Author name code: bloomfield
ADS astronomy entries on 2022-09-14
author:"Bloomfield, D. Shaun" 
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Title: The high-energy Sun - probing the origins of particle
    acceleration on our nearest star
Authors: Matthews, S. A.; Reid, H. A. S.; Baker, D.; Bloomfield, D. S.;
   Browning, P. K.; Calcines, A.; Del Zanna, G.; Erdelyi, R.; Fletcher,
   L.; Hannah, I. G.; Jeffrey, N.; Klein, L.; Krucker, S.; Kontar, E.;
   Long, D. M.; MacKinnon, A.; Mann, G.; Mathioudakis, M.; Milligan,
   R.; Nakariakov, V. M.; Pesce-Rollins, M.; Shih, A. Y.; Smith, D.;
   Veronig, A.; Vilmer, N.
Bibcode: 2021ExA...tmp..135M
Altcode:
  As a frequent and energetic particle accelerator, our Sun provides
  us with an excellent astrophysical laboratory for understanding
  the fundamental process of particle acceleration. The exploitation
  of radiative diagnostics from electrons has shown that acceleration
  operates on sub-second time scales in a complex magnetic environment,
  where direct electric fields, wave turbulence, and shock waves all
  must contribute, although precise details are severely lacking. Ions
  were assumed to be accelerated in a similar manner to electrons, but
  γ-ray imaging confirmed that emission sources are spatially separated
  from X-ray sources, suggesting distinctly different acceleration
  mechanisms. Current X-ray and γ-ray spectroscopy provides only a basic
  understanding of accelerated particle spectra and the total energy
  budgets are therefore poorly constrained. Additionally, the recent
  detection of relativistic ion signatures lasting many hours, without
  an electron counterpart, is an enigma. We propose a single platform
  to directly measure the physical conditions present in the energy
  release sites and the environment in which the particles propagate and
  deposit their energy. To address this fundamental issue, we set out
  a suite of dedicated instruments that will probe both electrons and
  ions simultaneously to observe; high (seconds) temporal resolution
  photon spectra (4 keV - 150 MeV) with simultaneous imaging (1 keV -
  30 MeV), polarization measurements (5-1000 keV) and high spatial and
  temporal resolution imaging spectroscopy in the UV/EUV/SXR (soft X-ray)
  regimes. These instruments will observe the broad range of radiative
  signatures produced in the solar atmosphere by accelerated particles.

Title: The flare likelihood and region eruption forecasting
(FLARECAST) project: flare forecasting in the big data &amp; machine
    learning era
Authors: Georgoulis, Manolis K.; Bloomfield, D. Shaun; Piana,
   Michele; Massone, Anna Maria; Soldati, Marco; Gallagher, Peter T.;
   Pariat, Etienne; Vilmer, Nicole; Buchlin, Eric; Baudin, Frederic;
   Csillaghy, Andre; Sathiapal, Hanna; Jackson, David R.; Alingery,
   Pablo; Benvenuto, Federico; Campi, Cristina; Florios, Konstantinos;
   Gontikakis, Constantinos; Guennou, Chloe; Guerra, Jordan A.;
   Kontogiannis, Ioannis; Latorre, Vittorio; Murray, Sophie A.; Park,
   Sung-Hong; von Stachelski, Samuelvon; Torbica, Aleksandar; Vischi,
   Dario; Worsfold, Mark
Bibcode: 2021JSWSC..11...39G
Altcode: 2021arXiv210505993G
  The European Union funded the FLARECAST project, that ran from January
  2015 until February 2018. FLARECAST had a research-to-operations
  (R2O) focus, and accordingly introduced several innovations into the
  discipline of solar flare forecasting. FLARECAST innovations were:
  first, the treatment of hundreds of physical properties viewed as
  promising flare predictors on equal footing, extending multiple
  previous works; second, the use of fourteen (14) different machine
  learning techniques, also on equal footing, to optimize the immense
  Big Data parameter space created by these many predictors; third,
  the establishment of a robust, three-pronged communication effort
  oriented toward policy makers, space-weather stakeholders and the wider
  public. FLARECAST pledged to make all its data, codes and infrastructure
  openly available worldwide. The combined use of 170+ properties (a
  total of 209 predictors are now available) in multiple machine-learning
  algorithms, some of which were designed exclusively for the project,
  gave rise to changing sets of best-performing predictors for the
  forecasting of different flaring levels, at least for major flares. At
  the same time, FLARECAST reaffirmed the importance of rigorous training
  and testing practices to avoid overly optimistic pre-operational
  prediction performance. In addition, the project has (a) tested new
  and revisited physically intuitive flare predictors and (b) provided
  meaningful clues toward the transition from flares to eruptive flares,
  namely, events associated with coronal mass ejections (CMEs). These
  leads, along with the FLARECAST data, algorithms and infrastructure,
  could help facilitate integrated space-weather forecasting efforts
  that take steps to avoid effort duplication. In spite of being
  one of the most intensive and systematic flare forecasting efforts
  to-date, FLARECAST has not managed to convincingly lift the barrier of
  stochasticity in solar flare occurrence and forecasting: solar flare
  prediction thus remains inherently probabilistic.

Title: Validation of Global EUV Wave MHD Simulations and Observational
    Techniques
Authors: Downs, Cooper; Warmuth, Alexander; Long, David M.; Bloomfield,
   D. Shaun; Kwon, Ryun-Young; Veronig, Astrid M.; Vourlidas, Angelos;
   Vršnak, Bojan
Bibcode: 2021ApJ...911..118D
Altcode:
  Global EUV waves remain a controversial phenomenon more than 20 yr
  after their discovery by SOHO/EIT. Although consensus is growing in the
  community that they are most likely large-amplitude waves or shocks,
  the wide variety of observations and techniques used to identify
  and analyze them have led to disagreements regarding their physical
  properties and interpretation. Here, we use a 3D magnetohydrodynamic
  (MHD) model of the solar corona to simulate an EUV wave event on 2009
  February 13 to enable a detailed validation of the various commonly used
  detection and analysis techniques of global EUV waves. The simulated
  event exhibits comparable behavior to that of a real EUV wave event,
  with similar kinematic behavior and plasma parameter evolution. The
  kinematics of the wave are estimated via visual identification and
  profile analysis, with both approaches providing comparable results. We
  find that projection effects can affect the derived kinematics of the
  wave, due to the variation in fast-mode wave speed with height in the
  corona. Coronal seismology techniques typically used for estimates
  of the coronal magnetic field are also tested and found to estimate
  fast-mode speeds comparable to those of the model. Plasma density
  and temperature variations of the wave front are also derived using
  a regularized inversion approach and found to be consistent with
  observed wave events. These results indicate that global waves are
  best interpreted as large-amplitude waves and that they can be used
  to probe the coronal medium using well-defined analysis techniques.

Title: The Spectrometer/Telescope for Imaging X-rays (STIX)
Authors: Krucker, Säm; Hurford, G. J.; Grimm, O.; Kögl, S.;
   Gröbelbauer, H. -P.; Etesi, L.; Casadei, D.; Csillaghy, A.; Benz,
   A. O.; Arnold, N. G.; Molendini, F.; Orleanski, P.; Schori, D.; Xiao,
   H.; Kuhar, M.; Hochmuth, N.; Felix, S.; Schramka, F.; Marcin, S.;
   Kobler, S.; Iseli, L.; Dreier, M.; Wiehl, H. J.; Kleint, L.; Battaglia,
   M.; Lastufka, E.; Sathiapal, H.; Lapadula, K.; Bednarzik, M.; Birrer,
   G.; Stutz, St.; Wild, Ch.; Marone, F.; Skup, K. R.; Cichocki, A.; Ber,
   K.; Rutkowski, K.; Bujwan, W.; Juchnikowski, G.; Winkler, M.; Darmetko,
   M.; Michalska, M.; Seweryn, K.; Białek, A.; Osica, P.; Sylwester, J.;
   Kowalinski, M.; Ścisłowski, D.; Siarkowski, M.; Stęślicki, M.;
   Mrozek, T.; Podgórski, P.; Meuris, A.; Limousin, O.; Gevin, O.; Le
   Mer, I.; Brun, S.; Strugarek, A.; Vilmer, N.; Musset, S.; Maksimović,
   M.; Fárník, F.; Kozáček, Z.; Kašparová, J.; Mann, G.; Önel,
   H.; Warmuth, A.; Rendtel, J.; Anderson, J.; Bauer, S.; Dionies, F.;
   Paschke, J.; Plüschke, D.; Woche, M.; Schuller, F.; Veronig, A. M.;
   Dickson, E. C. M.; Gallagher, P. T.; Maloney, S. A.; Bloomfield, D. S.;
   Piana, M.; Massone, A. M.; Benvenuto, F.; Massa, P.; Schwartz, R. A.;
   Dennis, B. R.; van Beek, H. F.; Rodríguez-Pacheco, J.; Lin, R. P.
Bibcode: 2020A&A...642A..15K
Altcode:
  <BR /> Aims: The Spectrometer Telescope for Imaging X-rays (STIX)
  on Solar Orbiter is a hard X-ray imaging spectrometer, which
  covers the energy range from 4 to 150 keV. STIX observes hard X-ray
  bremsstrahlung emissions from solar flares and therefore provides
  diagnostics of the hottest (⪆10 MK) flare plasma while quantifying
  the location, spectrum, and energy content of flare-accelerated
  nonthermal electrons. <BR /> Methods: To accomplish this, STIX applies
  an indirect bigrid Fourier imaging technique using a set of tungsten
  grids (at pitches from 0.038 to 1 mm) in front of 32 coarsely pixelated
  CdTe detectors to provide information on angular scales from 7 to 180
  arcsec with 1 keV energy resolution (at 6 keV). The imaging concept of
  STIX has intrinsically low telemetry and it is therefore well-suited
  to the limited resources available to the Solar Orbiter payload. To
  further reduce the downlinked data volume, STIX data are binned on
  board into 32 selectable energy bins and dynamically-adjusted time
  bins with a typical duration of 1 s during flares. <BR /> Results:
  Through hard X-ray diagnostics, STIX provides critical information
  for understanding the acceleration of electrons at the Sun and their
  transport into interplanetary space and for determining the magnetic
  connection of Solar Orbiter back to the Sun. In this way, STIX serves
  to link Solar Orbiter's remote and in-situ measurements.

Title: 2D and 3D Analysis of a Torus-unstable Quiet-Sun Prominence
    Eruption
Authors: Rees-Crockford, T.; Bloomfield, D. S.; Scullion, E.; Park,
   S. -H.
Bibcode: 2020ApJ...897...35R
Altcode:
  The role of ideal-MHD instabilities in a prominence eruption is
  explored through 2D and 3D kinematic analysis of an event observed
  with the Solar Dynamics Observatory and the Solar Terrestrial Relations
  Observatory between 22:06 UT on 2013 February 26 and 04:06 UT on 2013
  February 27. A series of 3D radial slits are used to extract height-time
  profiles ranging from the midpoint of the prominence leading edge to
  the southeastern footpoint. These height-time profiles are fit with a
  kinematic model combining linear and nonlinear rise phases, returning
  the nonlinear onset time (t<SUB>nl</SUB>) as a free parameter. A
  range (1.5-4.0) of temporal power indices (I.e., β in the nonlinear
  term ${(t-{t}_{\mathrm{nl}})}^{\beta }$ ) are considered to prevent
  prescribing any particular form of nonlinear kinematics. The decay
  index experienced by the leading edge is explored using a radial
  profile of the transverse magnetic field from a PFSS extrapolation
  above the prominence region. Critical decay indices are extracted for
  each slit at their own specific values of height at the nonlinear
  phase onset (h(t<SUB>nl</SUB>)) and filtered to focus on instances
  resulting from kinematic fits with ${\chi }_{\mathrm{red}}^{2}\lt 2$
  (restricting β to 1.9-3.9). Based on this measure of the critical
  decay index along the prominence structure, we find strong evidence
  that the torus instability is the mechanism driving this prominence
  eruption. Defining any single decay index as being "critical" is not
  that critical because there is no single canonical or critical value
  of decay index through which all eruptions must succeed.

Title: A Comparison of Flare Forecasting Methods. IV. Evaluating
    Consecutive-day Forecasting Patterns
Authors: Park, Sung-Hong; Leka, K. D.; Kusano, Kanya; Andries, Jesse;
   Barnes, Graham; Bingham, Suzy; Bloomfield, D. Shaun; McCloskey,
   Aoife E.; Delouille, Veronique; Falconer, David; Gallagher, Peter T.;
   Georgoulis, Manolis K.; Kubo, Yuki; Lee, Kangjin; Lee, Sangwoo; Lobzin,
   Vasily; Mun, JunChul; Murray, Sophie A.; Hamad Nageem, Tarek A. M.;
   Qahwaji, Rami; Sharpe, Michael; Steenburgh, R. A.; Steward, Graham;
   Terkildsen, Michael
Bibcode: 2020ApJ...890..124P
Altcode: 2020arXiv200102808P
  A crucial challenge to successful flare prediction is
  forecasting periods that transition between "flare-quiet" and
  "flare-active." Building on earlier studies in this series in which we
  describe the methodology, details, and results of flare forecasting
  comparison efforts, we focus here on patterns of forecast outcomes
  (success and failure) over multiday periods. A novel analysis is
  developed to evaluate forecasting success in the context of catching
  the first event of flare-active periods and, conversely, correctly
  predicting declining flare activity. We demonstrate these evaluation
  methods graphically and quantitatively as they provide both quick
  comparative evaluations and options for detailed analysis. For the
  testing interval 2016-2017, we determine the relative frequency
  distribution of two-day dichotomous forecast outcomes for three
  different event histories (I.e., event/event, no-event/event, and
  event/no-event) and use it to highlight performance differences between
  forecasting methods. A trend is identified across all forecasting
  methods that a high/low forecast probability on day 1 remains high/low
  on day 2, even though flaring activity is transitioning. For M-class
  and larger flares, we find that explicitly including persistence or
  prior flare history in computing forecasts helps to improve overall
  forecast performance. It is also found that using magnetic/modern
  data leads to improvement in catching the first-event/first-no-event
  transitions. Finally, 15% of major (I.e., M-class or above) flare
  days over the testing interval were effectively missed due to a lack
  of observations from instruments away from the Earth-Sun line.

Title: Feature Ranking of Active Region Source Properties in Solar
    Flare Forecasting and the Uncompromised Stochasticity of Flare
    Occurrence
Authors: Campi, Cristina; Benvenuto, Federico; Massone, Anna Maria;
   Bloomfield, D. Shaun; Georgoulis, Manolis K.; Piana, Michele
Bibcode: 2019ApJ...883..150C
Altcode: 2019arXiv190612094C
  Solar flares originate from magnetically active regions (ARs) but
  not all solar ARs give rise to a flare. Therefore, the challenge of
  solar flare prediction benefits from an intelligent computational
  analysis of physics-based properties extracted from AR observables,
  most commonly line-of-sight or vector magnetograms of the active
  region photosphere. For the purpose of flare forecasting, this
  study utilizes an unprecedented 171 flare-predictive AR properties,
  mainly inferred by the Helioseismic and Magnetic Imager on board the
  Solar Dynamics Observatory (SDO/HMI) in the course of the European
  Union Horizon 2020 FLARECAST project. Using two different supervised
  machine-learning methods that allow feature ranking as a function
  of predictive capability, we show that (i) an objective training and
  testing process is paramount for the performance of every supervised
  machine-learning method; (ii) most properties include overlapping
  information and are therefore highly redundant for flare prediction;
  (iii) solar flare prediction is still—and will likely remain—a
  predominantly probabilistic challenge.

Title: Which Photospheric Characteristics Are Most Relevant to
    Active-Region Coronal Mass Ejections?
Authors: Kontogiannis, Ioannis; Georgoulis, Manolis K.; Guerra,
   Jordan A.; Park, Sung-Hong; Bloomfield, D. Shaun
Bibcode: 2019SoPh..294..130K
Altcode: 2019arXiv190906088K
  We investigate the relation between characteristics of coronal mass
  ejections and parameterizations of the eruptive capability of solar
  active regions widely used in solar flare-prediction schemes. These
  parameters, some of which are explored for the first time, are
  properties related to topological features, namely, magnetic
  polarity-inversion lines (MPILs) that indicate large amounts of
  stored non-potential (i.e. free) magnetic energy. We utilize the
  Space Weather Database of Notifications, Knowledge, Information
  (DONKI) and the Large Angle and Spectrometric Coronograph (LASCO)
  databases to find flare-associated coronal mass ejections and
  their kinematic characteristics, while properties of MPILs are
  extracted from Helioseismic and Magnetic Imager (HMI) vector
  magnetic-field observations of active regions to extract the
  properties of source-region MPILs. The correlation between all
  properties and the characteristics of CMEs ranges from moderate to
  very strong. More significant correlations hold particularly for
  fast CMEs, which are most important in terms of adverse space-weather
  manifestations. Non-neutralized currents and the length of the main
  MPIL exhibit significantly stronger correlations than the rest of the
  properties. This finding supports a causal relationship between coronal
  mass ejections and non-neutralized electric currents in highly sheared,
  conspicuous MPILs. In addition, non-neutralized currents and MPIL length
  carry distinct, independent information as to the eruptive potential of
  active regions. The combined total amount of non-neutralized electric
  currents and the length of the main polarity-inversion line, therefore,
  reflect more efficiently than other parameters the eruptive capacity
  of solar active regions and the CME kinematic characteristics stemming
  from these regions.

