of coronal magnetic helicity, injection by differential rotation and
  ejection via CMEs) are compared, we find that surface differential
  rotation is a minor contributor to the helicity budget since CMEs carry
  away at least 10 times more helicity than the one differential rotation
  can provide. Therefore, the magnetic helicity flux needed in the global
  balance should come from localized photospheric motions that, at least
  partially, reflect the emergence of twisted flux tubes. We estimate
  that the total helicity carried away in CMEs can be provided by the
  end-to-end helicity of the flux tubes forming these ARs. Therefore,
  we conclude that most of the helicity ejected in CMEs is generated
  below the photosphere and emerges with the magnetic flux.

Title: Evidence of Magnetic Reconnection along Coronal Hole Boundaries
Authors: Madjarska, M. S.; Doyle, J. G.; van Driel-Gesztelyi, L.
Bibcode: 2004ApJ...603L..57M
Altcode:
  The present study reveals for the first time the existence of
  bidirectional jets, which are a signature of magnetic reconnection,
  occurring along coronal hole boundaries. The Solar Ultraviolet
  Measurement of Emitted Radiation spectrometer observations obtained
  in the N IV 765.15 Å (1.3×10<SUP>5</SUP> K) and Ne VIII 770.42
  Å (6×10<SUP>5</SUP> K) emission lines in an equatorial extension
  of a polar coronal hole, known as the ``Elephant's Trunk'' coronal
  hole, show small regions of a few arcseconds size with strong blue-
  and redshifted emission reaching Doppler shifts of up to 150 km
  s<SUP>-1</SUP>, i.e., bidirectional jets. The jets' number density
  along coronal hole boundaries was found to be about 4-5 times higher
  with respect to the quiet Sun.

Title: An Observational Test for Coronal Heating Models
Authors: van Driel-Gesztelyi, L.; Démoulin, P.; Mandrini, C. H.;
   Harra, L. K.; Klimchuk, J. A.
Bibcode: 2004IAUS..219..473V
Altcode: 2003IAUS..219E..97V
  We correlate the evolution of the mean X-ray flux emission measure
  and temperature (Yohkoh SXT &amp; BCS) with the magnetic flux density
  (SOHO/MDI) in active region NOAA 7978 from its birth throughout its
  decay for five solar rotations. We show that these plasma parameters
  together with other quantities deduced from them such as the density
  and the pressure follow power-law relationships with the mean magnetic
  flux density (bar{B}). We derive the dependence of the mean coronal
  heating rate on the magnetic flux density. We use the obtained scaling
  laws of coronal loops in thermal equilibrium to derive observational
  estimates of the scaling of the coronal heating with bar{B}. These
  results are used to test the validity of coronal heating models. We
  find that models invoking stochastic buildup of energy current layers
  and MHD turbulence are in best agreement with the observations. This
  narrows down the range of possible models retained by previous results
  obtained for individual coronal loops as well as for the global coronal
  emission of the Sun and cool stars.

Title: Bi-Directional Jets at Coronal Hole Boundaries
Authors: Madjarska, M. S.; Doyle, J. G.; van Driel-Gesztelyi, L.
Bibcode: 2004ESASP.547..397M
Altcode: 2004soho...13..397M
  Our study reveals, for the first time, the presence of bi-directional
  jets which are considered to be signatures of magnetic reconnection
  occurring along coronal hole boundaries. The SUMER observations obtained
  in Ne VIII 770.42 Å (6 10 K) and N IV 765.15 Å (1.3 10 K) show small
  regions of a few arcsec size with strong blueand red-shifted emission
  reaching Doppler shifts up to 150 km s which appear along the coronal
  hole boundaries where evolving loop systems are present.

Title: Intensity Variations in EIT Shutterless Mode: Waves or Flows?
Authors: de Groof, A.; Berghmans, D.; van Driel-Gesztelyi, L.;
   Poedts, S.
Bibcode: 2004ESASP.547..245D
Altcode: 2004soho...13..245D
  On 11 July 2001 an EIT shutterless campaign was conducted which provided
  120 high-cadence (68s) 304 Å images of the north eastern quarter of the
  Sun. The most interesting feature seen in the data is an off-limb half
  loop structure along which systematic intensity variations appear to
  propagate from the top of the loop towards its footpoint. We investigate
  the underlying cause of these propagating disturbances, i.e. whether
  they are caused by waves or by plasma flows. First we identify 7 blobs
  with the highest intensities and follow them along the loop. By means
  of a location-time plot, bulk velocities can be measured at several
  locations along the loop. The velocity curve found this way is then
  compared with characteristic wave speeds and with the free-fall speed
  in order to deduce the nature of the intensity variations. Additional
  information is derived by measuring the relative intensity enhancements
  and comparing the EIT 304 Å sequence with Big Bear and 171 Å data. The
  idea of slow magneto-acoustic waves is rejected, and we find several
  arguments supporting that these intensity variations are due to
  flowing/falling plasma blobs.

Title: Linking coronal observations of a `miniÂ´active region with
    its interplanetary manifestation
Authors: Dasso, S.; Mandrini, C. H.; Pohjolainen, S.; Green, L. M.;
   Démoulin, P.; van Driel-Gesztelyi, L.; Foley, C.; Copperwheat, C.
Bibcode: 2004BAAA...47...18D
Altcode:
  We analyze the smallest 'sigmoidal eruption - CME - interplanetary
  magnetic cloud' event even observed before. We find: (a) the same
  magnetic helicity sign and (b) similar magnetic flux values in the
  coronal source region and associated cloud, and (c) that the magnetic
  helicity changes, before and after the ejection, in approximately the
  same amount as the helicity content in the interplanetary cloud. These
  results stress the importance of complementary solar and interplanetary
  studies, to achieve a better understanding of the origin of eruptive
  phenomena.

Title: Flux Cancellation in a Decaying Active Region
Authors: Martinez Pillet, V.; Sainz Dalda, A.; van Driel-Gesztelyi, L.
Bibcode: 2004cosp...35.1133M
Altcode: 2004cosp.meet.1133M
  Flux Cancellation in a Decaying Active Region Flux cancellation
  is observed in many regions on the Sun as internetwork, network
  and active regions fields. It clearly plays a crucial role in the
  constant flux processing observed in the solar surface. During the
  decay of an active region, we have observed the in-situ dissapearance
  of 70 % of its flux (from SOHO/MDI). Active region flux decay is a
  global, large-scale, process crucial to the solar cycle. But the
  flux cancellations, where the flux actually disappears, do take
  place in very small scale regions. There opposite polarities meet and
  vanish. The process needs of observations with sufficient sensitivity
  and angular resolution. In the example presented here, we show how
  up to 4 of these cancellations are associated with outward moving
  material in the Corona (as observed by TRACE), including a major
  active region filament eruption. Solar Orbiter, profiting from the
  advantage observing position and near-corotation can follow these
  subtle, but crucial, processes with the necessary set of instruments:
  Magnetographs, Coronal imagers and spectrographs. For those events
  occurring in the spacecraft solar vertical, one should not exclude
  the detection of the phenomena in the in-situ instruments.

Title: The smallest source region of an interplanetary magnetic cloud:
    a mini-sigmoid
Authors: Mandrini, C.; Pohjolainen, S.; Dasso, S.; Green, L.; Demoulin,
   P.; van Driel-Gesztelyi, L.; Copperwheat, C.; Foley, C.
Bibcode: 2004cosp...35..290M
Altcode: 2004cosp.meet..290M
  Using multi-instrument and multi-wavelength observations (SOHO/MDI
  and EIT, TRACE and Yohkoh/SXT), as well as computing the coronal
  magnetic field of a tiny bipole combined with modelling of WIND in situ
  data, we provide evidence for the smallest sigmoid eruption - CME -
  interplanetary magnetic cloud event ever observed. The tiny bipole,
  which was observed very close to the solar disc centre, had 100 times
  less flux than an average active region (AR). In the corona it had a
  sigmoidal structure and we detected a very high level of twist. On 11
  May 1998, at about 8 UT, the sigmoid underwent eruption evidenced by
  expanding elongated EUV loops, dimmings and formation of a cusp. The
  WIND spacecraft detected 4.5 days later one of the smallest magnetic
  clouds (MC) ever identified (100 times less flux and radius than an
  average MC). The link between the sigmoidal EUV bright point eruption
  and the interplanetary magnetic cloud is supported by several pieces of
  evidence: good timing, same coronal loop and MC orientation relative
  to the ecliptic, same magnetic field direction and magnetic helicity
  sign in the coronal loops and in the MC, comparable magnetic flux
  measured in the dimming regions and in the interplanetary MC and,
  most importantly, the pre- to post-event change of magnetic helicity
  in the solar corona is found to be similar to the helicity content of
  the cloud, when assuming a length compatible with the fact that the
  cloud can be detached from the Sun one day after its ejection. These
  observations are a challenge to present theoretical CME models, and show
  us the need of missions such us Solar B and Stereo to contribute to our
  understanding of the broad spectrum covered by solar eruptive phenomena.

Title: How small can an interplanetary magnetic cloud source-region
    be?
Authors: Mandrini, C.; Pohjolainen, S.; Dasso, S.; Green, L.; Demoulin,
   P.; van Driel-Gesztelyi, L.; Copperwheat, C.; Foley, C.
Bibcode: 2004cosp...35..282M
Altcode: 2004cosp.meet..282M
  Using multi-instrument and multi-wavelength observations (SOHO/MDI
  and EIT, TRACE and Yohkoh/SXT), as well as computing the coronal
  magnetic field of a tiny bipole combined with modelling of WIND in situ
  data, we provide evidence for the smallest sigmoid eruption - CME -
  interplanetary magnetic cloud event ever observed. The tiny bipole,
  which was observed very close to the solar disc centre, had 100 times
  less flux than an average active region (AR). In the corona it had a
  sigmoidal structure and we detected a very high level of twist. On 11
  May 1998, at about 8 UT, the sigmoid underwent eruption evidenced by
  expanding elongated EUV loops, dimmings and formation of a cusp. The
  WIND spacecraft detected 4.5 days later one of the smallest magnetic
  clouds (MC) ever identified (100 times less flux and radius than an
  average MC). The link between the sigmoidal EUV bright point eruption
  and the interplanetary magnetic cloud is supported by several pieces of
  evidence: good timing, same coronal loop and MC orientation relative
  to the ecliptic, same magnetic field direction and magnetic helicity
  sign in the coronal loops and in the MC, comparable magnetic flux
  measured in the dimming regions and in the interplanetary MC and,
  most importantly, the pre- to post-event change of magnetic helicity
  in the solar corona is found to be similar to the helicity content
  of the cloud, when assuming a length compatible with the fact that
  thecloud can be dettached from the Sun one day after its ejection. These
  observations are a challenge to present theoretical CME models, and show
  us the need of missions such us Solar B and Stereo to contribute to our
  understandig of the broad spectrum covered by solar eruptive phenomena.

Title: An Introduction to Magnetohydrodynamics
Authors: van Driel-Gesztelyi, Lidia
Bibcode: 2004spsc.book..279V
Altcode:
  No abstract at ADS

Title: The possible back-rotation of sunspots
Authors: Williams, D. R.; van Driel-Gesztelyi, L.; Nakariakov, V. M.
Bibcode: 2004cosp...35.4391W
Altcode: 2004cosp.meet.4391W
  The curious case of sunspot rotation in two senses, presented by
  Kucera (1982), provided an interesting challenge to the idea of sunspot
  rotation being due simply to the differential rotation of the Sun above
  the tachocline. As the rotation rate and direction, in that case, are
  seen to vary as a damped sinusoid, this presents the possibility that
  such motion is the result of torsional waves trapped in the sunspot's
  sub-photospheric flux tube. We therefore analyse the rotation of a
  number of sunspots using SoHO/MDI and track their rotation, presenting
  evidence of 'back-rotation' -- rotational motion which reverses --
  in a several of these spots. Intuitively, this raises the possibility
  of extending the field of 'Coronal Seismology' back down to beneath
  the photosphere (where helioseismology already exists).

Title: Evidence of Flaring in a Transequatorial Loop on the Sun
Authors: Harra, Louise K.; Matthews, Sarah A.; van Driel-Gesztelyi,
   Lidia
Bibcode: 2003ApJ...598L..59H
Altcode:
  We present evidence of flaring behavior in a transequatorial loop (TEL)
  that lights up in soft X-rays on 2000 July 13. The large loop structure
  connects NOAA Active Regions 9070/9066 in the northern hemisphere and
  AR 9069/9068 in the southern hemisphere. We follow the loop systems for
  2 days and observe several pieces of evidence strongly suggesting flare
  behavior of the form seen in standard flaring in active regions. These
  include brightenings of the loop structure, cooling of plasma that is
  seen both in soft X-rays and in the transition region temperatures,
  morphological evidence of reconnection inflow, and blueshifts around
  the footpoint of the TEL suggestive of chromospheric evaporation. We
  present, to our knowledge for the first time, observations of TEL in
  the O V emission line.

Title: A catalogue of white-light flares observed by Yohkoh
Authors: Matthews, S. A.; van Driel-Gesztelyi, L.; Hudson, H. S.;
   Nitta, N. V.
Bibcode: 2003A&A...409.1107M
Altcode:
  The aspect camera of the Soft X-ray Telescope (SXT) on Yohkoh provided
  the first systematic survey of white-light flares from an observatory in
  space. The observations were made in the Fraunhofer g-band at a pixel
  size of 2.46 arcsec and a typical sample interval on the order of ten
  seconds. A total of 28 flares with clear white-light signatures were
  detected, corresponding to GOES events down to the C7.8 level in one
  case. Above the X-class threshold, all 5 events observed by SXT were
  observed in white light, and the maximum average contrast observed
  was 30% relative to the pre-flare continuum brightness of the flare
  location. We have made comprehensive comparisons of Yohkoh soft X-ray
  and hard X-ray data for this list of flares. In addition we compare
  the properties of the WLF sample to a sample of 31 flares that showed
  no white-light emission. These comparisons show that while white-light
  continuum emission has a strong association with hard X-ray emission
  it is also strongly related to coronal overpressure, as determined
  from the soft X-ray spectrum, indicating a component with a thermal,
  rather than non-thermal origin. <P />Appendices are only available in
  electronic form at http://www.edpsciences.org

Title: How are Emerging Flux, Flares and CMEs Related to Magnetic
    Polarity Imbalance in Midi Data?
Authors: Green, L. M.; Démoulin, P.; Mandrini, C. H.; Van
   Driel-Gesztelyi, L.
Bibcode: 2003SoPh..215..307G
Altcode: 2003astro.ph..4092G
  In order to understand whether major flares or coronal mass ejections
  (CMEs) can be related to changes in the longitudinal photospheric
  magnetic field, we study 4 young active regions during seven days of
  their disk passage. This time period precludes any biases which may
  be introduced in studies that look at the field evolution during the
  short-term flare or CME period only. Data from the Michelson Doppler
  Imager (MDI) with a time cadence of 96 min are used. Corrections are
  made to the data to account for area foreshortening and angle between
  line of sight and field direction, and also the underestimation of
  the flux densities. We make a systematic study of the evolution of the
  longitudinal magnetic field, and analyze flare and CME occurrence in
  the magnetic evolution. We find that the majority of CMEs and flares
  occur during or after new flux emergence. The flux in all four active
  regions is observed to have deviations from polarity balance both on
  the long term (solar rotation) and on the short term (few hours). The
  long-term imbalance is not due to linkage outside the active region; it
  is primarily related to the east-west distance from central meridian,
  with the sign of polarity closer to the limb dominating. The sequence
  of short-term imbalances are not closely linked to CMEs and flares and
  no permanent imbalance remains after them. We propose that both kinds
  of imbalance are due to the presence of a horizontal field component
  (parallel to the photospheric surface) in the emerging flux.

Title: The Long-Term Evolution of AR 7978: The Scalings of the
    Coronal Plasma Parameters with the Mean Photospheric Magnetic Field
Authors: van Driel-Gesztelyi, L.; Démoulin, P.; Mandrini, C. H.;
   Harra, L.; Klimchuk, J. A.
Bibcode: 2003ApJ...586..579V
Altcode:
  We analyze the evolution of the fluxes observed in X-rays and correlate
  them with the magnetic flux density in active region (AR) NOAA 7978
  from its birth throughout its decay, for five solar rotations. We
  use Solar and Heliospheric Observatory Michelson Doppler Imager
  (MDI) data, together with Yohkoh Soft X-Ray Telescope (SXT) and
  Yohkoh Bragg Crystal Spectrometer (BCS) data, to determine the global
  evolution of the temperature and the emission measure of the coronal
  plasma at times when no significant brightenings were observed. We
  show that the mean X-ray flux and derived parameters, temperature
  and emission measure (together with other quantities deduced from
  them, such as the density and the pressure), of the plasma in the AR
  follow power-law relationships with the mean magnetic flux density
  (B). The exponents (b) of these power-law functions (aB<SUP>b</SUP>)
  are derived using two different statistical methods, a classical
  least-squares method in log-log plots and a nonparametric method,
  which takes into account the fact that errors in the data may not be
  normally distributed. Both methods give similar exponents, within
  error bars, for the mean temperature and for both instruments (SXT
  and BCS); in particular, b stays in the range [0.27, 0.31] and [0.24,
  0.57] for full-resolution SXT images and BCS data, respectively. For
  the emission measure, the exponent b lies in the range [0.85, 1.35]
  and [0.45, 1.96] for SXT and BCS, respectively. The determination of
  such power-law relations, when combined with the results from coronal
  heating models, can provide us with powerful tools for determining the
  mechanism responsible for the existence of the high-temperature corona.

Title: The Long-Term Evolution of AR 7978: Testing Coronal Heating
    Models
Authors: Démoulin, P.; van Driel-Gesztelyi, L.; Mandrini, C. H.;
   Klimchuk, J. A.; Harra, L.
Bibcode: 2003ApJ...586..592D
Altcode:
  We derive the dependence of the mean coronal heating rate on the
  magnetic flux density. Our results are based on a previous study of
  the plasma parameters and the magnetic flux density (B) in the active
  region NOAA 7978 from its birth to its decay, throughout five solar
  rotations using the Solar and Heliospheric Observatory Michelson
  Doppler Imager, Yohkoh Soft X-Ray Telescope (SXT), and Yohkoh Bragg
  Crystal Spectrometer (BCS). We use the scaling laws of coronal loops
  in thermal equilibrium to derive four observational estimates of the
  scaling of the coronal heating with B (two from SXT and two from
  BCS observations). These results are used to test the validity of
  coronal heating models. We find that models based on the dissipation
  of stressed, current-carrying magnetic fields are in better agreement
  with the observations than models that attribute coronal heating to
  the dissipation of MHD waves injected at the base of the corona. This
  confirms, with smaller error bars, previous results obtained for
  individual coronal loops, as well as for the global coronal emission
  of the Sun and cool stars. Taking into account that the photospheric
  field is concentrated in thin magnetic flux tubes, both SXT and BCS
  data are in best agreement with models invoking a stochastic buildup
  of energy, current layers, and MHD turbulence.

Title: How to test coronal heating models?
Authors: Mandrini, C. H.; Démoulin, P.; van Driel-Gesztelyi, L.;
   Klimchuk, J. A.; Harra, L. K.
Bibcode: 2003BAAA...46....5M
Altcode:
  We have tested coronal heating models following two different
  approaches. In the first case, we compared the dependence of the
  coronal heating rate predicted by theoretical models with the
  observed one, deriving the scalings of parameters, such as: the
  density, temperature and intensity of the coronal magnetic field,
  with the length of magnetic field lines. To do so, we combined density
  and temperature measurements for 47 coronal loops with magnetic field
  models for 14 active regions. In the second case, we analyzed the long
  term evolution of an active region observed during seven rotations
  on the solar disk and we determined the dependence of the observed
  heating rate with the magnetic field density (bar{B}), after finding
  the scalings of plasma parameters with bar{B}. In both cases, we found
  that models based on the dissipation of stressed, current-carrying
  magnetic fields (called direct current models) are in better agreement
  with observations than models that attribute coronal heating to the
  dissipation of MHD waves injected at the base of the corona (called
  alternate current models). Taking into account that the photospheric
  field is concentrated in thin magnetic flux tubes, observations are
  in best agreement with models invoking a stochastic buildup of energy,
  current layers and MHD turbulence, within direct current models.

