mcateer

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Author name code: mcateer
ADS astronomy entries on 2022-09-14
author:"McAteer, R.T. James"

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Title: Call and Response: A Time-resolved Study of Chromospheric
Evaporation in a Large Solar Flare
Authors: Sellers, Sean G.; Milligan, Ryan O.; McAteer, R. T. James
2022ApJ...936...85S Altcode: 2022arXiv220814347S
We studied an X1.6 solar flare produced by NOAA Active Region 12602
on 2014 October 22. The entirety of this event was covered by RHESSI,
IRIS, and Hinode/EIS, allowing analysis of the chromospheric response
to a nonthermal electron driver. We derived the energy contained
in nonthermal electrons via RHESSI spectral fitting and linked the
time-dependent parameters of this call to the response in Doppler
velocity, density, and nonthermal width across a broad temperature
range. The total energy injected was 4.8 × 1030 erg and
lasted 352 s. This energy drove explosive chromospheric evaporation,
with a delineation in both Doppler and nonthermal velocities at
the flow reversal temperature, between 1.35 and 1.82 MK. The time
of peak electron injection (14:06 UT) corresponded to the time of
highest velocities. At this time, we found 200 km s-1
blueshifts in the core of Fe XXIV, which is typically assumed to be
at rest. Shortly before this time, the nonthermal electron population
had the shallowest spectral index (≍6), corresponding to the peak
nonthermal velocity in Si IV and Fe XXI. Nonthermal velocities in
Fe XIV, formed near the flow reversal temperature, were low and not
correlated with density or Doppler velocity. Nonthermal velocities in
ions with similar temperatures were observed to increase and correlate
with Doppler velocities, implying unresolved flows surrounding the flow
reversal point. This study provides a comprehensive, time-resolved
set of chromospheric diagnostics for a large X-class flare, along
with a time-resolved energy injection profile, ideal for further
modeling studies.

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Title: Detection of Venusian Aurora During Parker Solar Probe
Encounter
Authors: Kovac, Sarah; Gray, Candace; Arge, Charles; Mcateer,
R. T. James; Chanover, Nancy; Churchill, Chris; Szabo, Adam
2021AGUFM.P45F2487K Altcode:
We cannot fully understand key topics in planetary science, like
formation and evolution of planetary atmospheres, without accounting
for their interactions with the solar wind. The presence of aurora is an
important manifestation and tracer of the interaction between the solar
wind and planetary ionospheres. The OI (1S-1D) 557.7 nm (oxygen green
line) is a bright auroral line in the terrestrial atmosphere and is
detected on the Venusian nightside after major solar storms. Currently,
the processes responsible for producing the green line emission on Venus
are poorly understood, yet the observed variability of this feature
is clearly linked to the solar wind environment. Here, we use the
Wang-Sheeley-Arge (WSA) model and in situ data from Parker Solar Probe
(PSP) to look at the solar wind conditions during detections of the
Venusian green line when PSP was at its closest encounters with Venus.