Title: A Comparison of Flare Forecasting Methods. III. Systematic
    Behaviors of Operational Solar Flare Forecasting Systems
Authors: Leka, K. D.; Park, Sung-Hong; Kusano, Kanya; Andries, Jesse;
   Barnes, Graham; Bingham, Suzy; Bloomfield, D. Shaun; McCloskey,
   Aoife E.; Delouille, Veronique; Falconer, David; Gallagher, Peter
   T.; Georgoulis, Manolis K.; Kubo, Yuki; Lee, Kangjin; Lee, Sangwoo;
   Lobzin, Vasily; Mun, JunChul; Murray, Sophie A.; Hamad Nageem, Tarek
   A. M.; Qahwaji, Rami; Sharpe, Michael; Steenburgh, Robert A.; Steward,
   Graham; Terkildsen, Michael
Bibcode: 2019ApJ...881..101L
Altcode: 2019arXiv190702909L
  A workshop was recently held at Nagoya University (2017 October
  31-November 2), sponsored by the Center for International Collaborative
  Research, at the Institute for Space-Earth Environmental Research,
  Nagoya University, Japan, to quantitatively compare the performance
  of today’s operational solar flare forecasting facilities. Building
  upon Paper I of this series, in Paper II we described the participating
  methods for this latest comparison effort, the evaluation methodology,
  and presented quantitative comparisons. In this paper, we focus on
  the behavior and performance of the methods when evaluated in the
  context of broad implementation differences. Acknowledging the short
  testing interval available and the small number of methods available,
  we do find that forecast performance: (1) appears to improve by
  including persistence or prior flare activity, region evolution,
  and a human “forecaster in the loop” (2) is hurt by restricting
  data to disk-center observations; (3) may benefit from long-term
  statistics but mostly when then combined with modern data sources
  and statistical approaches. These trends are arguably weak and must
  be viewed with numerous caveats, as discussed both here and in Paper
  II. Following this present work, in Paper IV (Park et al. 2019) we
  will present a novel analysis method to evaluate temporal patterns of
  forecasting errors of both types (i.e., misses and false alarms). Hence,
  most importantly, with this series of papers, we demonstrate the
  techniques for facilitating comparisons in the interest of establishing
  performance-positive methodologies.

Title: A Comparison of Flare Forecasting Methods. II. Benchmarks,
    Metrics, and Performance Results for Operational Solar Flare
    Forecasting Systems
Authors: Leka, K. D.; Park, Sung-Hong; Kusano, Kanya; Andries, Jesse;
   Barnes, Graham; Bingham, Suzy; Bloomfield, D. Shaun; McCloskey,
   Aoife E.; Delouille, Veronique; Falconer, David; Gallagher, Peter
   T.; Georgoulis, Manolis K.; Kubo, Yuki; Lee, Kangjin; Lee, Sangwoo;
   Lobzin, Vasily; Mun, JunChul; Murray, Sophie A.; Hamad Nageem, Tarek
   A. M.; Qahwaji, Rami; Sharpe, Michael; Steenburgh, Robert A.; Steward,
   Graham; Terkildsen, Michael
Bibcode: 2019ApJS..243...36L
Altcode: 2019arXiv190702905L
  Solar flares are extremely energetic phenomena in our solar
  system. Their impulsive and often drastic radiative increases,
  particularly at short wavelengths, bring immediate impacts that motivate
  solar physics and space weather research to understand solar flares
  to the point of being able to forecast them. As data and algorithms
  improve dramatically, questions must be asked concerning how well the
  forecasting performs; crucially, we must ask how to rigorously measure
  performance in order to critically gauge any improvements. Building
  upon earlier-developed methodology of Paper I (Barnes et al. 2016),
  international representatives of regional warning centers and
  research facilities assembled in 2017 at the Institute for Space-Earth
  Environmental Research, Nagoya University, Japan to, for the first time,
  directly compare the performance of operational solar flare forecasting
  methods. Multiple quantitative evaluation metrics are employed, with the
  focus and discussion on evaluation methodologies given the restrictions
  of operational forecasting. Numerous methods performed consistently
  above the “no-skill” level, although which method scored top marks
  is decisively a function of flare event definition and the metric
  used; there was no single winner. Following in this paper series, we
  ask why the performances differ by examining implementation details
  (Leka et al. 2019), and then we present a novel analysis method to
  evaluate temporal patterns of forecasting errors in Paper IV (Park
  et al. 2019). With these works, this team presents a well-defined and
  robust methodology for evaluating solar flare forecasting methods in
  both research and operational frameworks and today’s performance
  benchmarks against which improvements and new methods may be compared.

Title: Solar Flare Forecasting from Magnetic Feature Properties
    Generated by the Solar Monitor Active Region Tracker
Authors: Domijan, Katarina; Bloomfield, D. Shaun; Pitié, François
Bibcode: 2019SoPh..294....6D
Altcode:
  We study the predictive capabilities of magnetic-feature properties (MF)
  generated by the Solar Monitor Active Region Tracker (SMART: Higgins
  et al. in Adv. Space Res.47, 2105, 2011) for solar-flare forecasting
  from two datasets: the full dataset of SMART detections from 1996 to
  2010 which has been previously studied by Ahmed et al. (Solar Phys.283,
  157, 2013) and a subset of that dataset that only includes detections
  that are NOAA active regions (ARs). The main contributions of this
  work are: we use marginal relevance as a filter feature selection
  method to identify the most useful SMART MF properties for separating
  flaring from non-flaring detections and logistic regression to derive
  classification rules to predict future observations. For comparison,
  we employ a Random Forest, Support Vector Machine, and a set of Deep
  Neural Network models, as well as lasso for feature selection. Using
  the linear model with three features we obtain significantly better
  results (True Skill Score: TSS = 0.84) than those reported by Ahmed
  et al. (Solar Phys.283, 157, 2013) for the full dataset of SMART
  detections. The same model produced competitive results (TSS = 0.67)
  for the dataset of SMART detections that are NOAA ARs, which can be
  compared to a broader section of flare-forecasting literature. We show
  that more complex models are not required for this data.

Title: Solar flare forecasting from magnetic feature properties
    generated by Solar Monitor Active Region Tracker
Authors: Domijan, Katarina; Bloomfield, D. Shaun; Pitie, Francois
Bibcode: 2018arXiv181202652D
Altcode:
  We study the predictive capabilities of magnetic feature properties
  (MF) generated by Solar Monitor Active Region Tracker (SMART) for
  solar flare forecasting from two datasets: the full dataset of SMART
  detections from 1996 to 2010 that has been previously studied by
  Ahmed et al. (2011) and a subset of that dataset which only includes
  detections that are NOAA active regions (ARs). Main contributions:
  we use marginal relevance as a filter feature selection method to
  identify most useful SMART MF properties for separating flaring from
  non-flaring detections and logistic regression to derive classification
  rules to predict future observations. For comparison, we employ a
  Random Forest, Support Vector Machine and a set of Deep Neural Network
  models, as well as Lasso for feature selection. Using the linear model
  with three features we obtain significantly better results (TSS=0.84)
  to those reported by Ahmed et al.(2011) for the full dataset of SMART
  detections. The same model produced competitive results (TSS=0.67)
  for the dataset of SMART detections that are NOAA ARs which can be
  compared to a broader section of flare forecasting literature. We show
  that more complex models are not required for this data.

Title: Photospheric Shear Flows in Solar Active Regions and Their
    Relation to Flare Occurrence
Authors: Park, Sung-Hong; Guerra, Jordan A.; Gallagher, Peter T.;
   Georgoulis, Manolis K.; Bloomfield, D. Shaun
Bibcode: 2018SoPh..293..114P
Altcode: 2018arXiv180707714P
  Solar active regions (ARs) that produce major flares typically exhibit
  strong plasma shear flows around photospheric magnetic polarity
  inversion lines (MPILs). It is therefore important to quantitatively
  measure such photospheric shear flows in ARs for a better understanding
  of their relation to flare occurrence. Photospheric flow fields were
  determined by applying the Differential Affine Velocity Estimator
  for Vector Magnetograms (DAVE4VM) method to a large data set of 2548
  coaligned pairs of AR vector magnetograms with 12-min separation over
  the period 2012 - 2016. From each AR flow-field map, three shear-flow
  parameters were derived corresponding to the mean («S »), maximum
  (S<SUB>max</SUB>) and integral (S<SUB>sum</SUB>) shear-flow speeds along
  strong-gradient, strong-field MPIL segments. We calculated flaring
  rates within 24 h as a function of each shear-flow parameter and we
  investigated the relation between the parameters and the waiting
  time (τ ) until the next major flare (class M1.0 or above) after
  the parameter observation. In general, it is found that the larger
  S<SUB>sum</SUB> an AR has, the more likely it is for the AR to produce
  flares within 24 h. It is also found that among ARs which produce major
  flares, if one has a larger value of S<SUB>sum</SUB> then τ generally
  gets shorter. These results suggest that large ARs with widespread
  and/or strong shear flows along MPILs tend to not only be more flare
  productive, but also produce major flares within 24 h or less.

Title: Flare forecasting using the evolution of McIntosh sunspot
    classifications
Authors: McCloskey, Aoife E.; Gallagher, Peter T.; Bloomfield, D. Shaun
Bibcode: 2018JSWSC...8A..34M
Altcode: 2018arXiv180500919M
  Most solar flares originate in sunspot groups, where magnetic
  field changes lead to energy build-up and release. However, few
  flare-forecasting methods use information of sunspot-group evolution,
  instead focusing on static point-in-time observations. Here, a new
  forecast method is presented based upon the 24-h evolution in McIntosh
  classification of sunspot groups. Evolution-dependent ≥C1.0 and
  ≥M1.0 flaring rates are found from NOAA-numbered sunspot groups over
  December 1988-June 1996 (Solar Cycle 22; SC22) before converting to
  probabilities assuming Poisson statistics. These flaring probabilities
  are used to generate operational forecasts for sunspot groups over July
  1996-December 2008 (SC23), with performance studied by verification
  metrics. Major findings are: (i) considering Brier skill score (BSS)
  for ≥C1.0 flares, the evolution-dependent McIntosh-Poisson method
  (BSS<SUB>evolution</SUB> = 0.09) performs better than the static
  McIntosh-Poisson method (BSS<SUB>static</SUB> = - 0.09); (ii) low BSS
  values arise partly from both methods over-forecasting SC23 flares
  from the SC22 rates, symptomatic of ≥C1.0 rates in SC23 being on
  average ≈80% of those in SC22 (with ≥M1.0 being ≈50%); (iii)
  applying a bias-correction factor to reduce the SC22 rates used in
  forecasting SC23 flares yields modest improvement in skill relative
  to climatology for both methods (BSS<SUB>static</SUB><SUP>corr</SUP> =
  0.09 and BSS<SUB>evolution</SUB><SUP>corr</SUP> = 0.0.20) and improved
  forecast reliability diagrams.

Title: Forecasting Solar Flares Using Magnetogram-based Predictors
    and Machine Learning
Authors: Florios, Kostas; Kontogiannis, Ioannis; Park, Sung-Hong;
   Guerra, Jordan A.; Benvenuto, Federico; Bloomfield, D. Shaun;
   Georgoulis, Manolis K.
Bibcode: 2018SoPh..293...28F
Altcode: 2018arXiv180105744F
  We propose a forecasting approach for solar flares based on data from
  Solar Cycle 24, taken by the Helioseismic and Magnetic Imager (HMI)
  on board the Solar Dynamics Observatory (SDO) mission. In particular,
  we use the Space-weather HMI Active Region Patches (SHARP) product that
  facilitates cut-out magnetograms of solar active regions (AR) in the
  Sun in near-realtime (NRT), taken over a five-year interval (2012 -
  2016). Our approach utilizes a set of thirteen predictors, which are
  not included in the SHARP metadata, extracted from line-of-sight and
  vector photospheric magnetograms. We exploit several machine learning
  (ML) and conventional statistics techniques to predict flares of
  peak magnitude &gt;M1 and &gt;C1 within a 24 h forecast window. The
  ML methods used are multi-layer perceptrons (MLP), support vector
  machines (SVM), and random forests (RF). We conclude that random
  forests could be the prediction technique of choice for our sample,
  with the second-best method being multi-layer perceptrons, subject to
  an entropy objective function. A Monte Carlo simulation showed that
  the best-performing method gives accuracy ACC =0.93 (0.00 ), true
  skill statistic TSS =0.74 (0.02 ), and Heidke skill score HSS =0.49
  (0.01 ) for &gt;M1 flare prediction with probability threshold 15%
  and ACC =0.84 (0.00 ), TSS =0.60 (0.01 ), and HSS =0.59 (0.01 ) for
  &gt;C1 flare prediction with probability threshold 35%.

Title: Active Region Photospheric Magnetic Properties Derived from
    Line-of-Sight and Radial Fields
Authors: Guerra, J. A.; Park, S. -H.; Gallagher, P. T.; Kontogiannis,
   I.; Georgoulis, M. K.; Bloomfield, D. S.
Bibcode: 2018SoPh..293....9G
Altcode: 2017arXiv171206902G
  The effect of using two representations of the normal-to-surface
  magnetic field to calculate photospheric measures that are related
  to the active region (AR) potential for flaring is presented. Several
  AR properties were computed using line-of-sight (B<SUB>los</SUB>) and
  spherical-radial (B<SUB>r</SUB>) magnetograms from the Space-weather HMI
  Active Region Patch (SHARP) products of the Solar Dynamics Observatory,
  characterizing the presence and features of magnetic polarity inversion
  lines, fractality, and magnetic connectivity of the AR photospheric
  field. The data analyzed correspond to ≈4 ,000 AR observations,
  achieved by randomly selecting 25% of days between September 2012 and
  May 2016 for analysis at 6-hr cadence. Results from this statistical
  study include: i) the B<SUB>r</SUB> component results in a slight
  upwards shift of property values in a manner consistent with a
  field-strength underestimation by the B<SUB>los</SUB> component;
  ii) using the B<SUB>r</SUB> component results in significantly lower
  inter-property correlation in one-third of the cases, implying more
  independent information as regards the state of the AR photospheric
  magnetic field; iii) flaring rates for each property vary between
  the field components in a manner consistent with the differences
  in property-value ranges resulting from the components; iv) flaring
  rates generally increase for higher values of properties, except the
  Fourier spectral power index that has flare rates peaking around a
  value of 5 /3 . These findings indicate that there may be advantages
  in using B<SUB>r</SUB> rather than B<SUB>los</SUB> in calculating
  flare-related AR magnetic properties, especially for regions located
  far from central meridian.

Title: The Next Level in Automated Solar Flare Forecasting: the EU
    FLARECAST Project
Authors: Georgoulis, M. K.; Bloomfield, D.; Piana, M.; Massone,
   A. M.; Gallagher, P.; Vilmer, N.; Pariat, E.; Buchlin, E.; Baudin,
   F.; Csillaghy, A.; Soldati, M.; Sathiapal, H.; Jackson, D.; Alingery,
   P.; Argoudelis, V.; Benvenuto, F.; Campi, C.; Florios, K.; Gontikakis,
   C.; Guennou, C.; Guerra, J. A.; Kontogiannis, I.; Latorre, V.; Murray,
   S.; Park, S. H.; Perasso, A.; Sciacchitano, F.; von Stachelski, S.;
   Torbica, A.; Vischi, D.
Bibcode: 2017AGUFMSA21C..07G
Altcode:
  We attempt an informative description of the Flare Likelihood And
  Region Eruption Forecasting (FLARECAST) project, European Commission's
  first large-scale investment to explore the limits of reliability
  and accuracy achieved for the forecasting of major solar flares. We
  outline the consortium, top-level objectives and first results of
  the project, highlighting the diversity and fusion of expertise
  needed to deliver what was promised. The project's final product,
  featuring an openly accessible, fully modular and free to download
  flare forecasting facility will be delivered in early 2018. The
  project's three objectives, namely, science, research-to-operations and
  dissemination / communication, are also discussed: in terms of science,
  we encapsulate our close-to-final assessment on how close (or far)
  are we from a practically exploitable solar flare forecasting. In
  terms of R2O, we briefly describe the architecture of the FLARECAST
  infrastructure that includes rigorous validation for each forecasting
  step. From the three different communication levers of the project we
  finally focus on lessons learned from the two-way interaction with the
  community of stakeholders and governmental organizations. The FLARECAST
  project has received funding from the European Union's Horizon 2020
  research and innovation programme under grant agreement No. 640216.

Title: Understanding the Physical Nature of Coronal "EIT Waves"
Authors: Long, D. M.; Bloomfield, D. S.; Chen, P. F.; Downs, C.;
   Gallagher, P. T.; Kwon, R. -Y.; Vanninathan, K.; Veronig, A. M.;
   Vourlidas, A.; Vršnak, B.; Warmuth, A.; Žic, T.
Bibcode: 2017SoPh..292....7L
Altcode: 2016arXiv161105505L
  For almost 20 years the physical nature of globally propagating waves in
  the solar corona (commonly called "EIT waves") has been controversial
  and subject to debate. Additional theories have been proposed over the
  years to explain observations that did not agree with the originally
  proposed fast-mode wave interpretation. However, the incompatibility
  of observations made using the Extreme-ultraviolet Imaging Telescope
  (EIT) onboard the Solar and Heliospheric Observatory with the fast-mode
  wave interpretation was challenged by differing viewpoints from the twin
  Solar Terrestrial Relations Observatory spacecraft and data with higher
  spatial and temporal resolution from the Solar Dynamics Observatory. In
  this article, we reexamine the theories proposed to explain EIT waves
  to identify measurable properties and behaviours that can be compared
  to current and future observations. Most of us conclude that the
  so-called EIT waves are best described as fast-mode large-amplitude
  waves or shocks that are initially driven by the impulsive expansion
  of an erupting coronal mass ejection in the low corona.