Title: Active region helicity evolution and related coronal mass
    ejection activity
Authors: Green, L. M.; López Fuentes, M. C.; Mandrini, C. H.; van
   Driel-Gesztelyi, L.; Démoulin, P.
Bibcode: 2003AdSpR..32.1959G
Altcode:
  The computation of magnetic helicity has become increasingly important
  in the studies of solar activity. Observations of helical structures
  in the solar atmosphere, and their subsequent ejection into the
  interplanetary medium, have resulted in considerable interest to find
  the link between the amount of helicity in the coronal magnetic field
  and the origin of coronal mass ejections (CMEs), which provide a natural
  method to remove helicity from the corona. Recent works have endeavored
  to find the source of helicity to explain the observed CME activity
  in specific cases. The main candidates being differential rotation,
  shear motions or a transfer of helicity from below the photosphere
  into the corona. We study an active region for several rotations
  during 1997 and 1998 to investigate the relative importance of these
  mechanisms. We find that photospheric differential rotation cannot
  provide the required magnetic helicity to the corona and the ejected
  CMEs. Localized photospheric motions can provide a larger helicity flux,
  though still not sufficient.

Title: Magnetic twist and writhe of active regions. On the origin
    of deformed flux tubes
Authors: López Fuentes, M. C.; Démoulin, P.; Mandrini, C. H.;
   Pevtsov, A. A.; van Driel-Gesztelyi, L.
Bibcode: 2003A&A...397..305L
Altcode: 2014arXiv1411.5626L
  We study the long term evolution of a set of 22 bipolar active regions
  (ARs) in which the main photospheric polarities are seen to rotate one
  around the other during several solar rotations. We first show that
  differential rotation is not at the origin of this large change in
  the tilt angle. A possible origin of this distortion is the nonlinear
  development of a kink-instability at the base of the convective zone;
  this would imply the formation of a non-planar flux tube which,
  while emerging across the photosphere, would show a rotation of its
  photospheric polarities as observed. A characteristic of the flux tubes
  deformed by this mechanism is that their magnetic twist and writhe
  should have the same sign. From the observed evolution of the tilt of
  the bipoles, we derive the sign of the writhe of the flux tube forming
  each AR; while we compute the sign of the twist from transverse field
  measurements. Comparing the handedness of the magnetic twist and writhe,
  we find that the presence of kink-unstable flux tubes is coherent with
  no more than 35% of the 20 cases for which the sign of the twist can
  be unambiguously determined. Since at most only a fraction of the tilt
  evolution can be explained by this process, we discuss the role that
  other mechanisms may play in the inferred deformation. We find that
  36% of the 22 cases may result from the action of the Coriolis force
  as the flux tube travels through the convection zone. Furthermore,
  because several bipoles overpass in their rotation the mean toroidal
  (East-West) direction or rotate away from it, we propose that a
  possible explanation for the deformation of all these flux tubes
  may lie in the interaction with large-scale vortical motions of the
  plasma in the convection zone, including also photospheric or shallow
  sub-photospheric large scale flows.

Title: Observations of magnetic helicity
Authors: van Driel-Gesztelyi, L.; Démoulin, P.; Mandrini, C. H.
Bibcode: 2003AdSpR..32.1855V
Altcode:
  The first observational signature of magnetic helicity in the solar
  atmosphere (sunspot whirls) was discovered 77 years ago. Since then,
  the existence of a cycle-invariant hemispheric helicity pattern has
  been firmly established through current helicity and morphological
  studies. During the last years, attempts were made to estimate/ measure
  magnetic helicity from solar and interplanetary observations. Magnetic
  helicity (unlike current helicity) is one of the few global quantities
  that is conserved even in resistive magnetohydrodynamics (MHD) on a
  timescale less than the global diffusion timescale, thus magnetic
  helicity studies make it possible to trace helicity as it emerges
  from the sub-photospheric layers to the corona and then is ejected via
  coronal mass ejections (CMEs) into the interplanetary space reaching
  the Earth in a magnetic cloud. We give an overview of observational
  studies on the relative importance of different sources of magnetic
  helicity, i.e. whether photospheric plasma motions (photospheric
  differential rotation and localized shearing motions) or the twist
  of the emerging flux tubes created under the photosphere (presumably
  by the radial shear in the differential rotation in the tachocline)
  is the dominant helicity source. We examine the sources of errors
  present in these early results and try to judge how realistic they are.

Title: Why to determine the magnetic helicity in corona and
    interplanetary medium?
Authors: Luoni, M. L.; Dasso, S.; Mandrini, C. H.; van Driel-Gesztelyi,
   L.; Démoulin, P.
Bibcode: 2003BAAA...46....8L
Altcode:
  Magnetic clouds are huge objects that travel in the interplanetary
  medium, transporting magnetic helicity (MH) produced by the Sun. Since
  the dissipation time of MH is much larger than the typical time
  associated with the dynamical processes in the solar corona and the
  heliosphere, MH is the natural magnetohydrodinamic (MHD) magnitude
  to compare interplanetary manifestations with the associated solar
  processes. In this work we study an active region that produced a
  coronal mass ejection (CME). We model the coronal magnetic field
  using a linear force free approach, and we calculate the magnetic
  flux and the variation of MH, before and after the ejection of
  the CME. We model also the magnetic field configuration of the
  associated interplanetary cloud, using several cylindrical models,
  and estimate the flux and the content of MH. Finally, we compare the
  coronal and the interplanetary values for the flux and the MH, and we
  find a very good agreement. The coronal flux is 10<SUP>22</SUP>Mx,
  while the magnetic flux for the cloud is around 10<SUP>21</SUP>Mx
  (∼ 10% of the coronal flux, as typically observed). The variation
  of the coronal MH turns out to be 3x10<SUP>42</SUP>Mx<SUP>2</SUP>,
  while we obtain that the MH contained in the magnetic cloud is in the
  range (2-8)x10<SUP>42</SUP>Mx<SUP>2</SUP>. Our results indicate that
  MH is a very useful tool to link phenomena in very different regimes
  and can be used to constrain both coronal and interplanetary models.

Title: CME shock warps coronal streamer - observation and MHD
    simulation
Authors: van der Holst, B.; van Driel-Gesztelyi, L.; Poedts, S.
Bibcode: 2002ESASP.506...71V
Altcode: 2002svco.conf...71V; 2002ESPM...10...71V
  A fast (v ≥ 1000 km s<SUP>-1</SUP>) CME was observed on 14 January
  2002, which was linked to an M4.4 long-duration flare event and
  a post-eruption loop system visible on, but partially occulted by,
  the SW limb. The fast expanding CME collided with a North-hemispheric
  helmet streamer, which was located above NOAA AR 9773 and was in 60°
  distance from the CME source region. An interaction with the CME (I)
  pushed the streamer aside and (II) created a deflection, setting off an
  outward propagating wavelike deformation along it. At the same time,
  a decametric-hectometric type-II radio burst was observed with the
  WAVES RAD2 instrument onboard the WIND spacecraft. Type-II bursts
  are indicative of shock waves. At about the time of the CME-streamer
  interaction a splitting was seen in the type-II emission, which
  indicated a shock continuing to propagate away from the Sun (thus
  getting into lower and lower density domains) and another branch,
  which indicated a shock propagating into denser plasma domain. We
  interpret this fine-structure of the type-II bursts as a result of the
  CME-streamer interaction. We suggest that the shock wave, which was
  associated with this fast CME, penetrated into the helmet streamer
  and then died away in the denser plasma (the splitting lasted for
  about 30 minutes). With our 2-D MHD code we simulate this CME-streamer
  interaction, using the observed configuration and magnetic topology. The
  simulation results confirm our hypothesis.

Title: Global budget for an eruptive active region . I. Equilibrium
    reconstruction approach
Authors: Bleybel, A.; Amari, T.; van Driel-Gesztelyi, L.; Leka, K. D.
Bibcode: 2002A&A...395..685B
Altcode:
  We present results on the magnetic structure of NOAA Active Region
  #7912 which was involved in a long duration flare on 14 October 1995,
  and was the source region for a magnetic cloud observed by the WIND
  spacecraft from October 18-20. Using vector magnetograms from the
  Imaging Vector Magnetograph (``IVM''), we reconstruct the magnetic
  field above this active region, assuming it is in a non-linear
  force-free state. This reconstruction is used to determine global
  properties of the active region magnetic field including topology,
  magnetic energy, and relative magnetic helicity. A comparison of some
  global quantities before and after the eruptive event is discussed. We
  show that the magnetic energy and relative helicity of the active
  region decreased after the eruption, consistent with the ejection
  of a large amount of helicity (in the magnetic cloud). We also show
  that the relaxed post-flare state still contains nonlinearities and is
  not consistent with a linear force-free state as predicted by Taylor's
  theory of relaxation. These results agree with those of recent numerical
  simulations concerning plasmoid ejection and helicity redistribution in
  the disruption of magnetic configurations. We propose as an explanation
  that the anchoring of field lines in the photosphere prevents a full
  cascade to the Taylor state, and that a variational formulation in which
  the action functional would describe this constraint should be derived.

Title: On the origin of peculiar active regions
Authors: Mandrini, C. H.; López Fuentes, M. C.; Démoulin, P.;
   van Driel-Gesztelyi, L.; Pevtsov, A. A.
Bibcode: 2002ESASP.505..121M
Altcode: 2002solm.conf..121M; 2002IAUCo.188..121M
  We study the long term evolution of a set of bipolar active regions
  (ARs) in which the main photospheric polarities are seen to rotate one
  around the other during several solar rotations. After showing that
  differential rotation cannot produce this large change in the tilt
  angle, we interpret this peculiar evolution as being the result of the
  emergence of magnetic flux tubes that are distorted with respect to
  the classical Ω-loop shape. A possible origin of this distortion is
  the nonlinear development of a kink-instability. Flux tubes deformed
  by this mechanism must have the same sign of twist and writhe. From
  the observed evolution of the tilt of the bipoles, we derive the
  sign of the writhe of the tube forming each AR; while we compute
  the sign of the twist from transverse field measurements. Comparing
  the handedness of the magnetic twist and writhe, we find that the
  presence of kink-unstable flux tubes is coherent with no more than 32%
  of the studied cases; so, a small fraction of these peculiar ARs can
  be explained by this process. Then we discuss the role that other
  mechanisms may play inducing the inferred deformation, such as the
  Coriolis force or external rotational motions of the plasma as the
  tube ascends in the convection zone.

Title: Dedication (SOLMAG 2002): Karen L. Harvey 1942 - 2002
Authors: Schrijver, Karel; van Driel-Gesztelyi, Lidia
Bibcode: 2002ESASP.505D..15S
Altcode: 2002IAUCo.188D..15S; 2002solm.confD..15S
  No abstract at ADS

Title: Emergence and loss of magnetic flux on the solar surface
Authors: van Driel-Gesztelyi, Lidia
Bibcode: 2002ESASP.505..113V
Altcode: 2002solm.conf..113V; 2002IAUCo.188..113V
  This review is focused on observations and theoretical advances
  on large-scale flux emergence and decay, which forms and dominates
  the magnetic field patterns on the Sun. The basic characteristics
  of emerging flux (asymmetry, inclination to the vertical, twist,
  sea-serpent-like appearance in the early stage of flux emergence in the
  photosphere) are described together with the results of relevant MHD
  simulations, which help us to interpret these observations. Magnetic
  flux emergence is far from being a random process in the active belt:
  it has a grouping (nesting) tendency, which has important implications
  for the operation of the solar dynamo. As soon as active regions are
  fully formed, they start decaying. Their magnetic flux gradually speads
  over an ever-increasing area and gets removed from the photosphere via
  small scale processes (e.g. Ohmic dissipation and flux cancellation,
  including flux submergence). Emergence of U-loops may play an important
  role in the removal of large-scale flux from the photopshere.

Title: The Magnetic Helicity Budget of a cme-Prolific Active Region
Authors: Green, L. M.; López fuentes, M. C.; Mandrini, C. H.;
   Démoulin, P.; Van Driel-Gesztelyi, L.; Culhane, J. L.
Bibcode: 2002SoPh..208...43G
Altcode:
  Coronal mass ejections (CMEs) are thought to be the way by which the
  solar corona expels accumulated magnetic helicity which is injected
  into the corona via several methods. DeVore (2000) suggests that a
  significant quantity is injected by the action of differential rotation,
  however Démoulin et al. (2002b), based on the study of a simple bipolar
  active region, show that this may not be the case. This paper studies
  the magnetic helicity evolution in an active region (NOAA 8100) in
  which the main photospheric polarities rotate around each other during
  five Carrington rotations. As a result of this changing orientation of
  the bipole, the helicity injection by differential rotation is not a
  monotonic function of time. Instead, it experiences a maximum and even
  a change of sign. In this particular active region, both differential
  rotation and localized shearing motions are actually depleting the
  coronal helicity instead of building it. During this period of five
  solar rotations, a high number of CMEs (35 observed, 65 estimated)
  erupted from the active region and the helicity carried away has
  been calculated, assuming that each can be modeled by a twisted flux
  rope. It is found that the helicity injected by differential rotation
  (≈−7×10<SUP>42</SUP> Mx<SUP>2</SUP>) into the active region cannot
  provide the amount of helicity ejected via CMEs, which is a factor 5
  to 46 larger and of the opposite sign. Instead, it is proposed that
  the ejected helicity is provided by the twist in the sub-photospheric
  part of the magnetic flux tube forming the active region.

Title: The Magnetic Helicity Injected by Shearing Motions
Authors: Démoulin, P.; Mandrini, C. H.; Van Driel-Gesztelyi, L.;
   Lopez Fuentes, M. C.; Aulanier, G.
Bibcode: 2002SoPh..207...87D
Altcode:
  Photospheric shearing motions are one of the possible ways to inject
  magnetic helicity into the corona. We explore their efficiency as
  a function of their particular properties and those of the magnetic
  field configuration. Based on the work of M. A. Berger, we separate
  the helicity injection into two terms: twist and writhe. For shearing
  motions concentrated between the centers of two magnetic polarities
  the helicity injected by twist and writhe add up, while for spatially
  more extended shearing motions, such as differential rotation, twist
  and writhe helicity have opposite signs and partially cancel. This
  implies that the amount of injected helicity can change in sign with
  time even if the shear velocity is time independent. We confirm the
  amount of helicity injected by differential rotation in a bipole
  in the two particular cases studied by DeVore (2000), and further
  explore the parameter space on which this injection depends. For a
  given latitude, tilt and magnetic flux, the generation of helicity is
  slightly more efficient in young active regions than in decayed ones
  (up to a factor 2). The helicity injection is mostly affected by the
  tilt of the AR with respect to the solar equator. The total helicity
  injected by shearing motions, with both spatial and temporal coherence,
  is at most equivalent to that of a twisted flux tube having the same
  magnetic flux and a number of turns of 0.3. In the solar case, where
  the motions have not such global coherence, the injection of helicity
  is expected to be much smaller, while for differential rotation this
  maximum value reduces to 0.2 turns. We conclude that shearing motions
  are a relatively inefficient way to bring magnetic helicity into the
  corona (compared to the helicity carried by a significantly twisted
  flux tube).

Title: Long-term helicity evolution in NOAA active region 8100
Authors: Green, L. M.; López Fuentes, M. C.; Mandrini, C. H.; van
   Driel-Gesztelyi, L.; Démoulin, P.
Bibcode: 2002ESASP.477...43G
Altcode: 2002scsw.conf...43G
  Magnetic helicity is the topological parameter used to describe
  the structure in the magnetic field and has become increasingly
  important in coronal studies. Helicity is well preserved in the
  corona even under non-ideal MHD conditions (see Biskamp 1993), and
  the Sun can avoid endless accumulation of helicity by ejecting it
  via the launch of coronal mass ejections (eg. Rust 1994; Low 1996;
  Devore 2000). Computations are made for NOAA active region 8100 to
  determine the coronal helicity and helicity injected into the region
  by differential rotation. These values are then compared to the total
  amount of helicity lost via coronal mass ejections to test whether
  differential rotation can inject a significant amount of helicity into
  the corona. It is found that differential rotation cannot inject a
  significant amount of helicity to be a viable source for the coronal
  mass ejection activity. Instead, helicity is likely to be brought into
  the corona by the emergence of twisted and distorted flux tubes.

Title: Numerical modeling of CME initiation and propagation
Authors: Poedts, S.; van der Holst, B.; de Sterck, H.; van
   Driel-Gesztelyi, L.; Csík, A.; Milesi, A.; Deconinck, H.
Bibcode: 2002ESASP.477..263P
Altcode: 2002scsw.conf..263P
  The shocks in the solar corona caused by fast Coronal Mass Ejections
  (CMEs) and the shock at the Earth's magnetosphere caused by the
  corresponding magnetic clouds (superposed on the solar wind) are studied
  in the framework of computational magnetohydrodynamics (MHD). Due to the
  presence of three characteristic velocities and the anisotropy induced
  by the magnetic field, MHD shocks can have a complicated structure
  including secondary shock fronts, overcompressive and compound shocks,
  etc. Numerical simulations show that CME shocks (in the lower corona)
  and the shock at the Earth's magnetosphere (at times of the impact of
  a magnetic cloud) have such a complex structure. The CME shocks are
  important for 'space weather' because they can easily be observed in
  radio wavelengths. This makes it possible to track the position of the
  CMEs/magnetic clouds and, hence, to follow their propagation through
  the corona. The collision of two such shocks is discussed. Also,
  the possibility of locating the magnetic cloud from the passage of
  a satellite through the leading shock front is discussed. Moreover,
  the topology of the shock at the Earth's magnetosphere at the impact
  of a magnetic cloud is important for the 'geo-effectiveness' of the
  magnetic storms. Hence, a detailed study of the MHD shocks generated
  by CMEs may reveal some of the key properties space weather.

Title: The distribution of peculiar active regions along two solar
    cycles
Authors: Mandrini, C. H.; López Fuentes, M. C.; Démoulin, P.;
   van Driel-Gesztelyi, L.
Bibcode: 2002ESASP.477...27M
Altcode: 2002scsw.conf...27M
  We perform a statistical study of the spatial and temporal distribution
  of "peculiar" active regions (ARs) along solar cycles 21 and 22. ARs
  usually appear in the photosphere in the form of bipolar concentrations
  of magnetic flux, by "peculiar" we mean regions in which the the
  main polarities rotate one around the other along several solar
  rotations. Our results show that these regions are spatially distributed
  as usual ARs when no selection on their magnetic flux is applied. When
  classified according to their flux, the latitudinal distribution of
  ARs above 10<SUP>22</SUP> Mx closely follow the butterfly diagram;
  while those with lower flux are more randomly distributed. The number
  of rotating ARs follow the activity cycle, with a tendency to dual-peak
  maxima.

Title: Magnetic build-up and precursors of CMEs
Authors: van Driel-Gesztelyi, Lidia; Schmieder, Brigitte; Poedts,
   Stefaan
Bibcode: 2002ESASP.477...47V
Altcode: 2002scsw.conf...47V
  CMEs are fundamentally magnetic phenomena, thus to improve CME forecast
  we have to find out more about the characteristics of the small and
  large-scale magnetic field in and around their source region prior
  to CME occurrence. In this paper we show examples of the magnetic
  evolution of CME-prolific active regions using SOHO/MDI data. It
  appears that CMEs are preceded by magnetic evolution during which
  the helicity of the source region is increasing due to twisted flux
  emergence, shearing motions between opposite polarity footpoints
  of subsequently emerging bipoles and, in a smaller extend, by the
  differential rotation acting on the emerged flux. Furthermore, we find
  short-term magnetic precursors of CME events, typically a combination of
  major flux emergence, cancellation and fast shearing motions in active
  regions with strong concentrated magnetic fields prior to flare-related
  CMEs and small-scale cancellation events along the magnetic inversion
  line in decayed active regions with low magnetic flux density prior to
  filament eruption-related CMEs. We make an overview of recent studies
  on magnetic helicity and suggest that such analyses will be able to
  provide a key to unlock the secrets of CME buildup and initiation.

