Author name code: patsourakos
ADS astronomy entries on 2022-09-14
author:"Patsourakos, Spiros" 
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Title: The Low-Corona Evolution of Coronal Mass Ejections: Solar
    Truth and Implications for Stellar Coronal Mass Ejections
Authors: Patsourakos, Spiros; Vourlidas, Angelos; Balmaceda, Laura
Bibcode: 2022cosp...44.1407P
Altcode:
  Once a Coronal Mass Ejection (CME) is underway, it sparks a variety
  of phenomena in the low corona including dimmings, waves and
  shocks. An important finding of multi-viewpoint and high-cadence
  imaging observations of the initial stages of CMEs from STEREO and
  SDO is that they evolve differently in the lateral compared to the
  radial direction. The CME lateral expansion in the low corona is of
  particular interest to solar-stellar studies because it occurs in the
  region that dominates the emission in stellar observations, and triggers
  wave and shock phenomena. With this presentation we will discuss: i)
  basic observational aspects of the lateral expansion of CMEs in the
  solar corona, and ii) how these may contribute to the hunt for stellar
  CMEs. We will show how our understanding of the low lateral expansion
  of CMEs in the solar corona may help into deciphering and eventually
  modeling of the light-curves of dimmings presumably associated with
  stellar CMEs.

Title: The lower solar atmosphere inside and outside coronal holes
    and the base of the Solar Wind
Authors: Gontikakis, Costis; Patsourakos, Spiros; Tsinganos, Kanaris;
   Koletti, Myrto
Bibcode: 2022cosp...44.1336G
Altcode:
  In this review, we will present the crucial observations that gave rise
  to current concepts on the formation of the solar wind, low in the solar
  atmosphere. We will discuss the differences between the fast solar wind
  originating from coronal holes and the slow solar wind emanating around
  solar streamers and closed solar magnetic structures. Observations
  from remote spectrographs that may constitute critical tests for the
  different solar wind acceleration models will be emphasized. Phenomena
  such as plumes and jets will also be examined. Finally, we will
  introduce the most recent SolO and PSP results on the origins and
  early stages of the solar wind.

Title: The impact of virtual mass and magnetic erosion on the
    propagation of fast ICMEs
Authors: Stamkos, Sotiris; Patsourakos, Spiros; Daglis, Ioannis A.;
   Vourlidas, Angelos
Bibcode: 2022cosp...44.1406S
Altcode:
  In order to enhance our understanding of the dynamic interactions of
  Interplanetary Coronal Mass Ejections (ICMEs) with the solar wind
  and interplanetary magnetic field, we investigate the effect of
  magnetic erosion on the well-known aerodynamic drag force acting on
  ICMEs. In particular, we generate empirical equations for the basic
  parameters of an ICME assuming a cylindrical morphology. Furthermore,
  we examine the impact of the virtual mass on the equation of motion
  by essentially studying a variable mass system. We quantify the
  effect of the reconnection process, which erodes part of the ICME's
  magnetic flux and outer-shell mass, on the drag acting on ICMEs and,
  eventually, we determine its impact on the time and speed of arrival
  of those transients at 1 AU.

Title: Assessment of near sun axial CME magnetic field.
Authors: Koya, Shifana; Patsourakos, Spiros; Georgoulis, Manolis K.;
   Nindos, Alexander
Bibcode: 2022cosp...44.1405K
Altcode:
  The magnetic origin and the role of magnetic helicity in solar eruptions
  are known for several years. Here we present a survey of near-Sun
  axial coronal mass ejection (CME) magnetic fields that are obtained
  by applying a semi-analytical method that calculates the magnetic
  helicity of the source active region relying primarily on photospheric
  vector magnetograms. The geometrical parameters of CMEs observed by
  STEREO/SECCHI and SOHO/LASCO are obtained by fitting the GCS magnetic
  flux rope model. We use the estimated near-Sun CME magnetic fields to
  infer ICME magnetic fields and to validate them with existing in-situ
  magnetometer observation at L1. We conclude that the proposed method,
  including the proposed inferences from the survey, is useful for CME
  magnetic field forecasting purposes, solar-stellar connection and
  projecting towards potential properties of stellar CMEs.

Title: When do solar erupting hot magnetic flux ropes form?
Authors: Nindos, Alexander; Zhang, Jie; Patsourakos, Spiros; Cheng,
   Xin; Vourlidas, Angelos
Bibcode: 2022cosp...44.2419N
Altcode:
  We investigate the formation times of eruptive magnetic flux ropes
  relative to the onset of solar eruptions, which is important for
  constraining models of coronal mass ejection (CME) initiation. We
  inspected uninterrupted sequences of 131 A images that spanned more than
  eight hours and were obtained by the Atmospheric Imaging Assembly on
  board the Solar Dynamics Observatory to identify the formation times
  of hot flux ropes that erupted in CMEs from locations close to the
  limb. The appearance of the flux ropes as well as their evolution toward
  eruptions were determined using morphological criteria. Two-thirds
  (20/30) of the flux ropes were formed well before the onset of the
  eruption (from 51 min to more than eight hours), and their formation
  was associated with the occurrence of a confined flare. We also found
  four events with preexisting hot flux ropes whose formations occurred
  a matter of minutes (from three to 39) prior to the eruptions without
  any association with distinct confined flare activity. Six flux ropes
  were formed once the eruptions were underway. However, in three of
  them, prominence material could be seen in 131 Å images, which may
  indicate the presence of preexisting flux ropes that were not hot. The
  formation patterns of the last three groups of hot flux ropes did not
  show significant differences. For the whole population of events, the
  mean and median values of the time difference between the onset of the
  eruptive flare and the appearance of the hot flux rope were 151 and 98
  min, respectively. Our results provide, on average, indirect support
  for CME models that involve preexisting flux ropes; on the other hand,
  for a third of the events, models in which the ejected flux rope is
  formed during the eruption appear more appropriate.

Title: Identifying the Terrestrial Exoplanets which Deserve More
Scrutiny for Atmosphere Viability: the mASC method
Authors: Samara, Evangelia; Patsourakos, Spiros; Georgoulis, Manolis K.
Bibcode: 2022cosp...44.1395S
Altcode:
  We introduce a practical and physically intuitive method to assess
  whether a given exoplanet is a viable candidate for the existence of
  an atmosphere, thanks to an efficient magnetospheric shielding from
  intense space weather activity from its host star. Our proposed mASC
  (magnetic Atmosphere Sustainability Constraint) relies on a best-case
  scenario for a dynamo-generated planetary magnetic field and subsequent
  magnetic pressure, and a worst-case scenario for the magnetic pressure
  of stellar CMEs. The method estimates a dimensionless ratio R whose
  excursion from unity implies accordingly an "atmosphere likely" (R
  &lt; 1) or an "atmosphere unlikely" (R &gt; 1) scenario. In this work,
  we implement our mASC on six "famous" exoplanets whose discovery was
  greeted with praise and hopes of habitability. These are Kepler-438b,
  Proxima-Centauri b, and Trappist-1d, -1e, -1f, -1g. We conclude that
  for none of them the existence of an atmosphere is likely while our
  findings are robust for five out of six cases. We conclude that the
  mASC ratio could help set observing priorities and suggest which
  exoplanets deserve further scrutiny, possibly toward the ultimate
  search of potential biosignatures, among other objectives.

Title: Investigating possible EUV precursors of major solar flares
Authors: AndrÉ-Hoffmann, Augustin; Patsourakos, Spiros; Georgoulis,
   Manolis K.; Nindos, Alexander
Bibcode: 2022cosp...44.2481A
Altcode:
  Large-scale solar eruptions that produce major flares and fast coronal
  mass ejections are often associated with precursor activity that
  may start several hours before the main event. Such activity may be
  observed from the photosphere all the way to the transition region
  and corona but it is not clear whether it plays an essential role in
  the eruption initiation. To investigate this question we search for
  precursor activity in Extreme Ultra-violet (EUV) images obtained by the
  Atmospheric Imaging Assembly (AIA) instrument on board Solar Dynamics
  Observatory (SDO) within a 24-hour window prior to large eruptive
  events and investigate whether they contribute to the restructuring and
  overall evolution of the magnetic field that leads to eruptions. We
  cross-check our findings by performing the same search in relatively
  quiet active regions. By comparing the results from the eruptive and
  quiet active regions we attempt to identify possible signatures that
  could be useful in both the short-term prediction of major flare events
  and an enhanced physical understanding of the preflare phase.

Title: First detection of metric emission from a solar surge
Authors: Alissandrakis, C. E.; Patsourakos, S.; Nindos, A.; Bouratzis,
   C.; Hillaris, A.
Bibcode: 2022A&A...662A..14A
Altcode: 2022arXiv220301043A
  We report the first detection of metric radio emission from a surge,
  observed with the Nançay Radioheliograph (NRH), STEREO, and other
  instruments. The emission was observed during the late phase of the
  M9 complex event SOL2010-02-012T11:25:00, described in a previous
  publication. It was associated with a secondary energy release,
  also observed in STEREO 304 Å images, and there was no detectable
  soft X-ray emission. The triangulation of the STEREO images allowed
  for the identification of the surge with NRH sources near the central
  meridian. The radio emission of the surge occurred in two phases and
  consisted of two sources, one located near the base of the surge,
  apparently at or near the site of energy release, and another in the
  upper part of the surge; these were best visible in the frequency
  range of 445.0 to about 300 MHz, whereas a spectral component of
  a different nature was observed at lower frequencies. Sub-second
  time variations were detected in both sources during both phases,
  with a 0.2-0.3 s delay of the upper source with respect to the lower,
  suggesting superluminal velocities. This effect can be explained if
  the emission of the upper source was due to scattering of radiation
  from the source at the base of the surge. In addition, the radio
  emission showed signs of pulsations and spikes. We discuss possible
  emission mechanisms for the slow time variability component of
  the lower radio source. Gyrosynchrotron emission reproduced the
  characteristics of the observed total intensity spectrum at the
  start of the second phase of the event fairly well, but failed to
  reproduce the high degree of the observed circular polarization or the
  spectra at other instances. On the other hand, type IV-like plasma
  emission from the fundamental could explain the high polarization
  and the fine structure in the dynamic spectrum; moreover, it gives
  projected radio source positions on the plane of the sky, as seen from
  STEREO-A, near the base of the surge. Taking all the properties into
  consideration, we suggest that type IV-like plasma emission with
  a low-intensity gyrosynchrotron component is the most plausible
  mechanism. <P />Movie associated to Fig. A.2 is available at <A
  href="https://www.aanda.org/10.1051/0004-6361/202243169/olm">https://www.aanda.org</A>

Title: Earth-affecting solar transients: a review of progresses in
    solar cycle 24
Authors: Zhang, Jie; Temmer, Manuela; Gopalswamy, Nat; Malandraki,
   Olga; Nitta, Nariaki V.; Patsourakos, Spiros; Shen, Fang; Vršnak,
   Bojan; Wang, Yuming; Webb, David; Desai, Mihir I.; Dissauer, Karin;
   Dresing, Nina; Dumbović, Mateja; Feng, Xueshang; Heinemann, Stephan
   G.; Laurenza, Monica; Lugaz, Noé; Zhuang, Bin
Bibcode: 2021PEPS....8...56Z
Altcode: 2020arXiv201206116Z
  This review article summarizes the advancement in the studies of
  Earth-affecting solar transients in the last decade that encompasses
  most of solar cycle 24. It is a part of the effort of the International
  Study of Earth-affecting Solar Transients (ISEST) project, sponsored
  by the SCOSTEP/VarSITI program (2014-2018). The Sun-Earth is an
  integrated physical system in which the space environment of the
  Earth sustains continuous influence from mass, magnetic field, and
  radiation energy output of the Sun in varying timescales from minutes to
  millennium. This article addresses short timescale events, from minutes
  to days that directly cause transient disturbances in the Earth's
  space environment and generate intense adverse effects on advanced
  technological systems of human society. Such transient events largely
  fall into the following four types: (1) solar flares, (2) coronal mass
  ejections (CMEs) including their interplanetary counterparts ICMEs,
  (3) solar energetic particle (SEP) events, and (4) stream interaction
  regions (SIRs) including corotating interaction regions (CIRs). In
  the last decade, the unprecedented multi-viewpoint observations of
  the Sun from space, enabled by STEREO Ahead/Behind spacecraft in
  combination with a suite of observatories along the Sun-Earth lines,
  have provided much more accurate and global measurements of the size,
  speed, propagation direction, and morphology of CMEs in both 3D and over
  a large volume in the heliosphere. Many CMEs, fast ones, in particular,
  can be clearly characterized as a two-front (shock front plus ejecta
  front) and three-part (bright ejecta front, dark cavity, and bright
  core) structure. Drag-based kinematic models of CMEs are developed to
  interpret CME propagation in the heliosphere and are applied to predict
  their arrival times at 1 AU in an efficient manner. Several advanced
  MHD models have been developed to simulate realistic CME events from
  the initiation on the Sun until their arrival at 1 AU. Much progress
  has been made on detailed kinematic and dynamic behaviors of CMEs,
  including non-radial motion, rotation and deformation of CMEs, CME-CME
  interaction, and stealth CMEs and problematic ICMEs. The knowledge
  about SEPs has also been significantly improved. An outlook of how to
  address critical issues related to Earth-affecting solar transients
  concludes this article.

Title: Which Terrestrial Exoplanets Deserve More Scrutiny for
    Atmosphere Viability?
Authors: Samara, Evangelia; Patsourakos, Spiros; Georgoulis, Manolis
Bibcode: 2021AGUFM.U44B..05S
Altcode:
  We introduce a practical and physically intuitive method to assess
  whether a given exoplanet is a viable candidate for the existence of
  an atmosphere thanks to an efficient magnetospheric shielding from
  intense space weather activity originating from its host star. Our
  proposed mASC (magnetic Atmosphere Sustainability Constraint) relies on
  a best-case scenario for the dynamo-generated planetary magnetic field
  and subsequent magnetic pressure, and a worst-case scenario for the
  magnetic pressure of stellar CMEs. It provides a dimensionless ratio
  R whose excursion from unity implies accordingly an atmosphere likely
  (R &lt; 1) or an atmosphere unlikely (R &gt; 1) scenario. In this work,
  we implement our mASC on six famous exoplanets whose discovery was
  greeted with praise and hopes of habitability. These are Kepler-438b,
  Proxima-Centauri b, and Trappist-1d, -1e, -1f, -1g. The results show
  that for none of them the existence of an atmosphere is likely while
  our findings are robust for five out of six cases. We conclude that
  the mASC ratio could help set observing priorities and suggest which
  exoplanets deserve further scrutiny, possibly toward the ultimate
  search of potential biosignatures, among other objectives.

Title: Multiwavelength observations of a metric type-II event
Authors: Alissandrakis, C. E.; Nindos, A.; Patsourakos, S.; Hillaris,
   A.
Bibcode: 2021A&A...654A.112A
Altcode: 2021arXiv210802855A
  We have studied a complex metric radio event that originated in a
  compact flare, observed with the ARTEMIS-JLS radiospectrograph on
  February 12, 2010. The event was associated with a surge observed at 195
  and 304 Å and with a coronal mass ejection observed by instruments on
  board STEREO A and B near the eastern and western limbs respectively. On
  the disk the event was observed at ten frequencies by the Nançay
  Radioheliograph (NRH), in Hα by the Catania observatory, in soft
  X-rays by GOES SXI and Hinode XRT, and in hard X-rays by RHESSI. We
  combined these data, together with MDI longitudinal magnetograms,
  to get as complete a picture of the event as possible. Our emphasis
  is on two type-II bursts that occurred near respective maxima in
  the GOES light curves. The first, associated with the main peak
  of the event, showed an impressive fundamental-harmonic structure,
  while the emission of the second consisted of three well-separated
  bands with superposed pulsations. Using positional information for the
  type-IIs from the NRH and triangulation from STEREO A and B, we found
  that the type-IIs were associated neither with the surge nor with the
  disruption of a nearby streamer, but rather with an extreme ultraviolet
  (EUV) wave probably initiated by the surge. The fundamental-harmonic
  structure of the first type-II showed a band split corresponding to
  a magnetic field strength of 18 G, a frequency ratio of 1.95 and a
  delay of 0.23−0.65 s of the fundamental with respect to the harmonic;
  moreover it became stationary shortly after its start and then drifted
  again. The pulsations superposed on the second type-II were broadband
  and had started before the burst. In addition, we detected another
  pulsating source, also before the second type-II, polarized in the
  opposite sense; the pulsations in the two sources were out of phase
  and hence hardly detectable in the dynamic spectrum. The pulsations
  had a measurable reverse frequency drift of about 2 s<SUP>−1</SUP>.

Title: ALMA observations of the variability of the quiet Sun at
    millimeter wavelengths
Authors: Nindos, A.; Patsourakos, S.; Alissandrakis, C. E.; Bastian,
   T. S.
Bibcode: 2021A&A...652A..92N
Altcode: 2021arXiv210604220N
  <BR /> Aims: We address the variability of the quiet solar chromosphere
  at 1.26 mm and 3 mm with a focus on the study of spatially resolved
  oscillations and transient brightenings, which are small, weak
  events of energy release. Both phenomena may have a bearing on the
  heating of the chromosphere. <BR /> Methods: We used Atacama Large
  Millimeter/submillimeter Array (ALMA) observations of the quiet Sun
  at 1.26 mm and 3 mm. The spatial and temporal resolution of the data
  were 1 − 2″ and 1 s, respectively. The concatenation of light
  curves from different scans yielded a frequency resolution in spectral
  power of 0.5−0.6 mHz. At 1.26 mm, in addition to power spectra of
  the original data, we degraded the images to the spatial resolution
  of the 3 mm images and used fields of view that were equal in area
  for both data sets. The detection of transient brightenings was made
  after the effect of oscillations was removed. <BR /> Results: At both
  frequencies, we detected p-mode oscillations in the range 3.6−4.4
  mHz. The corrections for spatial resolution and field of view at 1.26 mm
  decreased the root mean square (rms) of the oscillations by a factor of
  1.6 and 1.1, respectively. In the corrected data sets, the oscillations
  at 1.26 mm and 3 mm showed brightness temperature fluctuations of
  ∼1.7 − 1.8% with respect to the average quiet Sun, corresponding to
  137 and 107 K, respectively. We detected 77 transient brightenings at
  1.26 mm and 115 at 3 mm. Although their majority occurred in the cell
  interior, the occurrence rate per unit area of the 1.26 mm events was
  higher than that of the 3 mm events; this conclusion does not change
  if we take into account differences in spatial resolution and noise
  levels. The energy associated with the transient brightenings ranged
  from 1.8 × 10<SUP>23</SUP> to 1.1 × 10<SUP>26</SUP> erg and from 7.2
  × 10<SUP>23</SUP> to 1.7 × 10<SUP>26</SUP> erg for the 1.26 mm and
  3 mm events, respectively. The corresponding power-law indices of the
  energy distribution were 1.64 and 1.73. We also found that ALMA bright
  network structures corresponded to dark mottles or spicules that can be
  seen in broadband Hα images from the GONG network. <BR /> Conclusions:
  The fluctuations associated with the p-mode oscillations represent
  a fraction of 0.55−0.68 of the full power spectrum. Their energy
  density at 1.26 mm is 3 × 10<SUP>−2</SUP> erg cm<SUP>−3</SUP>. The
  computed low-end energy of the 1.26 mm transient brightenings is among
  the smallest ever reported, irrespective of the wavelength of the
  observation. Although the occurrence rate per unit area of the 1.26
  mm transient brightenings was higher than that of the 3 mm events,
  their power per unit area is smaller likely due to the detection of
  many weak 1.26 mm events.

Title: Tracking solar wind flows from rapidly varying viewpoints by
    the Wide-field Imager for Parker Solar Probe
Authors: Nindos, A.; Patsourakos, S.; Vourlidas, A.; Liewer, P. C.;
   Penteado, P.; Hall, J. R.
Bibcode: 2021A&A...650A..30N
Altcode: 2020arXiv201013140N
  <BR /> Aims: Our goal is to develop methodologies to seamlessly track
  transient solar wind flows viewed by coronagraphs or heliospheric
  imagers from rapidly varying viewpoints. <BR /> Methods: We
  constructed maps of intensity versus time and elongation (J-maps)
  from Parker Solar Probe (PSP) Wide-field Imager (WISPR) observations
  during the fourth encounter of PSP. From the J-map, we built an
  intensity on impact-radius-on-Thomson-surface map (R-map). Finally,
  we constructed a latitudinal intensity versus time map (Lat-map). Our
  methodology satisfactorily addresses the challenges associated with
  the construction of such maps from data taken from rapidly varying
  viewpoint observations. <BR /> Results: Our WISPR J-map exhibits
  several tracks, corresponding to transient solar wind flows ranging
  from a coronal mass ejection down to streamer blobs. The latter
  occurrence rate is about 4-5 per day, which is similar to the
  occurrence rate in a J-map made from ~1 AU data obtained with the
  Heliospheric Imager-1 (HI-1) on board the Solar Terrestrial Relations
  Observatory Ahead spacecraft (STEREO-A). STEREO-A was radially aligned
  with PSP during the study period. The WISPR J-map tracks correspond
  to angular speeds of 2.28 ± 0.7°/h (2.49 ± 0.95°/h), for linear
  (quadratic) time-elongation fittings, and radial speeds of about
  150-300 km s<SUP>−1</SUP>. The analysis of the Lat-map reveals
  a bifurcating streamer, which implies that PSP was flying through
  a slightly folded streamer during perihelion. <BR /> Conclusions:
  We developed a framework to systematically capture and characterize
  transient solar wind flows from space platforms with rapidly varying
  vantage points. The methodology can be applied to PSP WISPR observations
  as well as to upcoming observations from instruments on board the Solar
  Orbiter mission. <P />Movie associated to Fig. 8 is available at <A
  href="https://www.aanda.org/10.1051/0004-6361/202039414/olm">https://www.aanda.org</A>

Title: Relative field line helicity of a large eruptive solar
    active region
Authors: Moraitis, K.; Patsourakos, S.; Nindos, A.
Bibcode: 2021A&A...649A.107M
Altcode: 2021arXiv210303643M
  Context. Magnetic helicity is a physical quantity of great importance
  in the study of astrophysical and natural plasmas. Although a density
  for helicity cannot be defined, a good proxy for this quantity is field
  line helicity. The appropriate quantity for use in solar conditions
  is relative field line helicity (RFLH). <BR /> Aims: This work aims
  to study in detail the behaviour of RFLH, for the first time, in a
  solar active region (AR). <BR /> Methods: The target AR is the large,
  eruptive AR 11158. In order to compute RFLH and all other quantities
  of interest, we used a non-linear force-free reconstruction of the AR
  coronal magnetic field of excellent quality. <BR /> Results: We find
  that the photospheric morphology of RFLH is very different than that
  of the magnetic field or electrical current, and this morphology is
  not sensitive to the chosen gauge in the computation of RFLH. The
  value of helicity experiences a large decrease, that is ∼25% of
  its pre-flare value, during an X-class flare of the AR; this change
  is also depicted in the photospheric morphology of RFLH. Moreover,
  the area of this change coincides with the area that encompasses the
  flux rope, which is the magnetic structure that later erupted. <BR />
  Conclusions: The use of RFLH can provide important information about
  the value and location of the magnetic helicity expelled from the
  solar atmosphere during eruptive events.

Title: A Readily Implemented Atmosphere Sustainability Constraint
    for Terrestrial Exoplanets Orbiting Magnetically Active Stars
Authors: Samara, Evangelia; Patsourakos, Spiros; Georgoulis, Manolis K.
Bibcode: 2021ApJ...909L..12S
Altcode: 2021arXiv210207837S
  With more than 4300 confirmed exoplanets and counting, the next
  milestone in exoplanet research is to determine which of these
  newly found worlds could harbor life. Coronal mass ejections (CMEs),
  spawned by magnetically active, superflare-triggering dwarf stars,
  pose a direct threat to the habitability of terrestrial exoplanets, as
  they can deprive them of their atmospheres. Here we develop a readily
  implementable atmosphere sustainability constraint for terrestrial
  exoplanets orbiting active dwarfs, relying on the magnetospheric
  compression caused by CME impacts. Our constraint focuses on an
  understanding of CMEs propagation in our own Sun-heliosphere system
  that, applied to a given exoplanet requires as key input the observed
  bolometric energy of flares emitted by its host star. Application of our
  constraint to six famous exoplanets, Kepler-438b, Proxima Centauri b,
  and Trappist-1d, -1e, -1f, and -1g, within or in the immediate proximity
  of their stellar host's habitable zones showed that only for Kepler-438b
  might atmospheric sustainability against stellar CMEs be likely. This
  seems to align with some recent studies that, however, may require far
  more demanding computational resources and observational inputs. Our
  physically intuitive constraint can be readily and en masse applied, as
  is or generalized, to large-scale exoplanet surveys to detect planets
  that warrant further scrutiny for atmospheres and, perhaps, possible
  biosignatures at higher priority by current and future instrumentation.

Title: Properties Determining Eruption Initiation and
    Planeto-Effectiveness of Eruptive Transients in Magnetically Active
    Stars
Authors: Georgoulis, Manolis K.; Patsourakos, Spiros; Zhang, Hongqi;
   Nindos, Alexander; Samara, Evangelia; Sadykov, Viacheslav M.
Bibcode: 2021cosp...43E.993G
Altcode:
  We present a combined theoretical and data analysis approach to,
  first, understand why magnetic eruptions and corresponding ejecta are
  triggered in strong-field regions of the Sun and magnetically active
  stars and, second, assess the key physical parameters responsible for
  the planeto-effectiveness of these eruptions, both on Earth and in
  other (exo-)planets. This approach converges on one physical parameter
  besides magnetic energy, at least for stellar coronae of high magnetic
  Reynolds numbers allowing this parameter to be conserved even under
  confined energy release: magnetic helicity. Helicity, via the magnetic
  energy-helicity diagram, should be treated equally with magnetic
  energy. Due to magnetic helicity accumulation in solar active regions
  and its inverse cascading, solar - and stellar, correspondingly -
  eruptions may become inevitable after a certain 'point-of-no-return'
  is reached. We identify this critical instant as the time when
  magnetic polarity inversion lines in active-region photospheres
  accumulate fluxes that generate fields stronger than local equipartition
  values. Furthermore, using the conserved helicity budgets we abstractly
  model post-eruption flux ropes and their transit through astrospheres,
  reaching exoplanets and compressing their magnetospheres via magnetic
  pressure effects. A rudimentary validation between the near-Sun and
  L1 axial magnetic field values of these data-constrained flux ropes is
  encouraging and allows us to further constrain scaling laws appropriate
  for the astrospheric transit of these ropes. Importantly, we also find
  that exoplanets orbiting magnetically active dwarf stars at orbital
  radii that are fractions of an astronomical unit seem to be strong
  contenders for eruption-driven atmospheric erosion that may gradually
  even deprive them from their atmospheres. Some famous exoplanet cases
  are examined under this prism. Future improvements are expected by
  widely anticipated space- (Parker Solar Probe and Solar Orbiter)
  and ground-based (Daniel K. Inouye Solar Telescope) observations.