Title: Solar Magnetic Data Analysis for the FLARECAST Project
Authors: Guerra, J. A.; Park, S. H.; Kontogiannis, I.; Bloomfield,
   D.; Gallagher, P.; Georgoulis, M. K.
Bibcode: 2016AGUFMSH11C2234G
Altcode:
  The Flare Likelihood And Region Eruption foreCASTing (FLARECAST) project
  is an EU H2020-funded consortium project aiming to develop an advanced
  solar flare forecasting system by implementing state-of-the-art
  solar data analysis and flare prediction algorithms. The Solar
  Physics Group at Trinity College Dublin is in charge of the analysis
  of observational data to extract solar active region properties
  that serve as input for the prediction algorithms. The calculated
  active region properties correspond to a non-exhaustive list of
  parameters that have demonstrated a strong flare association, such as
  Schrijver's R-value, the Fourier power spectrum exponent, the effective
  connected magnetic field (Beff), the horizontal field decay index,
  and the weighted length of strong-gradient polarity inversion lines
  (WLSG). Parameters were calculated from Spaceweather HMI Active Region
  Patch (SHARP) magnetograms, a data product of the Helioseismic and
  Magnetic Imager (HMI) magnetograph on the Solar Dynamics Observatory
  (SDO). SHARPs provide photospheric vector-magnetic field (B) images
  in near-realtime. For this study, results from a statistical study
  performed on a robust subsample of the entire SHARP dataset will be
  presented. In the framework of the FLARECAST predictor component,
  this study focuses, for the first time, on differences between
  parameter values found when the radial magnetic field component, Br,
  is used instead of the line-of-sight component, Blos. The effect of
  active region longitudinal position is discussed, as well as the flare
  association of the properties.

Title: Community-wide space weather Scoreboards: Facilitating the
    Validation of Real-time CME, Flare, and SEP Forecasts
Authors: Mullinix, R.; Mays, M. L.; Kuznetsova, M. M.; Andries,
   J.; Bingham, S.; Bloomfield, D.; Boblitt, J. M.; Crosby, N. B.;
   Dierckxsens, M.; Guerra, J. A.; Leka, K. D.; Marsh, M. S.; Murray,
   S.; Wiegand, C.
Bibcode: 2016AGUFMSH11C2256M
Altcode:
  Confidence assessment of predictive space weather models ultimately
  determines the value of forecasts for end users. Testing predictive
  capabilities before event onset is important and especially relevant
  for validating space weather models. This poster presents three
  real-time forecast validation projects facilitated by the CCMC via
  forecast collection "scoreboards": (1) CME arrival time and geomagnetic
  storm strength, (2) flare occurrence probability, and (3) SEP onset,
  duration, peak flux, probability, and overall profile. The CME,
  Flare, and SEP scoreboards enable world-wide community involvement
  in real-time predictions, foster community validation projects,
  and ultimately help researchers improve their CME, flare, and
  SEP forecasts. All CME, Flare, SEP forecast modelers and experts
  worldwide are invited to advise or participate in this effort. The
  flare and SEP systems are automated such that model developers can
  routinely upload their predictions to an anonymous ftp and the data
  is accessible to anyone via an API. The "CME arrival time scoreboard"
  (https://kauai.ccmc.gsfc.nasa.gov/CMEscoreboard/) provides a central
  location for the community to: submit their CME arrival time forecast
  in real-time, quickly view all forecasts at once in real-time, and
  compare forecasting methods when the event has arrived. There are
  currently 19 registered CME arrival time prediction methods. The "Flare
  Scoreboard" (http://ccmc.gsfc.nasa.gov/challenges/flare.php) project
  is led by the UK Met Office.The full disk and active region flare
  forecasts can currently be viewed on an interactive display overlaid
  on an SDO/AIA or HMI image of the Sun and will be dynamically paired
  with a display of flare probability time series (coming soon). The
  "SEP Scoreboard" (http://ccmc.gsfc.nasa.gov/challenges/sep.php)
  project is led by BIRA-IASB and the UK Met Office. SEP forecasts can
  be roughly divided into three categories: continuous/Probabilistic,
  solar event triggered, non near real-time. The SEP scoreboard will
  focus on real-time forecasts, however the SEP scoreboard team can
  also coordinate a set of historical events for a "SEP challenge" with
  different models, particularly those physics-based models in the third
  category that are not ready or relevant for real-time modeling.

Title: Exploring Coronal Dynamics: A Next Generation Solar Physics
    Mission white paper
Authors: Morton, R. J.; Scullion, E.; Bloomfield, D. S.; McLaughlin,
   J. A.; Regnier, S.; McIntosh, S. W.; Tomczyk, S.; Young, P.
Bibcode: 2016arXiv161106149M
Altcode:
  Determining the mechanisms responsible for the heating of the
  coronal plasma and maintaining and accelerating the solar wind
  are long standing goals in solar physics. There is a clear need to
  constrain the energy, mass and momentum flux through the solar corona
  and advance our knowledge of the physical process contributing to
  these fluxes. Furthermore, the accurate forecasting of Space Weather
  conditions at the near-Earth environment and, more generally, the
  plasma conditions of the solar wind throughout the heliosphere, require
  detailed knowledge of these fluxes in the near-Sun corona. Here we
  present a short case for a space-based imaging-spectrometer coronagraph,
  which will have the ability to provide synoptic information on the
  coronal environment and provide strict constraints on the mass, energy,
  and momentum flux through the corona. The instrument would ideally
  achieve cadences of $\sim10$~s, spatial resolution of 1" and observe the
  corona out to 2~$R_{\sun}$. Such an instrument will enable significant
  progress in our understanding of MHD waves throughout complex plasmas,
  as well as potentially providing routine data products to aid Space
  Weather forecasting.

Title: A Comparison of Flare Forecasting Methods. I. Results from
    the “All-Clear” Workshop
Authors: Barnes, G.; Leka, K. D.; Schrijver, C. J.; Colak, T.;
   Qahwaji, R.; Ashamari, O. W.; Yuan, Y.; Zhang, J.; McAteer, R. T. J.;
   Bloomfield, D. S.; Higgins, P. A.; Gallagher, P. T.; Falconer, D. A.;
   Georgoulis, M. K.; Wheatland, M. S.; Balch, C.; Dunn, T.; Wagner, E. L.
Bibcode: 2016ApJ...829...89B
Altcode: 2016arXiv160806319B
  Solar flares produce radiation that can have an almost immediate effect
  on the near-Earth environment, making it crucial to forecast flares
  in order to mitigate their negative effects. The number of published
  approaches to flare forecasting using photospheric magnetic field
  observations has proliferated, with varying claims about how well
  each works. Because of the different analysis techniques and data
  sets used, it is essentially impossible to compare the results from
  the literature. This problem is exacerbated by the low event rates of
  large solar flares. The challenges of forecasting rare events have long
  been recognized in the meteorology community, but have yet to be fully
  acknowledged by the space weather community. During the interagency
  workshop on “all clear” forecasts held in Boulder, CO in 2009,
  the performance of a number of existing algorithms was compared
  on common data sets, specifically line-of-sight magnetic field and
  continuum intensity images from the Michelson Doppler Imager, with
  consistent definitions of what constitutes an event. We demonstrate
  the importance of making such systematic comparisons, and of using
  standard verification statistics to determine what constitutes a good
  prediction scheme. When a comparison was made in this fashion, no one
  method clearly outperformed all others, which may in part be due to the
  strong correlations among the parameters used by different methods to
  characterize an active region. For M-class flares and above, the set
  of methods tends toward a weakly positive skill score (as measured
  with several distinct metrics), with no participating method proving
  substantially better than climatological forecasts.

Title: Understanding the Physical Nature of Coronal "EIT Waves"
Authors: Long, D. M.; Bloomfield, D. S.; Chen, P. -F.; Downs,
   C.; Gallagher, P. T.; Kwon, R. -Y.; Vanninathan, K.; Veronig, A.;
   Vourlidas, A.; Vrsnak, B.; Warmuth, A.; Zic, T.
Bibcode: 2016usc..confE..24L
Altcode:
  For almost 20 years the physical nature of globally-propagating waves
  in the solar corona (commonly called "EIT waves") has been controversial
  and subject to debate. Additional theories have been proposed throughout
  the years to explain observations that did not fit with the originally
  proposed fast-mode wave interpretation. However, the incompatibility
  of observations made using the Extreme-ultraviolet Imaging Telescope
  (EIT) on the Solar and Heliospheric Observatory with the fast-mode
  wave interpretation have been challenged by differing viewpoints
  from the Solar Terrestrial Relations Observatory spacecraft and higher
  spatial/temporal resolution data from the Solar Dynamics Observatory. In
  this paper, we reexamine the theories proposed to explain "EIT waves"
  to identify measurable properties and behaviours that can be compared
  to current and future observations. Most of us conclude that "EIT
  waves" are best described as fast-mode large-amplitude waves/shocks,
  which are initially driven by the impulsive expansion of an erupting
  coronal mass ejection in the low corona.

Title: Flaring Rates and the Evolution of Sunspot Group McIntosh
    Classifications
Authors: McCloskey, Aoife E.; Gallagher, Peter T.; Bloomfield, D. Shaun
Bibcode: 2016SoPh..291.1711M
Altcode: 2016arXiv160700903M; 2016SoPh..tmp..116M
  Sunspot groups are the main source of solar flares, with the energy
  to power them being supplied by magnetic-field evolution (e.g. flux
  emergence or twisting/shearing). To date, few studies have investigated
  the statistical relation between sunspot-group evolution and flaring,
  with none considering evolution in the McIntosh classification
  scheme. Here we present a statistical analysis of sunspot groups from
  Solar Cycle 22, focusing on 24-hour changes in the three McIntosh
  classification components. Evolution-dependent ≥C 1.0 , ≥M 1.0 ,
  and ≥X 1.0 flaring rates are calculated, leading to the following
  results: i) flaring rates become increasingly higher for greater
  degrees of upward evolution through the McIntosh classes, with the
  opposite found for downward evolution; ii) the highest flaring rates
  are found for upward evolution from larger, more complex, classes
  (e.g. Zurich D- and E-classes evolving upward to F-class produce
  ≥C 1.0 rates of 2.66 ±0.28 and 2.31 ±0.09 flares per 24 hours,
  respectively); iii) increasingly complex classes give higher rates for
  all flare magnitudes, even when sunspot groups do not evolve over 24
  hours. These results support the hypothesis that injection of magnetic
  energy by flux emergence (i.e. increasing in Zurich or compactness
  classes) leads to a higher frequency and magnitude of flaring.

Title: Enabling Solar Flare Forecasting at an Unprecedented Level:
    the FLARECAST Project
Authors: Georgoulis, Manolis K.; Pariat, Etienne; Massone, Anna
   Maria; Vilmer, Nicole; Jackson, David; Buchlin, Eric; Csillaghy,
   Andre; Bommier, Veronique; Kontogiannis, Ioannis; Gallagher, Peter;
   Gontikakis, Costis; Guennou, Chloé; Murray, Sophie; Bloomfield,
   D. Shaun; Alingery, Pablo; Baudin, Frederic; Benvenuto, Federico;
   Bruggisser, Florian; Florios, Konstantinos; Guerra, Jordan; Park,
   Sung-Hong; Perasso, Annalisa; Piana, Michele; Sathiapal, Hanna;
   Soldati, Marco; Von Stachelski, Samuel; Argoudelis, Vangelis;
   Caminade, Stephane
Bibcode: 2016cosp...41E.657G
Altcode:
  We attempt a brief but informative description of the Flare
  Likelihood And Region Eruption Forecasting (FLARECAST) project,
  European Commission's first large-scale investment to explore the
  limits of reliability and accuracy for the forecasting of major solar
  flares. The consortium, objectives, and first results of the project
  - featuring an openly accessible, interactive flare forecasting
  facility by the end of 2017 - will be outlined. In addition, we will
  refer to the so-called "explorative research" element of project,
  aiming to connect solar flares with coronal mass ejections (CMEs)
  and possibly pave the way for CME, or eruptive flare, prediction. We
  will also emphasize the FLARECAST modus operandi, namely the diversity
  of expertise within the consortium that independently aims to science,
  infrastructure development and dissemination, both to stakeholders and
  to the general public. Concluding, we will underline that the FLARECAST
  project responds squarely to the joint COSPAR - ILWS Global Roadmap
  to shield society from the adversities of space weather, addressing
  its primary goal and, in particular, its Research Recommendations
  1, 2 and 4, Teaming Recommendations II and III, and Collaboration
  Recommendations A, B, and D. The FLARECAST project has received funding
  from the European Union's Horizon 2020 research and innovation programme
  under grant agreement No. 640216.

Title: Conditions for electron-cyclotron maser emission in the
    solar corona
Authors: Morosan, D. E.; Zucca, P.; Bloomfield, D. S.; Gallagher, P. T.
Bibcode: 2016A&A...589L...8M
Altcode: 2016arXiv160404788M
  Context. The Sun is an active source of radio emission ranging from
  long duration radio bursts associated with solar flares and coronal
  mass ejections to more complex, short duration radio bursts such as
  solar S bursts, radio spikes and fibre bursts. While plasma emission is
  thought to be the dominant emission mechanism for most radio bursts,
  the electron-cyclotron maser (ECM) mechanism may be responsible
  for more complex, short-duration bursts as well as fine structures
  associated with long-duration bursts. <BR /> Aims: We investigate the
  conditions for ECM in the solar corona by considering the ratio of the
  electron plasma frequency ω<SUB>p</SUB> to the electron-cyclotron
  frequency Ω<SUB>e</SUB>. The ECM is theoretically possible when
  ω<SUB>p</SUB>/ Ω<SUB>e</SUB>&lt; 1. <BR /> Methods: Two-dimensional
  electron density, magnetic field, plasma frequency, and electron
  cyclotron frequency maps of the off-limb corona were created using
  observations from SDO/AIA and SOHO/LASCO, together with potential
  field extrapolations of the magnetic field. These maps were then used
  to calculate ω<SUB>p</SUB>/Ω<SUB>e</SUB> and Alfvén velocity maps
  of the off-limb corona. <BR /> Results: We found that the condition
  for ECM emission (ω<SUB>p</SUB>/ Ω<SUB>e</SUB>&lt; 1) is possible at
  heights &lt;1.07 R<SUB>⊙</SUB> in an active region near the limb;
  that is, where magnetic field strengths are &gt;40 G and electron
  densities are &gt;3 × 10<SUP>8</SUP> cm<SUP>-3</SUP>. In addition, we
  found comparatively high Alfvén velocities (&gt;0.02c or &gt;6000 km
  s<SUP>-1</SUP>) at heights &lt;1.07 R<SUB>⊙</SUB> within the active
  region. <BR /> Conclusions: This demonstrates that the condition for
  ECM emission is satisfied within areas of the corona containing large
  magnetic fields, such as the core of a large active region. Therefore,
  ECM could be a possible emission mechanism for high-frequency radio
  and microwave bursts.

Title: Performance of Major Flare Watches from the Max Millennium
    Program (2001 - 2010)
Authors: Bloomfield, D. S.; Gallagher, P. T.; Marquette, W. H.;
   Milligan, R. O.; Canfield, R. C.
Bibcode: 2016SoPh..291..411B
Altcode: 2015arXiv151204518B; 2016SoPh..tmp....1B
  The physical processes that trigger solar flares are not well
  understood, and significant debate remains around processes governing
  particle acceleration, energy partition, and particle and energy
  transport. Observations at high resolution in energy, time, and
  space are required in multiple energy ranges over the whole course of
  many flares to build an understanding of these processes. Obtaining
  high-quality, co-temporal data from ground- and space- based instruments
  is crucial to achieving this goal and was the primary motivation for
  starting the Max Millennium program and Major Flare Watch (MFW) alerts,
  aimed at coordinating observations of all flares ≥ X1 GOES X-ray
  classification (including those partially occulted by the limb). We
  present a review of the performance of MFWs from 1 February 2001 to
  31 May 2010, inclusive, which finds that (1) 220 MFWs were issued
  in 3407 days considered (6.5 % duty cycle), with these occurring in
  32 uninterrupted periods that typically last 2 - 8 days; (2) 56%
  of flares ≥ X1 were caught, occurring in 19 % of MFW days; (3)
  MFW periods ended at suitable times, but substantial gain could have
  been achieved in percentage of flares caught if periods had started
  24 h earlier; (4) MFWs successfully forecast X-class flares with a
  true skill statistic (TSS) verification metric score of 0.500, that is
  comparable to a categorical flare/no-flare interpretation of the NOAA
  Space Weather Prediction Centre probabilistic forecasts (TSS = 0.488).

Title: CorPITA: An Automated Algorithm for the Identification and
    Analysis of Coronal "EIT Waves"
Authors: Long, D. M.; Bloomfield, D. S.; Gallagher, P. T.;
   Pérez-Suárez, D.
Bibcode: 2014SoPh..289.3279L
Altcode: 2014arXiv1403.6722L; 2014SoPh..tmp...66L
  The continuous stream of data available from the Atmospheric Imaging
  Assembly (AIA) telescopes onboard the Solar Dynamics Observatory (SDO)
  spacecraft has allowed a deeper understanding of the Sun. However,
  the sheer volume of data has necessitated the development of automated
  techniques to identify and analyse various phenomena. In this article,
  we describe the Coronal Pulse Identification and Tracking Algorithm
  (CorPITA) for the identification and analysis of coronal "EIT
  waves". CorPITA uses an intensity-profile technique to identify the
  propagating pulse, tracking it throughout its evolution before returning
  estimates of its kinematics. The algorithm is applied here to a data
  set from February 2011, allowing its capabilities to be examined and
  critiqued. This algorithm forms part of the SDO Feature Finding Team
  initiative and will be implemented as part of the Heliophysics Event
  Knowledgebase (HEK). This is the first fully automated algorithm
  to identify and track the propagating "EIT wave" rather than any
  associated phenomenon and will allow a deeper understanding of this
  controversial phenomenon.