Title: Multi-wavelength observations of an X-class flare without a
    coronal mass ejection.
Authors: Green, L. M.; Matthews, S. A.; van Driel-Gesztelyi, L.;
   Harra, L. K.; Culhane, J. L.
Bibcode: 2002SoPh..205..325G
Altcode:
  Developments in our knowledge of coronal mass ejections (CMEs) have
  shown that many of these transients occur in association with solar
  flares. On the occasions when there is a common occurrence of the
  eruption and the flare, it is most likely that the flare is of high
  intensity and/or long-duration (Burkepile, Hundhausen, and Webb,
  1994; Munro et al., 1979; Webb and Hundhausen, 1987). A model for
  the relationship between the long-duration event and eruption has
  been developed (Carmichael, 1964; Sturrock, 1966; Hirayama, 1974;
  Kopp and Pneuman, 1976), but not so for the high-intensity flares and
  eruptions. This work investigates the magnetic topology changes that
  occur for a X1.2 GOES classification flare which has no associated
  CME. It is found that the flare is likely to result from the interaction
  between two pre-existing loops low in the corona, producing a confined
  flare. Slightly higher in the corona, a loop is observed which
  exhibits an outward motion as a result of the reconfiguration during
  reconnection. The objective of this work is to gain insight on the
  magnetic topology of the event which is critical in order to determine
  whether a high-intensity flare is likely to be related to a CME or not.

Title: What is the source of the magnetic helicity shed by CMEs? The
    long-term helicity budget of AR 7978
Authors: Démoulin, P.; Mandrini, C. H.; van Driel-Gesztelyi, L.;
   Thompson, B. J.; Plunkett, S.; Kovári, Zs.; Aulanier, G.; Young, A.
Bibcode: 2002A&A...382..650D
Altcode:
  An isolated active region (AR) was observed on the Sun during seven
  rotations, starting from its birth in July 1996 to its full dispersion
  in December 1996. We analyse the long-term budget of the AR relative
  magnetic helicity. Firstly, we calculate the helicity injected
  by differential rotation at the photospheric level using MDI/SoHO
  magnetograms. Secondly, we compute the coronal magnetic field and
  its helicity selecting the model which best fits the soft X-ray loops
  observed with SXT/Yohkoh. Finally, we identify all the coronal mass
  ejections (CMEs) that originated from the AR during its lifetime using
  LASCO and EIT/SoHO. Assuming a one to one correspondence between CMEs
  and magnetic clouds, we estimate the magnetic helicity which could be
  shed via CMEs. We find that differential rotation can neither provide
  the required magnetic helicity to the coronal field (at least a factor
  2.5 to 4 larger), nor to the field ejected to the interplanetary
  space (a factor 4 to 20 larger), even in the case of this AR for
  which the total helicity injected by differential rotation is close
  to the maximum possible value. However, the total helicity ejected is
  equivalent to that of a twisted flux tube having the same magnetic flux
  as the studied AR and a number of turns in the interval [0.5,2.0]. We
  suggest that the main source of helicity is the inherent twist of the
  magnetic flux tube forming the active region. This magnetic helicity
  is transferred to the corona either by the continuous emergence of the
  flux tube for several solar rotations (i.e. on a time scale much longer
  than the classical emergence phase), or by torsional Alfvén waves.

Title: Relation between the coronal magnetic helicity to the helicity
    in interplanetary magnetic clouds
Authors: Luoni, M. L.; Mandrini, C. H.; Démoulin, P.; van
   Driel-Gesztelyi, L.; López Fuentes, M. C.
Bibcode: 2002BAAA...45...20L
Altcode:
  On October 18, 1995, the Solar Wind Experiment and the Magnetic
  Field Instrument on board the WIND spacecraft registered a magnetic
  cloud at 1 AU, which was followed by a strong geomagnetic storm. The
  solar source of this phenomenon was located in active region (AR) NOAA
  7912. On October 14, 1995, a C1.6 long duration event (LDE) started at
  approximately 5:00 UT and lasted for around 15 hours. In this work, we
  compute the variation of the coronal magnetic helicity using a linear
  force-free model of the field. We use magnetograms obtained at Kitt
  Peak National Solar Observatory as boundary conditions to extrapolate
  the photospheric magnetic field to the corona. The magnetic helicity
  is calculated at three different times, changing the parameters of the
  magnetic field model to fit the loops observed in soft X-rays by the
  Soft X-ray Telescope on board of Yohkoh (SXT/Yohkoh). The computations
  are done before the LDE, during its maximun and its decay phase. The
  variation of the coronal magnetic helicity is compared to the helicity
  of the interplanetary magnetic cloud observed by WIND. These values
  turn out to be quite similar, considering the errors involved. Our
  results confirm quantitatively the link between solar and interplanetary
  phenomena.

Title: Active region helicity evolution and related coronal mass
    ejection activity.
Authors: Green, L.; Mandrini, C.; van Driel-Gesztelyi, L.; Demoulin, P.
Bibcode: 2002cosp...34E1213G
Altcode: 2002cosp.meetE1213G
  The computation of magnetic helicity has become increasingly important
  in the studies of solar activity. Observations of helical structures
  in the solar atmosphere, and their subsequent ejection into the
  interplanetary medium, have resulted in considerable interest to find
  the link between the amount of helicity in the coronal magnetic field
  and the origin of coronal mass ejections (CMEs). This is reinforced by
  theory which shows magnetic helicity to be a well preserved quantity
  (Berger, 1984), and so with a continued injection into the corona an
  endless accumulation will occur. CMEs therefore provide a natural
  method to remove helicity from the corona. Recent works (DeVore,
  2000, Chae, 2001, Chae et al., 2001, Demoulin et al., 2002, Green et
  al., 2002) have endeavoured to find the source of helicity in the
  corona to explain the observed CME activity in specific cases. The
  main candidates being differential rotation, shear motions or a
  transfer of helicity from below the photosphere into the corona. In
  order to establish a confident relation between CMEs and helicity,
  these works needs to be expanded to include CME source regions with
  different characteristics. A study of a very different active region
  will be presented and the relationship between helicity content and
  CME activity will be discussed in the framework of the previous studies.

Title: Helicity Loading and Dissipation: The Helicity Budget of AR
    7978 from the Cradle to the Grave
Authors: van Driel-Gesztelyi, L.; Démoulin, P.; Mandrini, C. H.;
   Plunkett, S.; Thompson, B.; Kövári, Zs.; Aulanier, G.; Young, A.;
   López Fuentes, M.; Poedts, S.
Bibcode: 2002mwoc.conf..143V
Altcode:
  An isolated active region was observed on the Sun during seven
  rotations, starting in July 1996. I will present a study of its magnetic
  field, concentrating on its helicity budget. The photospheric field
  is extrapolated into the corona in a linear force-free approach,
  using SOHO/MDI magnetograms and Yohkoh/SXT images, allowing us to
  compute, in a crude way, the relative coronal magnetic helicity of
  the active region. Using the observed magnetic field distribution
  (SOHO/MDI magnetograms) we also calculate the helicity injected by
  the differential rotation during seven solar rotations. Finally, using
  SOHO/LASCO and EIT as well as Yohkoh/SXT observations, we identify all
  the 26 CMEs which originated from this active region during its lifetime
  and using average values of the field and radius of magnetic clouds,
  we estimate the helicity which should be shed via CMEs. We compare
  these three values to evaluate the importance of the differential
  rotation relative to twisted flux emergence as a source of magnetic
  helicity. We find that the differential rotation can neither provide
  enough helicity to account for the diagnosed coronal heicity values,
  nor for the helicity carried away by CMEs. We suggest that the main
  source of the magnetic helicity must be the inherent twist of the
  magnetic flux tube forming the active region. This magnetic helicity is
  transferred to the corona either by a slow continuous emergence of the
  flux tube or by torsional Alfven waves, during several solar rotations.

Title: Multi-Wavelength Observations of Yohkoh White-Light Flares
Authors: Matthews, S. A.; van Driel-Gesztelyi, L.; Hudson, H. S.;
   Nitta, N. V.
Bibcode: 2002mwoc.conf..289M
Altcode:
  The problem of accounting for the continuum emission that is observed
  in solar flares is still one which is largely unresolved. These
  white-light flares place severe constraints on the energy requirements
  and transport mechanisms operating in the flare, raising the question
  of whether partial or total in-situ heating is required to account for
  this deep atmospheric heating. Since it is widely believed that the
  energy release in solar flares occurs in the corona and that energy is
  then transported to the low chromosphere where the optical emission is
  produced, most attempts to explain the origin of white-light flares
  have centred on canonical mechanisms. However, it has become clear
  that the spatial and temporal correspondence between white-light and
  HXR is not one-to one. In order to further our understanding of these
  events we study the temporal and spatial relationships between emission
  in the visible, SXR and HXR regimes in all of the white-light flares
  observed by Yohkoh prior to the failure of the Soft X-ray Telescope
  (SXT) Aspect Camera in 1992; a total of approximately 30 events.

Title: Observations of emerging flux tubes
Authors: van Driel-Gesztelyi, Lidia
Bibcode: 2002ocnd.confE...6V
Altcode:
  No abstract at ADS

Title: Inferring the Writhe of Emerging Flux Tubes from the Evolution
    of the Orientation of Bipole Axes
Authors: López Fuentes, M. C.; Mandrini, C. H.; Démoulin, P.;
   van Driel-Gesztelyi, L.; Pevtsov, A.
Bibcode: 2002RMxAC..14..108L
Altcode:
  No abstract at ADS

Title: Observations of helicity
Authors: van Driel-Gesztelyi, L.
Bibcode: 2002cosp...34E1455V
Altcode: 2002cosp.meetE1455V
  I will review attempts made during the last decade to evaluate
  and measure current helicity and magnetic helicity from solar and
  interplanetary observations. I will show the main results of the current
  helicity studies, which led to important discoveries like e.g. the
  hemispheric helicity pattern. Then I give an overview of multiwavelength
  observational studies on magnetic helicity. Magnetic helicity (unlike
  current helicity) is one of the few global quantities, which is
  conserved even in resistive MHD on a timescale less than the global
  diffusion timescale, thus magnetic helicity studies make it possible
  to trace helicity as it emerges from the sub-photospheric layers
  to the corona and then is ejected via CMEs into the interplanetary
  space reaching the Earth in a magnetic cloud. I will give an overview
  of observational studies on the relative importance of different
  sources of magnetic helicity, i.e. whether photospheric plasma motions
  (differential rotation and localised shearing motions) generate the bulk
  of helicity ejected in CMEs or the twist of the emerging flux tubes
  created under the photosphere (presumably by differential rotation in
  the tachocline) is the dominant helicity source.

Title: Peculiar Active Regions during the Last Two Solar Cycles
Authors: López Fuentes, M. C.; Mandrini, C. H.; Démoulin, P.;
   van Driel-Gesztelyi, L.
Bibcode: 2002RMxAC..14R.107L
Altcode:
  No abstract at ADS

Title: Evolution of the source region of the interplanetary magnetic
    cloud of 18-20 Oct. 1995
Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Baranyi, T.
Bibcode: 2002AdSpR..29.1489V
Altcode:
  We follow the evolution and activity of the reversed polarity AR
  7912 using multi-wavelength observations. We find that the presence
  of high shear increased by flux emergence led to the occurrence
  of a long-duration eruptive flare on 14 October 1995, which was
  manifested in the SXR corona by an arcade of expanding sigmoidal
  loops. A twisted magnetic cloud was observed at 1 AU between October
  18-20. We propose that it was ejected from this reversed polarity AR,
  and it was associated with the expanding sigmoids.

Title: Relationships between CME's and prominences
Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Aulanier, G.;
   Démoulin, P.; Thompson, B.; De Forest, C.; Wiik, J. E.; Saint Cyr,
   C.; Vial, J. C.
Bibcode: 2002AdSpR..29.1451S
Altcode:
  We have studied the erupting prominences which were associated with
  coronal mass ejections during a series of campaigns involving both
  spacecraft and ground-based observatories. The evolution of the
  physical conditions within the prominences was established from Hα
  and magnetic field observations. Particular attention ahs been paid
  to the presence of mixed amgnetic polarity in the filament channel,
  the evolution of the shear of the large-scale magnetic field, and
  the existence of multiple magnetic inversion lines. We conclude that
  reconnection of large-scale coronal magnetic fields is responsible
  for both the CME and filament eruption.

Title: Long-Term Evolution of Active Regions
Authors: López Fuentes, M.; Mandrini, C. H.; Démoulin, P.; van
   Driel-Gesztelyi, L.
Bibcode: 2001ASPC..248..131L
Altcode: 2001mfah.conf..131L
  No abstract at ADS

Title: An Observational Test for Solar Atmospheric Heating
Authors: van Driel-Gesztelyi, L.; Démoulin, P.; Ireland, J.; Thompson,
   B.; Fludra, A.; Oláh, K.; Kövári, Zs.; Harra, L. K.; Mandrini,
   C. H.; Bocchialini, K.; Orlando, S.
Bibcode: 2001IAUS..203..514V
Altcode:
  We study the evolution of the emissivity and heating correlated with
  magnetic observables of an active region from its birth throughout
  its decay during seven solar rotations (July-Dec. 1996). Taking one
  "snapshot" per g:wq: Command not found. time of flares, we analyse
  multi-wavelength and multi-instrument data obtained from SOHO (MDI,
  EIT, CDS and SUMER), Yohkoh (SXT), GOES, SOLSTICE and 10.7 cm radio
  data from DRAO, Canada. We utilise our results to test the validity
  of coronal heating models. We find that models which are based on
  the dissipation of stressed, current-carrying magnetic fields are in
  better agreement with the observations than the models which attribute
  coronal heating to the dissipation of MHD waves.

Title: The Relationship between CMEs and Prominence Eruptions
Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Delannée, C.;
   Simnett, G. M.; Wiik, J. E.
Bibcode: 2001IAUS..203..310S
Altcode:
  From multi-wavelength studies of eruptions of prominences observed by
  Yohkoh, SoHO and ground-based observatories, we find a good correlation
  between prominence eruptions and CMEs (i.e. May 1 1996, Sept 25 1996,
  May 31 1997). Focusing our interest on their temporal relationship,
  we observe that it is not clear that filament eruption is prior to
  the CME. Nevertheless they are both signatures of destabilization of
  the global coronal magnetic field. The magnetic configuration in the
  corona should involve the initial presence of a twisted flux tube. The
  eruption could be driven by a fast increase of the poloidal field in
  the flux tube or by photospheric shearing motions of the flux tube.

Title: Magnetic Evolution of a Long-Lived Active Region: The Sources
    of Magnetic Helicity
Authors: Mandrini, C. H.; Démoulin, P.; van Driel-Gesztelyi, L.;
   Aulanier, G.; Thompson, B.; Plunkett, S.; Kövári, Zs.
Bibcode: 2001ASPC..248..139M
Altcode: 2001mfah.conf..139M
  No abstract at ADS

Title: Flux Ratios of Solar and Stellar Active Regions (CD-ROM
Directory: contribs/olah2)
Authors: Oláh, K.; van Driel-Gesztelyi, L.
Bibcode: 2001ASPC..223..709O
Altcode: 2001csss...11..709O
  No abstract at ADS

Title: Emergence of a U-loop - sub-photospheric link between solar
    active regions
Authors: van Driel-Gesztelyi, L.; Malherbe, J. -M.; Démoulin, P.
Bibcode: 2000A&A...364..845V
Altcode:
  Using SOHO/MDI magnetic maps we present the first direct observational
  evidence for the emergence of a U-loop in the solar photosphere. We
  show that two active regions (ARs), i.e. two adjacent Omega -loops,
  which were emerging at the same time at the same solar latitude,
  about 150000 km distance in longitude from each other, emerged from
  at least partially the same toroidal flux strand, and we bring five
  independent arguments to prove this assertion. The opposite polarity
  legs of the two Omega -loops were connected below the photosphere by a
  U-shaped loop. Following the emergence of the Omega -loops, the U-loop
  started emerging, manifested by the fast proper motion of the leading
  spots of the eastern (smaller) active region, which, after forming an
  elongated channel, collided with the following spots of the westerly
  AR and started cancelling with them. The full cancellation could not be
  followed because the ARs rotated out of sight. The total magnetic flux
  of the two ARs was unequal, the flux in the smaller AR was a quarter of
  that of the larger one. We propose scenarios for the formation of such
  a U-loop and discuss the implications of the confirmed existence of
  U-loops for the solution of such puzzles as the in-situ disappearance
  of magnetic flux from active regions, active nests and the formation
  of inter-AR filaments.

Title: Initiation of CMEs: the role of magnetic twist
Authors: van Driel-Gesztelyi, L.; Manoharan, P. K.; Démoulin, P.;
   Aulanier, G.; Mandrini, C. H.; Lopez-Fuentes, M.; Schmieder, B.;
   Orlando, S.; Thompson, B.; Plunkett, S.
Bibcode: 2000JASTP..62.1437V
Altcode: 2000JATP...62.1437V
  Recent multiwavelength observations, modelling results and
  theoretical developments indicate the importance of twisted magnetic
  configurations in solar active regions (ARs) in the initiation of
  coronal mass ejections (CMEs). Through multiwavelength analysis of a
  few representative events we make an attempt to provide constraints
  for CME models. The two events presented here in detail start with
  the expansion of sigmoids (S- or inverse S-shaped loops) observed in
  soft X-rays. Both events (on 25 October /1994 and 14 October /1995)
  occurred before the launch of the SOHO spacecraft, but indirect
  evidences (i.e. signatures of an outward propagation traced up to /~20
  solar radii and an associated magnetic cloud) suggest that both of them
  were related to CMEs. We show evidence that sigmoids are the coronal
  manifestations of twisted magnetic flux tubes, which start expanding
  presumably due to a loss of equilibrium. It is noteworthy that the
  analysed CMEs occurred in a complex (not simply bipolar) magnetic
  environment and in all cases we found evidences of the interaction
  (magnetic reconnection) with the surrounding fields. We propose a
  scenario for sigmoid expansion related CME events and suggest that
  twisted magnetic configurations are good candidates for being source
  regions of CMEs.

Title: The Counterkink Rotation of a Non-Hale Active Region
Authors: López Fuentes, M. C.; Demoulin, P.; Mandrini, C. H.; van
   Driel-Gesztelyi, L.
Bibcode: 2000ApJ...544..540L
Altcode: 2014arXiv1412.1456L
  We describe the long-term evolution of a bipolar non-Hale active region
  that was observed from 1995 October to 1996 January. During these
  four solar rotations the sunspots and subsequent flux concentrations,
  during the decay phase of the region, were observed to move in such a
  way that by December their orientation conformed to the Hale-Nicholson
  polarity law. The sigmoidal shape of the observed soft X-ray coronal
  loops allows us to determine the sense of the twist in the magnetic
  configuration. This sense is confirmed by extrapolating the observed
  photospheric magnetic field, using a linear force-free approach,
  and comparing the shape of computed field lines with the observed
  coronal loops. This sense of twist agrees with that of the dominant
  helicity in the solar hemisphere where the region lies, as well as
  with the evolution observed in the longitudinal magnetogram during
  the first rotation. At first sight the relative motions of the
  spots may be misinterpreted as the rising of an Ω loop deformed by
  a kink instability, but we deduce from the sense of their relative
  displacements a handedness for the flux-tube axis (writhe) that is
  opposite to that of the twist in the coronal loops and, therefore,
  to what is expected for a kink-unstable flux tube. After excluding
  the kink instability, we interpret our observations in terms of a
  magnetic flux tube deformed by external motions while rising through
  the convective zone. We compare our results with those of other related
  studies, and we discuss, in particular, whether the kink instability
  is relevant to explain the peculiar evolution of some active regions.