Title: Investigating the circumsolar wind with Parker Solar Probe
    near-imaging and in-situ high cadence observations
Authors: Patsourakos, Spiros; Liewer, Paulett; Stenborg, Guillermo;
   Howard, Russell; Hess, Phillip; Stevens, Michael; Vourlidas, Angelos;
   Kasper, Justin; Nindos, Alexander; Penteado, Paulo; Korreck, Kelly;
   Case, Anthony
Bibcode: 2021cosp...43E.940P
Altcode:
  The proposition of the existence of the solar wind and its subsequent
  discovery were major milestones at the dawn of the Space Age. Since
  then, the solar wind has been extensively observed by in-situ
  instruments at various locations in the inner and outer heliosphere
  but mainly at 1 AU, and by remote sensing instruments at 1 AU. Despite
  significant progress in the characterization and understanding of
  the solar wind, important questions about the nature of the solar
  wind remain unsettled. These questions include the nature of the
  launch and acceleration of the solar wind and whether it is steady,
  quasi-steady, periodic or intermittent. The recently launched Parker
  Solar Probe (PSP) mission, which has been already plunged several times
  in the solar corona, is ideally suited to shed more light into these
  lingering questions. We present a coordinated analysis of up-close
  and high-cadence imaging observations of the solar wind taken by WISPR
  and of in-situ solar-wind observations taken inside the solar corona
  by SWEAP during the first solar encounters of PSP. A discussion of
  instrumental and orbital aspects of the WISPR observations pertinent to
  our analysis is also included. Imaging data of the solar wind from ~
  1 AU by COR2 on STEREO-A spacecraft is also analyzed. We submit the
  time-series of the imaging and in-situ solar wind data to an array of
  methods aiming to map their properties. We conclude with a discussion
  of future PSP (WISPR and SWEAP) and Solar Orbiter (SoloHI) observing
  and analysis strategies pertinent to our science questions.

Title: Lower atmospheric consequences of Coronal Mass Ejections:
    waves, shocks and dimmings
Authors: Patsourakos, Spiros
Bibcode: 2021cosp...43E1735P
Altcode:
  Coronal Mass Ejections (CMEs) is a multi-facet phenomenon significantly
  perturbing and interacting with the solar, heliospheric and geospace
  environments. As far as the CME impact on the solar atmosphere
  is concerned, CMEs are intimately linked with a diverse array of
  large-scale and multi-wavelength phenomena including chromospheric
  and coronal waves, shocks and coronal dimmings. Characterizing and
  understanding these phenomena has important implications for not only
  CME physics, but also for coronal physics. We hereby supply a discussion
  of the state-of-the art regarding the atmospheric consequences of
  CMEs as resulting from observations of chromospheric and coronal
  waves and shocks and coronal dimmings. We will cover topics including
  their physical properties, their connection with CME expansion and
  evolution in the low solar atmosphere, their association with particle
  acceleration in the low corona, their use as a diagnostic probe of the
  properties of the ambient solar atmosphere, and their potential use
  for space-weather applications. Moving to stellar contexts, we discuss
  recent work on how coronal dimmings in active dwarfs may be be used
  in the detection of stellar CMEs. We finally close with a discussion
  of new areas in the research of the solar consequences of CMEs that
  could be possible with new instrumentation coming recently on-line
  including SolO and DKIST.

Title: Decoding the Pre-Eruptive Magnetic Field Configurations of
    Coronal Mass Ejections
Authors: Patsourakos, S.; Vourlidas, A.; Török, T.; Kliem, B.;
   Antiochos, S. K.; Archontis, V.; Aulanier, G.; Cheng, X.; Chintzoglou,
   G.; Georgoulis, M. K.; Green, L. M.; Leake, J. E.; Moore, R.; Nindos,
   A.; Syntelis, P.; Yardley, S. L.; Yurchyshyn, V.; Zhang, J.
Bibcode: 2020SSRv..216..131P
Altcode: 2020arXiv201010186P
  A clear understanding of the nature of the pre-eruptive magnetic
  field configurations of Coronal Mass Ejections (CMEs) is required
  for understanding and eventually predicting solar eruptions. Only
  two, but seemingly disparate, magnetic configurations are considered
  viable; namely, sheared magnetic arcades (SMA) and magnetic flux ropes
  (MFR). They can form via three physical mechanisms (flux emergence,
  flux cancellation, helicity condensation). Whether the CME culprit
  is an SMA or an MFR, however, has been strongly debated for thirty
  years. We formed an International Space Science Institute (ISSI) team to
  address and resolve this issue and report the outcome here. We review
  the status of the field across modeling and observations, identify
  the open and closed issues, compile lists of SMA and MFR observables
  to be tested against observations and outline research activities
  to close the gaps in our current understanding. We propose that the
  combination of multi-viewpoint multi-thermal coronal observations
  and multi-height vector magnetic field measurements is the optimal
  approach for resolving the issue conclusively. We demonstrate the
  approach using MHD simulations and synthetic coronal images.

Title: When do solar erupting hot magnetic flux ropes form?
Authors: Nindos, A.; Patsourakos, S.; Vourlidas, A.; Cheng, X.;
   Zhang, J.
Bibcode: 2020A&A...642A.109N
Altcode: 2020arXiv200804380N
  <BR /> Aims: We investigate the formation times of eruptive magnetic
  flux ropes relative to the onset of solar eruptions, which is
  important for constraining models of coronal mass ejection (CME)
  initiation. <BR /> Methods: We inspected uninterrupted sequences of
  131 Å images that spanned more than eight hours and were obtained
  by the Atmospheric Imaging Assembly on board the Solar Dynamics
  Observatory to identify the formation times of hot flux ropes that
  erupted in CMEs from locations close to the limb. The appearance
  of the flux ropes as well as their evolution toward eruptions were
  determined using morphological criteria. <BR /> Results: Two-thirds
  (20/30) of the flux ropes were formed well before the onset of the
  eruption (from 51 min to more than eight hours), and their formation
  was associated with the occurrence of a confined flare. We also found
  four events with preexisting hot flux ropes whose formations occurred
  a matter of minutes (from three to 39) prior to the eruptions without
  any association with distinct confined flare activity. Six flux ropes
  were formed once the eruptions were underway. However, in three of
  them, prominence material could be seen in 131 Å images, which may
  indicate the presence of preexisting flux ropes that were not hot. The
  formation patterns of the last three groups of hot flux ropes did not
  show significant differences. For the whole population of events, the
  mean and median values of the time difference between the onset of the
  eruptive flare and the appearance of the hot flux rope were 151 and 98
  min, respectively. <BR /> Conclusions: Our results provide, on average,
  indirect support for CME models that involve preexisting flux ropes; on
  the other hand, for a third of the events, models in which the ejected
  flux rope is formed during the eruption appear more appropriate. <P
  />Movies attached to Figs. 2, 5, 8, and 10 are available at <A
  href="https://www.aanda.org/10.1051/0004-6361/202038832/olm">http://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 Heliospheric Imager (SoloHI)
Authors: Howard, R. A.; Vourlidas, A.; Colaninno, R. C.; Korendyke,
   C. M.; Plunkett, S. P.; Carter, M. T.; Wang, D.; Rich, N.; Lynch,
   S.; Thurn, A.; Socker, D. G.; Thernisien, A. F.; Chua, D.; Linton,
   M. G.; Koss, S.; Tun-Beltran, S.; Dennison, H.; Stenborg, G.; McMullin,
   D. R.; Hunt, T.; Baugh, R.; Clifford, G.; Keller, D.; Janesick, J. R.;
   Tower, J.; Grygon, M.; Farkas, R.; Hagood, R.; Eisenhauer, K.; Uhl,
   A.; Yerushalmi, S.; Smith, L.; Liewer, P. C.; Velli, M. C.; Linker,
   J.; Bothmer, V.; Rochus, P.; Halain, J. -P.; Lamy, P. L.; Auchère,
   F.; Harrison, R. A.; Rouillard, A.; Patsourakos, S.; St. Cyr, O. C.;
   Gilbert, H.; Maldonado, H.; Mariano, C.; Cerullo, J.
Bibcode: 2020A&A...642A..13H
Altcode:
  <BR /> Aims: We present the design and pre-launch performance of
  the Solar Orbiter Heliospheric Imager (SoloHI) which is an instrument
  prepared for inclusion in the ESA/NASA Solar Orbiter mission, currently
  scheduled for launch in 2020. <BR /> Methods: The goal of this paper
  is to provide details of the SoloHI instrument concept, design, and
  pre-flight performance to give the potential user of the data a better
  understanding of how the observations are collected and the sources
  that contribute to the signal. <BR /> Results: The paper discusses
  the science objectives, including the SoloHI-specific aspects, before
  presenting the design concepts, which include the optics, mechanical,
  thermal, electrical, and ground processing. Finally, a list of planned
  data products is also presented. <BR /> Conclusions: The performance
  measurements of the various instrument parameters meet or exceed the
  requirements derived from the mission science objectives. SoloHI is
  poised to take its place as a vital contributor to the science success
  of the Solar Orbiter mission.

Title: Modeling the quiet Sun cell and network emission with ALMA
Authors: Alissandrakis, C. E.; Nindos, A.; Bastian, T. S.; Patsourakos,
   S.
Bibcode: 2020A&A...640A..57A
Altcode: 2020arXiv200609886A
  Observations of the Sun at millimeter wavelengths with the Atacama
  Large Millimeter/submillimeter Array (ALMA) offer a unique opportunity
  to investigate the temperature structure of the solar chromosphere. In
  this article we expand our previous work on modeling the chromospheric
  temperature of the quiet Sun, by including measurements of the
  brightness temperature in the network and cell interiors, from
  high-resolution ALMA images at 3 mm (Band 3) and 1.26 mm (Band 6). We
  also examine the absolute calibration of ALMA full-disk images. We
  suggest that the brightness temperature at the center of the solar disk
  in Band 6 is ∼440 K above the value recommended by White et al. (2017,
  Sol. Phys., 292, 88). In addition, we give improved results for the
  electron temperature variation of the average quiet Sun with optical
  depth and the derived spectrum at the center of the disk. We found
  that the electron temperature in the network is considerably lower
  than predicted by model F of Fontenla et al. (1993, ApJ, 406, 319)
  and that of the cell interior considerably higher than predicted by
  model A. Depending on the network/cell segregation scheme, the electron
  temperature difference between network and cell at τ = 1 (100 GHz)
  ranges from ∼660 K to ∼1550 K, compared to ∼3280 K predicted
  by the models; similarly, the electron temperature, T<SUB>e</SUB>
  ratio ranges from ∼1.10 to 1.24, compared to ∼1.55 of the model
  prediction. We also found that the network/cell T<SUB>e</SUB>(τ)
  curves diverge as τ decreases, indicating an increase of contrast
  with height and possibly a steeper temperature rise in the network
  than in the cell interior.

Title: Transient brightenings in the quiet Sun detected by ALMA at
    3 mm
Authors: Nindos, A.; Alissandrakis, C. E.; Patsourakos, S.; Bastian,
   T. S.
Bibcode: 2020A&A...638A..62N
Altcode: 2020arXiv200407591N
  <BR /> Aims: We investigate transient brightenings, that is, weak,
  small-scale episodes of energy release, in the quiet solar chromosphere;
  these episodes can provide insights into the heating mechanism of the
  outer layers of the solar atmosphere. <BR /> Methods: Using Atacama
  Large Millimeter/submillimeter Array (ALMA) observations, we performed
  the first systematic survey for quiet Sun transient brightenings at 3
  mm. Our dataset included images of six 87″ × 87″ fields of view
  of the quiet Sun obtained with angular resolution of a few arcsec at
  a cadence of 2 s. The transient brightenings were detected as weak
  enhancements above the average intensity after we removed the effect
  of the p-mode oscillations. A similar analysis, over the same fields
  of view, was performed for simultaneous 304 and 1600 Å data obtained
  with the Atmospheric Imaging Assembly. <BR /> Results: We detected 184
  3 mm transient brightening events with brightness temperatures from
  70 K to more than 500 K above backgrounds of ∼7200 - 7450 K. All
  events showed light curves with a gradual rise and fall, strongly
  suggesting a thermal origin. Their mean duration and maximum area were
  51.1 s and 12.3 Mm<SUP>2</SUP>, respectively, with a weak preference
  of appearing at network boundaries rather than in cell interiors. Both
  parameters exhibited power-law behavior with indices of 2.35 and 2.71,
  respectively. Only a small fraction of ALMA events had either 304
  or 1600 Å counterparts but the properties of these events were not
  significantly different from those of the general population except
  that they lacked their low-end energy values. The total thermal
  energies of the ALMA transient brightenings were between 1.5 ×
  10<SUP>24</SUP> and 9.9 × 10<SUP>25</SUP> erg and their frequency
  distribution versus energy was a power law with an index of 1.67 ±
  0.05. We found that the power per unit area provided by the ALMA events
  could account for only 1% of the chromospheric radiative losses (10%
  of the coronal ones). <BR /> Conclusions: We were able to detect, for
  the first time, a significant number of weak 3 mm quiet Sun transient
  brightenings. However, their energy budget falls short of meeting the
  requirements for the heating of the upper layers of the solar atmosphere
  and this conclusion does not change even if we use the least restrictive
  criteria possible for the detection of transient brightenings.

Title: Modeling of the Brightness of the Chromospheric Network Based
    on ALMA High Resolution Observations of the Quiet Sun
Authors: Alissandrakis, C. E.; Nindos, A.; Bastian, T.; Patsourakos, S.
Bibcode: 2020AAS...23610607A
Altcode:
  ALMA observations of the Sun at mm-λ offer a unique opportunity
  to investigate the temperature/density structure of the solar
  chromosphere. In a previous work (Alissandrakis et al 2017, A&amp;A
  605, A78) we measured the center-to-limb variation of the brightness
  temperature, T<SUB>b</SUB>, using low resolution ALMA full-disk
  observations in Band 3 (3mm) and Band 6 (1.26 mm), together with data
  at 0.85 mm from Bastian et al. 1993 (ApJ, 415, 364). Combining all
  data and inverting the solution of the transfer equation we found
  that the electron temperature, T<SUB>e</SUB>, in the range of 0.34
  &lt; τ<SUB>100</SUB> &lt; 12, where τ<SUB>100</SUB> is the optical
  depth at 100 GHz, was ~5% (~300 K) below the one predicted by model C
  (average quiet sun) of FAL93 (Fontenla, Avrett, &amp; Loeser, 1993,
  ApJ, 406, 319). Here we expand that work by including measurements
  of the brightness temperature in the network and cell interiors,
  from high resolution ALMA images in Bands 3 and 6. We found that
  the observed T<SUB>b</SUB> in the network is considerably lower
  than predicted by the FAL93 model F and that of the cell interior
  considerably higher than predicted by the FAL93 model A. The observed
  network/cell difference of brightness temperature at the center of the
  disk, at 100 GHz is about 920 K, compared to ~3250 K predicted by the
  FAL93 models; similarly, the T<SUB>b</SUB>, ratio is ~1.14, against
  ~1.51 of the model prediction. After inversion of the observed data,
  the electron temperature of cell interior at τ<SUB>100</SUB>=1 is
  ~390 K below the average (~600 K above model A) and of the network
  ~400 K above the average (~1800 K below model A). The implications of
  these results will be discussed. We will also discuss the question of
  the normalization of brightness temperature observed by ALMA.

Title: Interplanetary Coronal Mass Ejections as the Driver of
    Non-recurrent Forbush Decreases
Authors: Papaioannou, Athanasios; Belov, Anatoly; Abunina, Maria;
   Eroshenko, Eugenia; Abunin, Artem; Anastasiadis, Anastasios;
   Patsourakos, Spiros; Mavromichalaki, Helen
Bibcode: 2020ApJ...890..101P
Altcode:
  Interplanetary coronal mass ejections (ICMEs) are the counterparts of
  coronal mass ejections (CMEs) that extend in the interplanetary (IP)
  space and interact with the underlying solar wind (SW). ICMEs and their
  corresponding shocks can sweep out galactic cosmic rays (GCRs) and thus
  modulate their intensity, resulting in non-recurrent Forbush decreases
  (FDs). In this work, we selected all FDs that were associated with a
  sudden storm commencement (SSC) at Earth, and a solar driver (e.g., CME)
  was clearly identified as the ICME's source. We introduce and employ
  the t<SUB>H</SUB> parameter, which is the time delay (in hours) of the
  maximum strength of the interplanetary magnetic field from the FD onset
  (as is marked via the SSC), and consequently derive three groups of
  FD events (I.e., the early, medium, and late ones). For each of these
  we examine the mean characteristics of the FDs and the associated
  IP variations per group, as well as the resulting correlations. In
  addition, we demonstrate the outputs of a superposed epoch analysis,
  which led to an average time profile of the resulting FDs and the
  corresponding IP variations, per group. Finally, we interpret our
  results based on the theoretical expectations for the FD phenomenon. We
  find that both the shock sheath and the ejecta are necessary for
  deep GCR depressions and that the FD amplitude (A0) is larger for
  faster-propagating ICMEs. Additionally, we note the importance of the
  turbulent shock-sheath region across all groups. Finally, we present
  empirical relations connecting A0 to SW properties.

Title: Observations of solar chromospheric oscillations at 3 mm
    with ALMA
Authors: Patsourakos, S.; Alissandrakis, C. E.; Nindos, A.; Bastian,
   T. S.
Bibcode: 2020A&A...634A..86P
Altcode: 2019arXiv191203480P
  <BR /> Aims: We aim to study spatially resolved chromospheric
  oscillations of the quiet Sun (QS) in the mm-domain at a resolution
  of a few arcsec, typically 2.4″ × 4.5″. <BR /> Methods: We used
  Atacama Large millimeter and submillimeter Array (ALMA) time series
  of interferometric observations of the QS obtained at 3 mm with a 2-s
  cadence and a spatial resolution of a few arcsec. The observations were
  performed on March 16, 2017 and seven 80″ × 80″ fields of view
  (FoV) going from disk center to limb were covered, each one observed for
  10 min, therefore limiting the frequency resolution of the power spectra
  to 1.7 mHz. For each FoV, masks for cell and network were derived,
  and the averaged power spectral densities (PSDs) for the entire FoV,
  cell, and network were computed. The resulting power spectra were
  fit with an analytical function in order to derive the frequency
  and the root-mean-square (rms) power associated with the peaks. The
  same analysis, over the same FoVs and for the same intervals, was
  performed for simultaneous Atmospheric Imaging Assembly (AIA) image
  sequences in 1600 Å. <BR /> Results: Spatially resolved chromospheric
  oscillations at 3 mm, with frequencies of 4.2 ± 1.7 mHz are observed
  in the QS, in both cell and network. The coherence length-scale of
  the oscillations is commensurate with the spatial resolution of our
  ALMA observations. Brightness-temperature fluctuations in individual
  pixels could reach up to a few hundred K, while the spatially averaged
  PSDs yield rms in the range ≈55-75 K, i.e., up to ≈1% of the
  averaged brightness temperatures and exhibit a moderate increase
  towards the limb. For AIA 1600 Å, the oscillation frequency is 3.7
  ± 1.7 mHz. The relative rms is up to 6% of the background intensity,
  with a weak increase towards the disk center (cell, average). ALMA
  3 mm time-series lag AIA 1600 Å by ≈100 s, which corresponds to
  a formation-height difference of ≈1200 km, representing a novel
  determination of this important parameter. <BR /> Conclusions: The
  ALMA oscillations that we detected exhibit higher amplitudes than those
  derived from previous lower (≈10″) resolution observations at 3.5 mm
  by the Berkeley-Illinois-Maryland Array. Chromospheric oscillations are,
  therefore, not fully resolved at the length-scale of the chromospheric
  network, and possibly not even at the spatial resolution of our ALMA
  observations. Any study of transient brightenings in the mm-domain
  should take into account the oscillations.

Title: Magnetic Impact of Propagating Interplanetary Coronal Mass
    Ejections in the Solar and Stellar Habitability Zones
Authors: Georgoulis, M. K.; Samara, E.; Patsourakos, S.
Bibcode: 2019AGUFMSH43A..05G
Altcode:
  We recount recent results of a statistical method that assigns an
  axial magnetic field to CME flux ropes, inferred via the fundamental
  conservation principle of magnetic helicity in solar active region
  sources. We then extrapolate the near-Sun CME magnetic field to
  1 AU, juxtaposing the extrapolation with tens of magnetic-cloud
  observations. Uncertainties given, we manage to statistically
  reproduce observations, thereby proposing a simple method that
  alleviates unnecessary complexity, while featuring applicability on
  a case-by-case basis. At a second level, we generalize CME magnetic
  configurations and stellar activity, expanding to flaring M-dwarf
  and Sun-like stars. We correlate the magnetic energy of stellar,
  assumed eruptive, flares with their helicity and extrapolate again to
  stellar habitable zones. From assumed planetary equatorial magnetic
  fields we predict atmospheric erosion by CME activity for a number of
  recently discovered exoplanets (Keppler 438b; Proxima b; the TRAPPIST
  system), thought promising for harboring life. Preliminary results
  show that knowledge of the planetary equatorial magnetic field can
  impose a valuable constraint for exoplanet habitability. Meanwhile, (1)
  terrestrial atmospheric erosion seems unlikely even for unrealistically
  intense solar eruptions and (2) the likelihood of absence of atmosphere
  due to CME-induced erosion in many of the studied exoplanets seems high.

Title: Predicting the geoeffective properties of coronal mass
ejections: current status, open issues and path forward
Authors: Vourlidas, A.; Patsourakos, S.; Savani, N. P.
Bibcode: 2019RSPTA.37780096V
Altcode:
  Much progress has been made in the study of coronal mass ejections
  (CMEs), the main drivers of terrestrial space weather thanks to the
  deployment of several missions in the last decade. The flow of energy
  required to power solar eruptions is beginning to be understood. The
  initiation of CMEs is routinely observed with cadences of tens
  of seconds with arc-second resolution. Their inner heliospheric
  evolution can now be imaged and followed routinely. Yet relatively
  little progress has been made in predicting the geoeffectiveness of a
  particular CME. Why is that? What are the issues holding back progress
  in medium-term forecasting of space weather? To answer these questions,
  we review, here, the measurements, status and open issues on the main
  CME geoeffective parameters; namely, their entrained magnetic field
  strength and configuration, their Earth arrival time and speed, and
  their mass (momentum). We offer strategies for improving the accuracy
  of the measurements and their forecasting in the near and mid-term
  future. To spark further discussion, we incorporate our suggestions
  into a top-level draft action plan that includes suggestions for sensor
  deployment, technology development and modelling/theory improvements. <P
  />This article is part of the theme issue `Solar eruptions and their
  space weather impact'.

Title: Sheared Magnetic Arcades and the Pre-eruptive Magnetic
Configuration of Coronal Mass Ejections: Diagnostics, Challenges
    and Future Observables
Authors: Patsourakos, Spiros; Vourlidas, A.; Anthiochos, S. K.;
   Archontis, V.; Aulanier, G.; Cheng, X.; Chintzoglou, G.; Georgoulis,
   M. K.; Green, L. M.; Kliem, B.; Leake, J.; Moore, R. L.; Nindos, A.;
   Syntelis, P.; Torok, T.; Yardley, S. L.; Yurchyshyn, V.; Zhang, J.
Bibcode: 2019shin.confE.194P
Altcode:
  Our thinking about the pre-eruptive magnetic configuration of Coronal
  Mass Ejections has been effectively dichotomized into two opposing
  and often fiercely contested views: namely, sheared magnetic arcades
  and magnetic flux ropes. Finding a solution to this issue will have
  important implications for our understanding of CME initiation. We
  first discuss the very value of embarking into the arcade vs. flux rope
  dilemma and illustrate the corresponding challenges and difficulties to
  address it. Next, we are compiling several observational diagnostics of
  pre-eruptive sheared magnetic arcades stemming from theory/modeling,
  discuss their merits, and highlight potential ambiguities that could
  arise in their interpretation. We finally conclude with a discussion
  of possible new observables, in the frame of upcoming or proposed
  instrumentation, that could help to circumvent the issues we are
  currently facing.

Title: Deriving the Near-Sun Magnetic Field of Coronal Mass Ejections
    from Magnetic Helicity Conservation
Authors: Patsourakos, Spiros; Georgoulis, M. K.; Petroulea, G.;
   Vourlidas, A.; Nieves-Chinchilla, T.
Bibcode: 2019shin.confE.222P
Altcode:
  The near-Sun magnetic field of Coronal Mass Ejections represents
  a key parameter for assessing their energetics and structuring, and
  additionally, it is a major element of methods/applications/simulations
  aiming to predict the magnetic field of Earth-directed CMEs upon
  impact at geospace. Diagnostics of CME magnetic fields in the corona
  can be achieved via observations in the radio domain, which however,
  are currently not available on a regular basis. Therefore, several
  methods to infer the CME magnetic field in the corona have recently
  emerged. We developed one such method which is based on the magnetic
  helicity conservation principle applied to flux rope CMEs. Its
  input parameters could be readily retrieved from the analysis of
  HMI magnetograms and SOHO/STEREO WL coronagraph images. We present
  parametric and case-study applications of this method, and discuss how
  it be could be used to predict the CME magnetic field magnitude at 1 AU.

Title: ICSF: Intensity Conserving Spectral Fitting
Authors: Klimchuk, James A.; Patsourakos, Spiros; Tripathi, Durgesh
Bibcode: 2019ascl.soft03007K
Altcode:
  ICSF (Intensity Conserving Spectral Fitting) "corrects" (x,y) data in
  which the ordinate represents the average of a quantity over a finite
  interval in the abscissa. A typical example is spectral data, where
  the average intensity over a wavelength bin (the measured quantity)
  is assigned to the center of the bin. If the profile is curved, the
  average will be different from the discrete value at the bin center
  location. ICSF, written in IDL and available separately and as part of
  SolarSoft (ascl:1208.013), corrects the intensity using an iterative
  procedure and cubic spline. The corrected intensity equals the "true"
  intensity at bin center, rather than the average over the bin. Unlike
  other methods that are restricted to a single fitting function,
  typically a spline, ICSF can be used with any function, such as a
  cubic spline or a Gaussian, with slight changes to the code.

Title: Modeling of the Sunspot-Associated Microwave Emission Using
    a New Method of DEM Inversion
Authors: Alissandrakis, C. E.; Bogod, V. M.; Kaltman, T. I.;
   Patsourakos, S.; Peterova, N. G.
Bibcode: 2019SoPh..294...23A
Altcode: 2018arXiv181205751A
  We develope a method to compute the temperature and density structure
  along the line of sight by inversion of the differential emission
  measure (DEM), under the assumptions of stratification and hydrostatic
  equilibrium. We apply this method to the DEM obtained from the
  Atmospheric Imaging Assembly (AIA) observations and use the results,
  together with potential extrapolations of the photospheric magnetic
  field, to compute the microwave emission of three sunspots, which we
  compare with observations from the Academy of Sciences Radio Telescope
  - 600 (RATAN-600) radio telescope and the Nobeyama Radioheliograph
  (NoRH). Our DEM-based models reproduce very well the observations of
  the moderate-size spot on October 2011 and within 25% the data of a
  similar sized spot on March 2016, but predict too low values for the
  big spot of 14 April 2016. The latter is better fitted by a constant
  conductive flux atmospheric model which, however, cannot reproduce the
  peak brightness temperature of 4.7 ×10<SUP>6</SUP>K and the shape of
  the source at the NoRH frequency. We propose that these deviations are
  due to the low intensity non-thermal emission associated to a moving
  pore and to an opposite polarity light bridge. We also find that the
  double structure of the big spot at high RATAN-600 frequencies can be
  interpreted in terms of the variation of the angle between the magnetic
  field and the line of sight along the sunspot.

Title: First high-resolution look at the quiet Sun with ALMA at 3mm
Authors: Nindos, A.; Alissandrakis, C. E.; Bastian, T. S.; Patsourakos,
   S.; De Pontieu, B.; Warren, H.; Ayres, T.; Hudson, H. S.; Shimizu,
   T.; Vial, J. -C.; Wedemeyer, S.; Yurchyshyn, V.
Bibcode: 2018A&A...619L...6N
Altcode: 2018arXiv181005223N
  We present an overview of high-resolution quiet Sun observations,
  from disk center to the limb, obtained with the Atacama Large
  millimeter and sub-millimeter Array (ALMA) at 3 mm. Seven quiet-Sun
  regions were observed at a resolution of up to 2.5″ by 4.5″. We
  produced both average and snapshot images by self-calibrating the ALMA
  visibilities and combining the interferometric images with full-disk
  solar images. The images show well the chromospheric network, which,
  based on the unique segregation method we used, is brighter than the
  average over the fields of view of the observed regions by ∼305
  K while the intranetwork is less bright by ∼280 K, with a slight
  decrease of the network/intranetwork contrast toward the limb. At 3
  mm the network is very similar to the 1600 Å images, with somewhat
  larger size. We detect, for the first time, spicular structures,
  rising up to 15″ above the limb with a width down to the image
  resolution and brightness temperature of ∼1800 K above the local
  background. No trace of spicules, either in emission or absorption,
  is found on the disk. Our results highlight the potential of ALMA for
  the study of the quiet chromosphere.