Title: A study of sympathetic eruptions using the Heliophysics
    Events Knowledgebase
Authors: Higgins, Paul A.; Schrijver, Carolus J.; Title, Alan M.;
   Bloomfield, D. Shaun; Gallagher, Peter T
Bibcode: 2014AAS...22412316H
Altcode:
  Over the past few decades there have been a number of papers
  investigating the connection between flares occurring in
  succession. Statistically, any connection that affects the timing of
  successive flares that exists is found to be weak. However, the majority
  of previous investigations has been limited by only considering the
  causal connection between soft X-ray flares. More recent case studies
  have shown convincing evidence that large eruptions cause a global
  reorganization of overlying magnetic fields that can result in the
  eruption of both flares and filaments at large distances from the
  original event. In this work, the connection between GOES X-ray flares
  (C-, M-, and X-class) and filament eruptions occurring in succession in
  two different active regions is considered statistically. The filament
  eruptions are recorded in the Heliophysics Events Knowledgebase
  by observers using SDO/AIA data. A significant causal connection is
  found between the two event types, such that large flares are followed
  by filament eruptions within 24 hours much more often than they are
  preceded by filament eruptions. This stipulates that the flares either
  cause the filaments to erupt or affect the eruption timing such that
  the filament eruptions follow the flares more closely in time.

Title: The formation heights of coronal shocks from 2D density and
    Alfvén speed maps
Authors: Zucca, Pietro; Carley, Eoin P.; Bloomfield, D. Shaun;
   Gallagher, Peter T.
Bibcode: 2014A&A...564A..47Z
Altcode: 2014arXiv1402.4051Z
  Context. Super-Alfvénic shocks associated with coronal mass ejections
  (CMEs) can produce radio emission known as Type II bursts. In the
  absence of direct imaging, accurate estimates of coronal electron
  densities, magnetic field strengths, and Alfvén speeds are required
  to calculate the kinematics of shocks. To date, 1D radial models have
  been used, but these are not appropriate for shocks propagating in
  non-radial directions. <BR /> Aims: Here, we study a coronal shock
  wave associated with a CME and Type II radio burst using 2D electron
  density and Alfvén speed maps to determine the locations that shocks
  are excited as the CME expands through the corona. <BR /> Methods:
  Coronal density maps were obtained from emission measures derived
  from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic
  Observatory (SDO) and polarized brightness measurements from the Large
  Angle and Spectrometric Coronagraph (LASCO) on board the Solar and
  Heliospheric Observatory (SOHO). Alfvén speed maps were calculated
  using these density maps and magnetic field extrapolations from the
  Helioseismic and Magnetic Imager (SDO/HMI). The computed density and
  Alfvén speed maps were then used to calculate the shock kinematics in
  non-radial directions. <BR /> Results: Using the kinematics of the Type
  II burst and associated shock, we find our observations to be consistent
  with the formation of a shock located at the CME flanks where the
  Alfvén speed has a local minimum. <BR /> Conclusions: The 1D density
  models are not appropriate for shocks that propagate non-radially along
  the flanks of a CME. Rather, the 2D density, magnetic field and Alfvén
  speed maps described here give a more accurate method for determining
  the fundamental properties of shocks and their relation to CMEs.

Title: Quasiperiodic acceleration of electrons by a plasmoid-driven
    shock in the solar atmosphere
Authors: Carley, Eoin P.; Long, David M.; Byrne, Jason P.; Zucca,
   Pietro; Bloomfield, D. Shaun; McCauley, Joseph; Gallagher, Peter T.
Bibcode: 2013NatPh...9..811C
Altcode: 2014arXiv1406.0743C
  Cosmic rays and solar energetic particles may be accelerated to
  relativistic energies by shock waves in astrophysical plasmas. On
  the Sun, shocks and particle acceleration are often associated with
  the eruption of magnetized plasmoids, called coronal mass ejections
  (CMEs). However, the physical relationship between CMEs and shock
  particle acceleration is not well understood. Here, we use extreme
  ultraviolet, radio and white-light imaging of a solar eruptive event
  on 22 September 2011 to show that a CME-induced shock (Alfvén Mach
  number ) was coincident with a coronal wave and an intense metric
  radio burst generated by intermittent acceleration of electrons to
  kinetic energies of 2-46keV (0.1-0.4c). Our observations show that
  plasmoid-driven quasiperpendicular shocks are capable of producing
  quasiperiodic acceleration of electrons, an effect consistent with a
  turbulent or rippled plasma shock surface.

Title: The Bursty Nature of Solar Flare X-Ray Emission. II. The
    Neupert Effect
Authors: McAteer, R. T. James; Bloomfield, D. Shaun
Bibcode: 2013ApJ...776...66M
Altcode:
  We carry out a novel statistical test of the Neupert effect based
  on multifractal spectra. The multifractal spectrum is the number
  distribution of the strengths (i.e., the Hölder exponents) of bursts in
  a signal. This is tested on simulations and carried out on RHESSI X-ray
  data from a well observed GOES X4.8 magnitude flare. The multifractal
  spectra is ideally suited to quantifying the relative smooth and bursty
  signals typically found in (thermal) soft X-ray and (non-thermal)
  hard X-ray data of solar flares. We show that light curves from all
  energies between 3 keV and 25 keV are statistically similar, suggesting
  that all these signals are dominated by the same (presumably thermal)
  emission. Emission lying between 25 keV and 100 keV probably contains
  some contribution from both thermal and non-thermal sources. The
  multifractal spectrum of a signal and that of its (cumulative)
  temporal integration are statistically similar (i.e., low residuals
  upon subtraction), but shifted by one in the peak Hölder exponent. We
  find the pairs of 3-6 keV and 100-300 keV emissions, the 6-12 keV and
  100-300 keV emissions and the 12-25 keV and 100-300 keV emissions are
  all consistent with the Neupert effect. The best agreement with the
  Neupert effect is between the 12-25 keV and 100-300 keV pair, although
  possibly with some secondary source of thermal emission present.

Title: Oscillatory Behavior in the Corona
Authors: Calabro, B.; McAteer, R. T. J.; Bloomfield, D. S.
Bibcode: 2013SoPh..286..405C
Altcode:
  We detect and analyze the oscillatory behavior of waves using a
  coronal seismology tool on sequences of coronal images. We study
  extreme-ultraviolet image sequences of active and quiet Sun regions
  and of coronal holes we identify 3- and 5-minute periodicities. In
  each studied region the 3- and 5-minute periodicities are similarly
  frequent. The number of pixels exhibiting a 3-minute periodicity is
  between 6 % - 8 % and those pixels exhibiting a 5-minute periodicity is
  between 5 % - 9 % of the total number of observed pixels. Our results
  show 3-minute oscillations along coronal loop structures but do not show
  5-minute oscillations along these same loop structures. The number of
  pixels exhibiting 3- and 5-minute periodicities in one type of region
  (active Sun, quiet Sun, and coronal holes) is roughly the same for
  all observed regions, leading us to infer that the 3- and 5-minute
  oscillations are the result of a global mechanism.

Title: Improved methods for determining the kinematics of coronal
    mass ejections and coronal waves
Authors: Byrne, J. P.; Long, D. M.; Gallagher, P. T.; Bloomfield,
   D. S.; Maloney, S. A.; McAteer, R. T. J.; Morgan, H.; Habbal, S. R.
Bibcode: 2013A&A...557A..96B
Altcode: 2013arXiv1307.8155B
  Context. The study of solar eruptive events and associated phenomena is
  of great importance in the context of solar and heliophysics. Coronal
  mass ejections (CMEs) and coronal waves are energetic manifestations of
  the restructuring of the solar magnetic field and mass motion of the
  plasma. Characterising this motion is vital for deriving the dynamics
  of these events and thus understanding the physics driving their
  initiation and propagation. The development and use of appropriate
  methods for measuring event kinematics is therefore imperative. <BR
  /> Aims: Traditional approaches to the study of CME and coronal wave
  kinematics do not return wholly accurate nor robust estimates of the
  true event kinematics and associated uncertainties. We highlight the
  drawbacks of these approaches, and demonstrate improved methods for
  accurate and reliable determination of the kinematics. <BR /> Methods:
  The Savitzky-Golay filter is demonstrated as a more appropriate fitting
  technique for CME and coronal wave studies, and a residual resampling
  bootstrap technique is demonstrated as a statistically rigorous method
  for the determination of kinematic error estimates and goodness-of-fit
  tests. <BR /> Results: It is shown that the scatter on distance-time
  measurements of small sample size can significantly limit the ability
  to derive accurate and reliable kinematics. This may be overcome by
  (i) increasing measurement precision and sampling cadence; and (ii)
  applying robust methods for deriving the kinematics and reliably
  determining their associated uncertainties. If a priori knowledge
  exists and a pre-determined model form for the kinematics is available
  (or indeed any justified fitting-form to be tested against the data),
  then its precision can be examined using a bootstrapping technique to
  determine the confidence interval associated with the model/fitting
  parameters. <BR /> Conclusions: Improved methods for determining the
  kinematics of CMEs and coronal waves are demonstrated to great effect,
  overcoming many issues highlighted in traditional numerical differencing
  and error propagation techniques.

Title: The SWAP EUV Imaging Telescope Part I: Instrument Overview
    and Pre-Flight Testing
Authors: Seaton, D. B.; Berghmans, D.; Nicula, B.; Halain, J. -P.; De
   Groof, A.; Thibert, T.; Bloomfield, D. S.; Raftery, C. L.; Gallagher,
   P. T.; Auchère, F.; Defise, J. -M.; D'Huys, E.; Lecat, J. -H.; Mazy,
   E.; Rochus, P.; Rossi, L.; Schühle, U.; Slemzin, V.; Yalim, M. S.;
   Zender, J.
Bibcode: 2013SoPh..286...43S
Altcode: 2012SoPh..tmp..217S; 2012arXiv1208.4631S
  The Sun Watcher with Active Pixels and Image Processing (SWAP) is
  an EUV solar telescope onboard ESA's Project for Onboard Autonomy 2
  (PROBA2) mission launched on 2 November 2009. SWAP has a spectral
  bandpass centered on 17.4 nm and provides images of the low solar
  corona over a 54×54 arcmin field-of-view with 3.2 arcsec pixels and
  an imaging cadence of about two minutes. SWAP is designed to monitor
  all space-weather-relevant events and features in the low solar
  corona. Given the limited resources of the PROBA2 microsatellite,
  the SWAP telescope is designed with various innovative technologies,
  including an off-axis optical design and a CMOS-APS detector. This
  article provides reference documentation for users of the SWAP image
  data.

Title: The Projects for Onboard Autonomy (PROBA2) Science Centre:
    Sun Watcher Using APS Detectors and Image Processing (SWAP) and
    Large-Yield Radiometer (LYRA) Science Operations and Data Products
Authors: Zender, J.; Berghmans, D.; Bloomfield, D. S.; Cabanas Parada,
   C.; Dammasch, I.; De Groof, A.; D'Huys, E.; Dominique, M.; Gallagher,
   P.; Giordanengo, B.; Higgins, P. A.; Hochedez, J. -F.; Yalim, M. S.;
   Nicula, B.; Pylyser, E.; Sanchez-Duarte, L.; Schwehm, G.; Seaton,
   D. B.; Stanger, A.; Stegen, K.; Willems, S.
Bibcode: 2013SoPh..286...93Z
Altcode: 2012SoPh..tmp..142Z
  The PROBA2 Science Centre (P2SC) is a small-scale science operations
  centre supporting the Sun observation instruments onboard PROBA2:
  the EUV imager Sun Watcher using APS detectors and image Processing
  (SWAP) and Large-Yield Radiometer (LYRA). PROBA2 is one of ESA's
  small, low-cost Projects for Onboard Autonomy (PROBA) and part of
  ESA's In-Orbit Technology Demonstration Programme. The P2SC is hosted
  at the Royal Observatory of Belgium, co-located with both Principal
  Investigator teams. The P2SC tasks cover science planning, instrument
  commanding, instrument monitoring, data processing, support of outreach
  activities, and distribution of science data products. PROBA missions
  aim for a high degree of autonomy at mission and system level, including
  the science operations centre. The autonomy and flexibility of the P2SC
  is reached by a set of web-based interfaces allowing the operators as
  well as the instrument teams to monitor quasi-continuously the status of
  the operations, allowing a quick reaction to solar events. In addition,
  several new concepts are implemented at instrument, spacecraft, and
  ground-segment levels allowing a high degree of flexibility in the
  operations of the instruments. This article explains the key concepts
  of the P2SC, emphasising the automation and the flexibility achieved
  in the commanding as well as the data-processing chain.

Title: Temperature Response of the 171 Å Passband of the SWAP Imager
    on PROBA2, with a Comparison to TRACE, SOHO, STEREO, and SDO
Authors: Raftery, Claire L.; Bloomfield, D. Shaun; Gallagher, Peter
   T.; Seaton, Daniel B.; Berghmans, David; De Groof, Anik
Bibcode: 2013SoPh..286..111R
Altcode:
  We calculated the temperature response of the 171 Å passbands of
  the Sun Watcher using APS detectors and image Processing (SWAP)
  instrument onboard the PRoject for OnBoard Autonomy 2 (PROBA2)
  satellite. These results were compared to the temperature responses
  of the Extreme Ultraviolet Imaging Telescope (EIT) onboard the Solar
  and Heliospheric Observatory (SOHO), the Transition Region and Coronal
  Explorer (TRACE), the twin Extreme Ultraviolet Imagers (EUVI) onboard
  the Solar TErrestrial RElations Observatory (STEREO) A and B spacecraft,
  and the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics
  Observatory (SDO). Multiplying the wavelength-response functions
  for each instrument by a series of isothermal synthetic spectra and
  integrating over the range 165 - 195 Å produced temperature-response
  functions for the six instruments. Each temperature response was
  then multiplied by sample differential emission-measure functions
  for four different solar conditions. For any given plasma condition
  (e.g. quiet Sun, active region), it was found that the overall variation
  with temperature agreed remarkably well across the six instruments,
  although the wavelength responses for each instrument have some
  distinctly different features. Deviations were observed, however,
  when we compared the response of any one instrument to different solar
  conditions, particularly for the case of solar flares.

Title: Measuring the Diffusion of Solar Magnetic Flux on Large
    Spatio-Temporal Scales
Authors: Higgins, Paul Anthony; Bloomfield, D. Shaun; Gallagher,
   Peter T.
Bibcode: 2013shin.confE..91H
Altcode:
  We present an investigation of the large-scale flows that influence
  magnetic fields at the solar surface. The aim of this work is to
  accurately characterise the supergranular diffusion coefficient,
  D, that governs the dispersal rate of magnetic features in the
  photosphere. There is a disconnect between the measured rate of magnetic
  field dispersal ( 50 - 300 km2/s) and the value of D used in global
  simulations of solar magnetic field evolution ( 500 - 600 km2/s). We
  track the poleward motion of magnetic features in a latitude-time map
  and compare the poleward progression to a data-driven simulation that
  includes differential rotation, the meridional flow, and supergranular
  diffusion. We find that over a time scale of months, setting D = 100
  km2/s matches observations, but over a time scale of years, setting D =
  500 km2/s is a better match. This supports the idea that observational
  time scale causes the disconnect in D values, which leads us to the
  conclusion that the present magnetic surface flux transport model is
  not adequate to explain the observed evolution of the solar surface
  magnetic field.

Title: Solar Flare Prediction Using Advanced Feature Extraction,
    Machine Learning, and Feature Selection
Authors: Ahmed, Omar W.; Qahwaji, Rami; Colak, Tufan; Higgins, Paul
   A.; Gallagher, Peter T.; Bloomfield, D. Shaun
Bibcode: 2013SoPh..283..157A
Altcode: 2011SoPh..tmp..404A
  Novel machine-learning and feature-selection algorithms have been
  developed to study: i) the flare-prediction-capability of magnetic
  feature (MF) properties generated by the recently developed Solar
  Monitor Active Region Tracker (SMART); ii) SMART's MF properties that
  are most significantly related to flare occurrence. Spatiotemporal
  association algorithms are developed to associate MFs with flares
  from April 1996 to December 2010 in order to differentiate flaring
  and non-flaring MFs and enable the application of machine-learning and
  feature-selection algorithms. A machine-learning algorithm is applied to
  the associated datasets to determine the flare-prediction-capability of
  all 21 SMART MF properties. The prediction performance is assessed using
  standard forecast-verification measures and compared with the prediction
  measures of one of the standard technologies for flare-prediction
  that is also based on machine-learning: Automated Solar Activity
  Prediction (ASAP). The comparison shows that the combination of SMART
  MFs with machine-learning has the potential to achieve more accurate
  flare-prediction than ASAP. Feature-selection algorithms are then
  applied to determine the MF properties that are most related to flare
  occurrence. It is found that a reduced set of six MF properties can
  achieve a similar degree of prediction accuracy as the full set of 21
  SMART MF properties.

Title: The Coronal Pulse Identification and Tracking Algorithm
    (CorPITA)
Authors: Long, David M.; Bloomfield, D. Shaun; Feeney-Barry, R.;
   Gallagher, Peter T.; Pérez-Suárez, David
Bibcode: 2013enss.confE..68L
Altcode:
  The Coronal Pulse Identification and Tracking Algorithm (CorPITA) is an
  automated technique for detecting and analysing "EIT Waves" in data from
  the Solar Dynamics Observatory (SDO) spacecraft. CorPITA will operate as
  part of the Heliophysics Event Knowledgebase (HEK), providing unbiased,
  near-real-time identification of coronal pulses. When triggered by
  the start of a solar flare, the algorithm uses an intensity profile
  technique radiating from the source of the flare to examine the entire
  solar disk. If a pulse is identified, the kinematics and morphological
  variation of the pulse are determined for all directions along the
  solar surface. Here, CorPITA is applied to a test data-set encompassing
  a series of solar flares of different classes from 13-20 February
  2011. This allows the effectiveness of the algorithm in dealing with
  the varied morphology of different eruptions to be characterised. The
  automated nature of this approach will enable an unbiased examination of
  "EIT Waves" and their relationship to coronal mass ejections.