Title: Magnetic Activity Associated With Radio Noise Storms
Authors: Bentley, R. D.; Klein, K. -L.; van Driel-Gesztelyi, L.;
   Démoulin, P.; Trottet, G.; Tassetto, P.; Marty, G.
Bibcode: 2000SoPh..193..227B
Altcode:
  As it crossed the solar disk in May and June 1998, AR 8227 was tracked
  by TRACE, Yohkoh, SOHO, and many ground-based observatories. We have
  studied how the evolution of the magnetic field resulted in changes in
  activity in the corona. In particular, we examine how the evolving field
  may have led to the acceleration of electrons which emit noise storms
  observed by the Nançay Radio Heliograph between 30 May and 1 June
  1998, in the absence of any flare. The magnetic changes were related
  to moving magnetic features (MMFs) in the vicinity of the leading
  spot and are related to the decay of this spot. Within the limits of
  the instrumental capabilities, the location in time and space of the
  radio emissions followed the changes observed in the photospheric
  magnetograms. We have extrapolated the photospheric magnetic field
  with a linear force-free approximation and find that the active region
  magnetic field was very close to being potential. These computations
  show a complex magnetic topology associated to the MMFs. The observed
  photospheric evolution is expected to drive magnetic reconnection in
  such complex magnetic topology. We therefore propose that the MMFs
  are at the origin of the observed metric noise-storms.

Title: Large-Scale Evolution of the Active Region NOAA 7978, 7981,
    7986 Observed by Goes, Soho, and Yohkoh
Authors: Orlando, S.; Khan, J.; van Driel-Gesztelyi, L.; Thompson,
   B.; Fludra, A.; Foing, B.
Bibcode: 2000AdSpR..25.1913O
Altcode:
  We took part in a joint project aimed to study the large-scale
  evolution of an active region from its emergence throughout its decay
  for several solar rotations. Our interest focuses on the understanding
  of how energy is generated, released, deposited, and transformed in
  active regions. To this end, we determined physical parameters like
  intensity, temperature, and emission measure of the whole active region
  as a function of time for the entire period selected. We present the
  preliminary results of the analysis of GOES (Geosynchronous Operational
  Environmental Satellite), SOHO (Solar and Heliospheric Observatory)
  and Yohkoh data of the active region named NOAA 7978, 7981, and 7986
  observed between July and October 1996

Title: Yohkoh Observations of White-Light Flares
Authors: Matthews, S.; van Driel-Gesztelyi, L.; Hudson, H.; Nitta, N.
Bibcode: 2000ASPC..206..239M
Altcode: 2000hesp.conf..239M
  No abstract at ADS

Title: Long-term evolution of an AR
Authors: van Driel-Gesztelyi, L.
Bibcode: 2000ssls.work...95V
Altcode:
  I summarize the results of a complex and comprehensive analysis of
  the evolution of an isolated active region (AR) in the period of
  July-November 1996. Using SOHO/MDI full-disc magnetic maps, we follow
  the magnetic evolution of the AR for several months. We extrapolate the
  photospheric magnetic fields in the linear force-free approximation and
  match the modelled field lines with the soft X-ray loops observed with
  the Yohkoh/SXT in order to diagnose the coronal magnetic shear. We find
  that while the turbulent motions diffuse the flux, the differential
  rotation, and possibly twisted flux emergence, increase the magnetic
  shear. Flares are observed during the first three rotations, while CME
  events (observed by SOHO/EIT and LASCO) originate from this AR from its
  emergence throughout its decay. Several early CMEs, while none of the
  late CMEs, are related to flare events above the GOES B1 level. We find
  that the late CMEs occur when the magnetic shear, after accumulating
  for four rotations, reaches a high level and saturates. We propose that
  CME activity serves as a valve through which the AR could get rid of
  excess shear and helicity. Furthermore, we study the evolution of the
  emissivity and heating correlated with magnetic observables of the AR
  from its birth throughout its decay. Taking one "snapshot" per rotation
  at each consecutive central meridian passage (CMP) of the AR, outside
  the time of flares, we analyse multi-wavelength and multi-instrument
  data obtained from SOHO (MDI and SUMER), Yohkoh (SXT), GOES and 10.7 cm
  radio data from DRAO, Canada. We find that the magnetic flux density -
  emitted radiation relations follow a power-law with exponents which
  appear to depend on the formation temperature (height) of the emission.

Title: 3-D Magnetic Configurations for Filaments and Flares: The
    Role of ``Magnetic Dips'' and ``Bald Patches''
Authors: Aulanier, G.; Schmieder, B.; van Driel-Gesztelyi, L.; Kucera,
   T.; Démoulin, P.; Fang, C.; Mein, N.; Vial, J. -C.; Mein, P.; Tang,
   Y. H.; Deforest, C.
Bibcode: 2000AdSpR..26..485A
Altcode:
  The 3-D magnetic configuration of a filament and of a low energy
  flare is reconstructed, using linear mag- netohydrostatic (lmhs)
  extrapolations. In both cases, we find observational signatures
  of energy release at the locations of computed ``bald patches''
  separatrices, characterised by field lines which are tangent to
  the photosphere.The filament was observed on Sept. 25, 1996, in Hα
  with the MSDP on the German VTT, Tenerife, as well as in Si IV with
  SOHO/SUMER. It is modeled as a twisted flux-tube deformed by the
  magnetic polarities observed with SOHO/MDI. The shape and location of
  the computed dipped field lines are in good agreement with the shape of
  the filament and its feet observed in Hα. Some ``bald patches'' (BPs)
  are present where the distribution of dips reaches the photosphere. We
  show that some of the large scale field lines rooted in BPs can be
  related to bright fine structures in Si IV. We propose that the plasma
  there is heated by ohmic dissipation from the currents expected to be
  present along the BP separatrices.The flare was observed on May 18,
  1994, in soft X-rays with Yohkoh/SXT, and in Hα at Mitaka (Japan). The
  magnetic field is directly extrapolated from a photospheric magnetogram
  from Kitt Peak Observatory. The intersections with the photosphere of
  the computed separatrices match well the bright Hα ribbons. The later
  are associated to three BPs, with overlaying dipped field lines. We
  show that enhanced densities are present in these dips, which can be
  correlated with dark Hα fibrils.Both cases show the importance of
  dipped field lines and BPs in the solar atmosphere. Energy release
  via ohmic dissipation as well as reconnection along BP separatrices
  is proposed to provide heating observed as UV brightenings in filament
  channels and even as small flares

Title: Flares and Large Scale Evolution of a Solar Active Region
Observed in 1996 by GOES, SOHO and YOHKOH: Implications for X-Ray
    stellar Variability
Authors: Orlando, S.; van Driel-Gesztelyi, L.; Thomson, B.; Khan,
   J.; Foing, B. H.
Bibcode: 2000ASIC..544..783O
Altcode: 2000vsea.conf..783O
  No abstract at ADS

Title: What Can we Learn Studying Long-Term Magnetic Evolution of
    Solar Active Regions?
Authors: van Driel-Gesztelyi, L.; Kovari, Zs.; Lopez-Fuentes, M.;
   Mandrini, C. H.; Demoulin, P.
Bibcode: 2000ESASP.463..451V
Altcode: 2000sctc.proc..451V
  No abstract at ADS

Title: Non Linear Force-Free Reconstruction of a Flaring Active Region
Authors: Bleybel, A.; Amari, T.; van Driel-Gesztelyi, L.; Leka, K. D.
Bibcode: 1999ESASP.448..709B
Altcode: 1999ESPM....9..709B; 1999mfsp.conf..709B
  No abstract at ADS

Title: The Total Eclipse Experience in Hungary
Authors: van Driel-Gesztelyi, L.; Jankovics, I.; Kovács, J.;
   Schmieder, B.; Vincze, I. J.
Bibcode: 1999ESASP.448.1297V
Altcode: 1999ESPM....9.1297V; 1999mfsp.conf.1297V
  No abstract at ADS

Title: On the Topology of Magnetic Reconnection in Flares -
    Constraints from Multiwavelength Observations
Authors: van Driel-Gesztelyi, L.
Bibcode: 1999ESASP.448..901V
Altcode: 1999mfsp.conf..901V; 1999ESPM....9..901V
  No abstract at ADS

Title: Flare loop geometry
Authors: Nitta, N.; Van Driel-Gesztelyi, L.; Harra-Murnion, L. K.
Bibcode: 1999SoPh..189..181N
Altcode:
  In selected flares that occurred in AR 7260, we have studied
  the geometry of the brightest soft X-ray loop by tracing it on
  an image. Even under the assumption that the loop is contained
  in a plane, it is clear that a single image does not permit us to
  determine the full geometry. It only provides possible loop shapes as
  a function of the inclination angle of the loop plane with respect
  to the vertical. However, all the loops that reproduce the observed
  appearance give the same direction of increasing height as projected
  on to the image plane. This direction is compared with two relevant
  observations. Based on 2-D reconnection models that involve a cusp
  configuration, it is expected that the soft X-ray loop top source moves
  upward with time and that a higher temperature region exists above the
  loop top. Several flares are found to contradict these predictions,
  presumably implying the inadequacy of the models. Lastly we discuss
  a possibility of constraining the inclination angle (and hence the
  loop shape) with spatially-unresolved soft X-ray line spectra which
  are Doppler-shifted due to plasma upflows.

Title: Working Group 1: Magnetic Field Structuring
Authors: van Driel-Gesztelyi, L.; Martinez Pillet, V.
Bibcode: 1999ESASP.446...71V
Altcode: 1999soho....8...71V
  No abstract at ADS

Title: Long-Term Evolution Of Emissivity And Heating In A Solar
    Active Region
Authors: van Driel-Gesztelyi, L.; Thompson, B.; Démoulin, P.; Orlando,
   S.; Bocchialini, K.; Oláh, K.; Kövári, Z.; Deforest, C.; Khan,
   J.; Fludra, A.; Mandrini, C.
Bibcode: 1999ESASP.446..663V
Altcode: 1999soho....8..663V
  We study the evolution of the heating and emissivity of an active
  region from its birth throughout its decay during six solar rotations
  (July-Nov. 1996). We analyse multi-wavelength and multi-instrument
  data obtained from SOHO (EIT, SUMER, CDS, MDI), Yohkoh (SXT), GOES
  and 10.7cm radio data from DRAO, Canada. We take one "snapshot" per
  rotation at the time of the central meridian passage (CMP) of the
  AR, outside of time of flares, which appears to be representative
  enough to allow us to make some general conclusions about the
  long-term evolution. Deriving physical parameters like intensity
  (flux), temperature and emission measure of the entire AR vs. time,
  we formulate mathematically the change in radiation emitted by the
  decaying AR at several wavelengths. Combining the emissivity data with
  the evolution of magnetic flux density as the flux is being dispersed
  by small- and larger-scale convective motions, we make an attempt to
  understand the physics behind the emission and heating. We also analyse
  the effects of flaring on the heating of the AR, and study whether and
  how the flare properties evolve during the life of the active region.

Title: Analysis of evolution of NOAA 7912 active region on 19
    October 1995
Authors: Rudawy, P.; van Driel-Gesztelyi, L.; Cader-Sroka, B.; Mein,
   P.; Mein, N.; Schmieder, B.; Malherbe, J. -M.; Rompolt, B.
Bibcode: 1999A&AS..139...89R
Altcode:
  An analysis of a minor (B3.2) flare related to an X-ray jet in the
  reversed polarity NOAA 7912 active region is presented, focusing
  on various kinds of activity observed in the Hα line with the MSDP
  instrument. Using complementary Yohkoh soft X-ray observations and a
  Kitt Peak magnetic field map we study the influence of a rather low
  and graduate energy release on filaments, fibrils and chromospheric
  brightenings and their relevant coronal features. We find that this
  small flare affected the entire AR and was associated with strong up-
  and downflows along remote fibrils and filaments, which appear to be
  connected by large-scale loops. It is shown that at least one of the
  observed brightenings was caused by downflow of the matter, thus, by
  the kinematic heating of the material. The filament in the vicinity
  of the flare footpoints changed the most: it broke into two parts,
  temporarily rose to higher altitudes inside the AR and even erupted
  outside of the AR, re-forming only three hours later. We show that
  even a minor flare can lead to important morphological and dynamical
  changes in an active region.

Title: The Role of "Magnetic Dips" and "Bald Patches" for a Filament
    Observed by SOHO and GBO
Authors: Aulanier, G.; Schmieder, B.; Kucera, T.; van Driel-Gesztelyi,
   L.; Démoulin, P.; Mein, N.; Vial, J. -C.; Mein, P.
Bibcode: 1999ASPC..184..291A
Altcode:
  The studied filament was observed on Sept. 25, 1996, in Hα with
  the MSDP on the German VTT, Tenerife, as well as in Si IV with
  SOHO/SUMER. The 3-D magnetic configuration of the filament channel is
  reconstructed, using linear magnetohydrostatic (lmhs) extrapolations
  from a SOHO/MDI magnetogram, which is modified by a background magnetic
  component constraining a twisted flux-tube. This flux-tube is deformed
  by the magnetic polarities observed with SOHO/MDI. The shape and
  location of the computed "dipped field lines" are in good agreement
  with the shape of the filament and its feet observed in Hα. Some "bald
  patches" (BPs) are present where the distribution of dips reaches the
  photosphere. We find observational signatures in Si IV brightenings of
  energy release at the locations of computed "bald patch separatrices",
  defined by field lines which are tangent to the photosphere. We propose
  that the plasma is there heated by ohmic dissipation from the expected
  currents in the BP separatrices. The results show the importance of
  "dipped field lines" and "bald patches" in filament channels.

Title: Making sense of sunspot decay - II. Deviations from the Mean
    Law and Plage Effects
Authors: Petrovay, K.; Martínez Pillet, V.; van Driel-Gesztelyi, L.
Bibcode: 1999SoPh..188..315P
Altcode: 1999astro.ph..6258P
  In a statistical analysis of Debrecen Photoheliographic Results sunspot
  area data we find that the logarithmic deviation (log D)' of the area
  decay rate D from the parabolic mean decay law (derived in the first
  paper in this series) follows a Gaussian probability distribution. As
  a consequence, the actual decay rate D and the time-averaged decay
  rate are also characterized by approximately lognormal distributions,
  as found in an earlier work. The correlation time of (log D)' is about
  3 days. We find a significant physical anticorrelation between (log
  D)' and the amount of plage magnetic flux of the same polarity in an
  annulus around the spot on Kitt Peak magnetograms. The anticorrelation
  is interpreted in terms of a generalization of the turbulent erosion
  model of sunspot decay to the case when the flux tube is embedded in
  a preexisting homogeneous `plage' field. The decay rate is found to
  depend inversely on the value of this plage field, the relation being
  very close to logarithmic, i.e., the plage field acts as multiplicative
  noise in the decay process. A Gaussian probability distribution of
  the field strength in the surrounding plage will then naturally lead
  to a lognormal distribution of the decay rates, as observed. It is
  thus suggested that, beside other multiplicative noise sources, the
  environmental effect of surrounding plage fields is a major factor
  in the origin of lognormally distributed large random deviations from
  the mean law in the sunspot decay rates.

Title: Long-Term Magnetic Evolution of an AR and its CME Activity
Authors: van Driel-Gesztelyi, L.; Mandrini, C. H.; Thompson, B.;
   Plunkett, S.; Aulanier, G.; Démoulin, P.; Schmieder, B.; de Forest, C.
Bibcode: 1999ASPC..184..302V
Altcode:
  Using SOHO/MDI full-disc magnetic maps, we follow the magnetic
  evolution of a solar active region for several months in the period of
  July-November 1996. We extrapolate the photospheric magnetic fields in
  the linear force-free approximation and match the modelled field lines
  with the soft X-ray loops observed with the Yohkoh/SXT in order to
  diagnose the coronal magnetic shear. We find that while the turbulent
  motions diffuse the flux, the differential rotation, and possibly
  twisted flux emergence, increase the magnetic shear. Flares are observed
  during the first three rotations, while CME events (observed by SOHO/EIT
  and LASCO) originate from this AR from its emergence throughout its
  decay. Several early CMEs, while none of the late CMEs, are related to
  flare events above the GOES B1 level. We find that the late CMEs occur
  when the magnetic shear, after accumulating for four rotations, reaches
  a high level and saturates. We propose that CME activity serves as a
  valve through which the AR could get rid of excess shear and helicity.

Title: Modelling the Sun as an active star. I. A diagnosis of
    photometric starspot models
Authors: Oláh, K.; van Driel-Gesztelyi, L.; Kővári, Zs.; Bartus, J.
Bibcode: 1999A&A...344..163O
Altcode:
  We provide a diagnosis of photometric starspot models through modelling
  active areas on the Sun using softwares originally written for starspot
  modelling. The data we used were one-dimensional measurements of
  the Sun in radio (10.7 cm, DRAO, Canada) and in soft X-rays (GOES
  satellites). In these wavelengths the response to magnetic activity
  results in similar amplitude variability on the Sun to those we
  attribute to starspots in visual wavelengths. The modelling results
  were compared with contemporaneous direct images (obtained at Nobeyama,
  Japan and with the Yohkoh and SOHO spacecraft). We found that: a)
  knowing well the basic physical parameters of a star, the resulting
  total spotted area is a fairly good approximation of the reality, thus
  making sense of photometric starspot modelling; b) long-term variability
  coupled with the rotational modulation may result in artificially high
  latitude spots; c) in two- or multi-spot models a resulting small spot
  can account for short living spots; d) systematic change in spot size
  could be partially due to flux ratio changes. The contrast between
  the studied bright active region and the undisturbed area on the Sun
  decreased in time following roughly a power law. At the same time,
  the emission measure of the active region's core similarly decreased.

Title: 3-D magnetic configurations supporting
    prominences. III. Evolution of fine structures observed in a filament
    channel
Authors: Aulanier, G.; Démoulin, P.; Mein, N.; van Driel-Gesztelyi,
   L.; Mein, P.; Schmieder, B.
Bibcode: 1999A&A...342..867A
Altcode:
  On September 25() th 1996, a quiescent filament located near the
  center disc (S2, E5) was observed on the German VTT (Tenerife)
  with the MSDP instrument, in the Hα line center and wings. SOHO/MDI
  line-of-sight magnetograms were co-aligned with the MSDP images, showing
  the position and evolution of the lateral feet of the filament in the
  vicinity of the parasitic magnetic polarities observed in the filament
  channel. Using the assumptions developed in the previous papers of this
  series related to the reconstruction of the 3-D magnetic configuration
  of filaments, we perform ``linear magnetohydrostatic'' extrapolations
  (taking into account the effects of plasma pressure and gravity) on the
  SOHO/MDI magnetograms. The main hypothesis is the presence of a twisted
  flux-tube located above the photospheric inversion line. Assuming that
  the parameters of the model do not need to be significantly modified
  during the evolution of the configuration for a duration of 1 day,
  we have shown that the 3-D distribution of dipped field lines is well
  correlated with Hα dark absorbing features in the filament channel:
  the filament itself, its lateral feet and some of the surrounding dark
  fibrils. In this way we confirm what was suggested in our earlier
  papers, i.e. that the feet are composed of the dipped portions of
  some field lines, which form a continuous pattern from the corona
  to the photosphere. We propose the same explanation for the magnetic
  configuration of some of the dark Hα fibrils in the channel. We show
  that the plasma effects are not responsible for the existence of most
  of the magnetic dips, however their inclusion helps to get a better
  correspondence between the model and the observations. We find that the
  average Hα Doppler velocities associated with the filament and with
  the chromospheric fibrils is of the order of a few hundred m s(-1)
  (though it can go locally up to 3 km s(-1) in the filament). These
  upward velocities are consistent with a quasi-static evolution of
  the magnetic configuration and with the support of dense plasma in
  magnetic dips.