Title: Eruptive Flare Initiation and the CME Magnetic Field
Authors: Georgoulis, Manolis K.; Patsourakos, Spiros; Kontogiannis,
   Ioannis
Bibcode: 2018cosp...42E1180G
Altcode:
  We recount very recent results on the correlation between photospheric
  characteristics of eruptive solar active regions and coronal mass
  ejection (CME) occurrence / characteristics. In particular, we
  argue that one of the most relevant parameters for CME occurrence
  is the non-neutralized electric currents appearing exclusively along
  intense, shear-ridden magnetic polarity-inversion lines (PILs) in the
  photosphere of eruptive active regions. These currents are simply
  lacking in the absence of strong PILs and shear. While the physics
  underlying non-neutralized currents is rich and shows far-reaching
  ramifications, we will focus on the injection of magnetic helicity
  due to non-neutralized currents in the pre-eruption phase, that will
  then be bodily transported via the CME. For a conductive plasma of
  high magnetic Reynolds number, such as that of the solar corona,
  we show how the fundamental helicity conservation principle can lead
  to estimates of, first, the CME's axial magnetic field strength and,
  second, the anticipated magnetic field strength of the interplanetary
  CME (ICME) on the verge of geospace. We discuss how this analysis
  can be viewed as a meaningful initial or boundary condition for more
  elaborate inner-heliospheric propagation models that further consider
  the orientation of the ICME magnetic field, thus leading to an improved
  understanding and prediction of ICME geoeffectiveness. Part of this
  work has been supported by the EU Horizon-2020 FLARECAST project
  (grant agreement no. 640216).

Title: A New Spin to Exoplanet Habitability Criteria
Authors: Georgoulis, M. K.; Patsourakos, S.
Bibcode: 2017AGUFM.P53E2676G
Altcode:
  We describe a physically- and statistically-based method to infer
  the near-Sun magnetic field of coronal mass ejections (CMEs) and then
  extrapolate it to the inner heliosphere and beyond. Besides a ballpark
  agreement with in-situ observations of interplanetary CMEs (ICMEs) at
  L1, we use our estimates to show that Earth does not seem to be at risk
  of an extinction-level atmospheric erosion or stripping by the magnetic
  pressure of extreme solar eruptions, even way above a Carrington-type
  event. This does not seem to be the case with exoplanets, however,
  at least those orbiting in the classically defined habitability
  zones of magnetically active dwarf stars at orbital radii of a small
  fraction of 1 AU. We show that the combination of stellar ICMEs and
  the tidally locking zone of mother stars, that quite likely does not
  allow these exoplanets to attain Earth-like magnetic fields to shield
  themselves, probably render the existence of a proper atmosphere
  in them untenable. We propose, therefore, a critical revision of
  habitability criteria in these cases that would limit the number of
  target exoplanets considered as potential biosphere hosts.

Title: Center-to-limb observations of the Sun with ALMA . Implications
    for solar atmospheric models
Authors: Alissandrakis, C. E.; Patsourakos, S.; Nindos, A.; Bastian,
   T. S.
Bibcode: 2017A&A...605A..78A
Altcode:
  <BR /> Aims: We seek to derive information on the temperature structure
  of the solar chromosphere and compare these results with existing
  models. <BR /> Methods: We measured the center-to-limb variation of
  the brightness temperature, T<SUB>b</SUB>, from ALMA full-disk images
  at two frequencies and inverted the solution of the transfer equation
  to obtain the electron temperature, T<SUB>e</SUB> as a function of
  optical depth, τ. <BR /> Results: The ALMA images are very similar
  to AIA images at 1600 Å. The brightness temperature at the center
  of the disk is 6180 and 7250 K at 239 and 100 GHz, respectively,
  with dispersions of 100 and 170 K. Plage regions stand out clearly in
  the 239/100 GHz intensity ratio, while faculae and filament lanes do
  not. The solar disk radius, reduced to 1 AU, is 961.1 ± 2.5'' and 964.1
  ± 4.5'' at 239 and 100 GHz, respectively. A slight but statistically
  significant limb brightening is observed at both frequencies. <BR />
  Conclusions: The inversion of the center-to-limb curves shows that
  T<SUB>e</SUB> varies linearly with the logarithm of optical depth for
  0.34 &lt;τ<SUB>100 GHz</SUB>&lt; 12, with a slope dT<SUB>e</SUB>/
  dlnτ = -608 K. Our results are 5% lower than predicted by the average
  quiet Sun model C of Fontenla et al. (1993, ApJ. 406, 319), but do
  not confirm previous reports that the mm-λ solar spectrum is better
  fitted with models of the cell interior.

Title: A Helicity-Based Method to Infer the CME Magnetic Field
Magnitude in Sun and Geospace: Generalization and Extension to
    Sun-Like and M-Dwarf Stars and Implications for Exoplanet Habitability
Authors: Patsourakos, S.; Georgoulis, M. K.
Bibcode: 2017SoPh..292...89P
Altcode: 2017arXiv170703579P
  Patsourakos et al. (Astrophys. J.817, 14, 2016) and Patsourakos and
  Georgoulis (Astron. Astrophys.595, A121, 2016) introduced a method to
  infer the axial magnetic field in flux-rope coronal mass ejections
  (CMEs) in the solar corona and farther away in the interplanetary
  medium. The method, based on the conservation principle of magnetic
  helicity, uses the relative magnetic helicity of the solar source
  region as input estimates, along with the radius and length of the
  corresponding CME flux rope. The method was initially applied to
  cylindrical force-free flux ropes, with encouraging results. We hereby
  extend our framework along two distinct lines. First, we generalize
  our formalism to several possible flux-rope configurations (linear
  and nonlinear force-free, non-force-free, spheromak, and torus) to
  investigate the dependence of the resulting CME axial magnetic field
  on input parameters and the employed flux-rope configuration. Second,
  we generalize our framework to both Sun-like and active M-dwarf stars
  hosting superflares. In a qualitative sense, we find that Earth may
  not experience severe atmosphere-eroding magnetospheric compression
  even for eruptive solar superflares with energies ≈10<SUP>4</SUP>
  times higher than those of the largest Geostationary Operational
  Environmental Satellite (GOES) X-class flares currently observed. In
  addition, the two recently discovered exoplanets with the highest
  Earth-similarity index, Kepler 438b and Proxima b, seem to lie in the
  prohibitive zone of atmospheric erosion due to interplanetary CMEs
  (ICMEs), except when they possess planetary magnetic fields that are
  much higher than that of Earth.

Title: Evidence for two-loop interaction from IRIS and SDO
    observations of penumbral brightenings
Authors: Alissandrakis, C. E.; Koukras, A.; Patsourakos, S.; Nindos, A.
Bibcode: 2017A&A...603A..95A
Altcode: 2017arXiv170407344A
  <BR /> Aims: We investigate small scale energy release events which
  can provide clues on the heating mechanism of the solar corona. <BR />
  Methods: We analyzed spectral and imaging data from the Interface
  Region Imaging Spectrograph (IRIS), images from the Atmospheric
  Imaging Assembly (AIA) aboard the Solar Dynamics Observatoty (SDO),
  and magnetograms from the Helioseismic and Magnetic Imager (HMI)
  aboard SDO. <BR /> Results: We report observations of small flaring
  loops in the penumbra of a large sunspot on July 19, 2013. Our main
  event consisted of a loop spanning 15'', from the umbral-penumbral
  boundary to an opposite polarity region outside the penumbra. It lasted
  approximately 10 min with a two minute impulsive peak and was observed
  in all AIA/SDO channels, while the IRIS slit was located near its
  penumbral footpoint. Mass motions with an apparent velocity of 100 km
  s<SUP>-1</SUP> were detected beyond the brightening, starting in the
  rise phase of the impulsive peak; these were apparently associated
  with a higher-lying loop. We interpret these motions in terms of
  two-loop interaction. IRIS spectra in both the C II and Si iv lines
  showed very extended wings, up to about 400 km s<SUP>-1</SUP>, first
  in the blue (upflows) and subsequently in the red wing. In addition
  to the strong lines, emission was detected in the weak lines of Cl
  I, O I and C I, as well as in the Mg II triplet lines. Absorption
  features in the profiles of the C II doublet, the Si iv doublet and
  the Mg II h and k lines indicate the existence of material with a
  lower source function between the brightening and the observer. We
  attribute this absorption to the higher loop and this adds further
  credibility to the two-loop interaction hypothesis. Tilts were
  detected in the absorption spectra, as well as in the spectra of Cl I,
  O I, and C I lines, possibly indicating rotational motions from the
  untwisting of magnetic flux tubes. <BR /> Conclusions: We conclude
  that the absorption features in the C II, Si iv and Mg II profiles
  originate in a higher-lying, descending loop; as this approached
  the already activated lower-lying loop, their interaction gave rise
  to the impulsive peak, the very broad line profiles and the mass
  motions. <P />Movies associated to Figs. A.1-A.3 are available at <A
  href="http://www.aanda.org/10.1051/0004-6361/201730643/olm">http://www.aanda.org</A>

Title: Center-to-limb observations of the Sun with ALMA
Authors: Alissandrakis, C. E.; Patsourakos, S.; Nindos, A.; Bastian,
   T. S.
Bibcode: 2017arXiv170509008A
Altcode:
  We measured the center-to-limb variation of the brightness temperature,
  $T_b$, from ALMA full-disk images at two frequencies and inverted the
  solution of the transfer equation to obtain the electron temperature,
  $T_e$ as a function of optical depth, $\tau$. The ALMA images are very
  similar to AIA images at 1600Å. The brightness temperature at the
  center of the disk is 6180 and 7250 K at 239 and 100 GHz respectively,
  with dispersions of 100 and 170 K. Plage regions stand out clearly
  in the 239/100 GHz intensity ratio, while faculae and filament lanes
  do not. The solar disk radius, reduced to 1 AU, is $961.1\pm2.5$
  arcsec and $964.1\pm4.5$ arcsec at 239 and 100 GHz respectively. A
  slight but statistically significant limb brightening is observed at
  both frequencies. The inversion of the center-to-limb curves shows
  that $T_e$ varies linearly with the logarithm of optical depth for
  $0.34&lt;\tau_{100\,GHz}&lt;12$, with a slope $d\ln T_e/d\tau=-608$
  K. Our results are 5% lower than predicted by the average quiet sun
  model C of Fontenla et al. (1993), but do not confirm previous reports
  that the mm-$\lambda$ solar spectrum is better fitted with models of
  the cell interior.

Title: Near-Sun and 1 AU magnetic field of coronal mass ejections:
    a parametric study
Authors: Patsourakos, S.; Georgoulis, M. K.
Bibcode: 2016A&A...595A.121P
Altcode: 2016arXiv160900134P
  <BR /> Aims: The magnetic field of coronal mass ejections (CMEs)
  determines their structure, evolution, and energetics, as well as their
  geoeffectiveness. However, we currently lack routine diagnostics of
  the near-Sun CME magnetic field, which is crucial for determining the
  subsequent evolution of CMEs. <BR /> Methods: We recently presented
  a method to infer the near-Sun magnetic field magnitude of CMEs and
  then extrapolate it to 1 AU. This method uses relatively easy to deduce
  observational estimates of the magnetic helicity in CME-source regions
  along with geometrical CME fits enabled by coronagraph observations. We
  hereby perform a parametric study of this method aiming to assess its
  robustness. We use statistics of active region (AR) helicities and CME
  geometrical parameters to determine a matrix of plausible near-Sun CME
  magnetic field magnitudes. In addition, we extrapolate this matrix
  to 1 AU and determine the anticipated range of CME magnetic fields
  at 1 AU representing the radial falloff of the magnetic field in
  the CME out to interplanetary (IP) space by a power law with index
  α<SUB>B</SUB>. <BR /> Results: The resulting distribution of the
  near-Sun (at 10 R<SUB>⊙</SUB>) CME magnetic fields varies in the
  range [0.004, 0.02] G, comparable to, or higher than, a few existing
  observational inferences of the magnetic field in the quiescent
  corona at the same distance. We also find that a theoretically and
  observationally motivated range exists around α<SUB>B</SUB> = -1.6
  ± 0.2, thereby leading to a ballpark agreement between our estimates
  and observationally inferred field magnitudes of magnetic clouds (MCs)
  at L1. <BR /> Conclusions: In a statistical sense, our method provides
  results that are consistent with observations.

Title: Solar Coronal Jets: Observations, Theory, and Modeling
Authors: Raouafi, N. E.; Patsourakos, S.; Pariat, E.; Young, P. R.;
   Sterling, A. C.; Savcheva, A.; Shimojo, M.; Moreno-Insertis, F.;
   DeVore, C. R.; Archontis, V.; Török, T.; Mason, H.; Curdt, W.;
   Meyer, K.; Dalmasse, K.; Matsui, Y.
Bibcode: 2016SSRv..201....1R
Altcode: 2016arXiv160702108R; 2016SSRv..tmp...31R
  Coronal jets represent important manifestations of ubiquitous solar
  transients, which may be the source of significant mass and energy
  input to the upper solar atmosphere and the solar wind. While
  the energy involved in a jet-like event is smaller than that of
  "nominal" solar flares and coronal mass ejections (CMEs), jets
  share many common properties with these phenomena, in particular,
  the explosive magnetically driven dynamics. Studies of jets could,
  therefore, provide critical insight for understanding the larger,
  more complex drivers of the solar activity. On the other side of the
  size-spectrum, the study of jets could also supply important clues on
  the physics of transients close or at the limit of the current spatial
  resolution such as spicules. Furthermore, jet phenomena may hint to
  basic process for heating the corona and accelerating the solar wind;
  consequently their study gives us the opportunity to attack a broad
  range of solar-heliospheric problems.

Title: A Robust Method to Predict the Near-Sun and Interplanetary
Magnetic Field Strength of Coronal Mass Ejections: Parametric and
    Case Studies
Authors: Patsourakos, Spiros; Georgoulis, Manolis K.
Bibcode: 2016cosp...41E1531P
Altcode:
  Predicting the near-Sun, and particularly the Interplanetary (IP),
  magnetic field structure of Coronal Mass Ejections (CMEs) and
  interplanetary counterparts (ICMEs) is a topic of intense research
  activity. This is because Earth-directed CMEs with strong southward
  magnetic fields are responsible for the most powerful geomagnetic
  storms. We have recently developed a simple two-tier method to
  predict the magnetic field strength of CMEs in the outer corona
  and in the IP medium, using as input the magnetic-helicity budget
  of the source solar active region and stereoscopic coronagraphic
  observations. Near-Sun CME magnetic fields are obtained by utilizing
  the principle of magnetic helicity conservation of flux-rope CMEs
  for coronagraphic observations. Interplanetary propagation of the
  inferred values is achieved by employing power-law prescriptions of the
  radial evolution of the CME-ICME magnetic fields. We hereby present a
  parametric study of our method, based on the observed statistics of
  input parameters, to infer the anticipated range of values for the
  near-Sun and interplanetary CME-ICME magnetic fields. This analysis
  is complemented by application of our method to several well-observed
  major CME-ICME events.

Title: The 3D structure of Coronal Mass Ejections
Authors: Patsourakos, Spiros
Bibcode: 2016cosp...41E1532P
Altcode:
  Coronal Mass Ejections (CMEs) represent one of the most powerful
  energy release phenomena in the entire solar system and are a major
  driver of space weather. Prior to 2006, our observational access to
  CMEs was limited to single viewpoint remote sensing observations
  in the inner/outer corona, and in-situ observations further away,
  e.g. at 1 AU. Taking all these factors together, turned out to be
  a major obstacle in our understanding and characterizing of the 3D
  structure and evolution of CMEs. The situation improved dramatically
  with the availability of multi-viewpoint imaging observations of
  CMEs, all way through from the Sun to 1 AU, from the STEREO mission
  since 2006, combined with observations from other missions (SOHO,
  Hinode, SDO, IRIS). With this talk we will discuss several key recent
  results in CME science resulting from the analysis of multi-viewpoint
  observations. This includes: (1) shape and structure; (2) kinematics
  and energetics; (3) trajectories, deflections and rotations; (4)
  arrival times and velocities at 1 AU; (5) magnetic field structure;
  (6) relationships with coronal and interplanetary shocks and solar
  energetic particles. The implications of these results in terms of
  CME theories and models will be also addressed. We will conclude
  with a discussion of important open issues in our understanding of
  CMEs and how these could be addressed with upcoming (Solar Orbiter,
  Solar Probe Plus) and under-study missions (e.g., L5).

Title: Coronal Mass Ejections: From Sun to Earth
Authors: Patsourakos, S.
Bibcode: 2016Hipp....2m..17P
Altcode:
  Coronal Mass Ejections (CMEs) are gigantic expulsions of magnetized
  plasmas from the solar corona into the interplanetary (IP) space. CMEs
  spawn ~ 1015 gr of mass and reach speeds ranging between several hundred
  to a few thousand km/s (e.g., Gopalswamy et al. 2009; Vourlidas et
  al. 2010). It takes 1-5 days for a CME to reach Earth. CMEs are one
  of the most energetic eruptive manifestations in the solar system
  and are major drivers of space weather via their magnetic fields and
  energetic particles, which are accelerated by CME-driven shocks. In
  this review we give a short account of recent, mainly observational,
  results on CMEs from the STEREO and SDO missions which include the
  nature of their pre-eruptive and eruptive configurations and the CME
  propagation from Sun to Earth. We conclude with a discussion of the
  exciting capabilities in CME studies that will soon become available
  from new solar and heliospheric instrumentation.

Title: Multi-viewpoint Observations of a Widely distributed Solar
Energetic Particle Event: The Role of EUV Waves and White-light
    Shock Signatures
Authors: Kouloumvakos, A.; Patsourakos, S.; Nindos, A.; Vourlidas,
   A.; Anastasiadis, A.; Hillaris, A.; Sandberg, I.
Bibcode: 2016ApJ...821...31K
Altcode:
  On 2012 March 7, two large eruptive events occurred in the same active
  region within 1 hr from each other. Each consisted of an X-class flare,
  a coronal mass ejection (CME), an extreme-ultraviolet (EUV) wave,
  and a shock wave. The eruptions gave rise to a major solar energetic
  particle (SEP) event observed at widely separated (∼120°) points
  in the heliosphere. From multi-viewpoint energetic proton recordings
  we determine the proton release times at STEREO B and A (STB, STA)
  and the first Lagrange point (L1) of the Sun-Earth system. Using EUV
  and white-light data, we determine the evolution of the EUV waves in
  the low corona and reconstruct the global structure and kinematics of
  the first CME’s shock, respectively. We compare the energetic proton
  release time at each spacecraft with the EUV waves’ arrival times
  at the magnetically connected regions and the timing and location
  of the CME shock. We find that the first flare/CME is responsible
  for the SEP event at all three locations. The proton release at STB
  is consistent with arrival of the EUV wave and CME shock at the STB
  footpoint. The proton release time at L1 was significantly delayed
  compared to STB. Three-dimensional modeling of the CME shock shows
  that the particle release at L1 is consistent with the timing and
  location of the shock’s western flank. This indicates that at L1
  the proton release did not occur in low corona but farther away from
  the Sun. However, the extent of the CME shock fails to explain the
  SEP event observed at STA. A transport process or a significantly
  distorted interplanetary magnetic field may be responsible.

Title: The spectroscopic imprint of the pre-eruptive configuration
    resulting into two major coronal mass ejections
Authors: Syntelis, P.; Gontikakis, C.; Patsourakos, S.; Tsinganos, K.
Bibcode: 2016A&A...588A..16S
Altcode: 2016arXiv160203680S
  <BR /> Aims: We present a spectroscopic analysis of the pre-eruptive
  configuration of active region NOAA 11429, prior to two very fast
  coronal mass ejections (CMEs) on March 7, 2012 that are associated
  with this active region. We study the thermal components and the
  dynamics associated with the ejected flux ropes. <BR /> Methods: Using
  differential emission measure (DEM) analysis of Hinode/EIS and SDO/AIA
  observations, we identify the emission components of both the flux rope
  and the host active region. We then follow the time evolution of the
  flux rope emission components by using AIA observations. The plasma
  density and the Doppler and non-thermal velocities associated with
  the flux ropes are also calculated from the EIS data. <BR /> Results:
  The eastern and western parts of the active region, in which the two
  different fast CMEs originated during two X-class flares, were studied
  separately. In both regions we identified an emission component in the
  temperature range of log T = 6.8-7.1 associated with the presence of
  flux ropes. The time evolution of the eastern region showed an increase
  in the mean DEM in this temperature range by an order of magnitude, 5
  h prior to the first CME. This was associated with a gradual rise and
  heating of the flux rope as manifested by blue-shifts and increased
  non-thermal velocities in Ca xv 200.97 Å, respectively. An overall
  upward motion of the flux ropes was measured (relative blue-shifts of
  ~ 12 km s<SUP>-1</SUP>). The measured electron density was found to
  be 4 × 10<SUP>9</SUP>-2 × 10<SUP>10</SUP> cm<SUP>-3</SUP> (using
  the ratio of Ca xv 181.90 Å over Ca xv 200.97 Å). We compare our
  findings with other works on the same AR to provide a unified picture
  of its evolution.

Title: Predicting the near-Sun and Interplanetary Magnetic Field of
    CMEs using photospheric magnetograms and coronagraph images
Authors: Patsourakos, Spiros; Georgoulis, Manolis
Bibcode: 2016EGUGA..18.4784P
Altcode:
  Earth-directed Coronal Mass Ejections (CMEs) containing a strong
  southward magnetic-field component upon arrival at 1 AU statistically
  account for the most powerful geomagnetic storms. Unfortunately, though,
  we currently lack routine diagnostics of the magnetic field of CMEs
  and its evolution in the inner heliosphere and the interplanetary (IP)
  medium. We hereby present a simple, yet powerful and easy-to-implement,
  method to deduce the near-Sun and IP magnetic field entrained in CMEs,
  by using photospheric magnetograms of the solar source regions and
  multi-viewpoint coronagraph images of the corresponding CMEs. The
  method relies on the principle of magnetic-helicity conservation
  in low plasma-beta, flux-rope CMEs and a power-law prescription of
  the radial evolution of the CME magnetic field in the IP medium. We
  outline a parametric study based on the observed statistics of input
  parameters to calculate a matrix of magnetic-field solutions for 10000
  synthetic CMEs. The robustness and possible limitations / ramifications
  of the method are deduced by a comparison with the distributions of
  the predicted CME-ICME magnetic fields at 0.3 and 1 AU using actual
  Messenger and ACE published observations.

Title: The Major Geoeffective Solar Eruptions of 2012 March 7:
    Comprehensive Sun-to-Earth Analysis
Authors: Patsourakos, S.; Georgoulis, M. K.; Vourlidas, A.; Nindos,
   A.; Sarris, T.; Anagnostopoulos, G.; Anastasiadis, A.; Chintzoglou,
   G.; Daglis, I. A.; Gontikakis, C.; Hatzigeorgiu, N.; Iliopoulos, A. C.;
   Katsavrias, C.; Kouloumvakos, A.; Moraitis, K.; Nieves-Chinchilla, T.;
   Pavlos, G.; Sarafopoulos, D.; Syntelis, P.; Tsironis, C.; Tziotziou,
   K.; Vogiatzis, I. I.; Balasis, G.; Georgiou, M.; Karakatsanis, L. P.;
   Malandraki, O. E.; Papadimitriou, C.; Odstrčil, D.; Pavlos, E. G.;
   Podlachikova, O.; Sandberg, I.; Turner, D. L.; Xenakis, M. N.; Sarris,
   E.; Tsinganos, K.; Vlahos, L.
Bibcode: 2016ApJ...817...14P
Altcode:
  During the interval 2012 March 7-11 the geospace experienced a
  barrage of intense space weather phenomena including the second
  largest geomagnetic storm of solar cycle 24 so far. Significant
  ultra-low-frequency wave enhancements and relativistic-electron dropouts
  in the radiation belts, as well as strong energetic-electron injection
  events in the magnetosphere were observed. These phenomena were
  ultimately associated with two ultra-fast (&gt;2000 km s<SUP>-1</SUP>)
  coronal mass ejections (CMEs), linked to two X-class flares launched
  on early 2012 March 7. Given that both powerful events originated from
  solar active region NOAA 11429 and their onsets were separated by less
  than an hour, the analysis of the two events and the determination
  of solar causes and geospace effects are rather challenging. Using
  satellite data from a flotilla of solar, heliospheric and magnetospheric
  missions a synergistic Sun-to-Earth study of diverse observational
  solar, interplanetary and magnetospheric data sets was performed. It was
  found that only the second CME was Earth-directed. Using a novel method,
  we estimated its near-Sun magnetic field at 13 R<SUB>⊙</SUB> to be
  in the range [0.01, 0.16] G. Steep radial fall-offs of the near-Sun
  CME magnetic field are required to match the magnetic fields of the
  corresponding interplanetary CME (ICME) at 1 AU. Perturbed upstream
  solar-wind conditions, as resulting from the shock associated with the
  Earth-directed CME, offer a decent description of its kinematics. The
  magnetospheric compression caused by the arrival at 1 AU of the shock
  associated with the ICME was a key factor for radiation-belt dynamics.

Title: Intensity Conserving Spectral Fitting
Authors: Klimchuk, J. A.; Patsourakos, S.; Tripathi, D.
Bibcode: 2016SoPh..291...55K
Altcode: 2015SoPh..tmp..180K
  The detailed shapes of spectral-line profiles provide valuable
  information about the emitting plasma, especially when the plasma
  contains an unresolved mixture of velocities, temperatures, and
  densities. As a result of finite spectral resolution, the intensity
  measured by a spectrometer is the average intensity across a wavelength
  bin of non-zero size. It is assigned to the wavelength position at
  the center of the bin. However, the actual intensity at that discrete
  position will be different if the profile is curved, as it invariably
  is. Standard fitting routines (spline, Gaussian, etc.) do not account
  for this difference, and this can result in significant errors when
  making sensitive measurements. We have developed an iterative procedure
  that corrects for this effect. It converges rapidly and is very
  flexible in that it can be used with any fitting function. We present
  examples of cubic-spline and Gaussian fits and give special attention
  to measurements of blue-red asymmetries of coronal emission lines.

Title: EUV Coronal Waves: Atmospheric and Heliospheric Connections
    and Energetics
Authors: Patsourakos, S.
Bibcode: 2015AGUFMSH22A..03P
Altcode:
  Since their discovery in late 90's by EIT on SOHO, the study EUV coronal
  waves has been a fascinating andfrequently strongly debated research
  area. While it seems as ifan overall consensus has been reached about
  the nurture and nature of this phenomenon,there are still several
  important questions regarding EUV waves. By focusing on the most
  recentobservations, we will hereby present our current understanding
  about the nurture and nature of EUV waves,discuss their connections
  with other atmospheric and heliospheric phenomena (e.g.,flares and
  CMEs, Moreton waves, coronal shocks, coronal oscillations, SEP events)
  and finallyassess their possible energetic contribution to the overall
  budget of relatederuptive phenomena.