Title: Evidence for partial Taylor relaxation from changes in magnetic
    geometry and energy during a solar flare
Authors: Murray, S. A.; Bloomfield, D. S.; Gallagher, P. T.
Bibcode: 2013A&A...550A.119M
Altcode: 2012arXiv1212.5906M
  Context. Solar flares are powered by energy stored in the coronal
  magnetic field, a portion of which is released when the field
  reconfigures into a lower energy state. Investigation of sunspot
  magnetic field topology during flare activity is useful to improve our
  understanding of flaring processes. <BR /> Aims: Here we investigate
  the deviation of the non-linear field configuration from that of
  the linear and potential configurations, and study the free energy
  available leading up to and after a flare. <BR /> Methods: The evolution
  of the magnetic field in NOAA region 10953 was examined using data from
  Hinode/SOT-SP, over a period of 12 h leading up to and after a GOES B1.0
  flare. Previous work on this region found pre- and post-flare changes in
  photospheric vector magnetic field parameters of flux elements outside
  the primary sunspot. 3D geometry was thus investigated using potential,
  linear force-free, and non-linear force-free field extrapolations
  in order to fully understand the evolution of the field lines. <BR
  /> Results: Traced field line geometrical and footpoint orientation
  differences show that the field does not completely relax to a fully
  potential or linear force-free state after the flare. Magnetic and free
  magnetic energies increase significantly ~6.5-2.5 h before the flare
  by ~10<SUP>31</SUP> erg. After the flare, the non-linear force-free
  magnetic energy and free magnetic energies decrease but do not return to
  pre-flare "quiet" values. <BR /> Conclusions: The post-flare non-linear
  force-free field configuration is closer (but not equal) to that of the
  linear force-free field configuration than a potential one. However,
  the small degree of similarity suggests that partial Taylor relaxation
  has occurred over a time scale of ~3-4 h.

Title: Studying Sun-Planet Connections Using the Heliophysics
    Integrated Observatory (HELIO)
Authors: Pérez-Suárez, D.; Maloney, S. A.; Higgins, P. A.;
   Bloomfield, D. S.; Gallagher, P. T.; Pierantoni, G.; Bonnin, X.;
   Cecconi, B.; Alberti, V.; Bocchialini, K.; Dierckxsens, M.; Opitz,
   A.; Le Blanc, A.; Aboudarham, J.; Bentley, R. B.; Brooke, J.; Coghlan,
   B.; Csillaghy, A.; Jacquey, C.; Lavraud, B.; Messerotti, M.
Bibcode: 2012SoPh..280..603P
Altcode: 2012SoPh..tmp..215P
  The Heliophysics Integrated Observatory (HELIO) is a software
  infrastructure involving a collection of web services, heliospheric
  data sources (e.g., solar, planetary, etc.), and event catalogues -
  all of which are accessible through a unified front end. In this
  paper we use the HELIO infrastructure to perform three case studies
  based on solar events that propagate through the heliosphere. These
  include a coronal mass ejection that intersects both Earth and Mars,
  a solar energetic particle event that crosses the orbit of Earth, and
  a high-speed solar wind stream, produced by a coronal hole, that is
  observed in situ at Earth (L1). A ballistic propagation model is run as
  one of the HELIO services and used to model these events, predicting
  if they will interact with a spacecraft or planet and determining the
  associated time of arrival. The HELIO infrastructure streamlines the
  method used to perform these kinds of case study by centralising the
  process of searching for and visualising data, indicating interesting
  features on the solar disk, and finally connecting remotely observed
  solar features with those detected by in situ solar wind and energetic
  particle instruments. HELIO represents an important leap forward in
  European heliophysics infrastructure by bridging the boundaries of
  traditional scientific domains.

Title: The spectrometer telescope for imaging x-rays on board the
    Solar Orbiter mission
Authors: Benz, A. O.; Krucker, S.; Hurford, G. J.; Arnold, N. G.;
   Orleanski, P.; Gröbelbauer, H. -P.; Klober, S.; Iseli, L.; Wiehl,
   H. J.; Csillaghy, A.; Etesi, L.; Hochmuth, N.; Battaglia, M.;
   Bednarzik, M.; Resanovic, R.; Grimm, O.; Viertel, G.; Commichau, V.;
   Meuris, A.; Limousin, O.; Brun, S.; Vilmer, N.; Skup, K. R.; Graczyk,
   R.; Stolarski, M.; Michalska, M.; Nowosielski, W.; Cichocki, A.;
   Mosdorf, M.; Seweryn, K.; Przepiórka, A.; Sylwester, J.; Kowalinski,
   M.; Mrozek, T.; Podgorski, P.; Mann, G.; Aurass, H.; Popow, E.;
   Onel, H.; Dionies, F.; Bauer, S.; Rendtel, J.; Warmuth, A.; Woche,
   M.; Plüschke, D.; Bittner, W.; Paschke, J.; Wolker, D.; Van Beek,
   H. F.; Farnik, F.; Kasparova, J.; Veronig, A. M.; Kienreich, I. W.;
   Gallagher, P. T.; Bloomfield, D. S.; Piana, M.; Massone, A. M.;
   Dennis, B. R.; Schwarz, R. A.; Lin, R. P.
Bibcode: 2012SPIE.8443E..3LB
Altcode:
  The Spectrometer Telescope for Imaging X-rays (STIX) is one of 10
  instruments on board Solar Orbiter, a confirmed Mclass mission of the
  European Space Agency (ESA) within the Cosmic Vision program scheduled
  to be launched in 2017. STIX applies a Fourier-imaging technique
  using a set of tungsten grids (at pitches from 0.038 to 1 mm) in
  front of 32 pixelized CdTe detectors to provide imaging spectroscopy
  of solar thermal and non-thermal hard X-ray emissions from 4 to 150
  keV. The status of the instrument reviewed in this paper is based on
  the design that passed the Preliminary Design Review (PDR) in early
  2012. Particular emphasis is given to the first light of the detector
  system called Caliste-SO.

Title: Toward Reliable Benchmarking of Solar Flare Forecasting Methods
Authors: Bloomfield, D. Shaun; Higgins, Paul A.; McAteer, R. T. James;
   Gallagher, Peter T.
Bibcode: 2012ApJ...747L..41B
Altcode: 2012arXiv1202.5995B
  Solar flares occur in complex sunspot groups, but it remains unclear
  how the probability of producing a flare of a given magnitude relates
  to the characteristics of the sunspot group. Here, we use Geostationary
  Operational Environmental Satellite X-ray flares and McIntosh group
  classifications from solar cycles 21 and 22 to calculate average
  flare rates for each McIntosh class and use these to determine Poisson
  probabilities for different flare magnitudes. Forecast verification
  measures are studied to find optimum thresholds to convert Poisson
  flare probabilities into yes/no predictions of cycle 23 flares. A case
  is presented to adopt the true skill statistic (TSS) as a standard
  for forecast comparison over the commonly used Heidke skill score
  (HSS). In predicting flares over 24 hr, the maximum values of TSS
  achieved are 0.44 (C-class), 0.53 (M-class), 0.74 (X-class), 0.54
  (&gt;=M1.0), and 0.46 (&gt;=C1.0). The maximum values of HSS are 0.38
  (C-class), 0.27 (M-class), 0.14 (X-class), 0.28 (&gt;=M1.0), and 0.41
  (&gt;=C1.0). These show that Poisson probabilities perform comparably
  to some more complex prediction systems, but the overall inaccuracy
  highlights the problem with using average values to represent flaring
  rate distributions.

Title: The Evolution of Sunspot Magnetic Fields Associated with a
    Solar Flare
Authors: Murray, Sophie A.; Bloomfield, D. Shaun; Gallagher, Peter T.
Bibcode: 2012SoPh..277...45M
Altcode: 2011arXiv1105.1978M; 2011SoPh..tmp..129M; 2011SoPh..tmp..185M;
   2011SoPh..tmp..254M
  Solar flares occur due to the sudden release of energy stored in
  active-region magnetic fields. To date, the precursors to flaring are
  still not fully understood, although there is evidence that flaring is
  related to changes in the topology or complexity of an active-region's
  magnetic field. Here, the evolution of the magnetic field in active
  region NOAA 10953 was examined using Hinode/SOT-SP data over a period
  of 12 hours leading up to and after a GOES B1.0 flare. A number of
  magnetic-field properties and low-order aspects of magnetic-field
  topology were extracted from two flux regions that exhibited increased
  Ca II H emission during the flare. Pre-flare increases in vertical
  field strength, vertical current density, and inclination angle of
  ≈ 8° toward the vertical were observed in flux elements surrounding
  the primary sunspot. The vertical field strength and current density
  subsequently decreased in the post-flare state, with the inclination
  becoming more horizontal by ≈ 7°. This behavior of the field vector
  may provide a physical basis for future flare-forecasting efforts.

Title: Active Regions and the Global Magnetic Field of the Sun
Authors: Higgins, P. A.; Bloomfield, D. S.; Gallagher, P. T.
Bibcode: 2011AGUFMSH43B1940H
Altcode:
  The Sun follows an 11 year activity cycle, over which the global
  magnetic field begins highly dipolar, and becomes more complex at
  cycle maximum, until reverting back to a dipole state, but with
  reversed polarity. Many magnetic structures of varying complexity
  (active regions) are observed to emerge, evolve, and decay over
  the cycle. Beyond location and orientation, the dependence of active
  region magnetic properties on the phase of the solar cycle is not well
  known. Here, we use automated feature detection methods to detect and
  characterize thousands of active region detections and statistically
  investigate their physical properties. We find that the mean size and
  flux of magnetic features on the solar disk is dependent on the phase
  of the cycle. We establish a direct connection between the spatial
  distribution of active regions on the solar disk and the configuration
  of the global solar magnetic field by investigating the polarity
  imbalance of feature magnetic flux. Using a global potential field
  source surface model, we find that the shape of the global field is
  strongly dependent on the large scale distribution of imbalanced flux.

Title: Deceleration and dispersion of large-scale coronal bright
    fronts
Authors: Long, D. M.; Gallagher, P. T.; McAteer, R. T. J.; Bloomfield,
   D. S.
Bibcode: 2011A&A...531A..42L
Altcode: 2011arXiv1104.4334L
  Context. One of the most dramatic manifestations of solar activity
  are large-scale coronal bright fronts (CBFs) observed in extreme
  ultraviolet (EUV) images of the solar atmosphere. To date, the
  energetics and kinematics of CBFs remain poorly understood, due to
  the low image cadence and sensitivity of previous EUV imagers and the
  limited methods used to extract the features. <BR /> Aims: In this
  paper, the trajectory and morphology of CBFs was determined in order
  to investigate the varying properties of a sample of CBFs, including
  their kinematics and pulse shape, dispersion, and dissipation. <BR
  /> Methods: We have developed a semi-automatic intensity profiling
  technique to extract the morphology and accurate positions of CBFs
  in 2.5-10 min cadence images from STEREO/EUVI. The technique was
  applied to sequences of 171 Å and 195 Å images from STEREO/EUVI
  in order to measure the wave properties of four separate CBF
  events. <BR /> Results: Following launch at velocities of ~240-450
  km s<SUP>-1</SUP> each of the four events studied showed significant
  negative acceleration ranging from ~-290 to -60 m s<SUP>-2</SUP>. The
  CBF spatial and temporal widths were found to increase from ~50 Mm
  to ~200 Mm and ~100 s to ~1500 s respectively, suggesting that they
  are dispersive in nature. The variation in position-angle averaged
  pulse-integrated intensity with propagation shows no clear trend
  across the four events studied. These results are most consistent
  with CBFs being dispersive magnetoacoustic waves. <P />Figures 3-8,
  10, 11, 13-15, 17, 18 and the movie are available in electronic form
  at <A href="http://www.aanda.org">http://www.aanda.org</A>

Title: Solar magnetic feature detection and tracking for space
    weather monitoring
Authors: Higgins, P. A.; Gallagher, P. T.; McAteer, R. T. J.;
   Bloomfield, D. S.
Bibcode: 2011AdSpR..47.2105H
Altcode: 2010arXiv1006.5898H
  We present an automated system for detecting, tracking, and cataloging
  emerging active regions throughout their evolution and decay using SOHO
  Michelson Doppler Interferometer (MDI) magnetograms. The SolarMonitor
  Active Region Tracking (SMART) algorithm relies on consecutive
  image differencing to remove both quiet-Sun and transient magnetic
  features, and region-growing techniques to group flux concentrations
  into classifiable features. We determine magnetic properties such
  as region size, total flux, flux imbalance, flux emergence rate,
  Schrijver’s R-value, R<SUP>∗</SUP> (a modified version of R),
  and Falconer’s measurement of non-potentiality. A persistence
  algorithm is used to associate developed active regions with emerging
  flux regions in previous measurements, and to track regions beyond
  the limb through multiple solar rotations. We find that the total
  number and area of magnetic regions on disk vary with the sunspot
  cycle. While sunspot numbers are a proxy to the solar magnetic field,
  SMART offers a direct diagnostic of the surface magnetic field and
  its variation over timescale of hours to years. SMART will form the
  basis of the active region extraction and tracking algorithm for the
  Heliophysics Integrated Observatory (HELIO).

Title: Short-term Evolution of Coronal Hole Boundaries
Authors: Krista, Larisza D.; Gallagher, Peter T.; Bloomfield, D. Shaun
Bibcode: 2011ApJ...731L..26K
Altcode: 2011arXiv1103.2660K
  The interaction of open and closed field lines at coronal hole (CH)
  boundaries is widely accepted to be due to interchange magnetic
  reconnection. To date, it is unclear how the boundaries vary on short
  timescales and at what velocity this occurs. Here, we describe an
  automated boundary tracking method used to determine CH boundary
  displacements on short timescales. The boundary displacements were
  found to be isotropic and to have typical expansion/contraction speeds
  of &lt;=2 km s<SUP>-1</SUP>, which indicate magnetic reconnection rates
  of &lt;=3 × 10<SUP>-3</SUP>. The observed displacements were used in
  conjunction with the interchange reconnection model to derive typical
  diffusion coefficients of &lt;=3 × 10<SUP>13</SUP> cm<SUP>2</SUP>
  s<SUP>-1</SUP>. These results are consistent with an interchange
  reconnection process in the low corona driven by the random granular
  motions of open and closed fields in the photosphere.

Title: Automated Solar Feature Detection for Space Weather
    Applications
Authors: Pérez-Suárez, David; Higgins, Paul A.; Bloomfield, D. Shaun;
   McAteer, R. T. James; Krista, Larisza D.; Byrne, Jason P.; Gallagher,
   Peter. T.
Bibcode: 2011asip.book..207P
Altcode: 2011arXiv1109.6922P
  The solar surface and atmosphere are highly dynamic plasma
  environments, which evolve over a wide range of temporal and spatial
  scales. Large-scale eruptions, such as coronal mass ejections,
  can be accelerated to millions of kilometres per hour in a matter
  of minutes, making their automated detection and characterisation
  challenging. Additionally, there are numerous faint solar features,
  such as coronal holes and coronal dimmings, which are important for
  space weather monitoring and forecasting, but their low intensity and
  sometimes transient nature makes them problematic to detect using
  traditional image processing techniques. These difficulties are
  compounded by advances in ground- and space- based instrumentation,
  which have increased the volume of data that solar physicists are
  confronted with on a minute-by-minute basis; NASA's Solar Dynamics
  Observatory for example is returning many thousands of images per hour
  (~1.5 TB/day). This chapter reviews recent advances in the application
  of images processing techniques to the automated detection of active
  regions, coronal holes, filaments, CMEs, and coronal dimmings for the
  purposes of space weather monitoring and prediction.

Title: The Solar Cycle Dependence of Active Region Properties
Authors: Higgins, P.; Gallagher, P. T.; Bloomfield, D.
Bibcode: 2010AGUFMSH53B..01H
Altcode:
  The solar cycle dependence of global active region (AR) emergence and
  dynamics is analysed using the SolarMonitor Active Region Tracker
  (SMART), which automatically detects and characterises magnetic
  flux concentrations using full-disk magnetograms. SMART is run on
  a magnetogram data set ranging from 1997 to 2009, resulting in
  measurements of each AR on disk each day. AR properties such as
  heliographic location, orientation, magnetic flux, flux imbalance,
  Schrijver's R value, Falconer's WLSG proxy for non-potentiality,
  and flare productivity are compared over cycle 23. We find several
  solar cycle modulations in the globally summed AR flux which may
  help to characterize the subsurface solar dynamo as well as global
  magnetic flux transport. The global flare index is better correlated
  to the global R value than WLSG or magnetic flux. Also, the emergence
  of highly non-potential, flare-productive ARs is found to be more
  confined in latitude than ARs in general, with little dependence on
  the phase of the solar cycle.

Title: Solar flares: Multiscale detection and analysis
Authors: Bloomfield, D. Shaun
Bibcode: 2010ada..confE...6B
Altcode:
  No abstract at ADS

Title: The SolarMonitor Active Region Tracking (SMART) Algorithm:
    Variation of magnetic feature properties through solar cycle 23
Authors: Higgins, P.; Gallagher, P.; McAteer, R.; Bloomfield, D.
Bibcode: 2009AGUFMSH51B1278H
Altcode:
  The SolarMonitor Active Region Tracking (SMART) algorithm is an
  automated system for detecting, tracking, and cataloging magnetic
  features throughout their evolution and decay. The SMART method will
  form the basis of active region extraction and tracking within the
  Heliophysics Integrated Observatory (HELIO). Magnetic properties
  such as total flux, flux imbalance, flux emergence rate, Schrijver's
  R-value, R* (a modified version of R), and Falconer's measurement of
  non-potentiality are determined for individual features throughout solar
  cycle 23. The variation of these feature property distributions with
  progression through the solar cycle is presented. Feature detections
  using the SMART algorithm for line-of-sight level 1.8 SOHO/MDI
  magnetogram taken 22 October 2003 at 12:47. Active region candidates
  are denoted "AR", emerging flux concentrations are denoted "EF", plage
  regions are denoted "PL" and other flux concentrations are labeled "NF".

