bloomfield

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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.
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.

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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
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.

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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
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.

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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.
2020A&A...642A..15K Altcode:
 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. 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. 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.

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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.
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 (tnl) 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(tnl)) 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.

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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
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.

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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
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.

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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
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.

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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
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.

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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
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.

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Title: Solar Flare Forecasting from Magnetic Feature Properties
Generated by the Solar Monitor Active Region Tracker
Authors: Domijan, Katarina; Bloomfield, D. Shaun; Pitié, François
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.

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Title: Solar flare forecasting from magnetic feature properties
generated by Solar Monitor Active Region Tracker
Authors: Domijan, Katarina; Bloomfield, D. Shaun; Pitie, Francois
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.

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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
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
(Smax) and integral (Ssum) 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
Ssum 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 Ssum 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.

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Title: Flare forecasting using the evolution of McIntosh sunspot
classifications
Authors: McCloskey, Aoife E.; Gallagher, Peter T.; Bloomfield, D. Shaun
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
(BSSevolution = 0.09) performs better than the static
McIntosh-Poisson method (BSSstatic = - 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 (BSSstaticcorr =
0.09 and BSSevolutioncorr = 0.0.20) and improved
forecast reliability diagrams.

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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.
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%.

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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.
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 (Blos) and
spherical-radial (Br) 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 Br component results in a slight
upwards shift of property values in a manner consistent with a
field-strength underestimation by the Blos component;
ii) using the Br 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 Br rather than Blos 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.
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.
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.
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.
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.
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.
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.
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
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
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.
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. Aims: We investigate the
conditions for ECM in the solar corona by considering the ratio of the
electron plasma frequency ωp to the electron-cyclotron
frequency Ωe. The ECM is theoretically possible when
ωp/ Ωe&lt; 1. 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 ωp/Ωe and Alfvén velocity maps
of the off-limb corona. Results: We found that the condition
for ECM emission (ωp/ Ωe&lt; 1) is possible at
heights &lt;1.07 R⊙ in an active region near the limb;
that is, where magnetic field strengths are &gt;40 G and electron
densities are &gt;3 × 108 cm-3. In addition, we
found comparatively high Alfvén velocities (&gt;0.02c or &gt;6000 km
s-1) at heights &lt;1.07 R⊙ within the active
region. 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.
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.
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
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.
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. 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. 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. 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. 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.
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
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.
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.
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. 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. 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. 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. 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.
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.
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
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.
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
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
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.
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. 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. 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. 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 ~1031 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. 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.
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.
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.
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.
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.
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.
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. 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. 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. Results: Following launch at velocities of ~240-450
km s-1 each of the four events studied showed significant
negative acceleration ranging from ~-290 to -60 m s-2. 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. 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.
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∗ (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
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-1, which indicate magnetic reconnection rates
of &lt;=3 × 10-3. The observed displacements were used in
conjunction with the interchange reconnection model to derive typical
diffusion coefficients of &lt;=3 × 1013 cm2
s-1. 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.
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.
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
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.
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.
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 105 and 107 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.
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. 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. 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
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-1 within ~28 minutes of its
launch, varying in acceleration from 76 to -102 m s-2. 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-1 within ~20 minutes of launch,
with a variation in acceleration from 816 to -413 m s-2. 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.
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.
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.
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.
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.
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-1 and detect
a peak in the emitted flux between twist angles of 180° and 230°. 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.
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-1. 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.
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. 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. 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.
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.
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.
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.
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.
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.
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.
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.
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
3s3d3D3-3s4p3P2 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.
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.
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*) may be found in stars of all
classes, while the largest loops (with lengths up to 2R*)
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.
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 3P{2}-3p2 3P{1})/I(3s3p
3P{2}-3p2 1D{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.
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;=4×1010 ergs cm-2
s-1. The dynamic response of the atmosphere was determined
using CDS spectra; we found a mean upflow velocity of 230+/-38 km
s-1 in Fe XIX (592.23 Å) and associated downflows of
36+/-16 and 43+/-22 km s-1 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.
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 ~1010cm-3
in the active-region core to ~7 × 108cm-3
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 × 106 K in the active-region core and ~2.10 ×
106 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
(PH). 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
PH~Φ0.81+/-0.32tot. 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.
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 3D3-3s4p 3P2 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.
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 3s23p4-3s23p33d
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
Ne=109 and 1011 cm-3
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.
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.
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.
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.
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.
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 3s21S-3s3p 3P1 intercombination
line at 417.25 Åto the 3s21S-3s3p 1P resonance
transition at 284.16 Å.

---------------------------------------------------------
Title: Oscillatory phenomena in solar and stellar atmospheres
Authors: Bloomfield, David Shaun
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. 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. 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.
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.
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.
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 6×1010 cm-3 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.
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[Pλ1(t,ν)-Pλ1(t,ν)][Pλ2(t+Δt,ν)-Pλ2(t+Δt,ν)])/(sqrt(Σ[Pλ1(t,ν)-Pλ1(t,ν)]2Σ[Pλ2(t,ν)-Pλ2(t,ν)]2)).
(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. 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.
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 ∼1010cm-3 in the active region core, and
∼7x108cm-3 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 ∼2.2x106K in the active region core,
and ∼2.0x106K 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 tot = ∫ dA |Bz|)
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
Ptot} ∼Φ {tot0.95±0.07 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. 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.
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 b1 - 0.4 Å, Hα, and Ca II K3. 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-2), with the final case showing 2.0-2.2 mHz (with 142 Mx
cm-2). 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.
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.
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.
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.
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.
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.
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
K3, Hα core, Mg I b2, and Mg I b1-0.4
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.
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.
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 (1011 cm-3) 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 10-5 derived for the flare plasma.