Title: North-south asymmetry in the magnetic deflection of polar
    coronal hole jets
Authors: Nisticò, G.; Zimbardo, G.; Patsourakos, S.; Bothmer, V.;
   Nakariakov, V. M.
Bibcode: 2015A&A...583A.127N
Altcode: 2015arXiv150801072N
  Context. Measurements of the sunspots area, of the magnetic field in
  the interplanetary medium, and of the heliospheric current sheet (HCS)
  position, reveal a possible north-south (N-S) asymmetry in the magnetic
  field of the Sun. This asymmetry could cause the bending of the HCS of
  the order of 5-10 deg in the southward direction, and it appears to
  be a recurrent characteristic of the Sun during the minima of solar
  activity. <BR /> Aims: We study the N-S asymmetry as inferred from
  measurements of the deflection of polar coronal hole jets when they
  propagate throughout the corona. <BR /> Methods: Since the corona is
  an environment where the magnetic pressure is greater than the kinetic
  pressure (β ≪ 1), we can assume that the magnetic field controls the
  dynamics of plasma. On average, jets follow magnetic field lines during
  their propagation, highlighting their local direction. We measured
  the position angles at 1 R<SUB>⊙</SUB> and at 2 R<SUB>⊙</SUB> of
  79 jets, based on the Solar TErrestrial RElations Observatory (STEREO)
  ultraviolet and white-light coronagraph observations during the solar
  minimum period March 2007-April 2008. The average jet deflection is
  studied both in the plane perpendicular to the line of sight and, for
  a reduced number of jets, in 3D space. The observed jet deflection is
  studied in terms of an axisymmetric magnetic field model comprising
  dipole (g<SUB>1</SUB>), quadrupole (g<SUB>2</SUB>), and esapole
  (g<SUB>3</SUB>) moments. <BR /> Results: We found that the propagation
  of the jets is not radial, which is in agreement with the deflection
  due to magnetic field lines. Moreover, the amount of the deflection is
  different between jets over the north and those from the south pole. A
  comparison of jet deflections and field line tracing shows that a ratio
  g<SUB>2</SUB>/g<SUB>1</SUB> ≃ -0.5 for the quadrupole and a ratio
  g<SUB>3</SUB>/g<SUB>1</SUB> ≃ 1.6-2.0 for the esapole can describe
  the field. The presence of a non-negligible quadrupole moment confirms
  the N-S asymmetry of the solar magnetic field for the considered
  period. <BR /> Conclusions: We find that the magnetic deflection of
  jets is larger in the north than in the south of the order of 25-40%,
  with an asymmetry that is consistent with a southward deflection of
  the heliospheric current sheet of the order of 10 deg, consistent with
  that inferred from other independent datasets and instruments.

Title: A tiny event producing an interplanetary type III burst
Authors: Alissandrakis, C. E.; Nindos, A.; Patsourakos, S.;
   Kontogeorgos, A.; Tsitsipis, P.
Bibcode: 2015A&A...582A..52A
Altcode: 2015arXiv150708423A
  <BR /> Aims: We investigate the conditions under which small-scale
  energy release events in the low corona gave rise to strong
  interplanetary (IP) type III bursts. <BR /> Methods: We analyzed
  observations of three tiny events, detected by the Nançay Radio
  Heliograph (NRH), two of which produced IP type III bursts. We
  took advantage of the NRH positioning information and of the high
  cadence of AIA/SDO data to identify the associated extreme-UV (EUV)
  emissions. We measured positions and time profiles of the metric and
  EUV sources. <BR /> Results: We found that the EUV events that produced
  IP type III bursts were located near a coronal hole boundary, while the
  one that did not was located in a closed magnetic field region. In all
  three cases tiny flaring loops were involved, without any associated
  mass eruption. In the best observed case, the radio emission at the
  highest frequency (435 MHz) was displaced by ~55'' with respect to
  the small flaring loop. The metric type III emission shows a complex
  structure in space and in time, indicative of multiple electron
  beams, despite the low intensity of the events. From the combined
  analysis of dynamic spectra and NRH images, we derived the electron
  beam velocity as well as the height, ambient plasma temperature, and
  density at the level of formation of the 160 MHz emission. From the
  analysis of the differential emission measure derived from the AIA
  images, we found that the first evidence of energy release was at the
  footpoints, and this was followed by the development of flaring loops
  and subsequent cooling. <BR /> Conclusions: Even small energy release
  events can accelerate enough electrons to give rise to powerful IP
  type III bursts. The proximity of the electron acceleration site to
  open magnetic field lines facilitates the escape of the electrons
  into the interplanetary space. The offset between the site of
  energy release and the metric type III location warrants further
  investigation. <P />The movie is available in electronic form at <A
  href="http://www.aanda.org/10.1051/0004-6361/201526265/olm">http://www.aanda.org</A>

Title: Formation of Magnetic Flux Ropes during a Confined Flaring
    Well before the Onset of a Pair of Major Coronal Mass Ejections
Authors: Chintzoglou, Georgios; Patsourakos, Spiros; Vourlidas, Angelos
Bibcode: 2015ApJ...809...34C
Altcode: 2015arXiv150701165C
  NOAA active region (AR) 11429 was the source of twin super-fast
  coronal mass ejections (CMEs). The CMEs took place within an hour
  from each other, with the onset of the first taking place in the
  beginning of 2012 March 7. This AR fulfills all the requirements for
  a “super active region” namely, Hale's law incompatibility and a
  δ-spot magnetic configuration. One of the biggest storms of Solar
  Cycle 24 to date ({D}<SUB>{st</SUB>}=-143 nT) was associated with
  one of these events. Magnetic flux ropes (MFRs) are twisted magnetic
  structures in the corona, best seen in ∼10 MK hot plasma emission
  and are often considered the core of erupting structures. However,
  their “dormant” existence in the solar atmosphere (i.e., prior to
  eruptions), is an open question. Aided by multi-wavelength observations
  by the Solar Dynamics Observatory (SDO) and by the Solar Terrestrial
  Relations Observatory (STEREO) and a nonlinear force-free model for the
  coronal magnetic field, our work uncovers two separate, weakly twisted
  magnetic flux systems which suggest the existence of pre-eruption MFRs
  that eventually became the seeds of the two CMEs. The MFRs could have
  been formed during confined (i.e., not leading to major CMEs) flaring
  and sub-flaring events which took place the day before the two CMEs
  in the host AR 11429.

Title: How Common Are Hot Magnetic Flux Ropes in the Low Solar
    Corona? A Statistical Study of EUV Observations
Authors: Nindos, A.; Patsourakos, S.; Vourlidas, A.; Tagikas, C.
Bibcode: 2015ApJ...808..117N
Altcode: 2015arXiv150703766N
  We use data at 131, 171, and 304 Å from the Atmospheric Imaging
  Assembly on board the Solar Dynamics Observatory to search for hot
  flux ropes in 141 M-class and X-class solar flares that occurred at
  solar longitudes equal to or larger than 50°. Half of the flares were
  associated with coronal mass ejections. The goal of our survey is to
  assess the frequency of hot flux ropes in large flares irrespective
  of their formation time relative to the onset of eruptions. The flux
  ropes were identified in 131 Å images using morphological criteria and
  their high temperatures were confirmed by their absence in the cooler
  171 and 304 Å passbands. We found hot flux ropes in 45 of our events
  (32% of the flares); 11 of them were associated with confined flares
  while the remaining 34 were associated with eruptive flares. Therefore
  almost half (49%) of the eruptive events involved a hot flux rope
  configuration. The use of supplementary Hinode X-Ray Telescope data
  indicates that these percentages should be considered as lower limits
  of the actual rates of occurrence of hot flux ropes in large flares.

Title: Intensity Conserving Spline Interpolation (ICSI): A New Tool
    for Spectroscopic Analysis
Authors: Klimchuk, James A.; Patsourakos, Spiros; Tripathi, Durgesh
Bibcode: 2015TESS....120309K
Altcode: 2015arXiv150608102K
  Spectroscopy is an extremely powerful tool for diagnosing astrophysical
  and other plasmas. For example, the shapes of line profiles provide
  valuable information on the distribution of velocities along
  an optically thin line-of-sight and across the finite area of a
  resolution element. A number of recent studies have measured the
  asymmetries of line profiles in order to detect faint high-speed
  upflows, perhaps associated with coronal nanoflares or perhaps
  associated with chromospheric nanoflares and type II spicules. Over
  most of the Sun, these asymmetries are very subtle, so great care
  must be taken. A common technique is to perform a spline fit of the
  points in the profile in order to extract information at a spectral
  resolution higher than that of the original data. However, a fundamental
  problem is that the fits do not conserve intensity. We have therefore
  developed an iterative procedure called Intensity Conserving Spline
  Interpolation that does preserve the observed intensity within each
  wavelength bin. It improves the measurement of line asymmetries and
  can also help with the determination of line blends.

Title: Intensity Conserving Spline Interpolation (ICSI): A New Tool
    for Spectroscopic Analysis
Authors: Klimchuk, J. A.; Patsourakos, S.; Tripathi, D.
Bibcode: 2014AGUFMSH13B4109K
Altcode:
  Spectroscopy is an extremely powerful tool for diagnosing astrophysical
  and other plasmas. For example, the shapes of line profiles provide
  valuable information on the distribution of velocities along
  an optically thin line-of-sight and across the finite area of a
  resolution element. A number of recent studies have measured the
  asymmetries of line profiles in order to detect faint high-speed
  upflows, perhaps associated with coronal nanoflares or perhaps
  associated with chromospheric nanoflares and type II spicules. Over
  most of the Sun, these asymmetries are very subtle, so great care
  must be taken. A common technique is to perform a spline fit of the
  points in the profile in order to extract information at a spectral
  resolution higher than that of the original data. However, a fundamental
  problem is that the fits do not conserve intensity. We have therefore
  developed an iterative procedure called Intensity Conserving Spline
  Interpolation that does preserve the observed intensity within each
  wavelength bin. It improves the measurement of line asymmetries and
  can also help with the determination of line blends.

Title: CME Expansion as the Driver of Metric Type II Shock Emission
    as Revealed by Self-consistent Analysis of High-Cadence EUV Images
    and Radio Spectrograms
Authors: Kouloumvakos, A.; Patsourakos, S.; Hillaris, A.; Vourlidas,
   A.; Preka-Papadema, P.; Moussas, X.; Caroubalos, C.; Tsitsipis, P.;
   Kontogeorgos, A.
Bibcode: 2014SoPh..289.2123K
Altcode: 2013arXiv1311.5159K
  On 13 June 2010, an eruptive event occurred near the solar limb. It
  included a small filament eruption and the onset of a relatively narrow
  coronal mass ejection (CME) surrounded by an extreme ultraviolet
  (EUV) wave front recorded by the Solar Dynamics Observatory's (SDO)
  Atmospheric Imaging Assembly (AIA) at high cadence. The ejection was
  accompanied by a GOES M1.0 soft X-ray flare and a Type-II radio burst;
  high-resolution dynamic spectra of the latter were obtained by the
  Appareil de Routine pour le Traitement et l'Enregistrement Magnetique
  de l'Information Spectral (ARTEMIS IV) radio spectrograph. The combined
  observations enabled a study of the evolution of the ejecta and the
  EUV wave front and its relationship with the coronal shock manifesting
  itself as metric Type-II burst. By introducing a novel technique,
  which deduces a proxy of the EUV compression ratio from AIA imaging
  data and compares it with the compression ratio deduced from the
  band-split of the Type-II metric radio burst, we are able to infer
  the potential source locations of the radio emission of the shock on
  that AIA images. Our results indicate that the expansion of the CME
  ejecta is the source for both EUV and radio shock emissions. Early in
  the CME expansion phase, the Type-II burst seems to originate in the
  sheath region between the EUV bubble and the EUV shock front in both
  radial and lateral directions. This suggests that both the nose and
  the flanks of the expanding bubble could have driven the shock.

Title: Rapid CME Cavity Formation and Expansion
Authors: Kliem, Bernhard; Forbes, Terry G.; Patsourakos, Spiros;
   Vourlidas, Angelos
Bibcode: 2014AAS...22421206K
Altcode:
  A cavity is supposed to be a general feature of well-developed CMEs at
  the stage they can be imaged by white-light coronagraphs (in the outer
  corona and solar wind). The cavity is interpreted as the cross section
  of the CME flux rope in the plane of sky. Preexisting cavities are
  observed around some quiescent erupting prominences, but usually not in
  active regions. Observations of CME cavities in the inner corona, where
  most of them appear to form, have become possible only with the STEREO
  and SDO missions. These reveal a very rapid formation and expansion of
  "EUV cavities" in fast and impulsively commencing eruptions early in the
  phase of main CME acceleration and impulsive flare rise. Different from
  the white-light observations, the EUV cavity initially appears to be
  larger than the CME flux rope. However, it evolves into the white-light
  cavity subsequently. MHD simulations of flux rope eruptions conform to
  this picture of initially larger cavity but subsequently approaching
  cavity and flux rope size. The initial expansion of ambient flux can
  be understood as a "reverse pinch effect", driven by decreasing flux
  rope current as the rope rises.

Title: Independent CMEs from a Single Solar Active Region - The Case
    of the Super-Eruptive NOAA AR11429
Authors: Chintzoglou, Georgios; Patsourakos, Spiros; Vourlidas, Angelos
Bibcode: 2014AAS...22432328C
Altcode:
  In this investigation we study AR 11429, the origin of the twin
  super-fast CME eruptions of 07-Mar-2012. This AR fulfills all the
  requirements for the 'perfect storm'; namely, Hale's law incompatibility
  and a delta-magnetic configuration. In fact, during its limb-to-limb
  transit, AR 11429 spawned several eruptions which caused geomagnetic
  storms, including the biggest in Cycle 24 so far. Magnetic Flux Ropes
  (MFRs) are twisted magnetic structures in the corona, best seen in
  ~10MK hot plasma emission and are often considered as the culprit
  causing such super-eruptions. However, their 'dormant' existence in
  the solar atmosphere (i.e. prior to eruptions), is a matter of strong
  debate. Aided by multi-wavelength and multi-spacecraft observations
  (SDO/HMI &amp; AIA, HINODE/SOT/SP, STEREO B/EUVI) and by using a
  Non-Linear Force-Free (NLFFF) model for the coronal magnetic field,
  our work shows two separate, weakly-twisted magnetic flux systems
  which suggest the existence of possible pre-eruption MFRs.

Title: Core and Wing Densities of Asymmetric Coronal Spectral
Profiles: Implications for the Mass Supply of the Solar Corona
Authors: Patsourakos, S.; Klimchuk, J. A.; Young, P. R.
Bibcode: 2014ApJ...781...58P
Altcode: 2013arXiv1312.4842P
  Recent solar spectroscopic observations have shown that coronal spectral
  lines can exhibit asymmetric profiles, with enhanced emissions at their
  blue wings. These asymmetries correspond to rapidly upflowing plasmas
  at speeds exceeding ≈50 km s<SUP>-1</SUP>. Here, we perform a study
  of the density of the rapidly upflowing material and compare it with
  that of the line core that corresponds to the bulk of the plasma. For
  this task, we use spectroscopic observations of several active regions
  taken by the Extreme Ultraviolet Imaging Spectrometer of the Hinode
  mission. The density sensitive ratio of the Fe XIV lines at 264.78 and
  274.20 Å is used to determine wing and core densities. We compute the
  ratio of the blue wing density to the core density and find that most
  values are of order unity. This is consistent with the predictions for
  coronal nanoflares if most of the observed coronal mass is supplied
  by chromospheric evaporation driven by the nanoflares. However,
  much larger blue wing-to-core density ratios are predicted if most of
  the coronal mass is supplied by heated material ejected with type II
  spicules. Our measurements do not rule out a spicule origin for the
  blue wing emission, but they argue against spicules being a primary
  source of the hot plasma in the corona. We note that only about 40%
  of the pixels where line blends could be safely ignored have blue wing
  asymmetries in both Fe XIV lines. Anticipated sub-arcsecond spatial
  resolution spectroscopic observations in future missions could shed
  more light on the origin of blue, red, and mixed asymmetries.

Title: North-South Asymmetry in the Magnetic Deflection of Polar
    Coronal Jets
Authors: Nisticò, Giuseppe; Zimbardo, Gaetano; Bothmer, Volker;
   Patsourakos, Spiros
Bibcode: 2014cosp...40E2295N
Altcode:
  Solar jets observed with the Extreme Ultra-Violet Imager (EUVI) and
  CORonagraphs (COR) instruments aboard the STEREO mission provide a tool
  to probe and understand the magnetic structure of the corona. Since
  the corona is an environment where the magnetic pressure is greater
  than the kinetic pressure, the magnetic field controls the dynamics
  of plasma and, on average, jets during their propagation trace
  the magnetic field lines. We discuss the North-South asymmetry of
  the magnetic field of the Sun as inferred from measurements of the
  deflection of polar coronal hole jets when they propagate throughout
  the corona. We measured the position angle at 1 and at 2 solar radii
  for the 79 jets of the catalogue of Nisticò et al. (2009), based on
  the STEREO ultraviolet and visible observations, and we found that the
  propagation is not radial. The average jet deflection is studied both in
  the plane perpendicular to the line of sight, and, for a reduced number
  of jets in the three dimensional (3D) space. We find that the magnetic
  deflection of jets is larger in the North than in the South, with an
  asymmetry which is consistent with the N-S asymmetry of the heliospheric
  magnetic field inferred from the Ulysses in situ measurements, and
  gives clues to the study of the large scale solar magnetic field.

Title: Observations of CMEs-ICMEs: Results from Current Space Missions
    and Expectations from Future Instrumentation
Authors: Patsourakos, Spiros
Bibcode: 2014cosp...40E2464P
Altcode:
  Our understanding of the physics of CMEs and ICMEs has been
  substantially improved over the last 20 years, thanks particularly
  to a stream of space missions. While many questions regarding CMEs
  and ICMEs have been resolved there are still some important pending
  questions. With this talk we will focus on two important problems of
  CME and ICME physics, namely the determination of the CME pre-erupting
  structures and the physical processes behind their initiation as
  well as the properties of CME-ICME propagation in the IP medium. We
  will supply a review of recent results related to these two areas and
  discuss specific examples of how progress from future instrumentation
  may be expected.

Title: Sun-to-Earth Analysis of a Major Solar Eruption
Authors: Patsourakos, Spiros
Bibcode: 2014cosp...40E2465P
Altcode:
  During the interval of 7-10 March 2012, Earth's space environment
  experienced a barrage of space weather phenomena. Early during 7
  March 2012, the biggest proton event of 2012 took place, while on 8
  March 2012, an interplanetary shock and coronal mass ejection (CME)
  arrived at 1 AU. This sequence trigerred the biggest geomagnetic
  storm of cycle 24 so far. The solar source of these activities
  was a pair of homologous, eruptive X-class flares associated with
  two ultra-fast CMEs. The two eruptions originated from NOAA active
  region 11429 during the early hours of 7 March 2012 and within an
  hour from each other. Using satellite data from a flotilla of solar,
  heliospheric and magnetospheric missions and monitors, we perform
  a synergistic Sun-to-Earth study of various observational aspects
  of the event sequences. We will present an attempt to formulate a
  cohesive scenario which couples the eruption initiation, interplanetary
  propagation, and geospace consequences. Our main focus is on building
  a framework that starting from solar and near-Sun estimates of the
  magnetic and dynamic content and properties of the Earth-directed
  CME assess in advance the subsequent geomagnetic response expected,
  once the associated interplanetary CME reaches 1 AU. This research has
  been co-financed by the European Union (European Social Fund - ESF)
  and Greek national funds through the Operational Program "Education
  and Lifelong Learning" of the National Strategic Reference Framework
  (NSRF) - Research Funding Program: Thales. Investing in knowledge
  society through the European Social Fund.

Title: Microwave and EUV Observations of an Erupting Filament and
    Associated Flare and Coronal Mass Ejections
Authors: Alissandrakis, Costas E.; Kochanov, Alexey A.; Patsourakos,
   Spiros; Altyntsev, Alexander T.; Lesovoi, Sergey V.; Lesovoya, Nadya N.
Bibcode: 2013PASJ...65S...8A
Altcode: 2013arXiv1309.1703A
  A filament eruption was observed with the Siberian Solar Radio Telescope
  (SSRT) on 2012 June 23, starting at around 06:40 UT, beyond the west
  limb. The filament could be followed in SSRT images to heights above 1
  R<SUB>⊙</SUB>, and coincided with the core of the CME, seen in LASCO
  C2 images. We briefly discuss the dynamics of the eruption: the top of
  the filament showed a smooth acceleration up to an apparent velocity
  of ∼ 1100 km s<SUP>-1</SUP>. Images behind the limb from STEREO-A
  show a two-ribbon flare and the interaction of the main filament,
  located along the primary neutral line, with an arch-like structure,
  oriented in the perpendicular direction. The interaction was accompanied
  by strong emission and twisting motions. The microwave images show
  a low-temperature component, a high-temperature component associated
  with the interaction of the two filaments and another high-temperature
  component apparently associated with the top of flare loops. We
  computed the differential emission measure from the high-temperature
  AIA bands and from this the expected microwave brightness temperature;
  for emission associated with the top of the flare loops, the computed
  brightness was 35% lower than the observed value.

Title: Parametric study of drag force acting on interplanetary CME
Authors: Podladchikova, O.; Patsourakos, S.; Nindos, A.
Bibcode: 2013hell.confR..22P
Altcode:
  The interaction of an interplanetary coronal mass ejection (ICME)
  with the solar wind leads to an equalisation of the ICME and solar
  wind velocities at 1 AU. The forces acting on ICMEs have been
  evaluated so far in terms of an empirical drag coefficient C_D ~
  1 that describes the aerodynamic drag experienced by a typical ICME
  due to its interaction with the ambient solar wind. The consideration
  of viscous drag coefficients due to proton-magnetic kink encounters
  is more realistic for solar wind turbulence. We compare aerodynamic
  and viscous drag description and their impact on ICME propagation in
  solar wind. We also consider the impact of ICME distortions to their
  kinematics as they propagate in the inner heliosphere.

Title: The spatial relationship between coronal mass ejections and
    solar flares
Authors: Nikou, E.; Nindos, A.; Patsourakos, S.
Bibcode: 2013hell.conf...21N
Altcode:
  Using 19 well-observed eruptions that gave both coronal mass ejections
  (CMEs) and flares, we quantified the spatial relationship between pairs
  of CMEs and associated flares. The flare and CME source locations were
  identified using images obtained at 174 A by the SWAP instrument aboard
  PROBA 2 satellite. The SWAP data are suitable for this study because
  flare emission does not saturate much. To reduce saturation even more,
  our database did not contain any M-class or X-class flare events. We
  selected eruptions that occurred close to disk center, as viewed from
  Earth, whereas they appeared as limb events in images obtained by the
  EUV Imagers (EUVI) aboard the SECCHI/STEREO spacecraft. The centroids
  of the CME-associated EUV dimmings in the SWAP images were used as
  proxies for the CME source locations. For each event, we compared the
  location of the flare brightenings with the location of the dimmings'
  centroid at the time of CME initiation which was determined from
  the EUVI data. In six cases the CME location was cospatial with flare
  brightenings while in the remaining cases the distance between each pair
  of flare-CME locations varied from 4 to 191 arcsecs with a median value
  of 71 arcsecs. Furthermore, we investigated the CME source locations
  with respect to the underlying magnetic field structures.

Title: Particle acceleration and nanoflare heating in coronal loops
Authors: Gontikakis, C.; Patsourakos, S.; Efthymiopoulos, C.;
   Anastasiadis, A.; Georgoulis, M.
Bibcode: 2013hell.conf...18G
Altcode:
  We model nanoflare heating of extrapolated active-region coronal loops
  via the acceleration of electrons and protons in Harris-type current
  sheets. The kinetic energy of the accelerated particles is estimated
  using semi-analytical and test-particle-tracing approaches. Vector
  magnetograms and photospheric Doppler velocity maps of NOAA active
  region 09114, recorded by the Imaging Vector Magnetograph (IVM),
  were used for this analysis in order to compute a current-free field
  extrapolation of the active-region corona. The corresponding Poynting
  fluxes at the footpoints of 5000 extrapolated coronal loops were then
  calculated. Assuming that reconnecting current sheets develop along
  these loops, we utilized previous results to estimate the kinetic-energy
  gain of the accelerated particles and we related this energy to
  nanoflare heating and macroscopic loop characteristics. Kinetic
  energies of 0.1 to 8~keV (for electrons) and 0.3 to 470~keV (for
  protons) were found to cause heating rates ranging from 10^-6 to 1
  erg s^-1 cm^-3. Hydrodynamic simulations show that such heating rates
  can sustain plasma in coronal conditions inside the loops and generate
  plasma thermal distributions which are consistent with active region
  observations. We concluded the analysis by computing the form of Xray
  spectra generated by the accelerated electrons using the thick target
  approach that were found to be in agreement with observed X-ray spectra,
  thus supporting the plausibility of our nanoflare-heating scenario. This
  work is supported by EU's Seventh Framework Programme via a Marie Curie
  Fellowship and by the Hellenic National Space Weather Research Network
  (HNSWRN) via the THALIS Programme.

Title: Sun-to-Earth Analysis of a Major Geoeffective Solar Eruption
    within the Framework of the
Authors: Patsourakos, S.; Vlahos, L.; Georgoulis, M.; Tziotziou,
   K.; Nindos, A.; Podladchikova, O.; Vourlidas, A.; Anastasiadis, A.;
   Sandberg, I.; Tsinganos, K.; Daglis, I.; Hillaris, A.; Preka-Papadema,
   P.; Sarris, M.; Sarris, T.
Bibcode: 2013hell.conf...10P
Altcode:
  Transient expulsions of gigantic clouds of solar coronal plasma into
  the interplanetary space in the form of Coronal Mass Ejections (CMEs)
  and sudden, intense flashes of electromagnetic radiation, solar flares,
  are well-established drivers of the variable Space Weather. Given the
  innate, intricate links and connections between the solar drivers and
  their geomagnetic effects, synergistic efforts assembling all pieces
  of the puzzle along the Sun-Earth line are required to advance our
  understanding of the physics of Space Weather. This is precisely the
  focal point of the Hellenic National Space Weather Research Network
  (HNSWRN) under the THALIS Programme. Within the HNSWRN framework,
  we present here the first results from a coordinated multi-instrument
  case study of a major solar eruption (X5.4 and X1.3 flares associated
  with two ultra-fast (&gt;2000 km/s) CMEs) which were launched early
  on 7 March 2012 and triggered an intense geomagnetic storm (min Dst
  =-147 nT) approximately two days afterwards. Several elements of
  the associated phenomena, such as the flare and CME, EUV wave, WL
  shock, proton and electron event, interplanetary type II radio burst,
  ICME and magnetic cloud and their spatiotemporal relationships and
  connections are studied all way from Sun to Earth. To this end, we
  make use of satellite data from a flotilla of solar, heliospheric and
  magnetospheric missions and monitors (e.g., SDO, STEREO, WIND, ACE,
  Herschel, Planck and INTEGRAL). We also present our first steps toward
  formulating a cohesive physical scenario to explain the string of the
  observables and to assess the various physical mechanisms than enabled
  and gave rise to the significant geoeffectiveness of the eruption.

Title: Hot coronal loops associated with umbral brightenings
Authors: Alissandrakis, C. E.; Patsourakos, S.
Bibcode: 2013A&A...556A..79A
Altcode: 2013arXiv1307.3392A
  <BR /> Aims: We aim to investigate the association of umbral
  brightenings with coronal structures. <BR /> Methods: We analyzed
  AIA/SDO high-cadence images in all bands, HMI/SDO data, soft X-ray
  images from SXI/GOES-15, and Hα images from the GONG network. <BR
  /> Results: We detected umbral brightenings that were visible
  in all AIA bands as well as in Hα. Moreover, we identified
  hot coronal loops that connected the brightenings with nearby
  regions of opposite magnetic polarity. These loops were initially
  visible in the 94 Å band, subsequently in the 335 Å band, and
  in one case in the 211 Å band. A differential emission measure
  analysis revealed plasma with an average temperature of about 6.5
  × 10<SUP>6</SUP> K. This behavior suggests cooling of impulsively
  heated loops. <P />Two movies are available in electronic from at <A
  href="http://www.aanda.org">http://www.aanda.org</A>

Title: Where is Coronal Plasma Heated?
Authors: Klimchuk, James A.; Bradshaw, S.; Patsourakos, S.; Tripathi,
   D.
Bibcode: 2013SPD....4420006K
Altcode:
  The coupling between the chromosphere and corona is a question of
  great current interest. It has long been understood that coronal mass
  originates in the chromosphere and that the energy which powers the
  corona flows up through the chromosphere. However, the details of
  how this happens are now being questioned. In the traditional view,
  “mechanical” energy flows into the corona in the form of waves
  or gradually increasing magnetic stresses. The waves and stresses
  dissipate and heat the plasma. The resulting downward thermal conduction
  flux causes material to evaporate from the chromosphere and fill
  the corona. If the heating is steady, an equilibrium is established
  whereby radiation and thermal conduction balance the energy input. If
  the heating is impulsive (a nanoflare), the evaporated plasma cools
  and drains, only to reappear during the next event. In either case,
  the heating occurs in the corona. A new idea is that the heating
  occurs instead in the chromosphere. Cold plasma is directly heated
  to coronal temperatures and then flows upward due to expansion and
  perhaps also an ejection process. The hot tips of type II spicules
  are one example, though spicules need not be involved. I will discuss
  these two fundamentally different scenarios and the observational
  predictions that they make. A comparison with actual observations
  leads to the conclusion that only a small fraction of the hot plasma
  in the corona comes from chromospheric heating. Most coronal plasma
  is a consequence of heating that occurs in the corona itself.