Title: The Temperature Response of EUV Imagers
Authors: Raftery, Claire; Bloomfield, D. Shaun; Gallagher, P.
Bibcode: 2009SPD....40.1213R
Altcode:
  The temperature response of an EUV imager provides the user with
  the temperature range over which the instrument or passband is
  sensitive. These response curves appear to be highly peaked, implying
  a narrow range of temperature sensitivity. However, in the past,
  these response functions have been calculated using quiet sun spectra
  or constant density, assumptions which are relevant only in specific
  circumstances. The multithermal response of the EUV imagers - TRACE,
  SOHO/EIT, STEREO/EUVI, PROBA2/SWAP and SDO/AIA were investigated. It
  was found that a highly peaked response curve is only appropriate
  when looking at cooler material. However, studying higher temperature
  emission from e.g. active regions and flares produces a very broad,
  almost flat response between 10<SUP>5</SUP> and 10<SUP>7</SUP> K
  for all instruments. CLR is supported by an SPD studentship and the
  ESA/Prodex grant administered by Enterprise Ireland.

Title: Possible Connection Between Umbral and Bright Point
    Oscillations
Authors: Andic, Aleksandra; Jess, D. B.; Mathioudakis, M.; Keenan,
   F. P.; Bloomfield, D. S.
Bibcode: 2009SPD....40.0909A
Altcode:
  Active region NOAA 10794 was observed using the Rapid Dual Imager
  (RDI) instrument on the Dunn Solar Telescope at the National Solar
  Observatory, Sacramento Peak. G-band and H-alpha filters were employed
  for the observations, and the resulting data were subjected to both
  speckle reconstruction and wavelet analyses. <P />Intensity oscillations
  in the period range 8--584 s were detected. Those with frequencies
  near the Nyquist value of 125 mHz had a similar behavior to other
  oscillations detected in the period range of 8 - 60 s. <P />However,
  oscillations in the range around 180s observed above bright points
  show a temporal coincidence in the light curve shape and the number
  of the emitted frequencies in an umbral flash, indicating a possible
  connection.

Title: The Kinematics of a Globally Propagating Disturbance in the
    Solar Corona
Authors: Long, David M.; Gallagher, Peter T.; McAteer, R. T. James;
   Bloomfield, D. Shaun
Bibcode: 2008ApJ...680L..81L
Altcode: 2008arXiv0805.2023L
  The kinematics of a globally propagating disturbance (also known as
  an "EIT wave") is discussed using Extreme UltraViolet Imager (EUVI)
  data from the Solar Terrestrial Relations Observatory (STEREO). We
  show for the first time that an impulsively generated propagating
  disturbance has similar kinematics in all four EUVI passbands (304,
  171, 195, and 284 Å). In the 304 Å passband the disturbance shows a
  velocity peak of 238 ± 20 km s<SUP>-1</SUP> within ~28 minutes of its
  launch, varying in acceleration from 76 to -102 m s<SUP>-2</SUP>. This
  passband contains a strong contribution from a Si XI line (303.32 Å)
  with a peak formation temperature of ~1.6 MK. The 304 Å emission may
  therefore be coronal rather than chromospheric in origin. Comparable
  velocities and accelerations are found in the coronal 195 Å passband,
  while lower values are found in the lower cadence 284 Å passband. In
  the higher cadence 171 Å passband the velocity varies significantly,
  peaking at 475 ± 47 km s<SUP>-1</SUP> within ~20 minutes of launch,
  with a variation in acceleration from 816 to -413 m s<SUP>-2</SUP>. The
  high image cadence of the 171 Å passband (2.5 minutes compared to 10
  minutes for the similar temperature response 195 Å passband) is found
  to have a major effect on the measured velocity and acceleration of
  the pulse, which increase by factors of ~2 and ~10, respectively. This
  implies that previously measured values (e.g., using EIT) may have
  been underestimated. We also note that the disturbance shows strong
  reflection from a coronal hole in both the 171 and 195 Å passbands. The
  observations are consistent with an impulsively generated fast-mode
  magnetoacoustic wave.

Title: High frequency oscillations in the solar chromosphere and
    their connection with heating
Authors: Andic, Aleksandra; Mathioudakis, M.; Keenan, F. P.; Jess,
   D. B.; Bloomfield, D. S.
Bibcode: 2008IAUS..247..312A
Altcode: 2007IAUS..247..312A
  High frequency acoustic waves have been suggested as a source of
  mechanical heating in the quiet solar chromosphere. To investigate
  this, we have observed intensity oscillations of several lines in the
  frequency interval 1.64-70mHz using data from the VTT Tenerife and the
  Dunn Solar Telescope at the National Solar Observatory. Our analysis
  of Fe i 543.45 nm, Fe i 543.29 nm and the G-band, indicate that the
  majority of oscillations are connected with the magnetic fields and
  do not provide sufficient mechanical flux for the heating of the
  chromosphere. This correlation is also observed in quiet Sun areas.

Title: The nature of running penumbral waves revealed
Authors: Bloomfield, D. S.; Lagg, A.; Solanki, S. K.
Bibcode: 2008IAUS..247...55B
Altcode: 2007IAUS..247...55B
  We seek to clarify the nature of running penumbral (RP) waves:
  are they chromospheric trans-sunspot waves or a visual pattern of
  upward-propagating waves? Full Stokes spectropolarimetric time series
  of the photospheric Sii10827 Å line and the chromospheric Hei10830 Å
  multiplet were inverted using a Milne-Eddington code. Spatial pixels
  were paired between the outer umbral/inner penumbral photosphere
  and the penumbral chromosphere using inclinations retrieved by the
  inversion and the dual-height pairings of line-of-sight velocity time
  series were studied for signatures of wave propagation using a Fourier
  phase difference analysis. The dispersion relation for radiatively
  cooling acoustic waves, modified to incorporate an inclined propagation
  direction, fits well the observed phase differences between the pairs
  of photospheric and chromospheric pixels. We have thus demonstrated
  that RP waves are in effect low-β slow-mode waves propagating along
  the magnetic field.

Title: Twisting flux tubes as a cause of micro-flaring activity
Authors: Jess, D. B.; McAteer, R. T. J.; Mathioudakis, M.; Keenan,
   F. P.; Andic, A.; Bloomfield, D. S.
Bibcode: 2008IAUS..247..360J
Altcode: 2007IAUS..247..360J
  High-cadence optical observations of an H-α blue-wing bright point
  near solar AR NOAA 10794 are presented. The data were obtained with the
  Dunn Solar Telescope at the National Solar Observatory/Sacramento Peak
  using a newly developed camera system, the rapid dual imager. Wavelet
  analysis is undertaken to search for intensity-related oscillatory
  signatures, and periodicities ranging from 15 to 370 s are found with
  significance levels exceeding 95%. During two separate microflaring
  events, oscillation sites surrounding the bright point are observed to
  twist. We relate the twisting of the oscillation sites to the twisting
  of physical flux tubes, thus giving rise to reconnection phenomena. We
  derive an average twist velocity of 8.1 km/s and detect a peak in the
  emitted flux between twist angles of 180° and 230°.

Title: The Nature of Running Penumbral Waves Revealed
Authors: Bloomfield, D. Shaun; Lagg, Andreas; Solanki, Sami K.
Bibcode: 2007ApJ...671.1005B
Altcode: 2007arXiv0709.3731B
  We seek to clarify the nature of running penumbral (RP) waves:
  are they chromospheric trans-sunspot waves or a visual pattern of
  upward-propagating waves? Full Stokes spectropolarimetric time series of
  the photospheric Si I λ10827 line and the chromospheric He I λ10830
  multiplet were inverted using a Milne-Eddington atmosphere. Spatial
  pixels were paired between the outer umbral/inner penumbral photosphere
  and the penumbral chromosphere using inclinations retrieved by the
  inversion and the dual-height pairings of line-of-sight velocity time
  series were studied for signatures of wave propagation using a Fourier
  phase difference analysis. The dispersion relation for radiatively
  cooling acoustic waves, modified to incorporate an inclined propagation
  direction, fits well the observed phase differences between the pairs
  of photospheric and chromospheric pixels. We have thus demonstrated
  that RP waves are in effect low-β slow-mode waves propagating along
  the magnetic field.

Title: Twisting flux tubes as a cause of micro-flaring activity
Authors: Jess, D. B.; McAteer, R. T. J.; Mathioudakis, M.; Keenan,
   F. P.; Andic, A.; Bloomfield, D. S.
Bibcode: 2007A&A...476..971J
Altcode: 2007arXiv0709.2268J
  High-cadence optical observations of an H-α blue-wing bright point
  near solar AR NOAA 10794 are presented. The data were obtained with the
  Dunn Solar Telescope at the National Solar Observatory/Sacramento Peak
  using a newly developed camera system, the rapid dual imager. Wavelet
  analysis is undertaken to search for intensity-related oscillatory
  signatures, and periodicities ranging from 15 to 370 s are found with
  significance levels exceeding 95%. During two separate microflaring
  events, oscillation sites surrounding the bright point are observed to
  twist. We relate the twisting of the oscillation sites to the twisting
  of physical flux tubes, thus giving rise to reconnection phenomena. We
  derive an average twist velocity of 8.1 km s<SUP>-1</SUP> and detect
  a peak in the emitted flux between twist angles of 180° and 230°. <P
  />Figure 4 is available as a movie at http://www.aanda.org

Title: High-frequency oscillations in a solar active region observed
    with the RAPID DUAL IMAGER
Authors: Jess, D. B.; Andić, A.; Mathioudakis, M.; Bloomfield, D. S.;
   Keenan, F. P.
Bibcode: 2007A&A...473..943J
Altcode: 2007arXiv0707.2716J
  High-cadence, synchronized, multiwavelength optical observations
  of a solar active region (NOAA 10794) are presented. The data
  were obtained with the Dunn Solar Telescope at the National Solar
  Observatory/Sacramento Peak using a newly developed camera system:
  the rapid dual imager. Wavelet analysis is undertaken to search
  for intensity related oscillatory signatures, and periodicities
  ranging from 20 to 370 s are found with significance levels exceeding
  95%. Observations in the H-α blue wing show more penumbral oscillatory
  phenomena when compared to simultaneous G-band observations. The H-α
  oscillations are interpreted as the signatures of plasma motions with
  a mean velocity of 20 km s<SUP>-1</SUP>. The strong oscillatory power
  over H-α blue-wing and G-band penumbral bright grains is an indication
  of the Evershed flow with frequencies higher than previously reported.

Title: Modified p-modes in penumbral filaments?
Authors: Bloomfield, D. S.; Solanki, S. K.; Lagg, A.; Borrero, J. M.;
   Cally, P. S.
Bibcode: 2007A&A...469.1155B
Altcode: 2007arXiv0705.0481B
  Aims:The primary objective of this study is to search for and identify
  wave modes within a sunspot penumbra. <BR />Methods: Infrared
  spectropolarimetric time series data are inverted using a model
  comprising two atmospheric components in each spatial pixel. Fourier
  phase difference analysis is performed on the line-of-sight velocities
  retrieved from both components to determine time delays between the
  velocity signals. In addition, the vertical separation between the
  signals in the two components is calculated from the Stokes velocity
  response functions. <BR />Results: The inversion yields two atmospheric
  components, one permeated by a nearly horizontal magnetic field, the
  other with a less-inclined magnetic field. Time delays between the
  oscillations in the two components in the frequency range 2.5-4.5 mHz
  are combined with speeds of atmospheric wave modes to determine wave
  travel distances. These are compared to expected path lengths obtained
  from response functions of the observed spectral lines in the different
  atmospheric components. Fast-mode (i.e., modified p-mode) waves exhibit
  the best agreement with the observations when propagating toward the
  sunspot at an angle ~50° to the vertical.

Title: Observations of Running Waves in a Sunspot Chromosphere
Authors: Bloomfield, D. S.; Lagg, A.; Solanki, S. K.
Bibcode: 2007ASPC..368..239B
Altcode: 2007astro.ph..2056B
  Spectropolarimetric time series data of the primary spot of active
  region NOAA 9448 were obtained in the Si I 10827 Å line and the He I
  10830 Å multiplet with the Tenerife Infrared Polarimeter. Throughout
  the time series the spectrograph slit was fixed over a region covering
  umbra, a light bridge, penumbra, and quiet sun. We present speeds
  of running penumbral waves in the chromosphere, their relation to
  both photospheric and chromospheric umbral oscillations, and their
  dependence on the magnetic field topology.

Title: Detection of MHD waves in the solar chromosphere
Authors: Kontogiannis, Giannis; Bloomfield, D. Shaun; McAteer, James
   R. T.; Mathioudakis, Mihalis; Antonopoulou, E.
Bibcode: 2007AIPC..895...80K
Altcode:
  One of the main features of the quiet solar chromosphere is the Network
  Bright Points (NBP), formed by emerging magnetic flux at the boundaries
  of supergranular cells. Using SSW IDL routines and wavelet analysis
  of series of images in four bandpasses (CaIIK3, Mgb1, Mgb2 and Hα
  core) we have detected MHD wave modes in the Network Bright Points
  of the solar chromosphere. The observations have been analyzed using
  cross-correlation techniques and we have drawn conclusions on wave
  propagation and mode-coupling.

Title: Modified p-modes in penumbral filaments
Authors: Bloomfield, D. S.; Lagg, A.; Solanki, S. K.; Borrero, J. M.
Bibcode: 2007msfa.conf..241B
Altcode:
  A time series analysis was performed on velocity signals in a sunspot
  penumbra to search for possible wave modes. The spectropolarimetric
  photospheric data obtained by the Tenerife Infrared Polarimeter were
  inverted using the SPINOR code. An atmospheric model comprising two
  magnetic components and one stray-light component gave an optimal fit
  to the data. Fourier phase difference analysis between line-of-sight
  velocities of both magnetic components provided time delays between
  the two atmospheres. These delays were combined with the speeds of
  atmospheric wave modes and compared to height separations derived from
  velocity response functions to determine the wave mode.

Title: The Influence of Magnetic Field on Oscillations in the Solar
    Chromosphere
Authors: Bloomfield, D. Shaun; McAteer, R. T. James; Mathioudakis,
   Mihalis; Keenan, Francis P.
Bibcode: 2006ApJ...652..812B
Altcode: 2006astro.ph..8314B
  Two sequences of solar images obtained by the Transition Region and
  Coronal Explorer in three UV passbands are studied using wavelet
  and Fourier analysis and compared to the photospheric magnetic
  flux measured by the Michelson Doppler Interferometer on the Solar
  Heliospheric Observatory to study wave behavior in differing magnetic
  environments. Wavelet periods show deviations from the theoretical
  cutoff value and are interpreted in terms of inclined fields. The
  variation of wave speeds indicates that a transition from dominant
  fast-magnetoacoustic waves to slow modes is observed when moving from
  network into plages and umbrae. This implies preferential transmission
  of slow modes into the upper atmosphere, where they may lead to heating
  or be detected in coronal loops and plumes.

Title: The periodic variations of a white-light flare observed
    with ULTRACAM
Authors: Mathioudakis, M.; Bloomfield, D. S.; Jess, D. B.; Dhillon,
   V. S.; Marsh, T. R.
Bibcode: 2006A&A...456..323M
Altcode: 2006astro.ph..5196M
  High time resolution observations of a white-light flare on the active
  star EQ PegB show evidence of intensity variations with a period of
  ≈10 s. The period drifts to longer values during the decay phase of
  the flare. If the oscillation is interpreted as an impulsively-excited,
  standing-acoustic wave in a flare loop, the period implies a loop
  length of ≈3.4 Mm and ≈6.8 Mm for the case of the fundamental mode
  and the second harmonic, respectively. However, the small loop lengths
  imply a very high modulation depth making the acoustic interpretation
  unlikely. A more realistic interpretation may be that of a fast-MHD
  wave, with the modulation of the emission being due to the magnetic
  field. Alternatively, the variations could be due to a series of
  reconnection events. The periodic signature may then arise as a result
  of the lateral separation of individual flare loops or current sheets
  with oscillatory dynamics (i.e., periodic reconnection).

Title: Opacity in the upper atmospheres of active stars. II. AD Leonis
Authors: Christian, D. J.; Mathioudakis, M.; Bloomfield, D. S.;
   Dupuis, J.; Keenan, F. P.; Pollacco, D. L.; Malina, R. F.
Bibcode: 2006A&A...454..889C
Altcode: 2006astro.ph..2447C
  We present FUV and UV spectroscopic observations of AD Leonis, with
  the aim of investigating opacity effects in the transition regions
  of late-type stars. The C III lines in FUSE spectra show significant
  opacity during both the quiescent and flaring states of AD Leonis, with
  up to 30% of the expected flux being lost during the latter. Other FUSE
  emission lines tested for opacity include those of O VI, while C IV, Si
  IV and N V transitions observed with stis are also investigated. These
  lines only reveal modest amounts of opacity with losses during flaring
  of up to 20%. Optical depths have been calculated for homogeneous
  and inhomogeneous geometries, giving path lengths of ≈20-60 km and
  ≈10-30 km, respectively, under quiescent conditions. However path
  lengths derived during flaring are ≈2-3 times larger. These values
  are in excellent agreement with both estimates of the small-scale
  structure observed in the solar transition region, and path lengths
  derived previously for several other active late-type stars.