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Title: Critical Science Plan for the Daniel K. Inouye Solar Telescope
(DKIST)
Authors: Rast, Mark P.; Bello González, Nazaret; Bellot Rubio,
Luis; Cao, Wenda; Cauzzi, Gianna; Deluca, Edward; de Pontieu, Bart;
Fletcher, Lyndsay; Gibson, Sarah E.; Judge, Philip G.; Katsukawa,
Yukio; Kazachenko, Maria D.; Khomenko, Elena; Landi, Enrico; Martínez
Pillet, Valentín; Petrie, Gordon J. D.; Qiu, Jiong; Rachmeler,
Laurel A.; Rempel, Matthias; Schmidt, Wolfgang; Scullion, Eamon; Sun,
Xudong; Welsch, Brian T.; Andretta, Vincenzo; Antolin, Patrick; Ayres,
Thomas R.; Balasubramaniam, K. S.; Ballai, Istvan; Berger, Thomas E.;
Bradshaw, Stephen J.; Campbell, Ryan J.; Carlsson, Mats; Casini,
Roberto; Centeno, Rebecca; Cranmer, Steven R.; Criscuoli, Serena;
Deforest, Craig; Deng, Yuanyong; Erdélyi, Robertus; Fedun, Viktor;
Fischer, Catherine E.; González Manrique, Sergio J.; Hahn, Michael;
Harra, Louise; Henriques, Vasco M. J.; Hurlburt, Neal E.; Jaeggli,
Sarah; Jafarzadeh, Shahin; Jain, Rekha; Jefferies, Stuart M.; Keys,
Peter H.; Kowalski, Adam F.; Kuckein, Christoph; Kuhn, Jeffrey R.;
Kuridze, David; Liu, Jiajia; Liu, Wei; Longcope, Dana; Mathioudakis,
Mihalis; McAteer, R. T. James; McIntosh, Scott W.; McKenzie, David
E.; Miralles, Mari Paz; Morton, Richard J.; Muglach, Karin; Nelson,
Chris J.; Panesar, Navdeep K.; Parenti, Susanna; Parnell, Clare E.;
Poduval, Bala; Reardon, Kevin P.; Reep, Jeffrey W.; Schad, Thomas A.;
Schmit, Donald; Sharma, Rahul; Socas-Navarro, Hector; Srivastava,
Abhishek K.; Sterling, Alphonse C.; Suematsu, Yoshinori; Tarr, Lucas
A.; Tiwari, Sanjiv; Tritschler, Alexandra; Verth, Gary; Vourlidas,
Angelos; Wang, Haimin; Wang, Yi-Ming; NSO and DKIST Project; DKIST
Instrument Scientists; DKIST Science Working Group; DKIST Critical
Science Plan Community
2021SoPh..296...70R Altcode: 2020arXiv200808203R
The National Science Foundation's Daniel K. Inouye Solar Telescope
(DKIST) will revolutionize our ability to measure, understand,
and model the basic physical processes that control the structure
and dynamics of the Sun and its atmosphere. The first-light DKIST
images, released publicly on 29 January 2020, only hint at the
extraordinary capabilities that will accompany full commissioning of
the five facility instruments. With this Critical Science Plan (CSP)
we attempt to anticipate some of what those capabilities will enable,
providing a snapshot of some of the scientific pursuits that the DKIST
hopes to engage as start-of-operations nears. The work builds on the
combined contributions of the DKIST Science Working Group (SWG) and
CSP Community members, who generously shared their experiences, plans,
knowledge, and dreams. Discussion is primarily focused on those issues
to which DKIST will uniquely contribute.

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Title: Spatial and Temporal Analysis of 3 minute Oscillations in the
Chromosphere Associated with the X2.2 Solar Flare on 2011 February 15
Authors: Farris, Laurel; McAteer, R. T. James
2020ApJ...903...19F Altcode: 2020arXiv201110074F
Three minute oscillations in the chromosphere are attributed to
both slow magnetoacoustic waves propagating from the photosphere
and to oscillations generated within the chromosphere itself at its
natural frequency as a response to a disturbance. Here we present an
investigation of the spatial and temporal behavior of the chromospheric
3 minute oscillations before, during, and after the SOL2011-02-15T01:56
X2.2 flare. Observations in ultraviolet emission centered on 1600 and
1700 Å obtained at 24 s cadence from the Atmospheric Imaging Assembly
on board the Solar Dynamics Observatory are used to create power maps
as functions of both space and time. We observe higher 3 minute power
during the flare, spatially concentrated in small areas ∼10 pixels (
$\sim 4^{\prime\prime} $ ) across. This implies that the chromospheric
plasma is not oscillating globally as a single body. The locations
of increased 3 minute power are consistent with observations of HXR
flare emission from previous studies, suggesting that these small
areas are manifestations of the chromosphere responding to injection
of energy by nonthermal particles. This supports the theory that the
chromosphere oscillates at the acoustic cutoff frequency in response
to a disturbance.

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Title: The Slowly Varying Corona. II. The Components of F
10.7 and Their Use in EUV Proxies
Authors: Schonfeld, S. J.; White, S. M.; Henney, C. J.; Hock-Mysliwiec,
R. A.; McAteer, R. T. J.
2019ApJ...884..141S Altcode: 2019arXiv191012964S
Using four years of full-disk-integrated coronal differential emission
measures calculated in Schonfeld et al. (2017), we investigate the
relative contribution of bremsstrahlung and gyroresonance emission
in observations of F 10.7, the 10.7 cm (2.8 GHz) solar
microwave spectral flux density and commonly used activity proxy. We
determine that the majority of coronal F 10.7 is produced
by the bremsstrahlung mechanism, but the variability observed over
individual solar rotations is often driven by gyroresonance sources
rotating across the disk. Our analysis suggests that the chromosphere
may contribute significantly to F 10.7 variability and
that coronal bremsstrahlung emission accounts for 14.2 ± 2.1 sfu
(∼20%) of the observed solar minimum level. The bremsstrahlung
emission has a power-law relationship to the total F 10.7
at high activity levels, and this combined with the observed linearity
during low activity yields a continuously differentiable piecewise fit
for the bremsstrahlung component as a function of F 10.7. We
find that the bremsstrahlung component fit, along with the Mg II index,
correlates better with the observed 5-37 nm spectrum than the common
81 day averaged F 10.7 proxy. The bremsstrahlung component
of F 10.7 is also well approximated by the moderate-strength
photospheric magnetic field parameterization from Henney et al. (2012),
suggesting that it could be forecast for use in both atmospheric
research and operational models.