Title: Combining Particle Acceleration and Coronal Heating via
    Data-constrained Calculations of Nanoflares in Coronal Loops
Authors: Gontikakis, C.; Patsourakos, S.; Efthymiopoulos, C.;
   Anastasiadis, A.; Georgoulis, M. K.
Bibcode: 2013ApJ...771..126G
Altcode: 2013arXiv1305.5195G
  We model nanoflare heating of extrapolated active-region coronal loops
  via the acceleration of electrons and protons in Harris-type current
  sheets. The kinetic energy of the accelerated particles is estimated
  using semi-analytical and test-particle-tracing approaches. Vector
  magnetograms and photospheric Doppler velocity maps of NOAA active
  region 09114, recorded by the Imaging Vector Magnetograph, were
  used for this analysis. A current-free field extrapolation of the
  active-region corona was first constructed. The corresponding Poynting
  fluxes at the footpoints of 5000 extrapolated coronal loops were then
  calculated. Assuming that reconnecting current sheets develop along
  these loops, we utilized previous results to estimate the kinetic
  energy gain of the accelerated particles. We related this energy
  to nanoflare heating and macroscopic loop characteristics. Kinetic
  energies of 0.1-8 keV (for electrons) and 0.3-470 keV (for protons)
  were found to cause heating rates ranging from 10<SUP>-6</SUP> to 1
  erg s<SUP>-1</SUP> cm<SUP>-3</SUP>. Hydrodynamic simulations show
  that such heating rates can sustain plasma in coronal conditions
  inside the loops and generate plasma thermal distributions that are
  consistent with active-region observations. We concluded the analysis
  by computing the form of X-ray spectra generated by the accelerated
  electrons using the thick-target approach. These spectra were found
  to be in agreement with observed X-ray spectra, thus supporting the
  plausibility of our nanoflare-heating scenario.

Title: Spectral diagnostic of a microflare. Evidences of resonant
    scattering in C IV 1548 Å, 1550 Å lines
Authors: Gontikakis, C.; Winebarger, A. R.; Patsourakos, S.
Bibcode: 2013A&A...550A..16G
Altcode:
  <BR /> Aims: We study a microflare, classified as a GOES-A1 after
  background subtraction, which was observed in active region NOAA 8541
  on May 15, 1999. <BR /> Methods: We used TRACE filtergrams to study
  the morphology and time evolution. SUMER spectral lines were used to
  diagnose the chromospheric plasma (Si ii 1533 Å), transition region
  plasma (C iv 1548, 1550 Å), and coronal plasma (Ne viii 770 Å). <BR
  /> Results: In the 171 Å and 195 Å filtergrams, we measure apparent
  mass motions along two small loops that compose the microflare from
  the eastern toward the western footpoints. In SUMER, the microflare is
  detected as a small (47 Mm<SUP>2</SUP>), bright area at the western
  footpoints of the TRACE loops. The spectral profiles recorded over
  the bright area are complex. The Si ii 1533 Å line is self-reversed
  owing to opacity, and the coronal Ne viii line profile is composed of
  two Gaussian components, one of them systematically redshifted. The
  C iv 1548 Å and 1550 Å profiles are badly distorted because of the
  temporary depression of the detector local gain caused by the very
  high count rates reached in the flaring region and we can only confirm
  the presence of strong blueshifts of ≃ -200 km s<SUP>-1</SUP>. Few,
  unaffected C iv profiles show two spectral components. In the northern
  part of the bright area, all SUMER spectral lines have at least one
  blueshifted spectral component. In the southern region of the bright
  area the spectral lines are redshifted. Adjacent to the microflare we
  measure, for the first time on the solar disk, an intensity ratio of the
  1548 Å line to 1550 Å line with values of three to four, indicating
  that resonance scattering prevails in the lines formation. Moreover,
  the scattering region is found to be cospatial to a solar pore. <BR />
  Conclusions: The blueshifts in the footpoints of the microflare and
  the apparent mass motions observed with TRACE can be explained by
  a gentle chromospheric evaporation triggered by the microflare. The
  redshifted spectral components can be explained as cooling material
  that is falling back on the solar surface. The presence of resonant
  scattering can be explained by the low electron density expected in the
  transition region of a solar pore, combined with the high photon flux
  coming from the nearby microflare. We estimate that the lower limit
  of the electron density in the pore lies in the range 10<SUP>8</SUP>
  cm<SUP>-3</SUP> to 10<SUP>9</SUP> cm<SUP>-3</SUP>.

Title: Direct Evidence for a Fast Coronal Mass Ejection Driven by the
    Prior Formation and Subsequent Destabilization of a Magnetic Flux Rope
Authors: Patsourakos, S.; Vourlidas, A.; Stenborg, G.
Bibcode: 2013ApJ...764..125P
Altcode: 2012arXiv1211.7211P
  Magnetic flux ropes play a central role in the physics of coronal
  mass ejections (CMEs). Although a flux-rope topology is inferred for
  the majority of coronagraphic observations of CMEs, a heated debate
  rages on whether the flux ropes pre-exist or whether they are formed
  on-the-fly during the eruption. Here, we present a detailed analysis
  of extreme-ultraviolet observations of the formation of a flux rope
  during a confined flare followed about 7 hr later by the ejection of
  the flux rope and an eruptive flare. The two flares occurred during
  2012 July 18 and 19. The second event unleashed a fast (&gt;1000 km
  s<SUP>-1</SUP>) CME. We present the first direct evidence of a fast
  CME driven by the prior formation and destabilization of a coronal
  magnetic flux rope formed during the confined flare on July 18.

Title: On the Nature and Genesis of EUV Waves: A Synthesis of
    Observations from SOHO, STEREO, SDO, and Hinode (Invited Review)
Authors: Patsourakos, Spiros; Vourlidas, Angelos
Bibcode: 2012SoPh..281..187P
Altcode: 2012SoPh..tmp...93P; 2012arXiv1203.1135P
  A major, albeit serendipitous, discovery of the SOlar and
  Heliospheric Observatory mission was the observation by the Extreme
  Ultraviolet Telescope (EIT) of large-scale extreme ultraviolet (EUV)
  intensity fronts propagating over a significant fraction of the Sun's
  surface. These so-called EIT or EUV waves are associated with eruptive
  phenomena and have been studied intensely. However, their wave nature
  has been challenged by non-wave (or pseudo-wave) interpretations and
  the subject remains under debate. A string of recent solar missions
  has provided a wealth of detailed EUV observations of these waves
  bringing us closer to resolving the question of their nature. With
  this review, we gather the current state-of-the-art knowledge in the
  field and synthesize it into a picture of an EUV wave driven by the
  lateral expansion of the CME. This picture can account for both wave
  and pseudo-wave interpretations of the observations, thus resolving
  the controversy over the nature of EUV waves to a large degree but
  not completely. We close with a discussion on several remaining open
  questions in the field of EUV waves research.

Title: LEMUR: Large European module for solar Ultraviolet
    Research. European contribution to JAXA's Solar-C mission
Authors: Teriaca, Luca; Andretta, Vincenzo; Auchère, Frédéric;
   Brown, Charles M.; Buchlin, Eric; Cauzzi, Gianna; Culhane, J. Len;
   Curdt, Werner; Davila, Joseph M.; Del Zanna, Giulio; Doschek, George
   A.; Fineschi, Silvano; Fludra, Andrzej; Gallagher, Peter T.; Green,
   Lucie; Harra, Louise K.; Imada, Shinsuke; Innes, Davina; Kliem,
   Bernhard; Korendyke, Clarence; Mariska, John T.; Martínez-Pillet,
   Valentin; Parenti, Susanna; Patsourakos, Spiros; Peter, Hardi; Poletto,
   Luca; Rutten, Robert J.; Schühle, Udo; Siemer, Martin; Shimizu,
   Toshifumi; Socas-Navarro, Hector; Solanki, Sami K.; Spadaro, Daniele;
   Trujillo-Bueno, Javier; Tsuneta, Saku; Dominguez, Santiago Vargas;
   Vial, Jean-Claude; Walsh, Robert; Warren, Harry P.; Wiegelmann,
   Thomas; Winter, Berend; Young, Peter
Bibcode: 2012ExA....34..273T
Altcode: 2011ExA...tmp..135T; 2011arXiv1109.4301T
  The solar outer atmosphere is an extremely dynamic environment
  characterized by the continuous interplay between the plasma and the
  magnetic field that generates and permeates it. Such interactions play a
  fundamental role in hugely diverse astrophysical systems, but occur at
  scales that cannot be studied outside the solar system. Understanding
  this complex system requires concerted, simultaneous solar observations
  from the visible to the vacuum ultraviolet (VUV) and soft X-rays, at
  high spatial resolution (between 0.1'' and 0.3''), at high temporal
  resolution (on the order of 10 s, i.e., the time scale of chromospheric
  dynamics), with a wide temperature coverage (0.01 MK to 20 MK,
  from the chromosphere to the flaring corona), and the capability of
  measuring magnetic fields through spectropolarimetry at visible and
  near-infrared wavelengths. Simultaneous spectroscopic measurements
  sampling the entire temperature range are particularly important. These
  requirements are fulfilled by the Japanese Solar-C mission (Plan B),
  composed of a spacecraft in a geosynchronous orbit with a payload
  providing a significant improvement of imaging and spectropolarimetric
  capabilities in the UV, visible, and near-infrared with respect to
  what is available today and foreseen in the near future. The Large
  European Module for solar Ultraviolet Research (LEMUR), described
  in this paper, is a large VUV telescope feeding a scientific payload
  of high-resolution imaging spectrographs and cameras. LEMUR consists
  of two major components: a VUV solar telescope with a 30 cm diameter
  mirror and a focal length of 3.6 m, and a focal-plane package composed
  of VUV spectrometers covering six carefully chosen wavelength ranges
  between 170 Å and 1270 Å. The LEMUR slit covers 280'' on the Sun with
  0.14'' per pixel sampling. In addition, LEMUR is capable of measuring
  mass flows velocities (line shifts) down to 2 km s<SUP> - 1</SUP> or
  better. LEMUR has been proposed to ESA as the European contribution
  to the Solar C mission.

Title: On the Role of the Background Overlying Magnetic Field in
    Solar Eruptions
Authors: Nindos, A.; Patsourakos, S.; Wiegelmann, T.
Bibcode: 2012ApJ...748L...6N
Altcode:
  The primary constraining force that inhibits global solar eruptions is
  provided by the overlying background magnetic field. Using magnetic
  field data from both the Helioseismic and Magnetic Imager aboard the
  Solar Dynamics Observatory and the spectropolarimeter of the Solar
  Optical Telescope aboard Hinode, we study the long-term evolution of
  the background field in active region AR11158 that produced three major
  coronal mass ejections (CMEs). The CME formation heights were determined
  using EUV data. We calculated the decay index -(z/B)(∂B/∂z) of the
  magnetic field B (i.e., how fast the field decreases with height, z)
  related to each event from the time of the active region emergence until
  well after the CMEs. At the heights of CME formation, the decay indices
  were 1.1-2.1. Prior to two of the events, there were extended periods
  (of more than 23 hr) where the related decay indices at heights above
  the CME formation heights either decreased (up to -15%) or exhibited
  small changes. The decay index related to the third event increased (up
  to 118%) at heights above 20 Mm within an interval that started 64 hr
  prior to the CME. The magnetic free energy and the accumulated helicity
  into the corona contributed the most to the eruptions by their increase
  throughout the flux emergence phase (by factors of more than five and
  more than two orders of magnitude, respectively). Our results indicate
  that the initiation of eruptions does not depend critically on the
  temporal evolution of the variation of the background field with height.

Title: EBTEL: Enthalpy-Based Thermal Evolution of Loops
Authors: Klimchuk, J. A.; Patsourakos, S.; Cargill, P. J.
Bibcode: 2012ascl.soft03007K
Altcode:
  Observational and theoretical evidence suggests that coronal heating
  is impulsive and occurs on very small cross-field spatial scales. A
  single coronal loop could contain a hundred or more individual strands
  that are heated quasi-independently by nanoflares. It is therefore
  an enormous undertaking to model an entire active region or the
  global corona. Three-dimensional MHD codes have inadequate spatial
  resolution, and 1D hydro codes are too slow to simulate the many
  thousands of elemental strands that must be treated in a reasonable
  representation. Fortunately, thermal conduction and flows tend to
  smooth out plasma gradients along the magnetic field, so "0D models"
  are an acceptable alternative. We have developed a highly efficient
  model called Enthalpy-Based Thermal Evolution of Loops (EBTEL) that
  accurately describes the evolution of the average temperature, pressure,
  and density along a coronal strand. It improves significantly upon
  earlier models of this type-in accuracy, flexibility, and capability. It
  treats both slowly varying and highly impulsive coronal heating;
  it provides the differential emission measure distribution, DEM(T),
  at the transition region footpoints; and there are options for heat
  flux saturation and nonthermal electron beam heating. EBTEL gives
  excellent agreement with far more sophisticated 1D hydro simulations
  despite using four orders of magnitude less computing time. It promises
  to be a powerful new tool for solar and stellar studies.

Title: Nanoflare heating of coronal loops in an active region
    triggered by reconnecting current sheets
Authors: Gontikakis, C.; Patsourakos, S.; Efthymiopoulos, C.;
   Anastasiadis, A.; Georgoulis, M.
Bibcode: 2012hell.conf....7G
Altcode:
  The purpose of this work is to study the heating of coronal loops,
  produced by the acceleration of particles inside reconnecting current
  sheets (RCS) which represent nanoflares. We also study the hydrodynamic
  response of the loops atmosphere to such a heating event. The RCS are
  formed as discontinuities of the loop magnetic field caused by the
  photospheric shuffling motions. The coronal loops are represented
  by the closed magnetic lines of force calculated by the magnetic
  field extrapolation of the active region NOAA 9114 magnetogram. The
  photospheric motions at the loops footpoints are measured using local
  correlation tracking. The magnetic and electric fields accelerating
  particles at the RCS are computed using the loop magnetic fields and
  the photospheric motions. We further discuss the question of energy
  conservation inside the current sheet, and we present the statistical
  distributions of quantities relevant for particles acceleration and
  coronal heating for a number of the active region's coronal loops.

Title: Arrival Times of Interplanetary CMEs and Shocks into the
Earth's Vicinity: STEREO Observations and Analytical Modeling
Authors: Ontiveros, V.; Patsourakos, S.; Corona-Romero, P.;
   Gonzalez-Esparza, J. A.
Bibcode: 2012hell.conf....9O
Altcode:
  Interplanetary Coronal Mass Ejections (ICMEs) are one of the largest
  disturbances in the solar system. ICMEs and their associated shocks are
  the main cause of intense geomagnetic perturbations, that might affect
  satellite orbits and telecommunications among other systems. These
  important repercussions in the Space Weather have lead to a continuous
  effort to predict the arrival times of the ICMEs and their shocks
  into the Earth's vicinity, but still the current accuracy in their
  arrival time to Earth of few hours needs further ramification,
  in particular for operational purposes. White light images from the
  STEREO coronagraphs and heliospheric imagers provide an early detection
  of coronal mass ejections (CMEs) and ICMEs. In February 6, 2011,
  spacecrafts A and B were 180 degrees apart, each one looking down on a
  different hemisphere of the Sun and therefore they view from the side
  Earth-directed events, allowing a better determination of the physical
  parameters of the events and their kinematics in particular. We take
  advantage of this configuration and determine the kinematics of the
  CMEs and ICMEs of Feb 15th (01:56), March 7th (19:43) and June 21st
  (16:03 UT), 2011. These events have an interplanetary counterpart with
  Earth arrivals in Feb 18th (00:40 UT), March 10th (05:45 UT) and Jun
  23rd (02:18 UT) respectively, as observed by the ACE spacecraft. We
  perform 3D fittings of the CME-ICME-shock systems viewed by COR1, COR2
  HI1 and HI2 to deduce their kinematics and we use our measurements to
  constrain an analytical model of ICME and shock propagation from the
  Sun to Earth and compare with the in-situ arrival times to Earth's
  orbit. This model is applied where the dynamic pressure parameter
  dominates the solar wind dynamics and it is focused on the role of
  the transmission of momentum in the ICME-shock system.

Title: Multi-wavelength Observations of a Metric Type-II Event
Authors: Alissandrakis, C.; Nindos, A.; Patsourakos, S.; Hillaris,
   Al.; Artemis Group
Bibcode: 2012hell.conf....6A
Altcode:
  We have studied a complex metric radio event,observed with the ARTEMIS
  radiospectrogarph on February 12, 2010. The event was associated with
  a surge observed at 195 and 304 A and with a coronal mass ejection
  observed by STEREO A and B instruments near the East wnd West limbs
  respectively. On the disk the event was observed at 10 frequencies by
  the Nancay Radioheliograph (NRH), in H-alpha by the Catania observatory
  and in soft x-rays by GOES SXI. We combined these data, together with
  MDI longitudinal magnetic field, to get as complete a picture of the
  event as possible. Our emphasis is on two type-II bursts that occured
  near respective maxima in the GOES light curves. The first, associated
  with the main peak of the event, showed a clear foundamental-harmonic
  structure, while the emission of the second consisted of three
  well-separated bands. Using positional infornation for the type-IIs
  from the NRH we explore their possible association with the surge,
  the coronal front and the CME. We also studied fine structured and
  foundamental harmonic structure in the metric dynamic spectrum.

Title: Constraining a Model for EUV Wave Formation with SDO and
    STEREO Quadrature Observations
Authors: Patsourakos, S.; Vourlidas, A.; Olmedo, O.
Bibcode: 2012hell.conf....7P
Altcode:
  The generation mechanism(s) of large-scale propagating intensity fronts
  seen in the EUV, often called EUV waves, in association with impulsive
  Coronal Mass Ejection (CMEs) is currently a matter of debate. The strong
  lateral expansion which some impulsive CMEs undergo during their early
  phases, when they are observed in the inner corona by EUV imagers, is
  one possible mechanism for the generation of EUV waves. One impulsive
  CME - EUV wave pair was observed during 15 February 2011 in quadrature
  by SDO and STEREO. The source active region was close to disk center
  as seen by SDO and at the limb as seen by STEREO. This configuration
  allowed us to determine the kinematics of the EUV wave and of the
  early EUV CME by AIA/SDO and EUVI/STEREO respectively. The detailed
  kinematics of the early EUV CME (height and radius evolution of the
  erupting flux) were then used to constrain a simple model of EUV wave
  formation, invoking the erupting flux as the wave driver. The ground
  tracks of the EUV wave as predicted by this data-driven model were
  then compared with those of the observed wave.

Title: Determination of temperature maps of EUV coronal hole jets
Authors: Nisticò, Giuseppe; Patsourakos, Spiros; Bothmer, Volker;
   Zimbardo, Gaetano
Bibcode: 2011AdSpR..48.1490N
Altcode:
  Coronal hole jets are fast ejections of plasma occurring within
  coronal holes, observed at Extreme-UltraViolet (EUV) and X-ray
  wavelengths. Recent observations of jets by the STEREO and Hinode
  missions show that they are transient phenomena which occur at much
  higher rates than large-scale impulsive phenomena like flares and
  Coronal Mass Ejections (CMEs). In this paper we describe some typical
  characteristics of coronal jets observed by the SECCHI instruments
  of STEREO spacecraft. We show an example of 3D reconstruction of
  the helical structure for a south pole jet, and present how the
  angular distribution of the jet position angles changes from the
  Extreme-UltraViolet-Imager (EUVI) field of view to the CORonagraph1
  (COR1) (height ∼2.0 R<SUB>⊙</SUB> heliocentric distance) field
  of view. Then we discuss a preliminary temperature determination for
  the jet plasma by using the filter ratio method at 171 and 195 Å and
  applying a technique for subtracting the EUV background radiation. The
  results show that jets are characterized by electron temperatures
  ranging between 0.8 and 1.3 MK. We present the thermal structure of
  the jet as temperature maps and we describe its thermal evolution.

Title: Euv Imaging Of Shock Formation In The Low Corona With Sdo/aia
Authors: Vourlidas, Angelos; Patsourakos, S.; Kouloumvakos, T.
Bibcode: 2011SPD....42.0907V
Altcode: 2011BAAS..43S.0907V
  Shock generation in the low corona has long been inferred by spectral
  observations of drifting so-called type-II radio emission in the
  metric wavelengths. Type-IIs occur with coronal mass ejections (CMEs)
  and/or flares but not consistently. Therefore, the exact relationship
  has been difficult to pin down, mostly because of the lack of radio
  imaging capability and of the low cadence of EUV observations in the
  low corona during the flare/CME formation. The advent of ultra-high
  observations from the AIA imagers has changed all that. In this talk,
  we present several direct observations of shock formation in the EUV
  and their association to the accompanying type-IIs. We will show that
  the coronal expansion driven by the formation of the CME ejecta is
  responsible for both EUV and radio emissions.

Title: Erratum: "Comprehensive Analysis of Coronal Mass
    Ejection Mass and Energy Properties Over a Full Solar Cycle" <A
    href="/abs/2010ApJ...722.1522V">(2010, ApJ, 722, 1522)</A>
Authors: Vourlidas, A.; Howard, R. A.; Esfandiari, E.; Patsourakos,
   S.; Yashiro, S.; Michalek, G.
Bibcode: 2011ApJ...730...59V
Altcode:
  No abstract at ADS

Title: Evidence for a current sheet forming in the wake of a coronal
    mass ejection from multi-viewpoint coronagraph observations
Authors: Patsourakos, S.; Vourlidas, A.
Bibcode: 2011A&A...525A..27P
Altcode: 2010arXiv1010.0323P
  Context. Ray-like features observed by coronagraphs in the wake
  of coronal mass ejections (CMEs) are sometimes interpreted as the
  white light counterparts of current sheets (CSs) produced by the
  eruption. The 3D geometry of these ray-like features is largely
  unknown and its knowledge should clarify their association to the
  CS and place constraints on CME physics and coronal conditions. <BR
  /> Aims: If these rays are related to field relaxation behind CMEs,
  therefore representing current sheets, then they should be aligned to
  the CME axis. With this study we test these important implications for
  the first time. <BR /> Methods: An example of such a post-CME ray was
  observed by various coronagraphs, including these of the Sun Earth
  Connection Coronal and Heliospheric investigation (SECCHI) onboard
  the Solar Terrestrial Relations Observatory (STEREO) twin spacecraft
  and the Large Angle Spectrometric Coronagraph (LASCO) onboard the
  Solar and Heliospheric Observatory (SOHO). The ray was observed in
  the aftermath of a CME which occurred on 9 April 2008. The twin STEREO
  spacecraft were separated by about 48° on that day. This significant
  separation combined with a third “eye” view supplied by LASCO allow
  for a truly multi-viewpoint observation of the ray and of the CME. We
  applied 3D forward geometrical modeling to the CME and to the ray as
  simultaneously viewed by SECCHI-A and B and by SECCHI-A and LASCO,
  respectively. <BR /> Results: We found that the ray can be approximated
  by a rectangular slab, nearly aligned with the CME axis, and much
  smaller than the CME in both terms of thickness and depth (≈0.05
  and 0.15 R<SUB>⊙</SUB> respectively). The ray electron density and
  temperature were substantially higher than their values in the ambient
  corona. We found that the ray and CME are significantly displaced
  from the associated post-CME flaring loops. <BR /> Conclusions:
  The properties and location of the ray are fully consistent with
  the expectations of the standard CME theories for post-CME current
  sheets. Therefore, our multi-viewpoint observations supply strong
  evidence that the observed post-CME ray is indeed related to a post-CME
  current sheet. <P />Movies are only available in electronic form at
  <A href="http://www.aanda.org">http://www.aanda.org</A>

Title: Constraining the Initiation and Early Evolution of CMEs
Authors: Patsourakos, Spiros
Bibcode: 2011sswh.book...73P
Altcode:
  No abstract at ADS

Title: The Genesis of an Impulsive CME observed by AIA on SDO
Authors: Patsourakos, S.; Vourlidas, A.; Stenborg, G.
Bibcode: 2010AGUFMSH14A..03P
Altcode:
  Understanding the first moments in the life-time of Coronal Mass
  Ejections (CMEs), i.e. their genesis, represents possibly the key to
  unlock the physical processes responsible for their initiation. After
  this critical interval, which could last as little as few minutes for
  the most impulsive events, differences between various CME models become
  minimal. The recent launch of the SDO mission and the availability of
  high-quality EUV imaging from AIA in particular, opened a new avenue
  into CME initiation investigations with its unprecedented image cadence
  and multi-wavelength simultaneous coverage. We here report on AIA
  observations of an impulsive CME-flare-EUV wave event which took place
  during 13 June 2010. All the important dynamics (e.g., rise phase of
  the flare, impulsive acceleration of the CME) had a duration of only
  10 minutes making this event a perfect showcase event for AIA. Taking
  advantage of the unique aspects of AIA data (12 sec cadence and 7
  different EUV channels) we present a detailed analysis of this event
  which includes: (1) its kinematic behavior (acceleration profile);
  (2) radial and expansion speeds; (3) relationships between (1) and (2)
  with the flare energy release; (4) multi-temperature evolution of the
  early CME. All the above supply new strong constraints for the physics
  of impulsive CMEs.

Title: The Genesis of an Impulsive Coronal Mass Ejection Observed
    at Ultra-high Cadence by AIA on SDO
Authors: Patsourakos, S.; Vourlidas, A.; Stenborg, G.
Bibcode: 2010ApJ...724L.188P
Altcode: 2010arXiv1010.5234P
  The study of fast, eruptive events in the low solar corona is one
  of the science objectives of the Atmospheric Imaging Assembly (AIA)
  imagers on the recently launched Solar Dynamics Observatory (SDO), which
  take full disk images in 10 wavelengths with arcsecond resolution and
  12 s cadence. We study with AIA the formation of an impulsive coronal
  mass ejection (CME) which occurred on 2010 June 13 and was associated
  with an M1.0 class flare. Specifically, we analyze the formation of
  the CME EUV bubble and its initial dynamics and thermal evolution in
  the low corona using AIA images in three wavelengths (171 Å, 193 Å,
  and 211 Å). We derive the first ultra-high cadence measurements
  of the temporal evolution of the CME bubble aspect ratio (=bubble
  height/bubble radius). Our main result is that the CME formation
  undergoes three phases: it starts with a slow self-similar expansion
  followed by a fast but short-lived (~70 s) period of strong lateral
  overexpansion which essentially creates the CME. Then the CME undergoes
  another phase of self-similar expansion until it exits the AIA field of
  view. During the studied interval, the CME height-time profile shows a
  strong, short-lived, acceleration followed by deceleration. The lateral
  overexpansion phase coincides with the deceleration phase. The impulsive
  flare heating and CME acceleration are closely coupled. However,
  the lateral overexpansion of the CME occurs during the declining
  phase and is therefore not linked to flare reconnection. In addition,
  the multi-thermal analysis of the bubble does not show significant
  evidence of temperature change.