Title: Traveling Waves In Network Bright Points
Authors: Kontogiannis, G.; Bloomfield, D. Shaun; McAteer, J. R. T.;
   Mathioudakis, M.; Antonopoulou, E.
Bibcode: 2006AIPC..848..229K
Altcode:
  One of the main features of the quiet solar chromosphere is the
  Network Bright Points (NBP), formed by the emerging magnetic flux,
  at the boundaries of supergranular cells. Triggered by the motions
  of magnetic loop foot-points, at the top of the convection zone, MHD
  waves propagate inside the NBP's. Using SSW IDL routines and wavelet
  analysis of series of images in four bandpasses (CaII K3, Mgb1-0.4,
  Mgb2 and Ha core) we detected these MHD wave modes. The observations
  have been analyzed using cross-correlation techniques and we have
  drawn conclusions on wave propagation and mode coupling.

Title: Soft X-Ray Emission Lines of Fe XV in Solar Flare Observations
    and the Chandra Spectrum of Capella
Authors: Keenan, F. P.; Drake, J. J.; Chung, S.; Brickhouse, N. S.;
   Aggarwal, K. M.; Msezane, A. Z.; Ryans, R. S. I.; Bloomfield, D. S.
Bibcode: 2006ApJ...645..597K
Altcode: 2006astro.ph..1591K
  Recent calculations of atomic data for Fe XV have been used to generate
  theoretical line ratios involving n=3-4 transitions in the soft X-ray
  spectral region (~52-83 Å), for a wide range of electron temperatures
  and densities applicable to solar and stellar coronal plasmas. A
  comparison of these with solar flare observations from a rocket-borne
  spectrograph (X-Ray Spectrometer/Spectrograph Telescope [XSST]) reveals
  generally good agreement between theory and experiment. In particular,
  the 82.76 Å emission line in the XSST spectrum is identified, for
  the first time to our knowledge in an astrophysical source, as the
  3s3d<SUP>3</SUP>D<SUB>3</SUB>-3s4p<SUP>3</SUP>P<SUB>2</SUB> transition
  of Fe XV. Most of the Fe XV transitions that are blended have had
  the species responsible clearly identified, although there remain
  a few instances in which this has not been possible. The line ratio
  calculations are also compared with a co-added spectrum of Capella
  obtained with the Chandra satellite, which is probably the highest
  signal-to-noise ratio observation achieved for a stellar source in the
  ~25-175 Å soft X-ray region. Good agreement is found between theory
  and experiment, indicating that the Fe XV lines are reliably detected
  in Chandra spectra and hence may be employed as diagnostics to determine
  the temperature and/or density of the emitting plasma. However, the line
  blending in the Chandra data is such that individual emission lines
  are difficult to measure accurately, and fluxes may only be reliably
  determined via detailed profile fitting of the observations. The
  co-added Capella spectrum is made available to hopefully encourage
  further exploration of the soft X-ray region in astronomical sources.

Title: Opacity in the transition region of cool dwarfs: A powerful
    diagnostic
Authors: Mathioudakis, M.; Christian, D. J.; Bloomfield, D. S.;
   Keenan, F. P.; Linsky, J. L.; Dupuis, J.
Bibcode: 2006ASPC..348..159M
Altcode:
  A detailed study of the C III 1176Å multiplet in active cool stars
  has shown significant deviations of the line flux from the optically
  thin approximation. These deviations become more pronounced during
  flares. Opacity can be used as a powerful diagnostic to estimate path
  lengths in the transition region. Our analysis reveals that stellar
  transition regions have very small spatial characteristics typically
  in the range of 10 - 100 km. These path lengths are in agreement with
  the small scale structure seen in the solar transition region.

Title: A Comparative Study of Flaring Loops in Active Stars
Authors: Mullan, D. J.; Mathioudakis, M.; Bloomfield, D. S.; Christian,
   D. J.
Bibcode: 2006ApJS..164..173M
Altcode:
  Dynamo activity in stars of different types is expected to generate
  magnetic fields with different characteristics. As a result, a
  differential study of the characteristics of magnetic loops in a broad
  sample of stars may yield information about dynamo systematics. In the
  absence of direct imaging, certain physical parameters of a stellar
  magnetic loop can be extracted if a flare occurs in that loop. In
  this paper we employ a simple nonhydrodynamic approach introduced by
  Haisch, to analyze a homogeneous sample of all of the flares we could
  identify in the EUVE DS database: a total of 134 flares that occurred
  on 44 stars ranging in spectral type from F to M and in luminosity
  class from V to III. All of the flare light curves that have been
  used in the present study were obtained by a single instrument (EUVE
  DS). For each flare, we have applied Haisch's simplified approach
  (HSA) in order to determine loop length, temperature, electron density,
  and magnetic field. For each of our target stars, a literature survey
  has been performed to determine quantitatively the extent to which our
  results are consistent with independent studies. The results obtained
  by HSA are found to be well supported by results obtained by other
  methods. Our survey suggests that, on the main sequence, short loops
  (with lengths &lt;=0.5R<SUB>*</SUB>) may be found in stars of all
  classes, while the largest loops (with lengths up to 2R<SUB>*</SUB>)
  appear to be confined to M dwarfs. Based on EUVE data, the transition
  from small to large loops on the main sequence appears to occur between
  spectral types K2 and M0. We discuss the implications of this result
  for dynamo theories.

Title: An investigation of Fe XV emission lines in solar flare spectra
Authors: Keenan, F. P.; Aggarwal, K. M.; Bloomfield, D. S.; Msezane,
   A. Z.; Widing, K. G.
Bibcode: 2006A&A...449.1203K
Altcode: 2005astro.ph.12571K
  Previously, large discrepancies have been found between theory
  and observation for Fe XV emission line ratios in solar flare
  spectra covering the 224-327 Å wavelength range, obtained by the
  Naval Research Laboratory's S082A instrument on board Skylab. These
  discrepancies have been attributed to either errors in the adopted
  atomic data or the presence of additional atomic processes not
  included in the modelling, such as fluorescence. However our analysis
  of these plus other S082A flare observations (the latter containing
  Fe XV transitions between 321-482 Å), performed using the most
  recent Fe XV atomic physics calculations in conjunction with a
  chianti synthetic flare spectrum, indicate that blending of the
  lines is primarily responsible for the discrepancies. As a result,
  most Fe XV lines cannot be employed as electron density diagnostics
  for solar flares, at least at the spectral resolution of S082A and
  similar instruments (i.e. 0.1 Å). An exception is the intensity
  ratio I(3s3p <SUP>3</SUP>P{2}-3p<SUP>2</SUP> <SUP>3</SUP>P{1})/I(3s3p
  <SUP>3</SUP>P{2}-3p<SUP>2</SUP> <SUP>1</SUP>D{2}) = I(321.8 Å)/I(327.0
  Å), which appears to provide good estimates of the electron density
  at this spectral resolution.

Title: RHESSI and SOHO CDS Observations of Explosive Chromospheric
    Evaporation
Authors: Milligan, Ryan O.; Gallagher, Peter T.; Mathioudakis, Mihalis;
   Bloomfield, D. Shaun; Keenan, Francis P.; Schwartz, Richard A.
Bibcode: 2006ApJ...638L.117M
Altcode: 2005astro.ph..9664M
  Simultaneous observations of explosive chromospheric evaporation
  are presented using data from the Reuven Ramaty High-Energy Solar
  Spectroscopic Imager (RHESSI) and the Coronal Diagnostic Spectrometer
  (CDS) on board the Solar and Heliospheric Observatory. For the first
  time, cospatial imaging and spectroscopy have been used to observe
  explosive evaporation within a hard X-ray emitting region. RHESSI
  X-ray images and spectra were used to determine the flux of nonthermal
  electrons accelerated during the impulsive phase of an M2.2 flare. When
  we assumed a thick-target model, the injected electron spectrum was
  found to have a spectral index of ~7.3, a low-energy cutoff of ~20 keV,
  and a resulting flux of &gt;=4×10<SUP>10</SUP> ergs cm<SUP>-2</SUP>
  s<SUP>-1</SUP>. The dynamic response of the atmosphere was determined
  using CDS spectra; we found a mean upflow velocity of 230+/-38 km
  s<SUP>-1</SUP> in Fe XIX (592.23 Å) and associated downflows of
  36+/-16 and 43+/-22 km s<SUP>-1</SUP> at chromospheric and transition
  region temperatures, respectively, relative to an averaged quiet-Sun
  spectra. The errors represent a 1 σ dispersion. The properties of
  the accelerated electron spectrum and the corresponding evaporative
  velocities were found to be consistent with the predictions of theory.

Title: Plasma diagnostics of active-region evolution and implications
    for coronal heating
Authors: Milligan, R. O.; Gallagher, P. T.; Mathioudakis, M.; Keenan,
   F. P.; Bloomfield, D. S.
Bibcode: 2005MNRAS.363..259M
Altcode: 2005MNRAS.tmp..764M; 2005astro.ph..9219M
  A detailed study is presented of the decaying solar-active region NOAA
  10103 observed with the Coronal Diagnostic Spectrometer (CDS), the
  Michelson Doppler Imager (MDI) and the Extreme-ultraviolet Imaging
  Telescope (EIT) onboard the Solar and Heliospheric Observatory
  (SOHO). Electron-density maps formed using SiX (356.03 Å/347.41 Å)
  show that the density varies from ~10<SUP>10</SUP>cm<SUP>-3</SUP>
  in the active-region core to ~7 × 10<SUP>8</SUP>cm<SUP>-3</SUP>
  at the region boundaries. Over the 5d of observations, the average
  electron density fell by ~30 per cent. Temperature maps formed using
  FeXVI (335.41 Å)/FeXIV (334.18 Å) show electron temperatures of
  ~2.34 × 10<SUP>6</SUP> K in the active-region core and ~2.10 ×
  10<SUP>6</SUP> K at the region boundaries. Similarly to the electron
  density, there was a small decrease in the average electron temperature
  over the 5-d period. The radiative, conductive and mass-flow losses
  were calculated and used to determine the resultant heating rate
  (P<SUB>H</SUB>). Radiative losses were found to dominate the
  active-region cooling process. As the region decayed, the heating
  rate decreased by almost a factor of 5 between the first and last
  day of observations. The heating rate was then compared to the
  total unsigned magnetic flux , yielding a power law of the form
  P<SUB>H</SUB>~Φ<SUP>0.81+/-0.32</SUP><SUB>tot</SUB>. This result
  suggests that waves rather than nanoflares may be the dominant heating
  mechanism in this active region.

Title: Soft X-ray emission lines of Fe XV in spectra of the Sun
    and Capella
Authors: Drake, J. J.; Keenan, F. P.; Chung, S.; Brickhouse, N. S.;
   Aggarwal, K. M.; Msezane, A. Z.; Ryans, R. S. I.; Bloomfield, D. S.
Bibcode: 2005AIPC..774..349D
Altcode:
  Recent calculations of atomic data for Fe XV have been used to generate
  theoretical line ratios involving n = 3-4 transitions in the soft X-ray
  spectral region (~52-83 Å) for a wide range of electron temperatures
  and densities applicable to solar and stellar coronal plasmas. The
  line ratio calculations are compared with solar flare observations
  from a rocket-borne spectrograph (XSST) and with a co-added spectra
  of Capella obtained with the Chandra LETGS, representing the highest
  signal-to-noise observation achieved for a stellar source in the
  30-80 Å soft X-ray region. Results are promising for use of Fe XV
  as astrophysical plasma diagnostics: Agreement between theory and
  observation is generally good, after particular account is taken of line
  blending. The 82.76 Å emission line in the XSST spectrum is identified,
  for the first time to our knowledge in an astrophysical source, as
  the 3s3d <SUP>3</SUP>D3-3s4p <SUP>3</SUP>P2 transition of Fe XV.

Title: Fe XI Emission Lines in a High-Resolution Extreme-Ultraviolet
    Active Region Spectrum Obtained by the Solar Extreme Ultraviolet
    Research Telescope and Spectrograph
Authors: Keenan, F. P.; Aggarwal, K. M.; Ryans, R. S. I.; Milligan,
   R. O.; Bloomfield, D. S.; Brosius, J. W.; Davila, J. M.; Thomas, R. J.
Bibcode: 2005ApJ...624..428K
Altcode: 2005astro.ph..4106K
  New calculations of radiative rates and electron impact excitation cross
  sections for Fe XI are used to derive emission-line intensity ratios
  involving 3s<SUP>2</SUP>3p<SUP>4</SUP>-3s<SUP>2</SUP>3p<SUP>3</SUP>3d
  transitions in the 180-223 Å wavelength range. These ratios are
  subsequently compared with observations of a solar active region
  obtained during the 1995 flight of the Solar Extreme Ultraviolet
  Research Telescope and Spectrograph (SERTS). The version of SERTS flown
  in 1995 incorporated a multilayer grating that enhanced the instrumental
  sensitivity for features in the ~170-225 Å wavelength range, observed
  in second order between 340 and 450 Å. This enhancement led to the
  detection of many emission lines not seen on previous SERTS flights,
  which were measured with the highest spectral resolution (0.03 Å)
  ever achieved for spatially resolved active region spectra in this
  wavelength range. However, even at this high spectral resolution,
  several of the Fe XI lines are found to be blended, although the sources
  of the blends are identified in the majority of cases. The most useful
  Fe XI electron density diagnostic line intensity ratio is I(184.80
  Å)/I(188.21 Å). This ratio involves lines close in wavelength
  and free from blends, and it varies by a factor of 11.7 between
  N<SUB>e</SUB>=10<SUP>9</SUP> and 10<SUP>11</SUP> cm<SUP>-3</SUP>
  yet shows little temperature sensitivity. An unknown line in the
  SERTS spectrum at 189.00 Å is found to be due to Fe XI, the first
  time (to our knowledge) this feature has been identified in the solar
  spectrum. Similarly, there are new identifications of the Fe XI 192.88,
  198.56, and 202.42 Å features, although the latter two are blended
  with S VIII/Fe XII and Fe XIII, respectively.

Title: Wavelet Analysis Methods of Oscillatory Power in Chromospheric
    Lightcurves
Authors: McAteer, R. T.; Bloomfield, D. S.
Bibcode: 2005AGUSMSH13C..07M
Altcode:
  The symbiotic relationship between time-series oscillatory power
  and waves in the chromosphere is studied using several novel
  wavelet techniques. Theses include automated wave-packet searching
  routines for large datasets, correlation of wave-packets at multiple
  heights in the atmosphere, and a full multi-wavelength wavelet-phase
  analysis (including the cross transform, phase difference and phase
  coherence). In each study we interpret oscillatory power as a signature
  of waves in the quiet-Sun chromosphere and relate these wave modes to
  the underlying photospheric magnetic field.

Title: Intensity oscillations during a flare on EQ Peg
Authors: Mathioudakis, M.; Bloomfield, D. S.; Dhillon, V. S.; Marsh,
   T. R.
Bibcode: 2005ESASP.560..803M
Altcode: 2005csss...13..803M
  No abstract at ADS

Title: Magnetohydrodynamic mode coupling in the quiet-Sun network
Authors: Bloomfield, D. S.; McAteer, R. T. J.; Mathioudakis, M.;
   Williams, D. R.; Keenan, F. P.
Bibcode: 2005ESASP.560..449B
Altcode: 2005csss...13..449B
  No abstract at ADS

Title: Observations of Hα Intensity Oscillations in a Flare Ribbon
Authors: McAteer, R. T. James; Gallagher, Peter T.; Brown, Daniel S.;
   Bloomfield, D. Shaun; Moore, Ruth; Williams, David R.; Mathioudakis,
   Mihalis; Katsiyannis, A.; Keenan, Francis P.
Bibcode: 2005ApJ...620.1101M
Altcode:
  High-cadence Hα blue wing observations of a C9.6 solar flare
  obtained at Big Bear Solar Observatory using the Rapid Dual Imager
  are presented. Wavelet and time-distance methods were used to study
  oscillatory power along the ribbon, finding periods of 40-80 s during
  the impulsive phase of the flare. A parametric study found statistically
  significant intensity oscillations with amplitudes of 3% of the peak
  flare amplitude, periods of 69 s (14.5 mHz) and oscillation decay times
  of 500 s. These measured properties are consistent with the existence
  of flare-induced acoustic waves within the overlying loops.

Title: Emission lines of FeXV in spectra obtained with the Solar
    Extreme-Ultraviolet Research Telescope and Spectrograph
Authors: Keenan, F. P.; Aggarwal, K. M.; Milligan, R. O.; Ryans,
   R. S. I.; Bloomfield, D. S.; Srigengan, V.; O'Mullane, M. G.; Lawson,
   K. D.; Msezane, A. Z.; Brosius, J. W.; Davila, J. M.; Thomas, R. J.
Bibcode: 2005MNRAS.356.1592K
Altcode: 2004MNRAS.tmp..752K
  Recent R-matrix calculations of electron impact excitation rates
  in Mg-like FeXV are used to derive theoretical emission-line ratios
  involving transitions in the 243-418 Åwavelength range. A comparison
  of these with a data set of solar active region, subflare and off-limb
  spectra, obtained during rocket flights by the Solar Extreme-Ultraviolet
  Research Telescope and Spectrograph (SERTS), reveals generally
  very good agreement between theory and observation, indicating that
  most of the FeXV emission lines may be employed with confidence as
  electron density diagnostics. In particular, the 312.55-Åline of
  FeXV is not significantly blended with a CoXVII transition in active
  region spectra, as suggested previously, although the latter does
  make a major contribution in the subflare observations. Most of the
  FeXV transitions which are blended have had the species responsible
  clearly identified, although there remain a few instances where
  this has not been possible. We briefly address the long-standing
  discrepancy between theory and experiment for the intensity ratio of
  the 3s<SUP>21</SUP>S-3s3p <SUP>3</SUP>P<SUB>1</SUB> intercombination
  line at 417.25 Åto the 3s<SUP>21</SUP>S-3s3p <SUP>1</SUP>P resonance
  transition at 284.16 Å.