Title: What can we learn from Modelling the Sun as a Star?
Authors: Oláh, K.; van Driel-Gesztelyi, L.; Kővári, Zs.; Bartus, J.
Bibcode: 1999ASPC..158..170O
Altcode: 1999ssa..conf..170O
  No abstract at ADS

Title: The NOAA AR 6718 magnetic field extrapolation with localized
    current filaments.
Authors: Karlický, M.; Démoulin, P.; Aulanier, G.; van
   Driel-Gesztelyi, L.; Hénoux, J. C.; Jirička, K.
Bibcode: 1999joso.proc...97K
Altcode:
  The 3-D extrapolation of magnetic field lines of the July 11, 1991
  Kitt Peak magnetogram shows a differential magnetic field shear in
  the NOAA 6718 active region. A new combined extrapolation technique,
  which includes localized current filaments is suggested and applied in
  modelling of this shear. First, the potential field extrapolation is
  made and then force-free current paths for several current filaments
  in specific positions are computed. It is shown that with the electric
  current increase the localized magnetic field shear is increasing. The
  total electric current in 16 current filaments is considered up to
  1.2×10<SUP>12</SUP>A.

Title: On the role of beam driven return current instabilities in
    white-light flares
Authors: Matthews, S. A.; Brown, J. C.; van Driel-Gesztelyi, L.
Bibcode: 1998A&A...340..277M
Altcode:
  It has been shown previously that the low ionization levels in the
  deep chromosphere of solar flares can cause the return current driven
  by a thick target electron beam to be unstable to ion aoustic wave
  generation, contrary to conventional wisdom. We investigate, using
  Yohkoh data, the possibility that anomalous heating as a result of
  this instability is capable of producing sufficient heating, in the
  right places at the right times, to account for the enhanced continuum
  emission actually observed in white-light flares. The Soft X-ray
  Telescope (SXT) onboard \it Yohkoh incorporates an aspect camera which,
  prior to its failure in 1992, provided white-light images at 431 nm with
  a bandpass of 3 nm. A number of white-light flares were observed during
  its operational lifetime for which there was coincident hard X-ray data
  from the Hard X-ray Telescope (HXT), providing suitable candidates for
  study. Four such events are discussed, and the model found to be viable.

Title: Multi-wavelength observations of POST flare loops in two long
    duration solar flares
Authors: Harra-Murnion, L. K.; Schmieder, B.; van Driel-Gesztelyi,
   L.; Sato, J.; Plunkett, S. P.; Rudawy, P.; Rompolt, B.; Akioka, M.;
   Sakao, T.; Ichimoto, K.
Bibcode: 1998A&A...337..911H
Altcode:
  We have analysed two Long Duration solar Events (LDEs) which produced
  large systems of Post Flare Loops (PFLs) and which have been observed by
  Yohkoh and ground-based observatories. Using the Maximum Entropy Method
  (MEM) image synthesis technique with new modulation patterns we were
  able to make hard X-ray (HXR) images of the post flare loops recorded
  in the L Channel (13.9-22.7 keV) of the Yohkoh Hard X-ray Telescope. We
  obtained co-aligned 2-D maps in Hα (10(4) K), in soft X-rays (5x 10(6)
  K) and in hard X-rays (20x 10(6) K). We conclude that the soft X-ray
  (SXR) loops lie higher than the Hα loops and the former are overlaid
  by HXR emission. This is suggestive of the magnetic reconnection
  process. However some details are not consistent with the standard
  models. Firstly the separation between the HXR source and the SXR
  loop increases with time, with the HXR source being approximately
  a factor of five larger than the equivalent source in impulsive
  flares. Secondly the cooling times deduced from observations are longer
  than the theoretically expected ones and the discrepancy increases
  with time. We review the current models in view of these results.

Title: 3-D magnetic configurations supporting prominences. II. The
    lateral feet as a perturbation of a twisted flux-tube
Authors: Aulanier, G.; Demoulin, P.; van Driel-Gesztelyi, L.; Mein,
   P.; Deforest, C.
Bibcode: 1998A&A...335..309A
Altcode:
  In a previous paper we have shown that a twisted flux-tube is the
  most probable magnetic configuration supporting prominences. The
  model interprets many observations in a natural way (in particular
  the magnetic measurements in prominences and the chirality
  properties). Moreover, prominence feet appear as a direct consequence
  of the parasitic polarities present in the filament channel. Here we
  investigate further the link between feet and parasitic polarities
  by modelling explicitly these polarities. We show that the prominence
  lateral feet appear naturally, above secondary photospheric inversion
  lines and we describe the morphological change of feet as parasitic
  polarities evolve. This approach is applied to an observed filament
  in Hα with the MSDP on the German VTT (Tenerife) where SOHO/MDI
  magnetograms are available. We show that the shape of the prominence
  is defined by the distribution of the dips in the computed magnetic
  configuration. Then we analyse the topology of the magnetic field using
  the quasi-separatrix layers (QSLs) method. We describe the basic changes
  in the topology as the parasitic polarities evolve, in particular
  how the configuration pass from an OX to an OF topology. We find a
  correspondance between the computed QSLs and some of the chromospheric
  brightenings, observed around the feet of filaments in the y line (Ca
  II, 8542 Angstroms). It confirms the deduced magnetic configuration
  and shows that energy release is present at a low level in the complex
  topology of the filament configuration.

Title: The Postflare Loops and the Nearby Active Chromosphere of
1992 June 26: Addendum
Authors: Malherbe, J. -M.; Tarbell, T.; Wiik, J. E.; Schmieder, B.;
   Frank, Z.; Shine, R. A.; van Driel-Gesztelyi, L.
Bibcode: 1998ApJ...495..502M
Altcode:
  Video segments are presented that were processed from a quantitative
  study of the dynamics of the evolution of Hα postflare loops developed
  after a large solar flare. The high spatial resolution of the Swedish
  Vacuum Solar Telescope (SVST) at La Palma provided a unique set of
  data for such an event.

Title: Asymmetric Magnetic Field Distribution in Active Regions
Authors: Cauzzi, Gianna; van Driel-Gesztelyi, Lidia
Bibcode: 1998ASPC..140..105C
Altcode: 1998ssp..conf..105C
  No abstract at ADS

Title: Evolution of the Magnetic Field and Chromospheric Fine
    Structure in a Filament Channel
Authors: van Driel-Gesztelyi, L.; Mein, P.; Mein, N.; Schmieder,
   B.; Malherbe, J. -M.; Aulanier, G.; Démoulin, P.; Deforest, C.;
   Staiger, J.
Bibcode: 1998ASPC..155..321V
Altcode: 1998sasp.conf..321V
  No abstract at ADS

Title: Evolution and Decay of Active Regions (Invited review)
Authors: van Driel-Gesztelyi, L.
Bibcode: 1998ASPC..155..202V
Altcode: 1998sasp.conf..202V
  No abstract at ADS

Title: Reorganization of solar magnetic field by a flare event
Authors: Manoharan, P. K.; van Driel-Gesztelyi, L.; Pick, M.;
   Démoulin, P.
Bibcode: 1998BASI...26..319M
Altcode:
  No abstract at ADS

Title: Non potentiality of coronal loops above active regions
Authors: Aulanier, G.; Schmieder, B.; Démoulin, P.; van
   Driel-Gesztelyi, L.; Deforest, C.
Bibcode: 1998ASPC..155..105A
Altcode: 1998sasp.conf..105A
  No abstract at ADS

Title: Filament Disparition Brusque and CME - September 25-26,
    1996 Event
Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Aulanier, G.;
   Demoulin, P.; Martens, P. C. H.; Zarro, D.; Deforest, C.; Thompson,
   B.; St. Cyr, C.; Kucera, T.; Burkepile, J. T.; White, O. R.; Hanaoka,
   Y.; Nitta, N.
Bibcode: 1998ASPC..150..366V
Altcode: 1998IAUCo.167..366V; 1998npsp.conf..366V
  No abstract at ADS

Title: 3-D Modelling of a Filament Observed in Hα and with SOHO
Authors: Aulanier, G.; Schmieder, B.; Démoulin, P.; Mein, N.; van
   Driel-Gesztelyi, L.; Mein, P.; Vial, J. C.; Deforest, C.
Bibcode: 1998ESASP.417..217A
Altcode: 1998cesh.conf..217A
  No abstract at ADS

Title: A study of activity in interacting sunspot groups
Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Hénoux, J. -C.
Bibcode: 1998PAICz..88...13S
Altcode:
  No abstract at ADS

Title: 3-D Modelling of a Filament Observed in Hα and with SOHO/MDI
Authors: Aulanier, G.; Démoulin, P.; van Driel-Gesztelyi, L.; Mein,
   P.; Deforest, C.
Bibcode: 1998ASPC..155..326A
Altcode: 1998sasp.conf..326A
  No abstract at ADS

Title: Evolution of a reversed polarity active region NOAA 7912 in
    the photosphere, the chromosphere and the corona.
Authors: van Driel-Gesztelyi, L.; Baranyi, T.; Mein, N.; Cader-Sroka,
   B.; Rudawy, P.; Mein, P.; Rompolt, B.; Schmieder, B.; Malherbe,
   J. -M.; Willson, R.; Kile, J. N.; Raoult, A.
Bibcode: 1998joso.proc..103V
Altcode:
  The authors follow the evolution and activity of NOAA 7912, a reversed
  polarity region, in the photosphere (Kitt Peak magnetograms and Debrecen
  white-light photoheliograms), chromosphere (MSDP instrument mounted
  on the German VTT at Tenerife), and the corona (Yohkoh/SXT, Nançay
  radioheliograph and the VLA) between October 12-20, 1995. They find
  that in spite of the high shear and creation of several mixed-polarity
  regions through flux emergence, the flares in the group did not
  exceed the M-class level. This might be due to the fact that the
  highly inclined bipolar fields emerging in the following part of the
  primary reversed dipole were relatively small and quickly "consumed"
  by cancellation enhanced by sunspot motions. On the other hand, the
  presence of high shear and minor fast-moving parasitic polarities in
  NOAA 7912 was sufficient to produce eruptive events like X-ray jets
  with important coronal and interplanetary effects.

Title: X-Ray Jets and Their Radio Signatures at Metric and Centimeter
    Wavelenths
Authors: van Driel-Gesztelyi, L.; Willson, R. F.; Kile, J. N.; Raoult,
   A.; Klein, L.; Mein, N.; Rudawy, P.; Cader, B.; Rompolt, B.; Schmieder,
   B.; Mein, P.; Malherbe, J. M.
Bibcode: 1998ASPC..154..707V
Altcode: 1998csss...10..707V
  On October 19, 1995 at 10:30 UT and 17:00 UT, two semi-homologous X-ray
  jets were observed with the Yohkoh/SXT from AR 7912, a region having a
  reversed polarity group with vortex-like Hα fibril pattern and X-ray
  loops. The jets appeared over a mixed magnetic polarity region in
  the vicinity of the leading spot. The first event was also observed
  with the Nancay radio heliograph at 167, 236, and 327 MHz. Type III
  activity, indicating the presence of electron beams, superimposed on
  a noise-storm was clearly visible. Type III activity first appeared
  at 10:25 UT, coincident with the onset of the X-ray jet, at 164 MHz
  and 236 MHz close to the storm position, and in the direction of the
  X-ray jet. At 10:28:40 UT a new group of sources appeared eastward
  of the former activity, which may correspond to another jet branch
  along a more easterly path seen in the ohkoh} images. The second X-ray
  jet event was also observed with the Very Large Array (VLA) at 6.2,
  20.7, and 91.6 cm. For this event, VLA snapshot maps at 6.2 and 20.7
  cm reveal low-brightness temperature changes in source structure at
  the site of the X-ray jet during the preburst, impulsive, and decay
  phases. The VLA 91.6 cm observations also show noise storm emission
  above the active region but there is no clear temporal correlation
  between this later X-ray jet and the impulsive decimetric bursts that
  were observed during this period. Although the X-ray observations
  show that the two jets had similar temperatures, emission measures,
  speeds and trajectories they appear to have had dissimilar metric
  responses to these events. This surprising result may question our
  understanding of the process of electron beam acceleration in jets.

Title: Making Sense of Sunspot Decay. I. Parabolic Decay Law and
    Gnevyshev-Waldmeier Relation
Authors: Petrovay, K.; van Driel-Gesztelyi, L.
Bibcode: 1997SoPh..176..249P
Altcode: 1997astro.ph..6029P
  In a statistical study of the decay of individual sunspots based on
  DPR data we find that the mean instantaneous area decay rate is related
  to the spot radius r<SUB>o</SUB> and the maximum radius r<SUB>o</SUB>
  as D = C<SUB>D</SUB> r/r<SUB>o</SUB>, C<SUB>D</SUB> = 32.0±0.26 MSH
  day <SUP>-1</SUP>. This implies that sunspots on the mean follow a
  parabolic decay law; the traditional linear decay law is excluded
  by the data. The validity of the Gnevyshev-Waldmeier relationship
  between the maximum area A <SUB>0</SUB> and lifetime T of a spot group,
  A<SUB>0</SUB>/T ≃10 MSH day<SUP>-1</SUP>, is also demonstrated for
  individual sunspots. No evidence is found for a supposed supergranular
  `quantization' of sunspot areas. Our results strongly support the
  recent turbulent erosion model of sunspot decay while all other models
  are excluded.

Title: Magnetic reconnection driven by emergence of sheared magnetic
    field.
Authors: Schmieder, B.; Aulanier, G.; Demoulin, P.; van
   Driel-Gesztelyi, L.; Roudier, T.; Nitta, N.; Cauzzi, G.
Bibcode: 1997A&A...325.1213S
Altcode:
  Recurrent subflares (Class C) were observed in the NOAA 7608 active
  region on 27 October 1993. From multi-wavelength observations
  (white-light, magnetic field, H-alpha, X-ray), obtained during a
  coordinated campaign between Pic du Midi and Yohkoh, it appears that
  these flares were double ribbon flares caused by new flux emergence. As
  the flare begins, the X-ray emission observed with Yohkoh/SXT is
  loop-shaped with the axis almost parallel to the magnetic inversion
  line, while during the flare development, X-ray loops appear at the
  location of the emerging flux. The extrapolation of the photospheric
  magnetic field in a linear force-free field configuration allows
  identification of the magnetic configuration given by the flares. The
  Hα flare ribbons are located at the intersections of the computed
  quasi-separatrice layers (QSLs) with the chromosphere. We show that
  the initial loop-shaped X-ray emission region is in fact formed by
  several smaller loops directed in a nearly orthogonal direction with
  their feet anchored close to or in the Hα ribbons. During the flare
  development there are X-ray loops which represent only one foot of
  open or largescale magnetic loops. For the studied flares the puzzling
  soft X-rays observations could only be understood with the help of Hα
  and magnetic data combined with a modeling of the coronal magnetic
  field. Further, from the deduced magnetic field topology, the width
  of the QSLs and our present knowledge of 3-D magnetic reconnection,
  we conclude that the flare was due to magnetic reconnection driven
  by emergence of sheared magnetic field impacting in the pre-existing
  coronal field.

Title: Evidence of Magnetic Reconnection from Hα, Soft X-Ray and
    Photospheric Magnetic Field Observations
Authors: Mandrini, C. H.; DÉmoulin, P.; BagalÁ, L. G.; Van
   Driel-Gesztelyi, L.; HÉnoux, J. C.; Schmieder, B.; Rovira, M. G.
Bibcode: 1997SoPh..174..229M
Altcode:
  A conventional view of magnetic reconnection is mainly based on
  the 2-D picture of an X-type neutral point, or on the extension of
  it to 3-D, and it is thought to be accompanied by flux transport
  across separatrices (places where the field-line mapping is
  discontinuous). This view is too restrictive when we realize the variety
  of configurations that are seen flaring. We designed an algorithm,
  called Source Method (SM), to determine the magnetic topology of
  active regions (ARs). The observed photospheric field was extrapolated
  to the corona using subphotospheric sources and the topology was
  defined by the link between these sources. Hα flare brightenings
  were found to be located at the intersection with the chromosphere
  of the separatrices so defined. These results and the knowledge we
  gained on the properties of magnetic field-line linkage, led us to
  generalize the concept of separatrices to `quasi-separatrix layers'
  (QSLs) and to design a new method (`quasi-separatrix layers method',
  QSLM) to determine the magnetic topology of ARs. QSLs are regions where
  the magnetic field-line linkage changes drastically (discontinuously
  when they behave like separatrices) and the QSLM can be applied to ARs
  where the photospheric field has been extrapolated using any kind of
  technique. In this paper we apply the QSLM to observed flaring regions
  presenting very different configurations and also to a decaying AR where
  a minor phenomenon, like an X-ray bright point (XBP), is observed. We
  find that the locations of flare and XBP brightenings are related to the
  properties of the field-line linkage of the underlying magnetic region,
  as expected from recent developments of 3-D magnetic reconnection. The
  extrapolated coronal field lines representing the structures involved
  in the analyzed events have their photospheric footpoints located
  at both sides of QSLs. Our results strongly support the hypothesis
  that magnetic reconnection is at work in various coronal phenomena,
  ranging from the less energetic ones to large-scale eruptions.

Title: Post-Flare Loops of 26 June 1992 - IV. Formation and Expansion
    of Hot and Cool Loops
Authors: Van Driel-Gesztelyi, L.; Wiik, J. E.; Schmieder, B.; Tarbell,
   T.; Kitai, R.; Funakoshi, Y.; Anwar, B.
Bibcode: 1997SoPh..174..151V
Altcode:
  Observations of the post-flare loops after the X3.9 flare which occurred
  on 25 June, 1992 at 20:11 UT by the Yohkoh/SXT in X-rays, as well as
  in Hα obtained at 5 different observatories, have provided a unique,
  longest ever, set of data for a study of the relationship between the
  hot and cool post-flare loops as they evolve. At any given time, the
  altitude difference between the hot X-ray loops of 6-7× 10<SUP>6</SUP>
  K and the cool Hα loops of 1.5× 10<SUP>4</SUP> K is related to the
  expansion rate of the loop systems and their cooling time. Therefore,
  measurements of the expansion rate and relative height of hot and
  cool loops can provide direct observational values for their cooling
  times. We measured the altitude of hot and cool loops for 15 and 19
  hours, respectively, and found that the cooling time increased as the
  density of the loops decreased. We found a reasonably good agreement
  between the observed cooling times and those obtained from model
  calculations, although the observed values were always somewhat longer
  than the theoretical ones. Taking into account evolutionary effects,
  we also found similar shapes and configurations of hot and cool loops
  during the entire observing period and confirmed that, at any time,
  hot loops are at higher altitude than cool loops, suggesting that cool
  loops indeed evolve from hot loops. These results were used to check
  the validity of the reconnection model.

Title: The Postflare Loops and the Nearby Active Chromosphere of
    1992 June 26
Authors: Malherbe, J. -M.; Tarbell, T.; Wiik, J. E.; Schmieder, B.;
   Frank, Z.; Shine, R. A.; van Driel-Gesztelyi, L.
Bibcode: 1997ApJ...482..535M
Altcode:
  The main objective of this paper is to present a quantitative study
  of the dynamics of the evolution of Hα postflare loops developed
  after a large solar flare and the processed videos produced from the
  observations. The high spatial resolution of the Swedish Vacuum Solar
  Telescope (SVST) at La Palma has provided a unique set of data for such
  an event. A Gaussian fitting method is proposed to derive intensities
  and Doppler shifts from observations taken at three wavelengths (Hα
  center and Hα +/- 0.07 nm). Moving condensations or ``blobs'' of cold
  material provide transverse velocities, which, together with the radial
  component, enable us to derive their velocity vector magnitude. Plasma
  velocities are around free-fall velocities near the top of the loops
  but are significantly smaller close to their footpoints, suggesting
  a deceleration mechanism. The loops are anchored in the chromosphere,
  which shows tremendous activity in the active region and in the nearby
  ``quiet Sun.'' Spicules and ejection of plasmoids are also observed
  at the limb.