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Title: A Potential Field is Unique…Right?!? Summary of Evaluation
Methodology and Initial Results
Authors: Leka, K. D.; Barnes, Graham; McAteer, R. T. James
2019shin.confE.151L Altcode:
Given the normal component of the magnetic field on a closed surface,
the lowest-energy construct is the potential field, and mathematically
it is a unique construct. In solar physics, so much of what we are
interested in - free energy, magnetic shear, magnetic topology, helicity
- is estimated relative to the potential field. However, when methods
and results for quantities of interest (e.g. the Campaign on Energy
Storage session at SHINE 2015) what quickly becomes apparent is that
the methods of computing potential fields themselves can lead to wildly
different results - so that comparisons of, for example, NLFFF-derived
free energy are all but meaningless between publications. In
this session we explore computing this all-important starting point,
asking, (1) What is the magnitude of differences between different
potential-field calculations? (2) What implementations can mitigate
some of the worst discrepancies? with the goal of establishing
community-supported potential-field methodologies to bring better
quantitative prospects to our science. We focus separately on
global and local calculations with attention to boundary treatment,
resolution, and implementation details. Participants have prepared
potential-field calculations for 2012.06.13_11:36_TAI and/or NOAA AR
11504 for comparisons, as detailed in the session description. With
this session scheduled for Friday, we summarize in a poster the
submitted solutions (as of the start of the week, more welcome through
Wednesday!), evaluation methodologies, and results. In this way, SHINE
2019 participants can be aware of these results earlier in the week,
for context to discussions in earlier relevant sessions. This work
was partially funded by NASA HSR grant 80NSSC18K0071 and supported
by the US National Science Foundation under Grant No. 1630454. Any
opinions, findings, and conclusions or recommendations expressed in
this material are those of the authors and do not necessarily reflect
the views of the National Science Foundation.

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Title: Oscillatory power in the chromosphere: a multi-flare study
Authors: Farris, Laurel Elizabeth; McAteer, R. T. James
2019shin.confE.208F Altcode:
Preliminary results of the spatial distribution of acoustic oscillatory
power in the chromosphere associated with multiple flares are presented,
obtained using observations from SDO/AIA. We employ FFT and wavelet
analysis techniques to determine the location, time, and duration of
both enhancement and suppression of acoustic power in small subregions
of the active region before, during, and after the flare. Changes
in oscillatory behavior prior to flare onset may have significant
implications in the field of space weather prediction, while enhanced
oscillations that persist through the gradual phase and beyond will
provide further insight to the theory that the chromosphere naturally
oscillates at a frequency equal to the acoustic cutoff at approximately
5.6 mHz (3 minutes). Moreover, the investigation of multiple flares
will provide statistically significant results and will contribute to
the global understanding of the flaring chromosphere.

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Title: Synoptic Studies of the Sun as a Key to Understanding Stellar
Astrospheres
Authors: Martinez Pillet, Valentin; Hill, Frank; Hammel, Heidi B.;
de Wijn, Alfred G.; Gosain, Sanjay; Burkepile, Joan; Henney, Carl;
McAteer, R. T. James; Bain, Hazel; Manchester, Ward; Lin, Haosheng;
Roth, Markus; Ichimoto, Kiyoshi; Suematsu, Yoshinori
2019BAAS...51c.110M Altcode: 2019astro2020T.110M; 2019arXiv190306944M
Ground-based solar observations provide key contextual data (i.e., the
"big picture") to produce a complete description of the only astrosphere
we can study in situ: our Sun's heliosphere. This white paper outlines
the current paradigm for ground-based solar synoptic observations,
and indicates those areas that will benefit from focused attention.