Title: Oscillatory phenomena in solar and stellar atmospheres
Authors: Bloomfield, David Shaun
Bibcode: 2005PhDT........17B
Altcode:
  This thesis presents varying studies into the nature of intensity
  oscillations observed both on the Sun and two active cool stars. The
  first part concentrates on the detection of correlated oscillations
  occuring between differing heights in the solar atmosphere above
  quiet-Sun magnetic network bright points (NBPs), interpreted as
  signatures of energy propagation. This is achieved through correlating
  in time the wavelet power spectra of lightcurves from images obtained
  in several optical wavelengths. In four of the eleven NBPs studied,
  evidence is found for upwardly-propagating, low-frequency waves (1.4
  mHz, 2.1 mHz) in the lower chromosphere, decreasing in oscillatory
  power with the onset, or increase in power, of higher-frequency waves
  (2.9 mHz, 4.0 mHz) within the upper chromosphere. Moving higher into
  the atmosphere two of the four cases of higher frequency waves also show
  a decrease in power. These observational detections are interpreted as
  transverse-mode magnetohydrodynamic (MHD) waves undergoing non-linear
  mode coupling to longitudinal-modes at double the frequency, which
  shock or otherwise dissipate in the high chromosphere. Evidence is
  also found for additional upward- and downward- directed waves within
  all the NBPs studied. <P />The extension of wavelet power techniques
  into the analysis of phase difference and phase coherence is also
  presented, utilising UV intensities obtained from above a weak solar
  network element. The problems associated with the quantification of
  phase coherence values are outlined and a comparison of two differing
  methods is carried out. Changes observed in the evolution of phase
  difference between oscillations detected in the UV emission of the
  temperature minimum and low transition region are shown to be due
  to the alteration of the underlying magnetic topology, occuring
  when same polarity flux emerges nearby. <P />The final part of this
  thesis concerns the differing situation of intensity variations
  during energetic flare phenomena on two active cool stars. Repeated
  fluctuations are analysed in broad-band optical flare emission from
  the RS CVn binary II Peg and the B component of binary star EQ Peg,
  yielding medium- (220 s) and short- (10 s) oscillation periods,
  respectively. These periods are discussed in terms of a simplified
  model of standing waves within a closed coronal loop. In both cases the
  observed decrease of oscillation period up to flare peak and subsequent
  increase during initial flare decay follows the inverse proportionality
  to loop temperature expected by the simple model.

Title: GRB 050724: WHT optical observations.
Authors: Wiersema, K.; Rol, E.; Starling, R.; Tanvir, N.; Bloomfield,
   D. S.; Thompson, H.
Bibcode: 2005GCN..3699....1W
Altcode:
  No abstract at ADS

Title: Wavelet Phase Coherence Analysis: Application to a Quiet-Sun
    Magnetic Element
Authors: Bloomfield, D. Shaun; McAteer, R. T. James; Lites, Bruce W.;
   Judge, Philip G.; Mathioudakis, Mihalis; Keenan, Francis P.
Bibcode: 2004ApJ...617..623B
Altcode:
  A new application of wavelet analysis is presented that utilizes
  the inherent phase information residing within the complex Morlet
  transform. The technique is applied to a weak solar magnetic network
  region, and the temporal variation of phase difference between TRACE
  1700 Å and SOHO/SUMER C II 1037 Å intensities is shown. We present,
  for the first time in an astrophysical setting, the application of
  wavelet phase coherence, including a comparison between two methods
  of testing real wavelet phase coherence against that of noise. The
  example highlights the advantage of wavelet analysis over more
  classical techniques, such as Fourier analysis, and the effectiveness
  of the former to identify wave packets of similar frequencies but
  with differing phase relations is emphasized. Using cotemporal,
  ground-based Advanced Stokes Polarimeter measurements, changes in the
  observed phase differences are shown to result from alterations in
  the magnetic topology.

Title: A Detailed Study of Opacity in the Upper Atmosphere of
    Proxima Centauri
Authors: Christian, D. J.; Mathioudakis, M.; Bloomfield, D. S.;
   Dupuis, J.; Keenan, F. P.
Bibcode: 2004ApJ...612.1140C
Altcode:
  We present far-UV and UV spectroscopic observations of Proxima Centauri
  obtained as part of our continued investigation into the optically
  thin approximation assumed for the transition regions of late-type
  stars. Significant opacity is found in the C III lines during both
  the quiescent and flaring states of Proxima Cen, with up to 70% of the
  expected flux being lost in the latter. Our findings cast some doubt
  on the suitability of the C III λ977 line for estimating the electron
  density in stellar atmospheres. However, the opacity has no significant
  effect on the observed line widths. We calculate optical depths for
  homogeneous and inhomogeneous geometries and estimate an electron
  density of 6×10<SUP>10</SUP> cm<SUP>-3</SUP> for the transition region
  using the O IV line ratios at 1400 Å. The combination of electron
  density and optical depth indicates path lengths as low as ~10 km,
  which are in excellent agreement with estimates of the small-scale
  structure seen in the solar transition region.

Title: Erratum: ``Propagating Waves and Magnetohydrodynamic
    Mode Coupling in the Quiet-Sun Network'' (<A
    href="/abs/2004ApJ...604..936B">ApJ, 604, 936 [2004]</A>)
Authors: Bloomfield, D. Shaun; McAteer, R. T. James; Mathioudakis,
   Mihalis; Williams, David R.; Keenan, Francis P.
Bibcode: 2004ApJ...609..465B
Altcode:
  Proof corrections were not carried correctly to the
  final printed version of this paper, which resulted
  in an extra set of overbars appearing in both terms
  of the denominator of equation (3). The correct form of this equation
  is:C(Δt,ν)=(Σ[P<SUB>λ<SUB>1</SUB></SUB>(t,ν)-P<SUB>λ<SUB>1</SUB></SUB>(t,ν)][P<SUB>λ<SUB>2</SUB></SUB>(t+Δt,ν)-P<SUB>λ<SUB>2</SUB></SUB>(t+Δt,ν)])/(sqrt(Σ[P<SUB>λ<SUB>1</SUB></SUB>(t,ν)-P<SUB>λ<SUB>1</SUB></SUB>(t,ν)]<SUP>2</SUP>Σ[P<SUB>λ<SUB>2</SUB></SUB>(t,ν)-P<SUB>λ<SUB>2</SUB></SUB>(t,ν)]<SUP>2</SUP>)).
  (3)As noted in footnote 3, this correlation equation was stated
  incorrectly in our previous paper (eq. [4] in R. T. J. McAteer et al.,
  <A href="/abs/2004ApJ...604..936B">ApJ, 604, 936 [2004]</A>). However,
  the correct form of equation (3), now given here, was used for the
  analysis in both papers. <P />The press sincerely regrets this error.

Title: Plasma Diagnostics of Active Region Evolution and Implications
    for Coronal Heating
Authors: Milligan, R. O.; Gallagher, P. T.; Mathioudakis, M.;
   Bloomfield, D. S.; Keenan, F. P.
Bibcode: 2004AAS...204.9803M
Altcode: 2004BAAS...36..984M
  The decaying solar active region NOAA 10103 was observed during 2002
  September 10--14 using the Coronal Diagnostic Spectrometer (CDS) onboard
  the Solar and Heliospheric Observatory (SOHO). Electron density maps
  were created using the Si X (356Å/347Å) ratio, which show densities
  of ∼10<SUP>10</SUP>cm<SUP>-3</SUP> in the active region core, and
  ∼7x10<SUP>8</SUP>cm<SUP>-3</SUP> in the region boundaries. Over
  the five days of observations, the average electron density fell by
  approximately a factor of two. Temperature maps were created using
  the Fe XVI (335.4Å)/Fe XIV (334.2Å) ratio, which show electron
  temperatures of ∼2.2x10<SUP>6</SUP>K in the active region core,
  and ∼2.0x10<SUP>6</SUP>K in the region boundaries. Similarly to the
  electron density, the average electron temperature decreased over the
  five days, but by only ∼3%. The radiative and conductive losses, and
  resultant heating rate, were then calculated and compared to the total
  unsigned magnetic flux (Φ <SUB>tot</SUB> = ∫ dA |B<SUB>z|</SUB>)
  from Michelson Doppler Interferometer (MDI) magnetograms. Losses due to
  radiation were found to exceed conductive losses by a factor of ten. As
  the region decayed, the heating rate decreased by close to an order of
  magnitiude between the first and last day of observations. In line with
  several coronal heating theories, a power-law relationship of the form
  P<SUB>tot} ∼Φ <SUB>{tot</SUB><SUP>0.95±0.07</SUP></SUB> was found
  between the heating rate and the unsigned magnetic flux. This result
  provides further observational evidence for wave rather than nanoflare
  heating of solar active regions. <P />Ryan Milligan would like to
  thank the Solar Physics Division for being awarded an SPD Studentship.

Title: Propagating Waves and Magnetohydrodynamic Mode Coupling in
    the Quiet-Sun Network
Authors: Bloomfield, D. Shaun; McAteer, R. T. James; Mathioudakis,
   Mihalis; Williams, David R.; Keenan, Francis P.
Bibcode: 2004ApJ...604..936B
Altcode:
  High-cadence multiwavelength optical observations were taken with the
  Dunn Solar Telescope at the National Solar Observatory, Sacramento Peak,
  accompanied by Advanced Stokes Polarimeter vector magnetograms. A total
  of 11 network bright points (NBPs) have been studied at different
  atmospheric heights using images taken in wave bands centered on
  Mg I b<SUB>1</SUB> - 0.4 Å, Hα, and Ca II K<SUB>3</SUB>. Wavelet
  analysis was used to study wave packets and identify traveling
  magnetohydrodynamic waves. Wave speeds were estimated through the
  temporal cross-correlation of signals, in selected frequency bands
  of wavelet power, in each wavelength. Four mode-coupling cases were
  identified, one in each of four of the NBPs, and the variation of the
  associated Fourier power with height was studied. Three of the detected
  mode-coupling, transverse-mode frequencies were observed in the 1.2-1.6
  mHz range (mean NBP apparent flux density magnitudes over 99-111 Mx
  cm<SUP>-2</SUP>), with the final case showing 2.0-2.2 mHz (with 142 Mx
  cm<SUP>-2</SUP>). Following this, longitudinal-mode frequencies were
  detected in the range 2.6-3.2 mHz for three of our cases, with 3.9-4.1
  mHz for the remaining case. After mode coupling, two cases displayed a
  decrease in longitudinal-mode Fourier power in the higher chromosphere.

Title: Ultraviolet Oscillations in the Chromosphere of the Quiet Sun
Authors: McAteer, R. T. James; Gallagher, Peter T.; Bloomfield,
   D. Shaun; Williams, David R.; Mathioudakis, Mihalis; Keenan, Francis P.
Bibcode: 2004ApJ...602..436M
Altcode:
  Quiet-Sun oscillations in the four Transition Region and Coronal
  Explorer (TRACE) ultraviolet passbands centered on 1700, 1600,
  1216, and 1550 Å are studied using a wavelet-based technique. Both
  network and internetwork regions show oscillations with a variety of
  periods and lifetimes in all passbands. The most frequent network
  oscillation has a period of 283 s, with a lifetime of 2-3 cycles
  in all passbands. These oscillations are discussed in terms of
  upwardly propagating magnetohydrodynamic wave models. The most
  frequent internetwork oscillation has a period of 252 s, again with
  a lifetime of 2-3 cycles, in all passbands. The tendency for these
  oscillations to recur in the same position is discussed in terms of
  ``persistent flashers.'' The network contains greater oscillatory
  power than the internetwork at periods longer than 300 s in the
  low chromosphere. This value is shown to decrease to 250 s in the
  high chromosphere. The internetwork also displays a larger number of
  short-lifetime, long-period oscillations than the network, especially
  in the low chromosphere. Both network and internetwork regions contain
  a small number of nonrecurring long-lifetime oscillations.

Title: Intensity Oscillations During a flare on II Peg
Authors: Avgoloupis, S.; Seiradakis, J. H.; Mathioudakis, M.;
   Bloomfield, D. Shaun; McAteer, J.
Bibcode: 2004hell.conf..120A
Altcode:
  No abstract at ADS

Title: Oscillatory Signatures above Quiet Sun Magnetic Elements
Authors: Bloomfield, D. S.; McAteer, R. T. J.; Lites, B. W.; Judge,
   P. G.; Mathioudakis, M.; Keenan, F. P.
Bibcode: 2004ESASP.547...51B
Altcode: 2004soho...13...51B
  A new application of wavelet analysis is presented. The data used are
  part of Joint Observing Proposal 72 between SoHO and TRACE, obtained on
  1998 May 16 with accompanying groundbased data taken with the Dunn Solar
  Telescope at Sacramento Peak, New Mexico. A weak magnetic network region
  is studied and the temporal variation of phase difference between TRACE
  1700 Å and SoHO/SUMER C II intensities is shown. The example clearly
  highlights the advantages of wavelet analysis over more classical
  techniques such as Fourier analysis, where the effectiveness of the
  technique to identify wavepackets with differing phase difference
  relations is emphasised.

Title: An Automated Wavelet Analysis Approach to TRACE Quiet Sun
    Oscillations
Authors: McAteer, R. T. J.; Gallagher, P. T.; Williams, D. R. Williams
   D. R.; Bloomfield, D. S.; Mathioudakis, M.; Keenan, F. P.
Bibcode: 2004ESASP.547..139M
Altcode: 2004soho...13..139M
  An automated wavelet analysis approach to TRACE UV quiet Sun datasets
  is discussed. Periodicity and lifetime of oscillations present in the
  network and internetwork are compared and contrasted. This provides
  a means of extending previous Fourier results into the time-localised
  domain. The longest lifetime oscillations occur around the acoustic band
  and the network tends to dominate over the internetwork at periods 4
  mins. However, it is shown that the internetwork can dominate over the
  network at long periods (7 - 20 mins), but only for short lifetimes
  ( 3 complete oscillations). These results are discussed in terms of
  chromospheric heating theories.

Title: White-light oscillations during a flare on II Peg.
Authors: Mathioudakis, M.; Seiradakis, J. H.; Williams, D. R.;
   Avgoloupis, S.; Bloomfield, D. S.; McAteer, R. T. J.
Bibcode: 2003A&A...403.1101M
Altcode:
  We analyse the intensity oscillations observed in the gradual phase
  of a white-light flare on the RS CVn binary II Peg. Fast Fourier
  Transform power spectra and Wavelet analysis reveal a period of
  220 s. The reliability of the oscillation is tested using several
  criteria. Oscillating coronal loop models are used to derive physical
  parameters such as temperature, electron density and magnetic field
  strength associated with the coronal loop. The derived parameters
  are consistent with the near-simultaneous X-ray observations of the
  flare. There is no evidence for oscillations in the quiescent state
  of the binary.

Title: Observational Evidence for Mode Coupling in the Chromospheric
    Network
Authors: McAteer, R. T. James; Gallagher, Peter T.; Williams, David R.;
   Mathioudakis, Mihalis; Bloomfield, D. Shaun; Phillips, Kenneth J. H.;
   Keenan, Francis P.
Bibcode: 2003ApJ...587..806M
Altcode:
  Oscillations in network bright points (NBPs) are studied at a variety
  of chromospheric heights. In particular, the three-dimensional
  variation of NBP oscillations is studied using image segmentation
  and cross-correlation analysis between images taken in light of Ca II
  K<SUB>3</SUB>, Hα core, Mg I b<SUB>2</SUB>, and Mg I b<SUB>1</SUB>-0.4
  Å. Wavelet analysis is used to isolate wave packets in time and
  to search for height-dependent time delays that result from upward-
  or downward-directed traveling waves. In each NBP studied, we find
  evidence for kink-mode waves (1.3, 1.9 mHz), traveling up through the
  chromosphere and coupling with sausage-mode waves (2.6, 3.8 mHz). This
  provides a means for depositing energy in the upper chromosphere. We
  also find evidence for other upward- and downward-propagating waves in
  the 1.3-4.6 mHz range. Some oscillations do not correspond to traveling
  waves, and we attribute these to waves generated in neighboring regions.

Title: A Study Of Extreme Ultraviolet Flare Activity On Late-Type
    Stars
Authors: Bloomfield, D. S.; Mathioudakis, M.
Bibcode: 2002ASPC..277..425B
Altcode: 2002sccx.conf..425B
  No abstract at ADS

Title: Opacity in the upper atmosphere of AU Mic
Authors: Bloomfield, D. S.; Mathioudakis, M.; Christian, D. J.;
   Keenan, F. P.; Linsky, J. L.
Bibcode: 2002A&A...390..219B
Altcode:
  In this paper we investigate the validity of the optically thin
  assumption in the transition region of the late-type star AU Mic. We use
  Far-Ultraviolet Spectroscopic Explorer (FUSE) observations of the C Iii
  multiplet and O Vi resonance lines, hence yielding information at two
  different levels within the atmosphere. Significant deviations from the
  optically thin fluxes are found for C Iii in both quiescent and flare
  spectra, where only 60% of the flux is actually observed. This could
  explain the apparent deviation of C Iii observed in emission measure
  distributions. We utilize escape probabilities for both homogeneous and
  inhomogeneous geometries and calculate optical depths as high as 10 for
  the C Iii 1175.71 Åcomponent of the multiplet. Using a lower limit
  to the electron density (10<SUP>11</SUP> cm<SUP>-3</SUP>) we derive
  an effective thickness of &lt;100 km for the scattering layer. The
  emission originates from very small and compact regions, consistent
  with a filling factor of 10<SUP>-5</SUP> derived for the flare plasma.