Title: Solar Magnetic Field Events related to CMEs observed with SOHO
    (MDI, EIT, SUMER, LASCO)
Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Wiik, J. E.; Thompson,
   B.; de Forest, C.; Saint Cyr, C.; Vial, J. -C.; Nitta, N.; Simnett, G.
Bibcode: 1997IAUJD..19E..42S
Altcode:
  We shall present two CMEs observed by LASCO during the minimum of
  activity of the Sun. These are associated with filament disparitions
  brusques (DB). CME and DB definitively seem to be consequences of global
  magnetic field instability, which causes reconnection of pre-existing
  field lines in the corona. We shall demonstrate how cancelling flux
  and converging magnetic field in photosphere may destabilize coronal
  streamers overlying one or two filament channels.

Title: 3-D reconnection related to new emerging flux
Authors: Schmeider, B.; Démoulin, P.; Aulanier, G.; Malherbe, J. M.;
   van Driel-Gesztelyi, L.; Mandrini, C. H.; Roudier, T.; Nitta, N.;
   Harra-Murnion, L. K.
Bibcode: 1997AdSpR..19.1871S
Altcode:
  We present evidences that emergence of new flux in the lower
  atmosphere leads to magnetic reconnection of field lines. In a
  first phase the phenomenon is observed in the chromosphere by the
  formation of dark filaments (arch filament system) which are overlaid
  by bright loops visible in soft X-rays. Different types of event appear
  according to the magnetic field configuration and the amount of energy
  involved. 3-D modelling of the photospheric magnetic field provides a
  new tool for understanding reconnection in real configurations. The
  observed chromospheric and coronal loops are good diagnostics for
  the modelling. We document our statement by examples obtained during
  coordinated campaigns with the Hα Multichannel Subtractive Double
  Pass spectrographs-MSDP (Pic du Midi and Tenerife) and the Yohkoh
  instruments.

Title: Prominence Activity Related to CME Observed by SOHO, YOHKOH
    and Ground-Based Observatories
Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Wiik, J. E.; Kucera,
   T.; Thompson, B.; de Forest, C.; Saint Cyr, C.; Simnett, G. M.
Bibcode: 1997ESASP.404..663S
Altcode: 1997cswn.conf..663S
  No abstract at ADS

Title: Sunspot Decay as Turbulent Erosion of a Magnetic Flux Tube
Authors: Petrovay, K.; van Driel-Gesztelyi, L.
Bibcode: 1997ASPC..118..145P
Altcode: 1997fasp.conf..145P
  Decisive evidence is presented against the validity of the conventional
  linear decay law for sunspots. Preliminary results from a statistical
  analysis of Debrecen Photoheliographic Results data show that the decay
  rate of sunspots is significantly slower in late phases of the decay
  than in earlier phases. Our findings are compatible with the predictions
  of a recently developed turbulent erosion model for sunspot decay.

Title: East-West inclination of field lines in active regions
Authors: Cauzzi, G.; van Driel-Gesztelyi, L.
Bibcode: 1997MmSAI..68..487C
Altcode:
  No abstract at ADS

Title: Magnetic reconnection driven by an emerging flux.
Authors: Aulanier, G.; Démoulin, P.; Schmieder, B.; Malherbe, J. M.;
   van Driel-Gesztelyi, L.; Roudier, T.
Bibcode: 1997joso.proc...51A
Altcode:
  No abstract at ADS

Title: Analysis of long duration flares
Authors: Harra-Murnion, L. K.; Plunkett, S. P.; Helsdon, S. F.;
   Phillips, K. J. H.; van Driel-Gesztelyi, L.; Schmieder, B.; Rompolt,
   B.; Akioka, M.
Bibcode: 1997AdSpR..20.2333H
Altcode:
  Yohkoh has observed many long duration events permitting a statistical
  study of the properties of these interesting events. We have selected
  ten flares for analysis which have durations between 5 and 20 hours, and
  size ranging from C to X GOES class. Employing the Soft X-ray Telescope,
  the Bragg Crystal Spectrometer, GOES spacecraft, and ground-based
  H_alpha data, we examine the morphology, temperature, emission measure,
  location of the hard X-ray source, non-thermal velocities and upflows
  of the plasma at different stages in the flare development. Our results
  are used to address the question of the energy source that maintains the
  hot plasma at temperatures of several million degrees for many hours.

Title: Post-flare loops in the chromosphere and corona.
Authors: van Driel-Gesztelyi, L.; Wiik, J. E.; Schmieder, B.
Bibcode: 1997ASIC..494...85V
Altcode: 1997topr.conf...85V
  Post-flare loops, which may last for several hours during the gradual
  phase of powerful flares, can provide spectacular limb events during
  solar eclipses. According to models, on-going magnetic reconnection
  keeps creating new loops at an ever-increasing altitude. The newly
  formed hot loops can cool down to chromospheric temperatures quickly,
  in a few minutes, or slowly, over a few hours, depending on their
  density. A good test of the model is to measure the altitude difference
  between loops observed at different wavelengths which show the loops
  at different stages of the cooling process.

Title: Reorganization of the solar corona following a C4.7 flare
Authors: van Driel-Gesztelyi, L.; Manoharan, P. K.; Pick, M.;
   Démoulin, P. P.
Bibcode: 1997AdSpR..19.1883V
Altcode:
  Yohkoh X-ray images, multifrequency two-dimensional observations of
  the Nancay Radioheliograph, Kitt Peak and Mees magnetograms provide
  a unique set of data with which to study a C4.7 long-duration flare
  that was observed close to the equator (S07, W11) on 25 Oct. 1994
  at 09:49 UT. Linear force-free field extrapolations indicate a
  very high degree of non-potentiality in the active region. The
  X-ray flare started with the expansion of spectacular twisted
  loops. Fifteen minutes after the flare onset sporadic radio (type
  III) bursts were observed spreading over an area of almost &lt;FR
  SHAPE="SOL"&gt;1&lt;DE&gt;3&lt;/DE&gt;&lt;/FR&gt; of the solar disc
  and two remote X-ray brightenings appeared over quiet regions of
  opposite magnetic polarity located in on opposite hemispheres of the
  Sun. In the close vicinity of these remote brightenings two coronal
  holes formed. The timing and location of these events combined with
  the overall magnetic configuration provide evidence for a large-scale
  magnetic reconnection occurring between the expanding twisted loops
  and the overlying huge loops which inter-connect quiet solar regions.

Title: Emerging Flux Tube Geometry and Sunspot Proper Motions
Authors: van Driel-Gesztelyi, Lidia
Bibcode: 1997ASPC..118...81V
Altcode: 1997fasp.conf...81V
  As sunspots appear at the intersection of rising flux tubes with
  the photosphere, the observed proper motions of a bipolar sunspot
  pair is a good indicator of the geometry of the underlying emerging
  flux tube. An emerging bipole caused by a simple symmetric potential
  flux tube should display a symmetric divergence of the two spots in
  diametrically opposite directions, while the proper motions of bipolar
  spot-pairs belonging to tilted or/and twisted (non-potential) emerging
  flux tubes are more complicated: asymmetric, not diametrically opposite
  and may follow a curved pattern. Observation of such motions may help
  to prove that emerging flux tubes are tilted and frequently twisted,
  in good agreement with predictions by recent simulation studies.

Title: Evidence for Large-Scale Solar Magnetic Reconnection from
    Radio and X-Ray Measurements
Authors: Manoharan, P. K.; van Driel-Gesztelyi, L.; Pick, M.;
   Demoulin, P.
Bibcode: 1996ApJ...468L..73M
Altcode:
  Utilizing Yohkoh Soft X-ray Telescope and Nancay radioheliograph data,
  we present, for the first time, observations of expanding twisted
  X-ray loops and a series of nonthermal radio bursts that follow the
  loop expansion in time and space up to ~12' distance. The loops were
  produced during a long-duration C4.7 flare close to disk center on 1994
  October 25 at 1049 UT. The series of radio bursts were observed on the
  southern hemisphere above a weak positive-polarity region. The Kitt
  Peak magnetogram shows the existence of a weak negative-polarity region
  on the northern hemisphere at the same heliolongitude. Simultaneously
  with the nonthermal radio bursts, we observed the appearance of two
  remote X-ray brightenings and subsequent formation of two coronal
  holes above these weak (quiet) magnetic regions of opposite polarity,
  which strongly suggest the involvement of these remote regions in the
  event. During the 6 hr--long gradual phase of the flare, new X-ray
  loop connections developed among the active region and the remote
  quiet regions. A nonthermal radio continuum emission originating
  from the active region was also observed. We propose that the series
  of radio bursts, two remote X-ray brightenings, and new coronal loop
  connections were all signatures of a large-scale reconnection process
  between the expanding twisted flare loops and overlying transequatorial
  loops connecting quiet-Sun regions. The reconnection was only partial;
  the external part of the overlying large-scale fields were pushed out in
  the solar wind by the expanding twisted loops, leading to the formation
  of the coronal holes. The interaction between the active region and
  the large-scale fields seemed to be active during the entire gradual
  phase of the flare. This scenario may also explain the measurement of
  high-energy electrons in the interplanetary medium from 74 deg south
  heliolatitude as observed by Ulysses.

Title: 3D Magnetic Reconnection at an X-Ray Bright Point
Authors: Mandrini, C. H.; Démoulin, P.; Van Driel-Gesztelyi, L.;
   Schmieder, B.; Cauzzi, G.; Hofmann, A.
Bibcode: 1996SoPh..168..115M
Altcode:
  On May 1, 1993, a flaring X-ray bright point (XBP) was observed for
  about 16 hours in the old, disintegrating, bipolar active region (AR)
  NOAA 7493. During this period, a minor magnetic bipole (10<SUP>20</SUP>
  Mx) emerged in the region. We have found observational evidence showing
  that the XBP brightenings were due to magnetic reconnection between
  the new bipole and pre-existing plage fields. The aim of the present
  work is to substantiate with magnetic modelling what has been shown
  by the observations. For this purpose we extrapolate the observed
  photospheric magnetic fields in the linear force-free approximation
  and follow its evolution during the lifetime of the XBP. From the
  computed coronal field lines we determine the location of regions of
  drastic change in field-line linkage, called `quasi-separatrix layers'
  or QSLs. QSLs are open layers that behave physically like separatrices:
  the break down of ideal magnetohydrodynamics and the release of free
  magnetic energy may occur at these locations when their thickness
  is small enough. The extrapolated field lines, with photospheric
  footpoints on both sides of QSLs, match the observed chromospheric and
  coronal structures (arch filament system, XBP and faint X-ray loops
  (FXL)). We study also the evolution of the width of the QSL located
  over the new negative polarity pore: the calculated QSL is very thin
  (typically less than 100 m) during the lifetime of the XBP, but becomes
  much thicker (≥ 10<SUP>4</SUP> m) after the XBP has faded. Furthermore
  we show that peaks in X-ray brightness propagate along the FXL with a
  velocity of ≈ 670 km s<SUP>-1</SUP>, starting from the XBP location,
  implying that the energy is released where the emerging bipole impacts
  against pre-existing coronal loops. We discuss the possible mechanism
  of energy transport and conclude that the energy is conducted to the
  remote footpoints of the FXL by a thermal front. These results strongly
  support the supposition that the XBP brightness and flaring are due
  to the interaction of different flux systems, through 3D magnetic
  reconnection, at QSLs.

Title: Post-Flare Loops of 26 June 1992, II
Authors: Schmieder, B.; Heinzel, P.; Van Driel-Gesztelyi, L.; Lemen,
   J. R.
Bibcode: 1996SoPh..165..303S
Altcode:
  We observed the large post-flare loop system, which developed after the
  X 3.9 flare of 25 June 1992 at 20∶11 UT, in Hα with the Multichannel
  Subtractive Double Pass Spectrograph at Pic-du-Midi and in X-rays with
  the it Yohkoh/SXT instrument. Following the long-term development of
  cool and hot plasmas, we have determined the emission measure of the
  cool plasma and, for the first time, the temporal evolution of the
  hot-loop emission measure and temperature during the entire gradual
  phase. Thus, it was possible to infer the temporal variation of electron
  densities, leading to estimates of cooling times. A gradual decrease of
  the hot-loop emission measure was observed, from 4 × 10<SUP>30</SUP>
  cm<SUP>−5</SUP> at 23∶00 UT on 25 June 1992 to 3 × 10<SUP>28</SUP>
  cm<SUP>−5</SUP> at 13∶10 UT on 26 June 1992. During the same period,
  the temperature decreased only slowly from 7.2 to 6.0 × 10<SUP>6</SUP>
  K. Using recent results of NLTE modeling of prominence-like plasmas,
  we also derive the emission measure of cool Hα loops and discuss
  their temperature and ionisation degree. During two hours of Hα
  observations (11-13 hours after the flare) the averaged emission
  measure does not show any significant change, though the amount
  of visible cool material decreases and the volume of the loops
  increases. The emission measure in Hα, after correction for the
  Doppler-brightening effect, is slightly lower than in soft X-rays. Since
  the hot plasma seems to be more spatially extended, we arrive at
  electron densities in the range n<SUB>infe</SUB><SUP>supho</SUP>≤
  n<SUB>infe</SUB><SUP>supcool</SUP>∼ 2 × 10<SUP>10</SUP>
  cm<SUP>−3</SUP> at the time of the Hα observations.

Title: Evidence for Current-carrying Emerging Flux
Authors: Leka, K. D.; Canfield, R. C.; McClymont, A. N.; van
   Driel-Gesztelyi, L.
Bibcode: 1996ApJ...462..547L
Altcode:
  To determine the relationship between electric currents and magnetic
  flux in emerging sunspots, we use observations of the morphology,
  proper motion, magnetic flux, and currents associated with several
  well-observed growing bipoles. Our target was NOAA Active Region 7260,
  which included a preexisting large spot and a fast-growing area of new
  magnetic flux. Magnetic bipoles in this region are well documented
  by X-ray images from the Yohkoh spacecraft and optical images and
  vector magnetograms from several ground-based observatories. <P />In
  this paper we show that (1) the Hα and X-ray structures associated
  with these bipoles do not agree with potential-field extrapolations
  of magnetograms; (2) proper motions imply that the flux bundles that
  make up these new bipoles are twisted before they emerge; (3) these
  new bipoles are cospatial with significant vertical electric currents;
  (4) the morphology, proper motion, and measured currents of these
  bipoles all imply the same sense of twist; (5) this sense of twist
  is the same as the large-scale twist of the preexisting large spot;
  and (6) the increase of these currents, as new flux emerges, is not
  consistent with their generation by photospheric motions. <P />We
  conclude that the new magnetic flux that emerged in this active region
  carried currents generated below the photosphere.

Title: Flare Activity Associated with Large-Scale Loops in AR 7260
Authors: Nitta, N.; van Driel-Gesztelyi, L.
Bibcode: 1996AAS...188.1901N
Altcode: 1996BAAS...28..849N
  Active region NOAA AR 7260 (August 1992) is marked as one of the fastest
  growing regions in solar cycle 22 and has extensively been studied by
  several workers. We have learned from the Yohkoh SXT data that flares in
  this region were generally confined rather than eruptive. In addition
  to the flares, we notice the formation of large-scale X-ray loops
  connecting the large preceding spot and the emerging flux region as
  the latter became complexed. One of them produced a LDE after a cusp
  structure formed on top it. These loops were occasionally observed to
  erupt, perhaps responsible for coronal mass ejections. Even some of
  the apparently localized flares may have been due to interactions of
  compact loops with such large-scale loops. It is possible that they
  also caused sympathetic flares. We try to understand how such loops
  formed in the context of evolution of the region, which is known to
  have consisted of intrinsically twisted magnetic field.

Title: Chromospheric ejections and their signatures in X-ray observed
    by YOHKOH
Authors: Schmieder, B.; Mein, N.; Shibata, K.; van Driel-Gesztelyi,
   L.; Kurokawa, H.
Bibcode: 1996AdSpR..17d.193S
Altcode: 1996AdSpR..17..193S
  Surges, or condensations of chromospheric material, are commonly
  observed in active regions when new emerging magnetic flux (EMF)
  occurs. In order to study EMF-related phenomena in the corona, observing
  campaigns were organized with the Yohkoh X-ray satellite and ground
  based observatories. EMFs could be detected in magnetograms made in
  Potsdam and Hawaii, surge and arch filament system (AFS) events (on
  Oct 7 1991, May 1 1993, respectively) with the Multichannel Subtractive
  Double Pass instruments operating at Meudon and on the Canary Islands
  and with the Hida telescope at Kyoto University. Bright X-ray loops
  coincident with chromospheric surge activity were detected in the high
  resolution Yohkoh SXT images. We also found coincident brightness
  variations between an X-ray bright point (XBP) and the underlying
  chromospheric plage related to EMF. We interpret the appearance of
  AFS as condensation of material among magnetic field lines, the X-ray
  bright points as the result of a magnetic reconnection process, and
  surges as ejection of cold plasma bubbles squeezed between field lines
  as a result of reconnection.

Title: Emerging flux and flares in NOAA 7260
Authors: Nitta, N.; van Driel-Gesztelyi, L.; Leka, K. D.; Shibata, K.
Bibcode: 1996AdSpR..17d.201N
Altcode: 1996AdSpR..17..201N
  We have studied the relation between flux emergence and flare
  activity in the active region NOAA 7260, using images from the Soft
  X-ray Telescope aboard the Yohkoh spacecraft and other supporting
  ground-based data. It is found that microflares start around the time
  of flux emergence as recorded in white-light data, which generally
  precedes a major flare by several hours. We interpret the microflares as
  due to fast reconnection that takes place intermittently in the slow
  reconnection stage while more energy is accumulated in preparation
  for a larger flare.

Title: Flare Associated Large-Scale Magnetic Reconnection
Authors: Manoharan, P. K.; van Driel-Gesztelyi, L.; Pick, M.;
   Demoulin, P.
Bibcode: 1996ASPC..111..398M
Altcode: 1997ASPC..111..398M
  Reports a unique set of observations, for a low heliolatitude flare,
  obtained with the Yohkoh satellite and the Nançay radioheliograph. This
  flare starts with the expansion of spectacularly twisted loops,
  followed by sporadic radio bursts (some of them are detected at high
  heliolatitude, ≡65°S), appearance of two remote X-ray brightenings
  and formation of two coronal holes on opposite hemispheres of the
  Sun. The timing and location of these events provide evidence for
  a large-scale magnetic reconnection between the expanding twisted
  flare loops and overlying huge loops inter-connecting quiet regions
  on the Sun.

Title: Asymmetries in solar active regions and flux emergence models
Authors: Cauzzi, G.; Moreno-Insertis, F.; van Driel-Gesztelyi, L.
Bibcode: 1996ASPC..109..121C
Altcode: 1996csss....9..121C
  No abstract at ADS

Title: Beam Driven Return Current Instabilities and White-Light Flares
Authors: Matthews, S. A.; Brown, J. C.; van Driel-Gesztelyi, L.
Bibcode: 1996ASPC..111..304M
Altcode: 1997ASPC..111..304M
  It has been shown that the low ionization levels in the deep
  chromosphere of solar flares can cause the return current driven by a
  thick target flare beam to be unstable to ion acoustic wave generation,
  contrary to previous conventional wisdom. The authors investigate the
  possibility that anomalous heating as a result of this instability
  may produce sufficient heating to power the white-light flare. Four
  white-light flares observed by Yohkoh are examined: 1991 Oct 27,
  1991 Nov 15, 1992 Jan 26, and 1992 Feb 14.