Title: Simulations of Overexpanding CME Cavities
Authors: Kliem, B.; Forbes, T.; Vourlidas, A.; Patsourakos, S.
Bibcode: 2010AGUFMSH51A1661K
Altcode:
  Coronal mass ejection (CME) cavities seen in white-light coronagraphs
  expand nearly self similarly in the outer corona and inner solar
  wind. Little is known about their initial expansion in the inner
  corona. A two-phase evolution, consisting of an initial overexpansion
  up to a heliocentric front height of about 1.5 solar radii, followed by
  nearly self-similar expansion, was recently discovered in STEREO/SECCHI
  observations of a fast CME (Patsourakos et al. 2010). The overexpansion
  is expressed as a decrease of the cavity aspect ratio (center height
  by radius) by at least a factor of 2 during the rise phase of the
  main CME acceleration. We present MHD simulations of erupting flux
  ropes that show the initial overexpansion of a cavity in line with
  the observed evolution. The contributions of ideal-MHD expansion and
  of magnetic reconnection to the growth of the flux rope and cavity
  in the simulations will be quantified to identify the primary cause
  of the overexpansion. This assesses the diagnostic potential of the
  overexpansion for the change of flux rope current and the role of
  magnetic reconnection in the early evolution of CMEs.

Title: The Birth of Coronal Mass Ejections As Seen by STEREO and SDO
Authors: Vourlidas, A.; Patsourakos, S.
Bibcode: 2010AGUFMSH21C..07V
Altcode:
  Despite observations of thousands of coronal mass ejections (CMEs),
  the details of their formation still elude us. Impulsive CMEs, in
  particular, originate low in the corona, and form within 10-15 mins
  while accelerating rapidly. This region of the corona is regularly
  observed by EUV imagers but the rapid CME evolution requires high
  cadence and relatively large fields of view. Thanks to the operation of
  the STEREO and SDO missions, we are currently in a unique position to
  address the problem of CME formation. The two missions provide almost
  simultaneous observations from three viewpoints with 3 EUV imagers. The
  EUV instruments observe in the same (or similar) channels and have
  highly complimentary cadences and fields of view. In this paper, we
  discuss a coherent picture of the birth of CMEs based on a study of the
  first few-minute evolution of several impulsive CMEs. These CMEs seem
  to first undergo an non-linear expansion followed by a self-similar
  phase. We discuss the implication for CME initiation models.

Title: Toward understanding the early stages of an impulsively
    accelerated coronal mass ejection. SECCHI observations
Authors: Patsourakos, S.; Vourlidas, A.; Kliem, B.
Bibcode: 2010A&A...522A.100P
Altcode: 2010arXiv1008.1171P
  Context. The expanding magnetic flux in coronal mass ejections (CMEs)
  often forms a cavity. Studies of CME cavities have so far been limited
  to the pre-event configuration to evolved CMEs at great heights, and
  to two-dimensional imaging data. <BR /> Aims: Quantitative analysis of
  three-dimensional cavity evolution at CME onset can reveal information
  that is relevant to the genesis of the eruption. <BR /> Methods:
  A spherical model was simultaneously fit to Solar Terrestrial
  Relations Observatory (STEREO) Extreme Ultraviolet Imager (EUVI)
  and Inner Coronagraph (COR1) data of an impulsively accelerated CME
  on 25 March 2008, which displays a well-defined extreme ultraviolet
  (EUV) and white-light cavity of nearly circular shape already at low
  heights h ≈ 0.2 R_⊙. The center height h(t) and radial expansion
  r(t) of the cavity were obtained in the whole height range of the main
  acceleration. We interpret them as the axis height and as a quantity
  proportional to the minor radius of a flux rope. <BR /> Results:
  The three-dimensional expansion of the CME exhibits two phases in
  the course of its main upward acceleration. From the first h and r
  data points, taken shortly after the onset of the main acceleration,
  the erupting flux shows an overexpansion compared to its rise, as
  expressed by the decrease in the aspect ratio from κ = h/r ≈ 3
  to κ ≈ (1.5-2). This phase is approximately coincident with the
  impulsive rise in the acceleration and is followed by a phase of very
  gradual change in the aspect ratio (a nearly self-similar expansion)
  toward κ ~ 2.5 at h ~ 10 R_⊙. The initial overexpansion of the CME
  cavity can be caused by flux conservation around a rising flux rope
  of decreasing axial current and by the addition of flux to a growing,
  or by even newly formed, flux rope by magnetic reconnection. Further
  analysis will be required to decide which of these contributions is
  dominant. The data also suggest that the horizontal component of the
  impulsive cavity expansion (parallel to the solar surface) triggers the
  associated EUV wave, which subsequently detaches from the CME volume.

Title: Comprehensive Analysis of Coronal Mass Ejection Mass and
    Energy Properties Over a Full Solar Cycle
Authors: Vourlidas, A.; Howard, R. A.; Esfandiari, E.; Patsourakos,
   S.; Yashiro, S.; Michalek, G.
Bibcode: 2010ApJ...722.1522V
Altcode: 2010arXiv1008.3737V
  The LASCO coronagraphs, in continuous operation since 1995, have
  observed the evolution of the solar corona and coronal mass ejections
  (CMEs) over a full solar cycle with high-quality images and regular
  cadence. This is the first time that such a data set becomes available
  and constitutes a unique resource for the study of CMEs. In this paper,
  we present a comprehensive investigation of the solar cycle dependence
  on the CME mass and energy over a full solar cycle (1996-2009) including
  the first in-depth discussion of the mass and energy analysis methods
  and their associated errors. Our analysis provides several results
  worthy of further studies. It demonstrates the possible existence of
  two event classes: "normal" CMEs reaching constant mass for &gt;10
  R <SUB>sun</SUB> and "pseudo"-CMEs which disappear in the C3 field
  of view. It shows that the mass and energy properties of CME reach
  constant levels and therefore should be measured only above ~10 R
  <SUB>sun</SUB>. The mass density (g/R <SUP>2</SUP> <SUB>sun</SUB>)
  of CMEs varies relatively little (&lt; order of magnitude) suggesting
  that the majority of the mass originates from a small range in coronal
  heights. We find a sudden reduction in the CME mass in mid-2003 which
  may be related to a change in the electron content of the large-scale
  corona and we uncover the presence of a 6 month periodicity in the
  ejected mass from 2003 onward.

Title: Observational features of equatorial coronal hole jets
Authors: Nisticò, G.; Bothmer, V.; Patsourakos, S.; Zimbardo, G.
Bibcode: 2010AnGeo..28..687N
Altcode: 2010arXiv1002.2181N
  Collimated ejections of plasma called "coronal hole jets" are commonly
  observed in polar coronal holes. However, such coronal jets are not only
  a specific features of polar coronal holes but they can also be found
  in coronal holes appearing at lower heliographic latitudes. In this
  paper we present some observations of "equatorial coronal hole jets"
  made up with data provided by the STEREO/SECCHI instruments during
  a period comprising March 2007 and December 2007. The jet events
  are selected by requiring at least some visibility in both COR1 and
  EUVI instruments. We report 15 jet events, and we discuss their main
  features. For one event, the uplift velocity has been determined as
  about 200 km s<SUP>-1</SUP>, while the deceleration rate appears to
  be about 0.11 km s<SUP>-2</SUP>, less than solar gravity. The average
  jet visibility time is about 30 min, consistent with jet observed in
  polar regions. On the basis of the present dataset, we provisionally
  conclude that there are not substantial physical differences between
  polar and equatorial coronal hole jets.

Title: Extreme Ultraviolet Observations and Analysis of
    Micro-Eruptions and Their Associated Coronal Waves
Authors: Podladchikova, O.; Vourlidas, A.; Van der Linden, R. A. M.;
   Wülser, J. -P.; Patsourakos, S.
Bibcode: 2010ApJ...709..369P
Altcode:
  The Solar Terrestrial Relations Observatory EUV telescopes have
  uncovered small-scale eruptive events, tentatively referred to as
  "mini-CMEs" because they exhibit morphologies similar to large-scale
  coronal mass ejections (CMEs). Coronal waves and widespread diffuse
  dimmings followed by the expansion of the coronal waves are the most
  brightly manifestations of large-scale CMEs. The high temporal and
  spatial resolution of the EUV data allows us to detect and analyze
  these eruptive events, to resolve their fine structure, and to show that
  the observed "mini-waves" have a strong similarity to the large-scale
  "EIT' waves. Here, we analyze a micro-event observed on 2007 October 17
  by the Sun Earth Connection Coronal and Heliospheric Investigation EUV
  Imager (EUVI) in 171 Å (Fe IX) with a 2.5 minute cadence. The mini-CME
  differs from its large-scale counterparts by having smaller geometrical
  size, a shorter lifetime, and reduced intensity of coronal wave and
  dimmings. The small-scale coronal wave develops from micro-flaring
  sites and propagate up to a distance of 40,000 km in a wide angular
  sector of the quiet Sun over 20 minutes. The area of the small-scale
  dimming is two orders of magnitude smaller than for large-scale
  events. The average speed of the small-scale coronal wave studied is
  14 km s<SUP>-1</SUP>. Our observations give strong indications that
  small-scale EUV coronal waves associated with the micro-eruptions
  propagate in the form of slow mode waves almost perpendicular to the
  background magnetic field.

Title: The Structure and Dynamics of the Upper Chromosphere and Lower
    Transition Region as Revealed by the Subarcsecond VAULT Observations
Authors: Vourlidas, A.; Sanchez Andrade-Nuño, B.; Landi, E.;
   Patsourakos, S.; Teriaca, L.; Schühle, U.; Korendyke, C. M.;
   Nestoras, I.
Bibcode: 2010SoPh..261...53V
Altcode: 2009arXiv0912.2272V
  The Very high Angular resolution ULtraviolet Telescope (VAULT) is a
  sounding rocket payload built to study the crucial interface between
  the solar chromosphere and the corona by observing the strongest line
  in the solar spectrum, the Ly α line at 1216 Å. In two flights, VAULT
  succeeded in obtaining the first ever subarcsecond ( 0.5\hbox{$^''$}
  ) images of this region with high sensitivity and cadence. Detailed
  analyses of those observations contributed significantly to new
  ideas about the nature of the transition region. Here, we present
  a broad overview of the Ly α atmosphere as revealed by the VAULT
  observations and bring together past results and new analyses from the
  second VAULT flight to create a synthesis of our current knowledge
  of the high-resolution Ly α Sun. We hope that this work will serve
  as a good reference for the design of upcoming Ly α telescopes and
  observing plans.

Title: The nature of micro CMEs within coronal holes
Authors: Bothmer, Volker; Nistico, Giuseppe; Zimbardo, Gaetano;
   Patsourakos, Spiros; Bosman, Eckhard
Bibcode: 2010cosp...38.2840B
Altcode: 2010cosp.meet.2840B
  Whilst investigating the origin and characteristics of coronal jets
  and large-scale CMEs identi-fied in data from the SECCHI (Sun Earth
  Connection Coronal and Heliospheric Investigation) instrument suites
  on board the two STEREO satellites, we discovered transient events
  that originated in the low corona with a morphology resembling that of
  typical three-part struc-tured coronal mass ejections (CMEs). However,
  the CMEs occurred on considerably smaller spatial scales. In this
  presentation we show evidence for the existence of small-scale CMEs
  from inside coronal holes and present quantitative estimates of their
  speeds and masses. We interprete the origin and evolution of micro
  CMEs as a natural consequence of the emergence of small-scale magnetic
  bipoles related to the Sun's ever changing photospheric magnetic flux
  on various scales and their interactions with the ambient plasma and
  magnetic field. The analysis of CMEs is performed within the framework
  of the EU Erasmus and FP7 SOTERIA projects.

Title: Heatwaves on the Sun
Authors: Robbrecht, Eva; Wang, Yi-Ming; Vourlidas, Angelos;
   Patsourakos, Spiros
Bibcode: 2010cosp...38.1791R
Altcode: 2010cosp.meet.1791R
  Dimmings have been observed for several years now, but their
  interpretation is still problematic. A dimming is an observational
  effect of diminished brightness with respect to pre-event images, which
  is usually interpreted as a density depletion. But not all dimmings are
  what they appear to be. In this paper we report on an unusual "dimming
  wave" which is not a density depletion but rather a heat wave. Thanks
  to the stereoscopic view from the SECCHI/EUVI imagers we are able not
  only to uncover the nature of the wave, but also to understand its
  three dimensional evolution and its relationship to a quiet sun CME.

Title: What Is the Nature of EUV Waves? First STEREO 3D Observations
    and Comparison with Theoretical Models
Authors: Patsourakos, S.; Vourlidas, A.; Wang, Y. M.; Stenborg, G.;
   Thernisien, A.
Bibcode: 2009SoPh..259...49P
Altcode: 2009arXiv0905.2189P
  One of the major discoveries of the Extreme ultraviolet Imaging
  Telescope (EIT) on SOHO was the intensity enhancements propagating
  over a large fraction of the solar surface. The physical origin(s)
  of the so-called EIT waves is still strongly debated with either
  wave (primarily fast-mode MHD waves) or nonwave (pseudo-wave)
  interpretations. The difficulty in understanding the nature of EUV waves
  lies in the limitations of the EIT observations that have been used
  almost exclusively for their study. They suffer from low cadence and
  single temperature and viewpoint coverage. These limitations are largely
  overcome by the SECCHI/EUVI observations onboard the STEREO mission. The
  EUVI telescopes provide high-cadence, simultaneous multitemperature
  coverage and two well-separated viewpoints. We present here the first
  detailed analysis of an EUV wave observed by the EUVI disk imagers on 7
  December 2007 when the STEREO spacecraft separation was ≈ 45°. Both a
  small flare and a coronal mass ejection (CME) were associated with the
  wave. We also offer the first comprehensive comparison of the various
  wave interpretations against the observations. Our major findings are
  as follows: (1) High-cadence (2.5-minute) 171 Å images showed a strong
  association between expanding loops and the wave onset and significant
  differences in the wave appearance between the two STEREO viewpoints
  during its early stages; these differences largely disappeared later;
  (2) the wave appears at the active region periphery when an abrupt
  disappearance of the expanding loops occurs within an interval of 2.5
  minutes; (3) almost simultaneous images at different temperatures
  showed that the wave was most visible in the 1 - 2 MK range and
  almost invisible in chromospheric/transition region temperatures; (4)
  triangulations of the wave indicate it was rather low lying (≈ 90
  Mm above the surface); (5) forward-fitting of the corresponding CME as
  seen by the COR1 coronagraphs showed that the projection of the best-fit
  model on the solar surface was inconsistent with the location and size
  of the co-temporal EUV wave; and (6) simulations of a fast-mode wave
  were found in good agreement with the overall shape and location of the
  observed wave. Our findings give significant support for a fast-mode
  interpretation of EUV waves and indicate that they are probably
  triggered by the rapid expansion of the loops associated with the CME.

Title: Characteristics of EUV Coronal Jets Observed with STEREO/SECCHI
Authors: Nisticò, G.; Bothmer, V.; Patsourakos, S.; Zimbardo, G.
Bibcode: 2009SoPh..259...87N
Altcode: 2009arXiv0906.4407N
  In this paper we present the first comprehensive statistical study
  of EUV coronal jets observed with the SECCHI (Sun Earth Connection
  Coronal and Heliospheric Investigation) imaging suites of the two
  STEREO spacecraft. A catalogue of 79 polar jets is presented, identified
  from simultaneous EUV and white-light coronagraph observations, taken
  during the time period March 2007 to April 2008, when solar activity
  was at a minimum. The twin spacecraft angular separation increased
  during this time interval from 2 to 48 degrees. The appearances of
  the coronal jets were always correlated with underlying small-scale
  chromospheric bright points. A basic characterization of the morphology
  and identification of the presence of helical structure were established
  with respect to recently proposed models for their origin and temporal
  evolution. Though each jet appeared morphologically similar in the
  coronagraph field of view, in the sense of a narrow collimated outward
  flow of matter, at the source region in the low corona the jet showed
  different characteristics, which may correspond to different magnetic
  structures. A classification of the events with respect to previous
  jet studies shows that amongst the 79 events there were 37 Eiffel
  tower-type jet events, commonly interpreted as a small-scale (∼35
  arc sec) magnetic bipole reconnecting with the ambient unipolar open
  coronal magnetic fields at its loop tops, and 12 lambda-type jet events
  commonly interpreted as reconnection with the ambient field happening at
  the bipole footpoints. Five events were termed micro-CME-type jet events
  because they resembled the classical coronal mass ejections (CMEs) but
  on much smaller scales. The remaining 25 cases could not be uniquely
  classified. Thirty-one of the total number of events exhibited a helical
  magnetic field structure, indicative for a torsional motion of the jet
  around its axis of propagation. A few jets are also found in equatorial
  coronal holes. In this study we present sample events for each of
  the jet types using both, STEREO A and STEREO B, perspectives. The
  typical lifetimes in the SECCHI/EUVI (Extreme UltraViolet Imager)
  field of view between 1.0 to 1.7 R<SUB>⊙</SUB> and in SECCHI/COR1
  field of view between 1.4 to 4 R<SUB>⊙</SUB> are obtained, and the
  derived speeds are roughly estimated. In summary, the observations
  support the assumption of continuous small-scale reconnection as an
  intrinsic feature of the solar corona, with its role for the heating of
  the corona, particle acceleration, structuring and acceleration of the
  solar wind remaining to be explored in more detail in further studies.

Title: Estimating the Chromospheric Absorption of Transition Region
    Moss Emission
Authors: De Pontieu, Bart; Hansteen, Viggo H.; McIntosh, Scott W.;
   Patsourakos, Spiros
Bibcode: 2009ApJ...702.1016D
Altcode: 2009arXiv0907.1883D
  Many models for coronal loops have difficulty explaining the observed
  EUV brightness of the transition region, which is often significantly
  less than theoretical models predict. This discrepancy has been
  addressed by a variety of approaches including filling factors and
  time-dependent heating, with varying degrees of success. Here, we
  focus on an effect that has been ignored so far: the absorption of
  EUV light with wavelengths below 912 Å by the resonance continua
  of neutral hydrogen and helium. Such absorption is expected to occur
  in the low-lying transition region of hot, active region loops that
  is colocated with cool chromospheric features and called "moss" as a
  result of the reticulated appearance resulting from the absorption. We
  use cotemporal and cospatial spectroheliograms obtained with the Solar
  and Heliospheric Observatory/SUMER and Hinode/EIS of Fe XII 1242 Å,
  195 Å, and 186.88 Å, and compare the density determination from
  the 186/195 Å line ratio to that resulting from the 195/1242 Å line
  ratio. We find that while coronal loops have compatible density values
  from these two line pairs, upper transition region moss has conflicting
  density determinations. This discrepancy can be resolved by taking
  into account significant absorption of 195 Å emission caused by
  the chromospheric inclusions in the moss. We find that the amount of
  absorption is generally of the order of a factor of 2. We compare to
  numerical models and show that the observed effect is well reproduced
  by three-dimensional radiative MHD models of the transition region
  and corona. We use STEREO A/B data of the same active region and find
  that increased angles between line of sight and local vertical cause
  additional absorption. Our determination of the amount of chromospheric
  absorption of TR emission can be used to better constrain coronal
  heating models.

Title: No Trace Left Behind: STEREO Observation of a Coronal Mass
    Ejection Without Low Coronal Signatures
Authors: Robbrecht, Eva; Patsourakos, Spiros; Vourlidas, Angelos
Bibcode: 2009ApJ...701..283R
Altcode: 2009arXiv0905.2583R
  The availability of high-quality synoptic observations of the
  extreme-ultraviolet (EUV) and visible corona during the SOHO mission
  has advanced our understanding of the low corona manifestations of
  coronal mass ejections (CMEs). The EUV imager/white light coronagraph
  connection has been proven so powerful, it is routinely assumed that if
  no EUV signatures are present when a CME is observed by a coronagraph,
  then the event must originate behind the visible limb. This assumption
  carries strong implications for space weather forecasting but has not
  been put to the test. This paper presents the first detailed analysis
  of a frontside, large-scale CME that has no obvious counterparts in
  the low corona as observed in EUV and Hα wavelengths. The event was
  observed by the SECCHI instruments onboard the STEREO mission. The
  COR2A coronagraph observed a slow flux-rope-type CME, while an
  extremely faint partial halo was observed in COR2B. The event evolved
  very slowly and is typical of the streamer-blowout CME class. EUVI A
  171 Å images show a concave feature above the east limb, relatively
  stable for about two days before the eruption, when it rises into
  the coronagraphic fields and develops into the core of the CME. None
  of the typical low corona signatures of a CME (flaring, EUV dimming,
  filament eruption, waves) were observed in the EUVI B images, which we
  attribute to the unusually large height from which the flux rope lifted
  off. This interpretation is supported by the CME mass measurements
  and estimates of the expected EUV dimming intensity. Only thanks to
  the availability of the two viewpoints we were able to identify the
  likely source region. The event originated along a neutral line over
  the quiet-Sun. No active regions were present anywhere on the visible
  (from STEREO B) face of the disk. Leaving no trace behind on the solar
  disk, this observation shows unambiguously that a CME eruption does
  not need to have clear on-disk signatures. Also it sheds light on the
  question of "mystery" geomagnetic storms, storms without clear solar
  origin (formerly called problem storms). We discuss the implications
  for space weather monitoring. Preliminary inspection of STEREO data
  indicates that events like this are not uncommon, particularly during
  the ongoing period of deep solar minimum.

Title: "Extreme Ultraviolet Waves" are Waves: First Quadrature
    Observations of an Extreme Ultraviolet Wave from STEREO
Authors: Patsourakos, Spiros; Vourlidas, Angelos
Bibcode: 2009ApJ...700L.182P
Altcode: 2009arXiv0905.2164P
  The nature of coronal mass ejection (CME)-associated low corona
  propagating disturbances, "extreme ultraviolet (EUV) waves," has been
  controversial since their discovery by EIT on SOHO. The low-cadence,
  single-viewpoint EUV images and the lack of simultaneous inner corona
  white-light observations have hindered the resolution of the debate
  on whether they are true waves or just projections of the expanding
  CME. The operation of the twin EUV imagers and inner corona coronagraphs
  aboard STEREO has improved the situation dramatically. During early
  2009, the STEREO Ahead (STA) and Behind (STB) spacecrafts observed
  the Sun in quadrature having a ≈90° angular separation. An EUV
  wave and CME erupted from active region 11012, on February 13, when
  the region was exactly at the limb for STA and hence at disk center
  for STB. The STEREO observations capture the development of a CME
  and its accompanying EUV wave not only with high cadence but also in
  quadrature. The resulting unprecedented data set allowed us to separate
  the CME structures from the EUV wave signatures and to determine without
  doubt the true nature of the wave. It is a fast-mode MHD wave after all.

Title: Spectroscopic Observations of Hot Lines Constraining Coronal
    Heating in Solar Active Regions
Authors: Patsourakos, S.; Klimchuk, J. A.
Bibcode: 2009ApJ...696..760P
Altcode: 2009arXiv0903.3880P
  Extreme-ultraviolet observations of warm coronal loops suggest that they
  are bundles of unresolved strands that are heated impulsively to high
  temperatures by nanoflares. The plasma would then have the observed
  properties (e.g., excess density compared with static equilibrium)
  when it cools into the 1-2MK range. If this interpretation is correct,
  then very hot emission should be present outside of proper flares. It
  is predicted to be very faint, however. A critical element for proving
  or refuting this hypothesis is the existence of hot, yet faint plasmas
  which should be at amounts predicted by impulsive heating models. We
  report on the first comprehensive spectroscopic study of hot plasmas
  in active regions (ARs). Data from the Extreme-ultraviolet Imaging
  Spectrometer on Hinode were used to construct emission measure (EM)
  distributions in quiescent ARs in the 1-5 MK temperature range. The
  distributions are flat or slowly increasing up to approximately 3 MK
  and then fall off rapidly at higher temperatures. We show that AR models
  based on impulsive heating can reproduce the observed EM distributions
  relatively well. Our results provide strong new evidence that coronal
  heating is impulsive in nature.

Title: Spectroscopic Observations of Hot Lines Constraining Coronal
    Heating in Solar Active Regions
Authors: Patsourakos, Spiros; Klimchuk, J. A.
Bibcode: 2009SPD....40.1211P
Altcode:
  EUV observations of warm coronal loops suggest that they are bundles of
  unresolved strands that are heated impulsively to high temperatures by
  nanoflares. The plasma would then have the observed properties (e.g.,
  excess density compared to static equilibrium) when it cools into
  the 1-2 MK range. If this interpretation is correct, then very hot
  emission should be present outside of proper flares. It is predicted
  to be vey faint, however. A critical element for proving or refuting
  this hypothesis is the existence of hot, very faint plasmas which
  should be at amounts predicted by impulsive heating. We report on
  the first comprehensive spectroscopic study of hot plasmas in active
  regions. Data from the EIS spectrometer on Hinode were used to construct
  emission measure distributions in quiescent active regions in the 1-5 MK
  temperature range. The distributions are flat or slowly increasing up to
  approximately 3 MK and then fall off rapidly at higher temperatures. We
  show that active region models based on impulsive heating can reproduce
  the observed EM distributions relatively well. Our results provide
  strong new evidence that coronal heating is impulsive in nature.

Title: No trace left behind: STEREO Observation of a Coronal Mass
    Ejection Lacking Low Coronal Signatures
Authors: Vourlidas, Angelos; Robbrecht, E.; Patsourakos, S.
Bibcode: 2009SPD....40.2104V
Altcode:
  The availability of high quality synoptic observations of the EUV and
  visible corona during the SOHO mission has advanced our understanding
  of the low corona manifestations of CMEs. The EUV imager/White light
  coronagraph connection has been proven so powerful, it is routinely
  assumed that if no EUV signatures are present when a CME is observed
  by a coronagraph, then the event must originate behind the visible
  limb. This assumption carries strong implications for space weather
  forecasting but has not been put to the test. This paper presents the
  first detailed analysis of a frontside, large-scale CME that has no
  obvious counterparts in the low corona. The event was observed by the
  SECCHI instruments on the STEREO mission. The COR2A coronagraph observed
  the event as a typical flux-rope type CME, while an extremely faint
  partial halo was observed in COR2B. The event evolved very slowly and
  is typical of the streamer-blowout CME class. EUVI-A 171A images show
  a concave feature above the east limb, relatively stable for about
  two days before the eruption, when it rises into the coronagraphic
  fields and develops into the core of the CME. None of the typical low
  corona signatures of a CME (flaring, EUV dimming, filament eruption,
  waves) were observed. Thanks to the two STEREO viewpoints we were able
  to identify the likely source region. The event originated along a
  quiet sun neutral line. No active regions were present anywhere on the
  visible face of the disk. Leaving no trace behind, this observation
  shows unambiguously that a CME eruption does not need to have clear
  on-disk signatures. Also it sheds light on the question of `mystery'
  geomagnetic storms; storms without clear solar origin. Preliminary
  inspection of STEREO data indicates that events like this are not
  uncommon, particularly during the ongoing period of deep solar minimum.

Title: Quadrature STEREO Observations Determine the Nature of
    EUV Waves
Authors: Kliem, Bernhard; Patsourakos, S.; Vourlidas, A.; Ontiveros, V.
Bibcode: 2009SPD....40.2603K
Altcode:
  One of the major discoveries of EIT on SOHO was the observation of
  large-scale EUV intensity disturbances which travel over significant
  fractions of the solar disk. These `EUV waves' are associated with
  CME onsets and can be either an MHD wave triggered by the eruption or
  the footprints of the associated CME, which currently is a subject of
  intense debate. EUV waves are better observed when their source region
  is close to disk center, whereas CME onsets and CMEs in general are
  better observed off-limb. Therefore, simultaneous multi-viewpoint
  observations of EUV waves are best suited to clarify the nature of
  these transients and to determine their true relationship with CMEs. <P
  />We present here the first quadrature STEREO observations of an EUV
  wave. The wave was observed on 2009 February 13 by both satellites,
  which were at a separation of 90 degrees. The wave originated from
  an erupting active region near disk center as seen from SC B and
  propagated over almost the entire visible solar disk. For SC A the
  active region was at the east limb and showed a small erupting bubble,
  expanding impulsively in both radial and lateral directions and inducing
  deflections of nearby and remote coronal structures. We present high
  cadence EUVI and COR1 measurements of both the wave (SC B), and the
  expanding EUV bubble (SC A), and of the resulting white-light CME (SC A;
  COR1). These would allow to quantify for the first time the true sizes
  and expansion characteristics of both the EUV wave and the associated
  CME. <P />Finally, we search for wave-associated features in 3D MHD
  simulations of CME onsets based on ideal MHD instabilities. These are
  compared with the STEREO observations.