Title: X-Ray Bright Point Flares Due to Magnetic Reconnection
Authors: Van Driel-Gesztelyi, L.; Schmieder, B.; Cauzzi, G.; Mein,
   N.; Hofmann, A.; Nitta, N.; Kurokawa, H.; Mein, P.; Staiger, J.
Bibcode: 1996SoPh..163..145V
Altcode:
  Ground-based optical observations coordinated with Yohkoh/SXT X-ray
  observations of an old, disintegrating bipolar active region AR NOAA
  7493 (May 1, 1993) provided a multiwavelength data base to study
  a flaring `active region' X-ray bright point (XBP) of about 16 hr
  lifetime, and the activity related to it in different layers of the
  solar atmosphere. The XBP appeared to be related to a new minor bipole
  of about 10<SUP>20</SUP> Mx. Superposed on a global evolution of soft
  X-ray brightness, the XBP displayed changes of brightness, lasting for
  1-10 min. During the brightenings the XBP apparently had a spatial
  structure, which was (tiny) loop-like rather than point-like. The
  X-ray brightenings were correlated with chromospheric activity: (i)
  brightenings of underlying chromospheric faculae, and (ii) appearance
  of strong turbulent velocities in the arch filament system. We propose
  that the XBP brightenings were due to reconnection of the magnetic
  field lines (sketched in 3D) between the new bipole and a pre-existing
  plage field induced by the motion of one of the new pores (v = 0.2
  km s<SUP>−1</SUP>) towards the plage, and that the XBP itself was
  a reconnected hot loop between them.

Title: Hot and Cool Post-Flare Loops: Formation and Dynamics
Authors: Schmieder, B.; Heinzel, P.; van Driel-Gesztelyi, L.; Wiik,
   J. E.; Lemen, J.
Bibcode: 1996mpsa.conf..211S
Altcode: 1996IAUCo.153..211S
  No abstract at ADS

Title: Reconexión magnética en una región activa en decaimiento
Authors: Mandrini, C. H.; Démoulin, P.; van Driel-Gesztelyi, L.;
   Schmieder, B.; Bagalá, L. G.; Rovira, M. G.
Bibcode: 1996BAAA...40....5M
Altcode:
  Se han obtenido observaciones desde Tierra (Hα y magnetogramas)
  coordinadas con el Soft X-ray Telescope (SXT), a bordo del satélite
  japonés Yohkoh, de una región activa bipolar en decaimiento. Estos
  datos constituyen la base para el estudio de un punto brillante en rayos
  X (PBX) y de la actividad relacionada con el mismo en distintas capas
  de la atmósfera solar. Las observaciones muestran que el PBX está
  relacionado con la aparición de un bipolo menor (~ 10<SUP>20</SUP> Mx)
  y que su abrillantamiento continuo, así como sus aumentos de brillo
  esporádicos (``fulguraciones"), son el resultado de la reconexión
  entre el pequeño arco emergente (visto en Hα como un sistema de
  filamentos arqueados, SFA) y arcos mayores asociados al campo facular
  preexistente. Se ha extrapolado el campo magnético observado en la
  aproximación libre de fuerzas lineal y se ha seguido su evolución
  a lo largo de la vida del PBX. Se ha calculado la posición de las
  cuasiseparatrices (CSs) a partir del campo modelado. Las líneas de
  campo extrapoladas, cuyas bases fotosféricas se encuentran a ambos
  lados de las CSs, están de acuerdo con las estructuras cromosféricas
  y coronales observadas. Se ha calculado el espesor de la CD ubicada
  a lo largo de la polaridad negativa emergente, encontrándose que su
  variación está de acuerdo con la evolución de la intensidad del PBX;
  la CS es muy delgada durante la vida del PBX (~ 100 m), mientras que
  su espesor aumenta considerablemente (&gt;= 10^4 m) cuando el PBX
  desaparece de las imágenes del SXT. Estos resultados señalan que
  el abrillantamiento y las ``fulguraciones" de este PBX se deben al
  proceso de reconexión en 3D que tiene lugar en las CSs.

Title: Relative Altitude of Hot and Cool Post-Flare Loops
Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Wiik, J. E.; Tarbell,
   T.; Heinzel, P.; Kitai, R.; Funakoshi, Y.; Anwar, B.
Bibcode: 1996ASPC..111..359V
Altcode: 1997ASPC..111..359V
  The authors collected a unique set of data obtained simultaneously at
  4 different ground based observatories and with the Yohkoh satellite
  to study the relationship between hot X-ray and cool Hα post-flare
  loops as they evolved during the long gradual phase of the X3.9 flare
  which occurred on 25 June 1992. They found reasonably good agreement
  between the computed 'theoretical' cooling times and the 'observed'
  cooling times derived from the relative altitudes of hot and cool
  loops. Taking into account evolutionary effects, the authors also found
  similar shape and configuration of hot and cool loops during the entire
  observing period and confirmed that at any time hot loops are at higher
  altitude than cool loops, suggesting that cool loops indeed descend
  from hot loops. The results provide support for the reconnection model.

Title: Signatures of New Emerging Flux in the Solar Atmosphere
Authors: Schmieder, B.; Malherbe, J. M.; Mein, P.; Mein, N.; van
   Driel-Gesztelyi, L.; Roudier, T.; Nitta, N.; Harra-Murnion, L. K.
Bibcode: 1996ASPC..111...43S
Altcode: 1997ASPC..111...43S
  The emergence of new flux in the low atmosphere leads to magnetic
  reconnection of field lines. In a stable phase the phenomenon is
  observed in the chromosphere by the formation of dark filaments (arch
  filament system, AFS). The authors show how bright loops visible in soft
  X-rays are co-aligned with the AFS. Different types of events appear
  as the released energy increases. With less energetic phenomena than
  flares one observes surges, jets or X-ray bright points, according
  to the configuration of the field lines (open/closed). A low-level
  reconnection process is detectable as an X-ray bright point. If
  the energy is ≡10<SUP>28</SUP>ergs cm<SUP>-3</SUP>, one observes
  subflares. The authors document their statement by showing examples
  observed in coordinated observations obtained with the MSDP (Pic du
  Midi and Tenerife) and Yohkoh/SXT and BCS for the events occurring on
  Oct 5, 1994, Oct 27, 1993, and May 1, 1993.

Title: 3D Magnetic Reconnection: Example of an X-Ray Bright Point
Authors: Demoulin, P.; Mandrini, C. H.; van Driel-Gesztelyi, L.;
   Priest, E. R.; Henoux, J. C.; Schmieder, B.
Bibcode: 1996ASPC..111...49D
Altcode: 1997ASPC..111...49D
  In the classical view magnetic reconnection occurs at neutral points
  and implies transport of magnetic field-lines across separatrices. The
  authors show that reconnection may also occur in the absence of neutral
  points at so-called "quasi-separatrix layers" (QSLs), where there is a
  steep gradient in field-line linkage at the boundaries. Reconnection
  occurs in QSLs where the field-line velocity becomes larger than the
  allowed maximal plasma velocity or where the electric-current density
  becomes too great. The authors describe both a theoretical and an
  observed configuration. In the case of a simple sheared X-field they
  show that even a smooth continuous shear flow, imposed at the boundary,
  gives strong plasma jetting inside and parallel to the QSLs. Applying
  the QSL method to an X-ray bright point observed by Yohkoh, they find
  field lines in the extrapolated field which are on both sides of QSLs
  and which are in good agreement with loops observed in Hα and X-rays
  related to emerging flux. The evolution of the QSL width may explain
  the brightness evolution of the XBP.

Title: Emerging Flux, Reconnection, and XBP
Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Demoulin, P.;
   Mandrini, C.; Cauzzi, G.; Hofmann, A.; Nitta, N.; Kurokawa, H.; Mein,
   N.; Mein, P.
Bibcode: 1996mpsa.conf..459V
Altcode: 1996IAUCo.153..459V
  No abstract at ADS

Title: Emerging flux seen by Yohkoh.
Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Mandrini, C.;
   Démoulin, P.; Cauzzi, G.; Hofmann, A.; Nitta, N.; Kurokawa, H.;
   Mein, N.; Mein, P.
Bibcode: 1996joso.proc..124V
Altcode:
  No abstract at ADS

Title: Active Region Evolution and Flare Activity
Authors: Nitta, N.; van Driel-Gesztelyi, L.; Leka, K. D.; Hudson, H. S.
Bibcode: 1996mpsa.conf..515N
Altcode: 1996IAUCo.153..515N
  No abstract at ADS

Title: Hα surges and associated Soft X-ray loops
Authors: Schmieder, B.; Shibata, K.; van Driel-Gesztelyi, L.;
   Freeland, S.
Bibcode: 1995SoPh..156..245S
Altcode:
  A recurrent Hα surge was observed on 7 October, 1991 on the western
  solar limb with the Meudon MSDP spectrograph. The GOES satellite
  recorded X-ray subflares coincident with all three events. During
  two of the surges high-resolutionYohkoh Soft X-ray Telescope (SXT)
  images have been taken. Low X-ray loops overlying the active region
  where the surges occurred were continuously restructuring. A flare
  loop appeared at the onset of each surge event and somewhat separated
  from the footpoint of the surge. The loops are interpreted as causally
  related to the surges. It is suggested that surges are due to magnetic
  reconnection between a twisted cool loop and open field lines. Cold
  plasma bubbles or jets squeezed among untwisting magnetic field
  lines could correspond to the surge material. No detection was made
  of either X-ray emission along the path of the surges or X-ray jets,
  possibly because of the finite detection threshold of theYohkoh SXT.

Title: The Magnetic Evolution of the Activity Complex AR:7260 -
    a Roadmap
Authors: Leka, K. D.; Canfield, R. C.; Mickey, D. L.; van
   Driel-Gesztelyi, L.; Nitta, N.; Sakurai, T.; Ichimoto, K.
Bibcode: 1994SoPh..155..301L
Altcode:
  The active region NOAA 7260 rotated onto the north solar hemisphere
  as a mature bipole: a dominant negative-polarity sunspot with trailing
  plage and scattered small spots in attendance. The dominantp spot itself
  had strong magnetic fields and covered almost 400 × 10<SUP>−6</SUP>
  of a solar hemisphere. For a period of seven days beginning 14 August,
  1992 this active region displayed rapid and drastic evolution: no fewer
  than 50 magnetic bipoles emerged in the area trailing the large sunspot,
  increasing the region's magnetic flux by more than 10<SUP>22</SUP>
  Mx. This new group of sunspots formed a complexβγδ configuration
  with twoδ spots and a high degree of magnetic shear.

Title: A Yohkoh search for ``black-light flares''
Authors: van Driel-Gesztelyi, Lidia; Hudson, Hugh S.; Anwar, Bachtiar;
   Hiei, Eijiro
Bibcode: 1994SoPh..152..145V
Altcode: 1994svs..coll..145V; 1994IAUCo.143..145V
  Calculations which predict that a phenomenon analogous to stellar
  negative pre-flares could also exist on the Sun were published by
  Hénouxet al. (1990), and Aboudarhamet al., (1990), who showed that
  at the beginning of a solar white-light flare (WLF) event an electron
  beam can cause a transient darkening before the WLF emission starts,
  under certain conditions. They named this event a "black light flare"
  (BLF). Such a BLF event should appear as diffuse dark patches lasting
  for about 20 seconds preceding the WLF emission, which would coincide
  with intense and impulsive hard X-ray bursts. The BLF location would
  be at (or in the vicinity of) the forthcoming bright patches. Their
  predicted contrast depends on the position of the flare on the solar
  disc and on the wavelength band of the observation.

Title: Erratum: A study of surges and flares within an active region
Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Gerlei, O.; Simnett,
   G. M.
Bibcode: 1994SoPh..151..399S
Altcode:
  No abstract at ADS

Title: Relationship between electric currents, photospheric motions,
    chromospheric activity, and magnetic field topology
Authors: van Driel-Gesztelyi, L.; Hofmann, A.; Demoulin, P.; Schmieder,
   B.; Csepura, G.
Bibcode: 1994SoPh..149..309V
Altcode:
  Through coordinated observations made during the Max'91 campaign in June
  1989 in Potsdam (magnetograms), Debrecen (white light and Hα), and
  Meudon (MSDP), we follow the evolution of the sunspot group in active
  region NOAA 5555 for 6 days. The topology of the coronal magnetic field
  is investigated by using a method based on the concept of separatrices -
  applied previously (Mandriniet al., 1991) to a magnetic region slightly
  distorted by field-aligned currents. The present active region differs
  by having significant magnetic shear. We find that the Hα flare
  kernels and the main photospheric electric current cells are located
  close to the intersection of the separatrices with the chromosphere,
  in a linear force-free field configuration adapted to the observed
  shear. Sunspot motions, strong currents, isolated polarities, or
  intersecting separatrices are not in themselves sufficient to produce a
  flare. A combination of them all is required. This supports the idea
  that flares are due to magnetic reconnection, when flux tubes with
  field-aligned currents move towards the separatrix locations.

Title: Evidence for Twisted Emerging Flux in NOAA AR 7260
Authors: Leka, K. D.; van Driel-Gesztelyi, L.; Canfield, R. C.
Bibcode: 1994ASPC...68..145L
Altcode: 1994sare.conf..145L
  No abstract at ADS

Title: Diagnostics of Twisted Flux Emergence (noaa AR7260)
Authors: Leka, K. D.; van Driel-Gesztelyi, L.; Anwar, B.; Canfield,
   R. C.; Hudson, H. S.; Metcalf, T. R.; Mickey, D. L.; Nitta, N.;
   Kurokawa, H.
Bibcode: 1994xspy.conf...25L
Altcode:
  No abstract at ADS

Title: Flares in Active Region NOAA 7260
Authors: Nitta, N.; van Driel-Gesztelyi, L.; Leka, K. D.; Sakurai,
   T.; Shibata, K.; Ichimoto, K.; Canfield, R. C.; Wülser, J. -P.;
   Metcalf, T. R.; Mickey, D. L.
Bibcode: 1994xspy.conf..111N
Altcode:
  No abstract at ADS

Title: Emerging Flux Tube Geometry and Sunspot Proper Motions
Authors: van Driel-Gesztelyi, L.; Leka, K. D.
Bibcode: 1994ASPC...68..138V
Altcode: 1994sare.conf..138V
  No abstract at ADS

Title: Twisted Flux Tubes and Sunspot Motions in AR 5555
Authors: van Driel-Gesztelyi, L.; Démoulin, P.; Schmieder, B.;
   Hofmann, A.; Csepura, G.
Bibcode: 1994emsp.conf..115V
Altcode:
  No abstract at ADS

Title: A Study of Surges and Flares Within an Active Region
Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Gerlei, O.; Simnett,
   G. M.
Bibcode: 1993SoPh..146..163S
Altcode:
  Active region 2684 was observed by the Solar Maximum Mission and
  ground-based observatories simultaneously for over 12 hours on September
  23, 1980. During these observations, recurrent surges were detected
  above an area with complex parasitic magnetic polarity located at the
  periphery of the active region. The time evolution of the Hα surges,
  CIV brightenings and X-ray spikes leads to the conclusion that the
  energy source is in the corona, from magnetic reconnection. The energy
  is transported by energetic charged particles along the loops, thereby
  heating the chromosphere as the particles lose their energy. The
  divergent motion of the spots corresponding to small dipoles at
  the base of the surge indicates that there is important magnetic
  reorganisation. According to the magnetic field-line configuration
  (large loop or open structures), X-rays can (or cannot) be associated
  with surges.

Title: Evidence for Twisted Emerging Flux: NOAA AR 7260
Authors: Leka, K. D.; van Driel-Gesztelyi, L.; Canfield, R. C.; Anwar,
   B.; Metcalf, T. R.; Mickey, D. L.; Nitta, N.
Bibcode: 1993BAAS...25R1187L
Altcode:
  No abstract at ADS

Title: Common Evolution of Adjacent Sunspot Groups
Authors: van Driel-Gesztelyi, L.; Csepura, G.; Nagy, I.; Gerlei, O.;
   Schmieder, B.; Rayrole, J.; Demoulin, P.
Bibcode: 1993SoPh..145...77V
Altcode:
  The evolution of two adjacent bipolar sunspot groups is studied using
  Debrecen full-disc, white-light photoheliograms and Hα filtergrams
  as well as Meudon magnetograms. The proper motions of the principal
  preceding spots of both groups show quite similar patterns; the
  spots move along almost parallel tracks and change the direction
  of their motion on the same day at almost the same heliographic
  longitude. Also, three simultaneous emergences of magnetic flux were
  observed in both groups. These observations support the idea that
  these adjacent sunspot groups were magnetically linked below the
  photosphere. Matching the extrapolated magnetic field lines with the
  chromospheric fibril structure appears to be different in the two groups
  since they indicate quite different model solutions for each group,
  i.e., a near-potential magnetic field configuration in the older group
  (1) and a twisted force-free field configuration in the younger group
  (2). The latter configuration could be created by a considerable twist
  of the main bunch of flux tubes in Group 2, which is reflected in the
  relative sunspot motions. It is also showed how this twist contributed
  to the formation of a filament between the two groups.

Title: Evidence for magnetic reconnection in solar flares
Authors: Demoulin, P.; van Driel-Gesztelyi, L.; Schmieder, B.; Hemoux,
   J. C.; Csepura, G.; Hagyard, M. J.
Bibcode: 1993A&A...271..292D
Altcode:
  From a study of the magnetic field topology in an active region,
  evidence is derived that solar flares are produced by magnetic
  reconnection. We study a complex group with two active regions (AR
  25 t 1 and AR 2512) for three consecutive days, June 13-15 1980. The
  observed longitudinal magnetic field is used to model the coronal
  magnetic field by the potential field created by a series of magnetic
  charges. This computed field matches satisfactorily the Ho fibrils
  and the observed transverse field direction. A set of flares occurs
  principally in the northern group (AR 2511). During these three days,
  two different magnetic configurations in succession are responsible
  for the occurrence of these flares: first the intrusion of a new
  opposite flux in the following polarity, secondly the emergence of new
  flux between the main polarities. In this last case flares occurred,
  although the emerging bipole is almost parallel to the main bipole. We
  show that even in this bipolar configuration a separator is present
  and that observed H flare ribbons are located near the intersection of
  the computed separatrices with the photosphere. This provides strong
  support to a model where reconnection releases the stored magnetic
  energy. The induced evolution of the magnetic field forces reconnection
  along others separators. They are connected by magnetic field lines
  to fainter kernels.

Title: Book reviews
Authors: van Driel-Gesztelyi, L.; Meynet, G.; Gaizauskas, V.; Cook,
   J. W.; McKenna-Lawlor, S. M. P.; Garmany, C. D.; Jugaku, Jun; Lamers,
   Henny J. G. L. M.; Achterberg, A.; De Greve, J. P.; Dommanget, J.;
   van der Kruit, P. C.
Bibcode: 1993SSRv...64..165V
Altcode:
  No abstract at ADS

Title: Rotation Rates of Active Nests on the Sun
Authors: van Driel-Gesztelyi, L.; van der Zalm, E. B. J.; Zwaan, C.
Bibcode: 1993ASPC...46..504V
Altcode: 1993mvfs.conf..504V; 1993IAUCo.141..504V
  No abstract at ADS

Title: Book Review: Solar observations: techniques and interpretation
    / Cambridge U Press, 1991
Authors: van Driel Gesztelyi, L.
Bibcode: 1993SSRv...64..167V
Altcode: 1993SSRv...64..167S; 1993SSRv...64..167G
  No abstract at ADS

Title: Book Review: Opening the frontiers in solar research /
    Pergamon, 1991
Authors: van Driel-Gesztelyi, Lidia; Bumba, V.; van Driel Gesztelyi, L.
Bibcode: 1992SoPh..141..203V
Altcode: 1992SoPh..141..203F
  No abstract at ADS

Title: Active Nests on the Sun
Authors: van Driel-Gesztelyi, Lidia; van der Zalm, Ed B. J.; Zwaan,
   Cornelis
Bibcode: 1992ASPC...27...89V
Altcode: 1992socy.work...89V
  No abstract at ADS

Title: Conditions for flare and filament formation in interacting
    solar active regions
Authors: Schmieder, B.; Henoux, J. -C.; van Driel-Gesztelyi, L.;
   Simnett, G. M.
Bibcode: 1991A&A...244..533S
Altcode:
  The evolution of two interacting sunspot groups of different ages is
  traced over a period of three days. The photospheric velocity field is
  obtained and compared with the general evolution of the region in an
  attempt to better understand the conditions that lead to flare activity
  and filament formation. It is shown that the observed photospheric
  motions can generate dc electric currents, which, in effect, could
  lead to energy storage.