Title: STEREO Observations of a post-CME Current Sheet
Authors: Patsourakos, S.; Vourlidas, A.; Stenborg, G.
Bibcode: 2008AGUFMSH13B1552P
Altcode:
  Ray-like features in the wake of Coronal Mass Ejections (CMEs) are
  often interpreted as current sheets produced by the eruption. The 3D
  geometry of such post-CME current sheets is largely unknown and its
  knowledge should place important constraints on CME physics and coronal
  conditions. An example of a post-CME current sheet was observed on April
  9th 2008, in the aftermath of the 'cartwheel' CME, which was observed
  by Hinode, SoHO, STEREO and TRACE. The CME and the corresponding current
  sheet were well-observed by both STEREO spacecraft, which were separated
  by about 48 degrees the day of the event. We present here an analysis
  of the 3D morphology of the current sheet using data from the COR1 and
  COR2 coronagraphs from both STEREO spacecraft. We will attempt various
  forward models (e.g., slabs, cylinders) of the current sheet as seen by
  the COR1 and COR2 coronagraphs from both STEREO spacecraft. This will
  characterize the 3D geometry of the current sheet and more precisely
  its shape and its real width and length. Our forward modeling will also
  supply the radial variation of the density along the current sheet. This
  information will supply some estimates of the temperature and magnetic
  field distributions in and out the current sheet respectively.

Title: First STEREO observation of a quiet sun CME
Authors: Robbrecht, E.; Patsourakos, S.; Vourlidas, A.
Bibcode: 2008AGUFMSH13B1560R
Altcode:
  Streamer-blowouts form a particular class of CMEs characterized by a
  slow rise and swelling of the streamer that can last for days. While
  they are more massive than the average CME, their slow development
  complicates their association with features/activity in the low
  corona and hampers studies on their initiation mechanism(s). This
  paper reports on the first observation from 2 viewpoints of a streamer
  blowout CME. The event was observed by the SECCHI/COR2 A instrument
  as a typical flux-rope type CME, while a very faint partial halo was
  observed in COR2-B. The CME erupted from the east limb in the COR2 A
  field of view. EUVI-171 A images show a bright feature above the limb,
  traveling from the southern hemisphere towards the equator after which
  it slowly rises into the coronagraphic fields of view developing into
  the flux-rope structure CME. At the time of eruption the separation
  between the two STEREO spacecraft is sufficiently large (54 deg) to
  observe the source region face-on in STEREO-B. However, inspection of
  EUVI B data didn't reveal any particular source region, other than the
  quiet sun. No flaring activity could be related to the eruption. This
  observation shows unambiguously that a CME eruption does not necessarily
  have clear on-disk signature. Also it sheds light on the long-standing
  question of the necessity of having a flare for producing a CME. This
  result supplies strong constraints for CME initiation models. This type
  of observation could not have been achieved without the multi-viewpoint
  observations by STEREO.

Title: Comparison of Automated Flare Location Algorithm Results to
    Solar Truth
Authors: Plunkett, S. P.; Newmark, J. S.; Kunkel, V.; Patsourakos,
   S.; McMullin, D. R.; Hill, S. M.
Bibcode: 2008AGUFMSA51A1534P
Altcode:
  Accurate and timely detection of solar flares and determination of
  their heliocentric coordinates are key requirements for space weather
  forecasting. We report the results of a study to compare the results
  of multiple algorithms for automated determination of flare locations
  to "solar truth". The XFL algorithm determines flare locations in near
  real-time using GOES-12 SXI image data, and is triggered by GOES-12 XRS
  flare detections. We also consider H-alpha flare locations reported
  in the FLA data set, and the Latest Events (LEV) locations produced
  by LMSAL, based on GOES-12 SXI or SOHO EIT observations. We compare
  the results of each of these algorithms to solar truth heliocentric
  flare locations determined from analysis of GOES-12 SXI images of
  several hundred flares of C class and higher, during periods of high,
  moderate, and low solar activity between 2003 and 2006. We also compare
  the relative effectiveness of each of these algorithms for determining
  flare locations in near real-time, considering both timeliness and
  accuracy of the reported flare locations.

Title: Observations and analysis of the April 9, 2008 CME using
    STEREO, Hinode TRACE and SoHO data
Authors: Reeves, K. K.; Patsourakos, S.; Stenborg, G.; Miralles, M.;
   Deluca, E.; Forbes, T.; Golub, L.; Kasper, J.; Landi, E.; McKenzie,
   D.; Narukage, N.; Raymond, J.; Savage, S.; Su, Y.; van Ballegooijen,
   A.; Vourlidas, A.; Webb, D.
Bibcode: 2008AGUFMSH12A..04R
Altcode:
  On April 9, 2008 a CME originating from an active region behind the limb
  was well-observed by STEREO, Hinode, TRACE and SoHO. Several interesting
  features connected to this eruption were observed. (1) The interaction
  of the CME with open field lines from a nearby coronal hole appeared
  to cause an abrupt change in the direction of the CME ejecta. (2) The
  prominence material was heated, as evidenced by a change from absorption
  to emission in the EUV wavelengths. (3) Because the active region was
  behind the limb, the X-Ray Telescope on Hinode was able to take long
  enough exposure times to observe a faint current- sheet like structure,
  and it was able to monitor the dynamics of the plasma surrounding this
  structure. This event is also being studied in the context of activity
  that occurred during the Whole Heliosphere Interval (WHI).

Title: Static and Impulsive Models of Solar Active Regions
Authors: Patsourakos, S.; Klimchuk, J. A.
Bibcode: 2008ApJ...689.1406P
Altcode: 2008arXiv0808.2745P
  The physical modeling of active regions (ARs) and of the global corona
  is receiving increasing interest lately. Recent attempts to model ARs
  using static equilibrium models were quite successful in reproducing AR
  images of hot soft X-ray (SXR) loops. They however failed to predict
  the bright extreme-ultraviolet (EUV) warm loops permeating ARs: the
  synthetic images were dominated by intense footpoint emission. We
  demonstrate that this failure is due to the very weak dependence of
  loop temperature on loop length which cannot simultaneously account for
  both hot and warm loops in the same AR. We then consider time-dependent
  AR models based on nanoflare heating. We demonstrate that such models
  can simultaneously reproduce EUV and SXR loops in ARs. Moreover, they
  predict radial intensity variations consistent with the localized core
  and extended emissions in SXR and EUV AR observations, respectively. We
  finally show how the AR morphology can be used as a gauge of the
  properties (duration, energy, spatial dependence, and repetition time)
  of the impulsive heating.

Title: 3D Numerical Simulation of a New Model for Coronal Jets
Authors: Pariat, E.; Antiochos, S.; DeVore, C. R.; Patsourakos, S.
Bibcode: 2008ESPM...12.3.28P
Altcode:
  Recent solar observations with STEREO and HINODE have revealed evidence
  of twisting motions during the evolution of coronal jets. Furthermore,
  the observations indicate that some jets achieve near-Alfvenic
  velocities. Most models of jet are not capable of explaining these
  new observational features. In addition, the impulsiveness of jets,
  manifested as a brief, violent energy release phase in contrast to a
  slow, quasi-static energy storage phase storage, is an issue not easily
  addressed. <P />We will present the results of 3D numerical simulations
  of our model for coronal jets. The simulations were performed with our
  state-of-art adaptive mesh MHD solver ARMS. The basic idea of the model
  is that a jet is due to the release of magnetic twist when a closed
  field region undergoes interchange reconnection with surrounding open
  field. The fast reconnection between open and closed field results
  in the generation of nonlinear Alfven waves that propagate along
  the open field, accelerating plasma upward. We will show how the new
  stereoscopically-observed features of jets can be explained by the
  results of our numerical simulations

Title: Highly Efficient Modeling of Dynamic Coronal Loops
Authors: Klimchuk, J. A.; Patsourakos, S.; Cargill, P. J.
Bibcode: 2008ApJ...682.1351K
Altcode: 2007arXiv0710.0185K
  Observational and theoretical evidence suggests that coronal heating
  is impulsive and occurs on very small cross-field spatial scales. A
  single coronal loop could contain a hundred or more individual strands
  that are heated quasi-independently by nanoflares. It is therefore an
  enormous undertaking to model an entire active region or the global
  corona. Three-dimensional MHD codes have inadequate spatial resolution,
  and one-dimensional (1D) hydrodynamic codes are too slow to simulate
  the many thousands of elemental strands that must be treated in
  a reasonable representation. Fortunately, thermal conduction and
  flows tend to smooth out plasma gradients along the magnetic field,
  so zero-dimensional (0D) models are an acceptable alternative. We
  have developed a highly efficient model called "enthalpy-based thermal
  evolution of loops" (EBTEL), which accurately describes the evolution
  of the average temperature, pressure, and density along a coronal
  strand. It improves significantly on earlier models of this type—in
  accuracy, flexibility, and capability. It treats both slowly varying
  and highly impulsive coronal heating; it provides the time-dependent
  differential emission measure distribution, DEM(T), at the transition
  region footpoints; and there are options for heat flux saturation and
  nonthermal electron beam heating. EBTEL gives excellent agreement with
  far more sophisticated 1D hydrodynamic simulations despite using 4
  orders of magnitude less computing time. It promises to be a powerful
  new tool for solar and stellar studies.

Title: STEREO SECCHI Stereoscopic Observations Constraining the
    Initiation of Polar Coronal Jets
Authors: Patsourakos, S.; Pariat, E.; Vourlidas, A.; Antiochos, S. K.;
   Wuelser, J. P.
Bibcode: 2008ApJ...680L..73P
Altcode: 2008arXiv0804.4862P
  We report on the first stereoscopic observations of polar coronal jets
  made by the EUVI/SECCHI imagers on board the twin STEREO spacecraft. The
  significantly separated viewpoints (~11°) allowed us to infer the 3D
  dynamics and morphology of a well-defined EUV coronal jet for the first
  time. Triangulations of the jet's location in simultaneous image pairs
  led to the true 3D position and thereby its kinematics. Initially the
  jet ascends slowly at ≈10-20 km s<SUP>-1</SUP> and then, after an
  apparent "jump" takes place, it accelerates impulsively to velocities
  exceeding 300 km s<SUP>-1</SUP> with accelerations exceeding the solar
  gravity. Helical structure is the most important geometrical feature
  of the jet which shows evidence of untwisting. The jet structure
  appears strikingly different from each of the two STEREO viewpoints:
  face-on in one viewpoint and edge-on in the other. This provides
  conclusive evidence that the observed helical structure is real and
  does not result from possible projection effects of single-viewpoint
  observations. The clear demonstration of twisted structure in polar jets
  compares favorably with synthetic images from a recent MHD simulation of
  jets invoking magnetic untwisting as their driving mechanism. Therefore,
  the latter can be considered as a viable mechanism for the initiation
  of polar jets.

Title: Hot Spectral Emissions in Quiescent Active Regions and
    Nanoflare Heating
Authors: Patsourakos, S.; Klimchuk, J. A.
Bibcode: 2008AGUSMSP43C..02P
Altcode:
  A leading candidate for the heating of active region (AR) coronal loops
  is the nanoflare model. This model treats coronal loops as collections
  of impulsively heated sub-resolution strands and explains several
  key observational aspects of warm (1-2 MK) coronal loops. However,
  the basic requirement of this model is that the strands initially reach
  very high temperatures of several MK before they cool down to canonical
  coronal temperatures. Therefore, the detection of hot plasmas in AR
  loops represents a stringest test of the nanoflare model. Previous
  work has shown that the best way to observe the postulated hot
  plasmas is by the means of spectroscopic observations in hot lines
  (T &gt; 3 MK). The emission is predicted to be quite faint, but the
  EIS spectrometer onboard Hinode has sufficient sensitivity to allow us
  to perform such a test for the first time. We will present an analysis
  of the emission characteristics of quiescent coronal loops in a number
  of hot lines spanning approximately 3-12 MK (Ni XVII, Ca XV, Fe XVII,
  Ca XVII, Fe XXIII). We will show that hot plasmas are ubiquitous over
  entire active regions, and we will compare the measured intensities
  of both hot and warm lines with predictions of nanoflare models.

Title: 3D Numerical Simulation and Stereoscopic Observations of
    Coronal Jets
Authors: Pariat, E.; Antiochos, S. K.; Patsourakos, S.; DeVore, C. R.
Bibcode: 2008AGUSMSP53A..05P
Altcode:
  Recent solar observations have revealed that coronal jets are a more
  frequent phenomenon than previously believed. It is widely accepted
  that magnetic reconnection is the fundamental mechanism that gives
  rise to the jets. The improved spatial and temporal resolution of
  the STEREO observations in combination with stereoscopy yields new
  insights into the origins of coronal jets, and provides detailed data
  that can be used to test and refine models. We present the results
  of 3D numerical simulations of our model for coronal jets. The
  simulations were performed with our state-of-art adaptive mesh MHD
  solver ARMS. The basic idea of the model is that a jet is due to
  the release of twist as a closed field region undergoes interchange
  reconnection with surrounding open field. The photospheric driven
  evolution of the structure results in the generation of a non linear
  Alfven wave along the open fields. Using stereoscopic EUVI images,
  we reveal the presence of such twisted structure in a coronal jet
  event. This work was supported, in part, by NASA and ONR.

Title: Understanding the Initiation of Polar Coronal Jets with
    STEREO/SECCHI Stereoscopic Observations
Authors: Vourlidas, A.; Patsourakos, S.; Pariat, E.; Antiochos, S.
Bibcode: 2008AGUSMSH23A..02V
Altcode:
  Polar coronal jets are collimated transient ejections of plasma
  occurring in polar coronal holes. The kinematics and mostly the 3D
  morphology of jets place strong constraints on the physical mechanism(s)
  responsible for their initiation, and were not accessible before
  the STEREO mission. We report on the first stereoscopic observations
  of polar coronal jets made by the EUVI/SECCHI imagers on-board the
  twin STEREO spacecraft at spacecraft separations of ~ 11° and ~
  45°. Triangulations of the jet locations in simultaneous image pairs
  led to the true 3D position and thereby their kinematics. The most
  important geometrical feature of the observed jets is helical structures
  showing evidence of untwisting. The jet structure appear strikingly
  different from each of the two STEREO viewpoints: face-on in the
  one viewpoint and edge-on in the other. This provides solid evidence
  that the observed helical structure is real and not resulting from
  possible projection effects of single viewpoint observations. The clear
  demonstration of twisted structure in polar jets compares favorably
  with synthetic images from a recent MHD simulation of jets invoking
  magnetic untwisting as their driving mechanism.

Title: Understanding Warm Coronal Loops
Authors: Klimchuk, J. A.; Karpen, J. T.; Patsourakos, S.
Bibcode: 2007AGUFMSH51C..05K
Altcode:
  One of the great mysteries of coronal physics that has come to light
  in the last few years is the discovery that warm (~ 1 MK) coronal loops
  are much denser than expected for quasi-static equilibrium. It has been
  shown that the excess density can be explained if loops are bundles
  of unresolved strands that are heated impulsively and quasi-randomly
  to very high temperatures. This picture of nanoflare heating predicts
  that neighboring strands of different temperature should coexist and
  therefore that loops should have multi-thermal cross sections. In
  particular, emission should be produced at temperatures hotter than 2
  MK. Such emission is sometimes but not always seen, however. We offer
  two possible explanations for the existence of over-dense warm loops
  without corresponding hot emission: (1) loops are bundles of nanoflare
  heated strands, but a significant fraction of the nanoflare energy takes
  the form of a nonthermal electron beam rather then direct heating;
  (2) loops are bundles of strands that undergo thermal nonequilibrium
  that results when steady heating is sufficiently concentrated near
  the footpoints. We verify these possibilities with numerical hydro
  simulations. Time permitting, we will show FeXVII line profile
  observations from EIS/Hinode that support the existence of nanoflare
  heating. Work supported by NASA and ONR.

Title: Comparison of 3D Numerical Simulations with STEREO Observations
    of Coronal Jets
Authors: Pariat, E.; Patsourakos, S.; Antiochos, S. K.; DeVore, C. R.
Bibcode: 2007AGUFMSH41B..03P
Altcode:
  Recent solar observations have revealed that coronal jets are a more
  frequent phenomenon than previously believed. It is widely accepted that
  magnetic reconnection is the fundamental mechanism that gives rise to
  the jets. The improved spatial and temporal resolution of the STEREO
  observations in combination with stereoscopy yields new insights into
  the origins of coronal jets, and provides detailed data that can be
  used to test and refine models. We present the results of a 3D numerical
  simulation of our model for coronal jets. The simulations were performed
  with our state-of-art adaptive mesh MHD solver ARMS. The basic idea
  of the model is that a jet is due to the release of twist as a closed
  field region undergoes interchange reconnection with surrounding open
  field. We compare the structure and dynamics of the simulated jet with
  actual EUVI observations, focusing on how the reconfiguration of the
  3D magnetic field explains observed properties of the jet. We also
  discuss possible signatures for STEREO of twisted structures within
  jets. Finally, we discuss the implications of our simulations for
  future stereoscopic observations with STEREO. This work was supported,
  in part, by NASA and ONR.

Title: Towards a Better Understanding of CME Onsets with SECCHI
    on STEREO
Authors: Patsourakos, S.; Vourlidas, A.
Bibcode: 2007AGUFMSH32A0779P
Altcode:
  Observations of the first minutes in the life of Coronal Mass Ejections
  (CMEs) represent the main key into identifying the physical mechanism(s)
  behind them. Previous observations of CME onsets were limited by factors
  such as low cadence, small field of view, single-temperature coverage,
  and lack of 3D information. These limitations are significantly
  mitigated by the availability of SECCHI observations onboard the
  STEREO mission. We analyze a series of high-cadence, multi-temperature
  observations of CME onsets taken with the EUVI/SECCHI imagers tied with
  high-cadence coronagraphic COR1/SECCHI observations. We discuss how
  our perception of well-known features pertinent to CME onsets such as
  dimmings, EIT waves and cavities is shaped by the unique characteristics
  of SECCHI observations, and of the 3D information available in STEREO
  obervations in particular. We finally discuss how the generic elements
  of our observations compare with the expectations of CME models in an
  attempt to place some constraints on them.

Title: The Cross-Field Thermal Structure of Coronal Loops from
    Triple-Filter TRACE Observations
Authors: Patsourakos, S.; Klimchuk, J. A.
Bibcode: 2007ApJ...667..591P
Altcode:
  The highly suppressed thermal transport across the magnetic field
  in the solar corona makes the determination of the cross-field
  thermal distribution within coronal loops a powerful diagnostic
  of the properties of the heating process itself. The cross-field
  thermal structure is currently being strongly debated. Spectroscopic
  observations with high temperature fidelity but low spatial resolution
  indicate that some observed loops are multithermal, whereas imaging
  observations with high spatial resolution but low temperature fidelity
  indicate more isothermal conditions. We report here on triple filter
  observations of coronal loops made by the Transition Region and Coronal
  Explorer (TRACE), which has the best spatial resolution currently
  available. We tested the isothermal hypothesis using the emission
  measure loci technique and found that the loops are consistent with
  an isothermal plasma near 1.5 MK only if a generous estimate of
  the photometric uncertainties is used. A more restrictive estimate
  based on discussions with the TRACE experimenters rules out the
  isothermal hypothesis. The observations are much better explained by
  a multithermal plasma with significant emission measure throughout the
  range 1-3 MK. The details of the emission measure distribution are not
  well defined, however. Future subarcsecond spectroscopic observations
  covering a wide range of temperatures are the most promising means of
  unlocking the thermal structure of the corona.

Title: The Quiet Sun Network at Subarcsecond Resolution: VAULT
    Observations and Radiative Transfer Modeling of Cool Loops
Authors: Patsourakos, S.; Gouttebroze, P.; Vourlidas, A.
Bibcode: 2007ApJ...664.1214P
Altcode:
  One of the most enigmatic regions of the solar atmosphere is the
  transition region (TR), corresponding to plasmas with temperatures
  intermediate of the cool, few thousand K, chromosphere and the hot,
  few million K, corona. The traditional view is that the TR emission
  originates from a thin thermal interface in hot coronal structures,
  connecting their chromosphere with their corona. This paradigm fails
  badly for cool plasmas (~T&lt;10<SUP>5</SUP> K), since it predicts
  emission orders of magnitude less than what it is observed. It was
  therefore proposed that the ``missing'' TR emission could originate from
  tiny, isolated from the hot corona, cool loops at TR temperatures. A
  major problem in investigating this proposal is the very small sizes
  of the hypothesized cool loops. Here, we report the first spatially
  resolved observations of subarcsecond-scale looplike structures seen
  in the Lyα line made by the Very High Angular Resolution Ultraviolet
  Telescope (VAULT). The subarcsecond (~0.3") resolution of VAULT allows
  us to directly view and resolve looplike structures in the quiet Sun
  network. We compare the observed intensities of these structures with
  simplified radiative transfer models of cool loops. The reasonable
  agreement between the models and the observations indicates that an
  explanation of the observed fine structure in terms of cool loops
  is plausible.

Title: Modeling Active Regions with Steady and Impulsive Heating
Authors: Patsourakos, Spiros; Klimchuk, J.
Bibcode: 2007AAS...210.9124P
Altcode: 2007BAAS...39..208P
  There has been considerable recent interest in constructing physical
  models of active regions (ARs) and the global coronal. Models based on
  static equilibrium theory are quite successful at reproducing soft X-ray
  (SXR) images of active regions. They however fail to predict the warm
  ( 1 MK) loops that are seen to permeate ARs in the EUV. Instead, the
  synthetic EUV images are dominated by intense footpoint emission. We
  demonstrate that the failure of static models to predict EUV loops is
  associated with the very weak dependence of loop temperature on loop
  length in models that are based on a single heating mechanism and
  that match the SXR observations. The models predict either SXR loops
  or EUV loops, but not both. We therefore consider time-dependent AR
  models based on nanoflare heating. We demonstrate that such models
  can simultaneously reproduce both SXR and EUV loops. Moreover, they
  explain the general tendency for SXR emission to dominate in the cores
  of ARs and EUV emission to dominate in the periphery. We finally show
  how the properties of nanoflares (energy, duration, spatial dependence,
  repetition time) can affect the AR morphology. <P />Research supported
  by NASA and ONR.

Title: Impulsive Coronal Heating At Sub- Arcsecond Scales: What Is
    The Best Diagnostic?
Authors: Patsourakos, S.; Klimchik, J. A.
Bibcode: 2007ESASP.641E..22P
Altcode:
  Significant observational and theoretical evidence suggests that coronal
  heating operates at sub- rcsecond, currently unresolved, spatial scales
  and is impulsive in time. We demonstrate that the most sensitive
  diagnostic for this type of heating is provided by spectroscopic
  observations in the early phase of such events. We demonstrate that the
  spectra of hot lines ( 5 MK), observed at arcsecond resolution with the
  EIS spectrometer onboard the recently launched Hinode mission, hold
  the signature of the impulsive heating process via the development
  of asymmetric profiles. Solar Orbiter (SolO) will provide a unique
  opportunity to directly view the postulated sub-arcsecond impulsive
  energy releases. We demonstrate that the superior spatial resolution
  of the Orbiter EUV remote sensing instrumentation should be tuned to
  high temperature plasmas in order to resolve the individual strands.

Title: Nonthermal Spectral Line Broadening and the Nanoflare Model
Authors: Patsourakos, S.; Klimchuk, J. A.
Bibcode: 2006ApJ...647.1452P
Altcode:
  A number of theoretical and observational considerations suggest
  that coronal loops are bundles of unresolved, impulsively heated
  strands. This ``nanoflare'' model, as it is sometimes called,
  predicts high-speed evaporative upflows, which might be revealed as
  nonthermal broadening of spectral line profiles. We have therefore
  generated synthetic line profile observations based on one-dimensional
  hydrodynamic simulations for comparison with actual observations. The
  predicted profiles for Ne VIII (770.4 Å), a transition region line,
  and Mg X (624.9 Å), a warm coronal line, have modest broadening that
  agrees well with existing observations. The predicted profiles for
  Fe XVII (254.87 Å), a hot line that will be observed by the Extreme
  Ultraviolet Imaging Spectrometer (EIS) on the Solar-B mission, are
  somewhat broader and are also consistent with the limited number of hot
  line observations that are currently available. Moreover, depending on
  the properties of the assumed nanoflare and other parameters of the
  simulation, the Fe XVII profile can have distinctive enhancements in
  the line wing. This indicates a powerful diagnostic capability that
  can be exploited once Solar-B is launched.

Title: Testing Nanoflare Heating in Coronal Loops With Observations
    From the Extreme Ultraviolet Imaging Spectrometer On-board the
    SOLAR-B Mission
Authors: Patsourakos, Spiros; Klimchuk, J. A.
Bibcode: 2006SPD....37.0124P
Altcode: 2006BAAS...38..219P
  A number of theoretical and observational considerations suggest
  that coronal loops are bundles of unresolved, impulsively heated
  strands. This "nanoflare" model, as it is sometimes called,
  predicts high-speed evaporative upflows, which might be revealed as
  non-thermal broadening of spectral line profiles. We have therefore
  generated synthetic line profile observations based on 1D hydrodynamic
  simulations of nanoflare heated loop bundles.We will show that hot lines
  (T&gt;5MK) hold the imprints of the heating process via the development
  of distinct enhancements in the line wings. These signatures do not
  appear in the profiles of cooler lines, which is fully consistent
  with existing observations. We will demonstrate how the spectra of hot
  lines from the Extreme Ultraviolet Imaging Spectrometer (EIS) on-board
  the upcoming SOLAR-B mission can be used to test the basic nanoflare
  picture and perhaps even to pinpoint the properties of the nanoflares,
  such as their energy content, duration, and spatial dependence. We
  will present sample observing programs for studying nanoflare heating
  in coronal loops that utilize EIS and other instrumentation on-board
  SOLAR-B and STEREO.Research supported by NASA and ONR.

Title: Coronal Loop Heating by Nanoflares: The Impact of the
    Field-aligned Distribution of the Heating on Loop Observations
Authors: Patsourakos, S.; Klimchuk, J. A.
Bibcode: 2005ApJ...628.1023P
Altcode:
  Nanoflares occurring at subresolution strands with repetition times
  longer than the coronal cooling time are a promising candidate
  for coronal loop heating. To investigate the impact of the spatial
  distribution of the nanoflare heating on loop observables, we compute
  hydrodynamic simulations with several different spatial distributions
  (uniform, loop top, randomly localized, and footpoint). The outputs
  of the simulations are then used to calculate density and temperature
  diagnostics from synthetic TRACE and SXT observations. We find that
  the diagnostics depend only weakly on the spatial distribution of the
  heating and therefore are not especially useful for distinguishing among
  the different possibilities. Observations of the very high temperature
  plasmas that are present only in the earliest stages of nanoflares
  can shed more light on the field-aligned distribution of the heating.

Title: Coronal Loop Heating by Nanoflares: Non-thermal Velocities
Authors: Patsourakos, S.; Klimchuk, J. A.
Bibcode: 2005AGUSMSP41A..06P
Altcode:
  Spectroscopic observations show non-negligible non-thermal velocities
  under coronal conditions. These motions place tight constraints on any
  coronal heating mechanism that should be able to reproduce them. We
  calculate the non-thermal velocities predicted by the nanoflare
  model. We perform 1D time-dependent hydrodynamic simulations of
  nanoflares occurring at sub-resolution strands, that make up the
  observed coronal loops and calculate profiles for representative
  spectral lines. We show that: (1) the calculated non-thermal velocities
  compare favorably with observations of cool and warm spectral
  lines and (2) the profiles of hot lines, that would be available in
  observations from the Extreme Ultraviolet Imaging Spectrometer (EIS)
  spectrometer onboard the SOLAR-B mission, can exhibit significant
  blue-wing asymmetries which can be used as a monitor of nanoflare
  properties. Research supported by NASA and ONR.