Title: Flares and filament formation due to the interaction between
    two active regions
Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Hénoux, J. C.;
   Simnett, G.
Bibcode: 1991AdSpR..11e..95S
Altcode: 1991AdSpR..11...95S
  We follow the evolution (flare activity, filament formation) of two
  interacting active regions of different ages over three days, through
  observations at white-light, Hα, UV, and X-ray wavelengths. We show
  that the observed photospheric motions could generate DC electric
  currents and that they could lead to free energy storage. Flares
  were observed more-or-less simultaneously in remote locations of the
  sunspot group. This suggests that the same perturbation affected an
  ensemble of lines of force. Filament formation took place due to DC
  current generation by photospheric shearing motions with a velocity
  up to 350 m s<SUP>-1</SUP>.

Title: Effect of Electron Beams during Solar Flares
Authors: Aboudarham, J.; Henoux, J. C.; Brown, J. C.; van den Oord,
   G. H. J.; van Driel-Gesztelyi, L.; Gerlei, O.
Bibcode: 1990SoPh..130..243A
Altcode:
  Electron bombardment of the solar atmosphere has two effects: one is
  to enhance hydrogen recombination emission, the other is to increase
  the opacity via an increase of H<SUP>−</SUP> population. The first
  effect is the most important in the upper part of the atmosphere and
  the second in the lower part. We predict that, when enhanced absorption
  dominates in the part of the atmosphere where radiation originates,
  there will be a decrease in the white-light emission, leading to a
  `negative flare', or what we call a `Black-Light Flare'. This phenomenon
  occurs only for a short duration, not more than ∼ 20 s. `Black-Light
  Flares' have already been observed in the case of flare stars and we
  suggest here that they could also be present on the Sun, just prior
  to a White-Light Flare.

Title: Homologous and Homologous like Microwave Solar Radio Bursts
Authors: Trevisan, R. H.; Sawant, H. S.; Kalman, B.; Gesztelyi, L.
Bibcode: 1990RMxAA..21..557T
Altcode:
  ABSTRACT. Solar radio observations at 1.6 GHz were carried out in the
  month of July, 1985 by using 13.7 m diameter Itapetinga antenna with
  time resolution of 3 ms. Homologous Bursts, with total duration of
  about couple of seconds and repeated by some seconds were observed
  associated with Homologous H- flares. These H- flares were having
  periodicities of about 40 min. Observed long periodicities were
  attributed to oscillation of prominences, and small periods were
  attributed to removal of plasma from the field interaction zone. Also
  observed are "Homologous-Like" bursts. These bursts are double peak
  bursts with same time profile repeating in time. In addition to this,
  the ratio of the total duration of the bursts to time difference in
  the peaks of bursts remain constant. Morphological studies of these
  bursts have been presented. Keq tuoit : SUN-BURSTS - SUN-FLARE

Title: Black and white flares?
Authors: Henoux, J. -C.; Aboudarham, J.; Brown, J. C.; van den Oord,
   G. H. J.; van Driel-Gesztelyi, L.
Bibcode: 1990A&A...233..577H
Altcode:
  It is shown that the nonthermal ionization of a solar flare atmosphere
  by beam bombardment can result, in the initial stages of a flare, in
  dimunitions in the continuum solar flare brightness (termed 'black
  light flares'). The most favorable conditions for observing this
  diagnostic phenomenon are investigated in terms of flare location and
  wavelength. In terms of bombarding beam parameters, electron beams
  of large peak flux are shown to be the most favorable as are target
  atmospheres with minimal preheating.

Title: Asymmetric Flux Loops in Active Regions - Part Two
Authors: Petrovay, K.; Brown, J. C.; van Driel-Gesztelyi, L.; Fletcher,
   L.; Marik, M.; Stewart, G.
Bibcode: 1990SoPh..127...51P
Altcode:
  We propose that magnetic flux loops in the subphotospheric layers
  of the Sun are seriously asymmetrical as a consequence of the drag
  force exerted on them because of the different rotational rate of the
  surrounding plasma. In numerical models of stationary slender flux
  loops in the plane parallel approximation we show that a serious
  tilt is both possible and probable. Observational facts (see van
  Driel-Gesztelyi and Petrovay, 1989; Paper I) strongly support the case
  for high asymmetry. The different stability of p and f spots may also
  be related to such an asymmetry.

Title: Asymmetric flux loops in active regions, I
Authors: van Driel-Gesztelyi, L.; Petrovay, K.
Bibcode: 1990SoPh..126..285V
Altcode: 1990SoPh..126..285G
  We investigate asymmetries of bipolar sunspot groups. We find that
  the magnetic field distribution of simple bipolar sunspot groups is
  significantly asymmetrical: the polarity inversion line is usually
  nearer to the main following polarity spot than to the main preceding
  one. This asymmetry grows with the age of the sunspot group. We suggest
  that this asymmetry has a causal link with two long-established
  asymmetries- the one in the proper motions of young sunspots, the
  other in the relative stability of p and f spots.

Title: Negative Flares on the Sun
Authors: van Driel-Gesztelyi, L.; Brown, J. C.; Hénoux, J. -C.;
   Aboudarham, J.; van den Oord, G. H. J.; Gerlei, O.; Fárnik, F.
Bibcode: 1990PDHO....7..202V
Altcode: 1990dysu.conf..202V; 1990ESPM....6..202V
  The authors showed that under certain conditions at the beginning
  of a solar white-light flare (WLF) event an electron beam can cause
  a transient darkening before the WLF emission starts. They propose
  optimal conditions for possible observation of solar negative flares and
  present an observation, which may be the first identified observation
  of such events.

Title: Interaction between Bipolar Sunspot Groups
Authors: Csepura, G.; van Driel-Gesztelyi, L.; Nagy, I.; Gerlei, O.;
   Schmieder, B.; Rayrole, J.
Bibcode: 1990PDHO....7...88C
Altcode: 1990ESPM....6...88C; 1990dysu.conf...88C
  The authors find some evidence for the interaction of two close-by
  developing sunspot groups.

Title: Photospheric-induced destabilization and ejection of prominence
    material
Authors: Raadu, M. A.; Schmieder, B.; Mein, N.; Gesztelyi, L.
Bibcode: 1988A&A...197..289R
Altcode:
  The sequence of events leading up to prominence activation in two
  different cases is studied. In one case, observed on September 3, 1980,
  strong velocity shears were produced indicating filament twisting. In
  the other case, observed on June 22, 1980, activation results in the
  ejection of prominence material. The paper presents new evidence for a
  common initial triggering mechanism, the birth or motion of pores at one
  end of the activated filament sections. This is taken as an indication
  of emerging magnetic flux and current induction in the filaments. The
  difference in the final results is partly due to the different ambient
  magnetic field structures. In particular in the case leading to material
  ejection there is a subsequent associated flare occurred indicating
  the storage of magnetic energy in the region. Models are proposed for
  the two sequences of events, clarifying the underlying similarities
  and interpreting the distinct features of the two sets of observations.

Title: Solar Global Background Magnetic Field Changes Accompanying the
    Development of the White-Light Flare Region of April 1984 (NOAA 4474)
Authors: Bumba, V.; Gesztelyi, L.
Bibcode: 1988BAICz..39....1B
Altcode:
  In investigating the large-scale distribution changes of solar
  background magnetic field during a wide time interval around the
  formation of this very complex region, it is demonstrated that this
  development must be taken as part of a global process in the solar
  atmosphere. Complete reorganizations are seen in the magnetic active
  longitude patterns and the solar magnetic-field sector structure,
  clearly related to its maximum stage. It is also shown that, at
  the same time, restructuralization of coronal holes took place. The
  relation of large-scale cellularlike structures to this development
  is also studied. It is concluded that the formation of this strong
  white-light flare region was casually related to the rebuilding of
  the global solar magnetic field.

Title: Rotation of Individual Background Magnetic Field Components
    During the Formation of the White-Light Flare Region of April 1984
    (NOAA 4474)
Authors: Bumba, V.; Gesztelyi, L.
Bibcode: 1987BAICz..38..351B
Altcode:
  In the present continuation of their study of processes related to the
  development of the white-light flare region of April 1984, the authors
  pay greater attention to the problem of rotation rates of certain
  components of the background magnetic field, constituting the main
  patterns of the weak as well as strong fields, from three points of
  view: as they are demonstrated by the distribution of chromospheric
  filaments, from point of view of the existence of so-called "pivot
  points" (Mouradian et al., 1987) and of the rotation of the strongest
  magnetic flux sources.

Title: Local rigid rotation and the emergence of active centres
Authors: Mouradian, Z.; Martres, M. J.; Soru-Escaut, I.; Gesztelyi, L.
Bibcode: 1987A&A...183..129M
Altcode:
  Deviations from the mean solar rotation rule of filaments are
  frequent. They correspond to real physical behaviour. Using filaments as
  tracers, limited solar areas of rigid rotation are observed: these are
  "pivot points" around which the filaments rotate during two or more
  successive rotations. It is shown that a relation exists between the
  pivot points and Active Centres: many Active Centres appear close to a
  pivot point whatever their latitude, whereas filaments which reveal the
  classical differential rotation do not generate any Active Centres. The
  magnetic flux emergence is associated in time with apparent reduced
  speed of the filament tilt about the pivot point. Some examples show
  that the relation exists using a reduced time scale of several days
  as well. The new Active Centre may destroy or displace the associated
  pivot point.

Title: Photospheric Induced Destabilization and Ejection of Prominence
    Material
Authors: Raadu, M. A.; Schmieder, B.; Mein, N.; Gesztelyi, L.
Bibcode: 1987HvaOB..11..105R
Altcode:
  The cause of the sudden activation of solar prominences is not
  clear. The authors present observations of two cases which were preceded
  by the emergence and motion of pores (new flux) in the near vicinity
  of the filaments, which seem to be closely related to the process which
  triggered the filament destabilization. These observations may be well
  described by a theoretical model in which the new flux interacts with
  the older "stable" magnetic field.

Title: High flare activity and redistribution of solar global
    magnetic fields.
Authors: Bumba, V.; Hejna, L.; Gesztelyi, L.
Bibcode: 1987PAICz..66..129B
Altcode: 1987eram....1..129B
  The authors demonstrate that both in the global scale and in the
  scale of large and complex active regions the high flare activity
  is closely related to the changes in the whole background magnetic
  field distribution.

Title: Starspot proper motion in HK Lac.
Authors: Oláh, K.; Gesztelyi, L.; Holl, A.
Bibcode: 1987PAICz..70...95O
Altcode: 1987eram....5...95O
  HK Lac is a long period RS CVn system with complex behaviour due to
  spots on the surface of the primary. Significant spot changes occur on
  long time scales (years), sometimes changes are seen over a few stellar
  rotation (months). The authors try to interpret these occasional events
  as spot proper motions on the primary star of the system.

Title: Sunspot groups as tracers of radial differential rotation.
Authors: Gesztelyi, L.; Pap, J.
Bibcode: 1987PAICz..66...77G
Altcode: 1987eram....1...77G
  Measurements of the proper motions of young bipolar sunspot groups show
  that these groups rotate faster than the surrounding photosphere. The
  faster proper motion of the young sunspot groups as well as the 24
  days periodicity of the young active spot areas might indicate that
  the young sunspots are connected to the deeper regions of the Sun
  which rotate faster than the photosphere. Thus, the sunspot groups
  in the early stage of their life would be an indicator of rotation of
  the deeper layers of the Sun.

Title: Filament eruption connected to photospheric activity.
Authors: Simon, G.; Gesztelyi, L.; Schmieder, B.; Mein, N.
Bibcode: 1986NASCP2442..229S
Altcode: 1986copp.nasa..229S
  Two cases of activation of filaments that occured in regions of
  intense magnetic activity was studied. The simultaneous observations
  from Debrecen Observatory (white light and H alpha filtergram), and
  from Meudon Observatory (magnetogram, MSDP dopplergram and intensity
  maps in H alpha) gave a complementary set of data from which can be
  produced evidence of the influence of the photospheric magnetic field
  on the destabilization process of the filaments. On June 22, 1980,
  the eruption of the filament is associated with the motion of pores,
  which are manifestations of emerging flux knots. On September 3, 1980,
  the twisting motions in the filament are associated to the birth of
  a pore in its neighborhood. These observations are discussed.

Title: White light flares and atmospheric modeling (Working Group
    report).
Authors: Machado, M. E.; Avrett, E. H.; Falciani, R.; Fang, C.;
   Gesztelyi, L.; Henoux, J. -C.; Hiei, E.; Neidig, D. F.; Rust, D. M.;
   Sotirovski, P.; Svestka, Z.; Zirin, H.
Bibcode: 1986lasf.conf..483M
Altcode:
  The authors give a short summary of their discussions, and a set
  of recommendations which may help in the study of white light flare
  emission processes.

Title: Motion of small sunspots in a channel
Authors: Gesztelyi, L.
Bibcode: 1986CoSka..15..251G
Altcode:
  In the old bipolar sunspot group in Hale region 17117 new fluxes
  emerged. Numerous small spots became settled to a curved shape channel
  around the old leader spot. During 5 days (11 - 15 Sept. 1980) the
  spots were emerging and moving along this channel or joined it,
  irrespective of their polarities. This channel of sunspot motion
  might be in connection with large-scale flows of photospheric or
  sub-photospheric layers, perhaps with supergranular flows.

Title: Sunspot proper motions in connection with the white-light
    flare of 25 April 1984
Authors: Gesztelyi, L.; Kalman, B.
Bibcode: 1986AdSpR...6f..21G
Altcode: 1986AdSpR...6...21G
  During the descending phase of the present cycle of solar activity
  one of the largest events was the 3B/X13.0 white-light flare in
  NOAA Active Region No. 4474 near the eastern limb on 24/25 April
  1984. We present a study of the evolution of the very complex and
  extended active region 4474, the proper motion of the sunspots and
  the changes in the magnetic field in connection with the large flare,
  with special emphasis on the magnetic shear and other possible types
  of motion leading to flare build-up, and following the flare.

Title: White-light flare of 26 July 1981.
Authors: Gesztelyi, L.; Karlicky, M.; Farnik, F.; Gerlei, O.;
   Valnicek, B.
Bibcode: 1986lasf.conf..163G
Altcode: 1986lasf.symp..163G
  Making use of series of white light heliograms the authors studied
  the development of a flare-active sunspot group in Hale region 17760,
  where a white-light flare (WLF) was observed on 26 July 1981. The
  WLF appeared in a disintegrating delta-configuration, where rapid
  motion of newly emerged spots and of separating fragments of older
  umbrae was shearing and distorting the magnetic field. On the basis
  of optical, X-ray and radio observations the authors analysed the WLF
  event. Some observational indications exist supporting the hypothesis
  that the WLF knots are situated in the places of concentrated electric
  current which electrically couples sub-photospheric, photospheric
  and higher layers. Provided this is true the WL emission has been
  interpreted as the response of deep layers of the solar atmosphere to
  the dissipation-spreading process propagating along the electric current
  system. Intensity of the WLF knots relatively to the photosphere has
  been deduced and the power emitted between 545 and 555 nm estimated. The
  total energy emitted by the WLF knots is roughly estimated.

Title: Preflare Activity of Solar Prominences
Authors: Simon, G.; Mein, N.; Mein, P.; Gesztelyi, L.
Bibcode: 1984SoPh...93..325S
Altcode:
  The preflare activity of a plage filament is analysed from Hα
  observations made with the Multichannel Subtractive Double Pass
  Spectrograph (MSDP) of the Meudon Solar Tower. The June 22, 1980
  event is studied and interpreted in terms of preflare heating of a
  filament, connected to the rise of emerging flux, and the relative
  approach of pores of different magnetic polarity, prior to the onset
  of a two-ribbon flare.

Title: Relationships of a growing magnetic flux region to flares
Authors: Martin, S. F.; Bentley, R. D.; Schadee, A.; Antalova, A.;
   Kucera, A.; Dezső, L.; Gesztelyi, L.; Harvey, K. L.; Jones, H.;
   Livi, S. H. B.; Wang, J.
Bibcode: 1984AdSpR...4g..61M
Altcode: 1984AdSpR...4...61M
  Some sites for solar flares are known to develop where new magnetic
  flux emerges and becomes abutted against opposite polarity pre-existing
  magnetic flux (review by Galzauskas/1/). We have identified and analyzed
  the evolution of such flare sites at the boundaries of a major new and
  growing magnetic flux region within a complex of active regions, Hale
  No. 16918. This analysis was done as a part of a continuing study of the
  circumstances associated with flares in Hale Region 16918, which was
  designated as an FBS target during the interval 18 - 23 June 1980. We
  studied the initiation and development of both major and minor flares in
  Hα images in relation to the identified potential flare sites at the
  boundaries of the growing flux region and to the general development
  of the new flux. This study lead to our recognition of a spectrum of
  possible relationships of growing flux regions to flares as follows:
  (1) intimate interaction with adjacent old flux - flare sites centered
  at new/old flux boundary, (2) forced or ``intimidated'' interaction
  in which new flux pushes old field having lower flux density towards a
  neighboring old polarity inversion line where a flare then takes place,
  (3) ``influential'' interaction - magnetic lines of force over an old
  polarity inversion line, typically containing a filament, reconnect to
  the new emerging flux; a flare occurs with erupting filament when the
  magnetic field overlying the filament becomes too weak to prevent its
  eruption, (4) inconsequential interaction - new flux region is too small
  or has wrong orientation for creating flare conditions, (5) incidental -
  flare occurs without any significant relationship to new flux regions.

Title: Consecutive homologous flares and their relation to sunspot
    motions
Authors: Gesztelyi, L.
Bibcode: 1984AdSpR...4g..19G
Altcode: 1984AdSpR...4Q..19G
  The large sunspot group in Hale region 17098 was in the decaying
  phase of its development when a new flux emerged in its middle part
  on 3 September 1980. This region displayed chromospheric activity
  all that day. By the next day the spot of highest velocity (0.37 km
  s<SUP>-1</SUP>) formed a delta-configuration with one of the spots of
  following polarity of the old group. The centre of the observed flares
  was not in the vicinity of this spot moving parallel to the magnetic
  zero-line, it was in the western part of the group, where two spots
  were moving nearly perpendicularly to the magnetic zero-line (v=0.09
  km s<SUP>-1</SUP>), and deformed the border of a gulf of opposite
  polarity. With the changing configuration the form of the observed
  flares also changed.

Title: The development of activity in Hale region 17098 (28 August -
    8 September 1980).
Authors: Gesztelyi, L.; Kondás, L.
Bibcode: 1983PDHO....5..133G
Altcode: 1984PDHO....5..133G
  Proper motions and some respects of chromospheric activities of a
  relatively simple large sunspot group were studied on the basis of
  full-disc white light photoheliograms and Hα filtergrams. The large
  sunspot group consisted of two, subsequently developing groups. In
  the course of their development, the umbrae of the two groups collided
  with each other. The observed chromospheric activity was relatively low.

Title: Motions in the solar atmosphere associated with the white
    light flare of 11 July 1978
Authors: Dezso, L.; Gesztelyi, L.; Kondas, L.; Kovacs, A.; Rostas, S.
Bibcode: 1980SoPh...67..317D
Altcode:
  Series of white light heliograms and oft- and on-band Hα filtergrams
  have been obtained, with an average spatial resolution of 1″, to study
  the flare active McMath region 15403 on 11 July, 1978. A great number
  of accurate heliographic positions were determined for the umbrae, the
  white light flare patches and several bright Hα flare knots, as well
  as along the principal zero filament and an arch prominence. Using the
  measured heliographic coordinates of these objects their motions could
  be analyzed in some detail. The velocities of several different objects
  could be deduced from the coordinates. Since the heliocentric angle
  of the region was about 45°, the variation in apparent heliographic
  coordinates also enabled some variations in heights to be determined.

Title: Umbral proper motions in the large sunspot group of the great
    flare activity of August 1972.
Authors: Gesztelyi, L.
Bibcode: 1977PDHO....3...93G
Altcode:
  No abstract at ADS