Title: Coronal Loop Heating by Nanoflares: The Influence of the
    Field-aligned Distribution of the Heating on Observables
Authors: Patsourakos, S.; Klimchuk, J. A.
Bibcode: 2005AGUSMSP41A..05P
Altcode:
  We investigate the effect of the spatial distribution of nanoflare
  heating on loop observables. We perform 1D time-dependent hydrodynamic
  simulations of nanoflares occurring at sub-resolution strands, that make
  up the observed coronal loops. The simulations use different spatial
  forms for the nanoflare heating (randomly localized, footpoint, uniform
  loop top). The outputs of the simulations are then used to calculate
  diagnostics from synthetic TRACE and SXT observations. We find that
  the diagnostics depend only weakly on the spatial distribution of the
  heating, and therefore are not especially useful for distinguishing
  among the different possibilities. We propose that the best way to
  study the field-aligned spatial distribution of nanoflare heating is
  to observe the very high temperature plasmas that are present only in
  the earliest stages of an event. Research supported by NASA and ONR.

Title: Highly Efficient Modeling of Dynamic Coronal Loops
Authors: Klimchuk, J. A.; Patsourakos, S.; Cargill, P. J.
Bibcode: 2005AGUSMSP14A..03K
Altcode:
  It now seems clear that many coronal loops, especially those observed
  by TRACE and EIT, are inherently dynamic and composed of large numbers
  of impulsively-heated strands. Modeling these loops in full detail is
  extremely challenging, and modeling entire active regions or the whole
  Sun is completely out of the question unless approximate techniques are
  used. We have developed a simplified set of equations that is remarkably
  accurate at describing the evolution of the thermodynamic variables
  (T, P, n, v) averaged along the magnetic field of an individual
  strand. The equations can be solved ten thousand times more quickly
  than the full 1D hydro equations. This "0D" model relaxes two key
  assumptions of Cargill's (1994) nanoflare model: (1) the heating can
  have any time-dependent profile and need not be instantaneous; and
  (2) thermal conduction cooling and radiation cooling occur together
  at all times, in varying proportions. We here describe the essential
  features of the model and show examples of how well it works.

Title: The Effect of the Spatial Distribution of Nanoflare Heating
    on Loop Observables
Authors: Patsourakos, S.; Klimchuk, J. A.
Bibcode: 2004ESASP.575..297P
Altcode: 2004soho...15..297P
  No abstract at ADS

Title: A Model for Bright Extreme-Ultraviolet Knots in Solar Flare
    Loops
Authors: Patsourakos, S.; Antiochos, S. K.; Klimchuk, J. A.
Bibcode: 2004ApJ...614.1022P
Altcode:
  EUV observations often indicate the presence of bright knots in flare
  loops. The temperature of the knot plasma is of the order of 1 MK,
  and the knots themselves are usually localized somewhere near the loop
  tops. We propose a model in which the formation of EUV knots is due
  to the spatial structure of the nonflare active region heating. We
  present the results of a series of one-dimensional hydrodynamic,
  flare-loop simulations, which include both an impulsive flare heating
  and a background, active region heating. The simulations demonstrate
  that the formation of the observed knots depends critically on
  the spatial distribution of the background heating during the decay
  phase. In particular, the heating must be localized far from the loop
  apex and have a magnitude comparable to the local radiative losses of
  the cooling loop. Our results, therefore, provide strong constraints
  on both coronal heating and postflare conditions.

Title: Bright EUV Knots in Solar Flare Loops: Constraints on Coronal
    Heating
Authors: Patsourakos, S.; Antiochos, S.; Klimchuk, J.
Bibcode: 2004AAS...204.8705P
Altcode: 2004BAAS...36Q.819P
  EUV observations often indicate the presence of bright knots in flare
  loops. The temperature of the knot plasma is of order 1MK, and the
  knots themselves are usually localized somewhere near the loop tops. We
  propose a model in which the formation of EUV knots is due to the
  spatial structure of the non-flare active region heating. We present
  the results of a series of 1D hydrodynamic, flare-loop simulations,
  which include both an impulsive flare heating and a background, active
  region heating. The simulations demonstrate that the formation of the
  observed knots depends critically on the spatial distribution of the
  background heating during the decay phase. In particular, the heating
  must: (1) be localized, (2) be situated far from the loop apex and (3)
  have a magnitude comparable with the local radiative losses of the
  cooling loop. Our results, therefore, provide strong constraints on
  both coronal heating and post-flare conditions. <P />Research supported
  by NASA and ONR.

Title: Mass and Kinetic Energy Distributions of Coronal Mass Ejections
    in 1996-2002
Authors: Vourlidas, A.; Patsourakos, S.
Bibcode: 2004AAS...204.7303V
Altcode: 2004BAAS...36..800V
  We present the mass and kinetic energy distributions of coronal mass
  ejections observed by LASCO between 1996 and 2002. The sample includes
  more than 4000 events. Events with projected widths larger than 120
  deg were excluded because of uncertainties in the calculation of the
  mass and speed for such large events. <P />We compare the LASCO mass
  and energy distribution to similar distributions from Solwind and
  soft x-ray flares. In particular, we find that the CME kinetic energy
  distribution follows a power law similar to the one found for solar
  flares. The implications of our findings are discussed in the paper.

Title: The Inability of Steady-Flow Models to Explain the
    Extreme-Ultraviolet Coronal Loops
Authors: Patsourakos, S.; Klimchuk, J. A.; MacNeice, P. J.
Bibcode: 2004ApJ...603..322P
Altcode:
  Recent observations from the Transition Region and Coronal Explorer
  (TRACE) and the EUV Imaging Telescope (EIT) show that warm (T~1-1.5 MK)
  EUV coronal loops in active regions generally have enhanced densities,
  enhanced pressure scale heights, and flat filter ratio (temperature)
  profiles in comparison with the predictions of static-equilibrium
  theory. It has been suggested that mass flows may explain these
  discrepancies. We investigate this conjecture using one-dimensional
  hydrodynamic simulations of steady flows in coronal loops. The flows
  are driven by asymmetric heating that decreases exponentially along
  the loop from one footpoint to the other. We find that a sufficiently
  large heating asymmetry can produce density enhancements consistent
  with a sizable fraction of the observed loops, but that the pressure
  scale heights are smaller than the corresponding gravitational scale
  heights, and that the filter ratio profiles are highly structured,
  in stark contrast to the observations. We conclude that most warm EUV
  loops cannot be explained by steady flows. It is thus likely that the
  heating in these loops is time dependent.

Title: Solar Physics from Space for the Next Solar Cycle
Authors: Vourlidas, Angelos; Patsourakos, Spiros
Bibcode: 2004hell.conf...78V
Altcode:
  No abstract at ADS

Title: Coronal Loop Heating by Nanoflares: Some Observational
    Implications
Authors: Patsourakos, S.; Klimchuk, J. A.
Bibcode: 2004hell.conf...35P
Altcode:
  No abstract at ADS

Title: Are All Coronal Loops Heated by Nanoflares?
Authors: Klimchuk, J. A.; Patsourakos, S.; Winebarger, A. R.
Bibcode: 2003SPD....34.1006K
Altcode: 2003BAAS...35R.825K
  Observations from TRACE, SOHO, and Yohkoh have revealed new details
  of coronal loops that make them more mysterious than ever. One of
  the biggest puzzles concerns the loop density. Hot (&gt; 2 MK) loops
  observed by Yohkoh tend to be under dense compared to the predictions
  of equilibrium theory, while warm ( 1 MK) loops observed by TRACE
  and EIT tend to be over dense. Some over dense loops can be explained
  by steady heating that is concentrated near one or both of the loop
  legs, but a majority of these loops cannot. <P />We here consider
  the possibility that observed loops are comprised of large numbers
  of unresolved strands that are heated impulsively and randomly by
  nanoflares. The loops appear quasi-steady even though the individual
  sub-strands are highly time dependent. When the strands are hot,
  they cool primarily by thermal conduction and are under dense, but
  when they are warm, they cool primarily by radiation and are over
  dense. Since Yohkoh and TRACE are sensitive to different strands,
  we might expect them to observe the under and over densities that
  they do. <P />To evaluate the feasibility of this universal model
  of coronal loops, we have performed 1D hydrodynamic simulations of
  impulsively heated strands and compared them with observations from
  Yohkoh and TRACE. The results are encouraging in many respects, but
  difficulties remain. In this presentation, we discuss the successes
  and failures of the model. <P />This work was supported by NASA and ONR.

Title: Can Steady-state Mass Flows Explain the Non-hydrostatic Cool
    EUV Coronal Loops in Active Regions?
Authors: Patsourakos, S.; Klimchuk, J. A.
Bibcode: 2003SPD....34.1009P
Altcode: 2003BAAS...35..826P
  Recent EIT/TRACE observations of cool (≈ 1-1.5 MK) EUV coronal loops
  in active regions showed that these loops are very often characterized
  by greatly enhanced pressure scale-heights and densities compared to
  the predictions of static equilibrium theory. It has been suggested
  that mass flows may explain these over-dense and over-pressure
  loops. We investigate this conjecture by the means of 1D hydrodynamic
  simulations of steady-state mass flows in coronal loops. The mass flows
  in our calculations are driven by asymmetric heating that decreases
  exponentially along the loop from one footpoint all way to the
  other. By considering several representative cases for the magnitude
  and the length scale of the applied asymmetric heating, we determine
  how steady-state mass flows affect the thermodynamic structure of
  coronal loops and assess whether they can lead to enhanced pressure
  scale-heights and densities. Research supported in part by NASA and ONR.

Title: Bright Knots in EUV Post-flare Loops : TRACE Observations
    and 1D Hydrodynamic Modeling
Authors: Patsourakos, S.; Antiochos, S. K.; Klimchuk, J. A.
Bibcode: 2002AGUFMSH21C..04P
Altcode:
  EUV post-flare loops often possess bright knots along them. Some
  examples of such post-flare loops seen by TRACE will be shown, along
  with a brief outline of their properties. We will then present the
  results of a series of 1D hydrodynamic simulations of flaring loops,
  which employ different heating functions for the impulsive and decay
  phase of the simulated flares. It will be demonstrated that the creation
  of these knots depends crucially on the spatio-temporal distribution of
  the heating during the decay phase. This provides strong constraints
  on both post-flaring conditions and AR loop heating. We will finally
  briefly outline how SDO instrumentation could improve our knowledge
  of this topic. Research supported in part by NASA and ONR.

Title: Ion Effective Temperatures in Polar Coronal Holes: Observations
    versus Ion-Cyclotron Resonance
Authors: Patsourakos, S.; Habbal, S. R.; Hu, Y. Q.
Bibcode: 2002ApJ...581L.125P
Altcode:
  The resonant cyclotron interaction between ion-cyclotron waves and
  solar wind species is considered nowadays to be a strong candidate
  for heating and acceleration of protons, α-particles, and heavy
  ions. A crucial physical parameter for determining the amount and
  the location of significant heating and acceleration, which the
  different solar wind ions receive from the waves in the frame of the
  ion-cyclotron mechanism, is their charge-to-mass ratio q/m. Therefore,
  comparisons of ion temperatures derived from spectroscopic observations
  and calculated by ion-cyclotron models, for ions that span a broad
  range in q/m, would provide a rigorous test for such models. By using
  an ion-cyclotron model, we calculate the effective temperatures for
  10 different ions that cover the range 0.16-0.37 in q/m. Effective
  temperatures correspond to unresolved thermal motions and wave
  motions. The good agreement between our calculations, based on the
  specific mechanism that we employed here (ion-cyclotron resonance)
  and on spectroscopic observations of effective temperatures in polar
  coronal holes, provides support that the above mechanism accounts for
  the energetics and kinematics of fast solar wind heavy ions. However,
  such an agreement does not prove that other potential mechanisms can
  be excluded.

Title: Fuzzy hot post-flare loops versus sharp cool post-flare loops
Authors: Patsourakos, S.; Antiochos, S. K.; Klimchuk, J. A.
Bibcode: 2002ESASP.505..207P
Altcode: 2002solm.conf..207P; 2002IAUCo.188..207P
  By using high spatial resolution TRACE EUV observations we show that hot
  (≍2 MK) post-flare loops are fuzzier than the cooler (≍1 MK) ones. A
  simple 0d model of a cooling loop arcade, where different loops in the
  arcade start to cool down at slightly different initial conditions,
  is sufficient to reproduce qualitatively the observed behavior of the
  EUV post-flare loops.

Title: Soho Contribution to Prominence Science
Authors: Patsourakos, Spiros; Vial, Jean-Claude
Bibcode: 2002SoPh..208..253P
Altcode:
  We present the main current issues concerning prominence studies. We
  recall the large range of plasma parameters found in prominences
  which makes the work of the MHD modeler more difficult. We also
  summarize the capabilities of the SOHO instrumentation. We present and
  discuss the most recent SOHO results concerning the determination of
  temperature, densities, and velocities. We put some emphasis on the
  different morphologies observed, the diagnostic capabilities of the
  Lyman lines profiles when accompanied by improved non-LTE modeling,
  and the information gathered from the first prominence oscillations
  measured from space. We also make an account of eruptive prominences. We
  finally discuss what could be done with present and future SOHO data
  to improve our understanding of prominences.

Title: Solar cycle variation of the temperature structure within
    the cores of coronal streamers
Authors: Culhane, J. L.; Foley, C. R.; Patsourakos, S.; Mackay, D.
Bibcode: 2002ESASP.508..371C
Altcode: 2002soho...11..371C
  We use the Coronal Diagnostic Spectrometer onboard the Solar and
  Heliospheric Observatory (SOHO) to analyze conditions in coronal
  streamer structures observed close to solar minimum (1996, July 8) and
  near maximum (1999, August 5). From emission line intensities (Fe IX-XV
  ions), the line ratio method gives the radial temperature behaviour. The
  solar minimum peak values were about 1.4 MK at 1.3 R<SUB>0</SUB>, while
  near solar maximum values were consistent with Yohkoh observations at
  the last maximum, displaying an asymptotic temperature of around 2.2
  MK above 1.2 R<SUB>0</SUB>. We discuss the observations in relation to
  possible mechanisms for energy deposition in large coronal structures.

Title: Hot versus cool coronal loops
Authors: Patsourakos, S.; Klimchuk, J. A.; Antiochos, S. K.
Bibcode: 2002AAS...200.0209P
Altcode: 2002BAAS...34..640P
  EUV and SXR observations show respectively that cool (1 MK) loops are
  finer and maybe more dynamic than hotter (2 MK) ones. Whether this
  reflects a fundamental difference in the properties of the heating
  mechanism in action in each loop class is not yet clear. We will address
  some aspects of this issue by combining EUV and SXR observations of
  such loops with eventually hydrodynamic simulations of a nano-flare
  heated corona. Research supported in part by ONR and NASA.

Title: Intermittent behavior in the transition region and the low
    corona of the quiet Sun
Authors: Patsourakos, S.; Vial, J. -C.
Bibcode: 2002A&A...385.1073P
Altcode:
  We present an analysis of light-curves obtained in the O IV and Ne
  VIII transition region and low corona lines, that were simultaneously
  recorded in a quiet Sun region by SUMER/SOHO. By using the flatness
  spectrum of the observed light-curves we searched for intermittency
  signatures. It was found that a significant proportion of points
  in the observed area exhibit clear indications of intermittency,
  irrespectively of their intrinsic intensity. Our findings give favor to
  an impulsively heated transition region and corona via intermittent-type
  MHD turbulence.

Title: What are the Origins of Quiescent Coronal Soft X-Rays?
Authors: Foley, C. R.; Culhane, J. L.; Patsourakos, S.; Yurow, R.;
   Moroney, C.; Mackay, D.
Bibcode: 2002mwoc.conf..341F
Altcode:
  We have examined the evolution and modulation of the Sun's atmosphere
  from the photosphere up to the outer corona through the decline and
  rise of solar cycles 22, and 23 respectfully. For this we have used
  Yohkoh soft X-ray telescope (SXT) images, Kitt peak magnetograms and EUV
  spectra provided by the Coronal Diagnostic Spectrometer (CDS). We find
  as Hara (1996, 1997) found, that there is a modulation of the coronal
  brightness which varies annually in the high latitude activity zones,
  and that this is linked to the presence and disappearance of active
  regions on the sun's disk. We interpret our results with regards to the
  emergence and diffusion of magnetic flux. We find that the appearance
  of high latitude activity zones may be explained simply by the decay
  of diffused active region flux, We also find evidence for a positive
  temperature gradient within the corona from the emission profiles in
  the different lines.

Title: Solar cycle variation of the temperature structure within
    the cores of coronal streamers
Authors: Foley, C. R.; Patsourakos, S.; Culhane, J. L.; MacKay, D.
Bibcode: 2002A&A...381.1049F
Altcode:
  We use the Coronal Diagnostic Spectrometer onboard the Solar and
  Heliospheric Observatory (SOHO) to analyze conditions in coronal
  streamer structures observed close to solar minimum (1996 July 8)
  and near maximum (1999 August 5). We measured the intensities of
  emission lines from Fe IX-XV ions and found the most intense emission
  to be from Fe XI at solar minimum and from Fe XV at solar maximum. We
  then used the line ratio method with transitions in selected ions to
  extract the radial temperature behavior in the structures. The solar
  minimum peak values were about 1.4 MK at 1.3 R<SUB>sun</SUB>, while
  values derived close to solar maximum were consistent with the Yohkoh
  observations at the last maximum, displaying an apparently asymptotic
  temperature of around 2.2 MK above 1.2 R<SUB>sun</SUB>. We discuss the
  observations in relation to possible mechanisms for energy deposition
  in large coronal structures at different phases of the solar cycle.

Title: The polar coronal holes and the fast solar wind: Some recent
    results
Authors: Patsourakos, S.; Habbal, S. -R.; Vial, J. -C.; Hu, Y. Q.
Bibcode: 2001AIPC..598..299P
Altcode: 2001sgc..conf..299P
  We report on recent results on the source regions of the fast solar
  wind: the Polar Coronal Holes (PCH). They concern a comparison
  between the effective temperatures for a large set of different ions
  obtained from observations in the inner corona of PCH and from a fast
  wind numerical model based on the ion-cyclotron resonant dissipation
  of high-frequency Alfvén waves. We also report on some preliminary
  results from our modeling concerning the Fe/O ratio in the inner corona
  in PCH. .

Title: Analysis of a UV Event in a Polar Coronal Hole
Authors: Patsourakos, Spiros; Vial, Jean-Claude
Bibcode: 2001SoPh..203...39P
Altcode:
  We present observations of a UV event which occurred in a polar coronal
  hole. They were obtained by SUMER on SOHO in several chromospheric and
  transition region spectral lines. Its birth site was about 50 arc sec
  inside the limb and in a network lane showing a net outflow before
  its initiation. The event had an extension of about 5 arc sec along
  the slit, a duration of about 3 min and was characterized by a large
  increase of intensity together with a significant line broadening
  with, however, downflows of about 50 km s<SUP>−1</SUP> being
  dominant. Proper motions with a velocity of about 10 km s<SUP>−1</SUP>
  were also observed. The event appeared at middle transition (O vi)
  temperatures and it simultaneously showed up in chromospheric (O i,
  Ly β) and low transition region (C ii) temperatures. We discuss this
  event in view of different scenarios to account for it. Our event could
  be a part of the large family of quiet-Sun explosive events observed
  by Ryutova and Tarbell (2000) taking place in polar coronal holes that
  are triggered by magnetic reconnection in the low solar atmosphere.

Title: High-resolution EUV imaging and spectroscopy of the corona
Authors: Patsourakos, Spiros; Vial, J. -C.
Bibcode: 2001ESASP.493...13P
Altcode: 2001sefs.work...13P
  We present a set of imagers and spectrometer which have been proposed as
  a strawman payload on board the Solar Orbiter mission. The scientific
  requirements of the mission are put in the context of the main issues
  presently discussed in solar physics. The on-going successful space
  solar missions have evidenced a very fine structuring of the solar
  atmosphere and its role in various processes at work for coronal
  heating, wind acceleration, flaring activity, etc. This is especially
  true for magnetic reconnection which seems to proceed at many different
  scales. These results point at the need of observations substantially
  improving both the spatial resolution and the multi-temperature
  (multi-wavelength) coverage. Solar Orbiter offers a unique opportunity
  to analyze this fine structure (e.g. the internal structure of the
  thin loops observed by TRACE) in closed and open fields. It will allow
  for a diagnostic of regions such as the magnetic network which seems
  to play a major role in the wind acceleration, in conjunction with
  in-situ observations of the ejected plasma.

Title: Searching the source regions of the fast solar wind in polar
coronal holes: some recent SOHO/eclipse results and the potential
    of the Solar Orbiter
Authors: Patsourakos, Spiros; Vial, J. -C.
Bibcode: 2001ESASP.493..321P
Altcode: 2001sefs.work..321P
  No abstract at ADS

Title: Outflow velocity of interplume regions at the base of Polar
    Coronal Holes
Authors: Patsourakos, S.; Vial, J. -C.
Bibcode: 2000A&A...359L...1P
Altcode:
  We report on SUMER/SOHO observations at 1.05 R<SUB>sun</SUB> of a well
  identified interplume region in a South Pole Coronal Hole. Combination
  of Doppler shifts and Doppler dimming measurements allowed to
  determine, for the first time, the total wind outflow velocity (~ 67 km
  s<SUP>-1</SUP>) at this height. Our calculations of the outflow velocity
  benefit from co-spatial and almost co-temporal observations. This large
  outflow velocity is a strong argument in favour of the interplumes
  being the main source of the fast solar wind. We find that the mass
  flux density through the observed interplume is 4.8 10<SUP>-10</SUP>
  g cm<SUP>-2</SUP>s<SUP>-1</SUP> which yields 10<SUP>-15</SUP> g
  cm<SUP>-2</SUP>s<SUP>-1</SUP> at 1 AU with an expansion factor of 11.

Title: Contribution a l'etude du chauffage de la couronne solaire et
de l'acceleration du vent solaire dans les trous coronaux Title:
    Contribution a l'etude du chauffage de la couronne solaire et
de l'acceleration du vent solaire dans les trous coronaux Title:
    Investigation of coronal heating and solar wind acceleration in
    coronal holes;
Authors: Patsourakos, Spiros
Bibcode: 2000PhDT.......234P
Altcode:
  No abstract at ADS

Title: Transition-Region Network Boundaries in the Quiet Sun: Width
    Variation with Temperature as Observed with CDS on SOHO
Authors: Patsourakos, S.; Vial, J. -C.; Gabriel, A. H.; Bellamine, N.
Bibcode: 1999ApJ...522..540P
Altcode:
  We report here the results of a study of the temperature variation
  of the network boundary thicknesses in the quiet-Sun transition
  region. A Fourier-based two-dimensional autocorrelation method has
  been applied to 240<SUP>''</SUP>×240<SUP>''</SUP> rasters obtained in
  several transition-region lines by the CDS spectrometer on SOHO. The
  quantitative variation of the network boundary width with temperature
  has been obtained for the first time in a full two-dimensional field. It
  appears that network boundaries have an almost constant width up to
  a temperature of about 10<SUP>5.4</SUP> K and then fan out rapidly at
  coronal temperatures. This expansion of the transition-region network
  boundaries with temperature is found to be quantitatively in agreement
  with earlier theoretical models of the transition region.

Title: Coordinated observations between SOHO/SUMER and ground during
the 1998 total eclipse: Non-thermal line broadenings and electron
    densities in a polar coronal hole
Authors: Patsourakos, S.; Vial, J. -C.; Gabryl, J. -R.; Koutchmy,
   S.; Schühle, U.
Bibcode: 1999AIPC..471..285P
Altcode: 1999sowi.conf..285P
  Alfvén waves represent one of the most prominent ways of heating the
  solar corona and accelerating the solar wind. One of their signatures
  is to broaden the spectral lines in excess of their thermal width. Here
  we aim to combine observations of non-thermal broadenings measured
  by SUMER in OVI (1037.6 Å) line and electronic densities derived
  from white-light observations during the 1998 total eclipse. After
  checking the validity of the frequently-used assumption of equal ion
  and electron temperatures, we compute the variation of the non-thermal
  velocity as a function of height in an interplume region within the
  south polar coronal hole.

Title: Outflow Velocities at the Base of a Polar Coronal Hole During
    the 1998 Total Eclipse
Authors: Patsourakos, S.; Vial, J. -C.; Gabryl, J. -R.; Koutchmy,
   S.; Schühle, U.
Bibcode: 1999SSRv...87..291P
Altcode:
  Polar coronal holes represent the most convincing site from which the
  high-speed solar wind originates. Here we report high-accuracy Doppler
  shifts measured in the O VI (1037.6 Å) line obtained by SUMER on SOHO
  inside an interplume region within the south polar coronal hole. We
  infer limits on the outflow velocity and draw hints about the flow
  geometry.

Title: Solar chromospheric structures observed in UV ressonance
lines : a multivariate analysis approach
Authors: Patsourakos, S.; Bocchialini, K.; Vial, J. -C.
Bibcode: 1999CR2...322..337P
Altcode:
  We present the results of a statistical analysis carried out from a data
  base of 6 solar chromospheric emission lines recorded simultaneously
  and with high spectral resolution. An empirical and a clustering method
  for separating the different solar structures contributions have been
  used and been found in a good agreement. Mean profiles corresponding to
  the different populations have been built. Correlations of different
  parameters for each profile allowed us to deduce different properties
  of the solar chromosphere, such as the existence of magnetic canopies
  and downflows in active regions.

Title: Solar chromospheric structures observed in UV resonance lines:
    a multivariate analysis approach.
Authors: Patsourakos, S.; Bocchialini, K.; Vial, J. -C.
Bibcode: 1998CRASB.326..337P
Altcode:
  The authors present the results of a statistical analysis carried out
  from a data base of six solar chromospheric emission lines recorded
  simultaneously and with high spectral resolution. An empirical and
  a clustering method for separating the different solar structure
  contributions have been used and found to be in good agreement. Mean
  profiles corresponding to the different populations have been
  built. Correlations of different parameters for each profile allowed
  one to deduce different properties of the solar chromosphere, such as
  the existence of magnetic canopies and downflows in active regions.

Title: Simulated white-light images of coronal structures as obtained
    by the CORI imager on-board a solar probe
Authors: Patsourakos, S.; Vial, J. -C.
Bibcode: 1997AIPC..385..129P
Altcode: 1997recs.conf..129P
  A white-light coronal imager called CORI to be implemented on a solar
  probe has been proposed by Habbal et al. (1995). Its scientific
  objectives concern the investigation of the solar corona and the
  source of the solar wind. It is aimed as a complement to the in-situ
  instruments. This paper presents some simulations of the images
  that will be recorded when observing solar structures of increasing
  complexity during the close encounter phase of the trajectory. These
  attempts should be considered as a first step towards the assessment
  of the full scientific capabilities of CORI and the definition of the
  observing strategy.

Title: Low Transition-Region Characteristics of Equatorial Coronal
    Holes
Authors: Patsourakos, S.; Bocchialini, K.; Vial, J. -C.
Bibcode: 1997ESASP.404..577P
Altcode: 1997cswn.conf..577P
  No abstract at ADS

Title: First Results of SOHO's Joint Observing Programme 40
Authors: Patsourakos, S.; Bocchialini, K.; Vial, J. -C.
Bibcode: 1997IAUJD..19E..38P
Altcode:
  The first results of SOHO's JOP 40 are presented. This program
  proposes to study the chromospheric to transition region of equatorial
  coronal holes in order to derive parameters such as the temperature,
  the density, using different lines formed at different altitudes,
  in different places: the boundary of a coronal hole or the central
  region, on the disk. The two components of the chromospheric quiet
  Sun, network and internetwork, should be observed, in and out of an
  equatorial coronal hole.