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Title: Spatial and temporal localization of enhanced chromospheric
3-minute oscillations before, during, and after the 2011-February-15
X2.2 flare
Authors: Farris, Laurel Elizabeth; McAteer, Robert T. J.
2018shin.confE.257F Altcode:
The ubiquitous 3-minute oscillations of the chromosphere are
attributed to both slow magnetoacoustic waves with frequencies
higher than the acoustic cutoff propagating from the photosphere,
and to oscillations generated as a response to a disturbance within
the chromosphere itself at its natural frequency. Here we present an
analysis of ultraviolet images obtained at 24-second cadence from
the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics
Observatory (SDO) to investigate the spatial and temporal behavior
of the chromospheric 3-minute oscillations before, during, and after
the SOL2011-02-15T01:56 X2.2 flare. A Fourier transform is applied to
the intensity signal over time segments of 25.6 minutes, and shifted
through a five-hour time series centered on the flare. This was done for
individual pixels to generate power maps that allow the examination of
the 3-minute power in both space and time. We find that enhancement in
the 3-minute power is concentrated in small areas over sunspot umbral
regions. Temporal variations of the 3-minute power from a non-detrended
signal show an enhancement during the flare with several distinct peaks,
though improved temporal resolution is likely needed for conclusive
results. The potential correlation between 3-minute power and magnetic
field strength is discussed, along with formation height dependencies.

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Title: EUV Irradiance from the EVE MEGS-A Dataset and its Implications
for F10.7
Authors: Schonfeld, Samuel; White, Stephen M.; Hock-Mysliwiec, Rachel;
Henney, Carl J.; Mcateer, R. T. James
2018tess.conf40906S Altcode:
We present analysis of the complete spectral dataset from the
Extreme-ultraviolet (EUV) Variability Experiment (EVE) MEGS-A
instrument. Using these data, we construct daily differential emission
measures (DEMs) and use them to analyze the long-term variability
of the global corona and the irradiance it produces. We identify a
discontinuity in the EUV irradiance and DEMs separating solar minimum
and maximum conditions. Using the DEMs we also study the relationship
between EUV and F10.7, the 10.7 cm (2.8 GHz) solar activity
proxy. We compare predictions of the geoeffective F10.7
from the DEMs and photospheric magnetic field observations with the
commonly used 81-day averaged F10.7 to investigate their
uses in parameterizing the solar EUV irradiance. We demonstrate a
fundamental variability in the relationship between F10.7
and EUV associated with the two coronal sources of F10.7
emission.

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Title: Pipeline development for routine chromospheric magnetic field
inversions of DST/FIRS observations
Authors: Wang, Shuo; Schad, Thomas A.; Mcateer, R. T. James
2018tess.conf30819W Altcode:
The Facility Infrared Spectropolarimeter (FIRS) at the Dunn Solar
Telescope (DST) provides efficient mapping of the full Stokes vector
in the chromospheric He I triplet at 1083 nm across solar targets. The
inversion of this type of data to achieve measurements of the magnetic
field vector plays a key role in understanding chromospheric active
region topologies and is especially useful in studying solar filaments
and prominences. As a baseline supporting future synoptic magnetic
observations of solar filaments at the DST, we demonstrate first
steps in implementing a new pipeline that inverts FIRS data using
the "Hanle and Zeeman Light" (HAZEL) code, which incorporates all the
relevant atomic-level and Zeeman effect mechanisms. Inverted wide-field
observations (170” x 70”) of NOAA AR 12470 on December 14, 2015,
exhibit our ability to recover reliable field measurements using
multiple parallel FIRS slits. Using this pipeline, further analysis
of active region magnetic fields may shed light on the formation and
eruption processes of active region filaments.

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Title: Prediction of Solar Flares from Magnetograms using Transfer
Learning on Convolutional Neural Networks
Authors: Vincent, Ty; Boucheron, Laura; Mcateer, R. T. James
2018tess.conf32203V Altcode:
Solar flares are the result of the rapid conversion of stored magnetic
energy to particle acceleration and radiation in the corona. Most
current automated methods for predicting solar flares from magnetograms
use a process of feature extraction followed by classification. In
feature extraction some number of features are extracted from the
magnetogram image in order to quantify and characterize the state and
complexity of the photospheric magnetic field. The classification
algorithm then learns to separate flaring from non-flaring regions
within the feature space by defining a decision boundary that separates
the two classes. In contrast recent advances in deep learning, namely
convolutional neural networks (CNNs), have introduced methods that can
simultaneously learn both the features and the decision boundary. A
CNN-based flare prediction thus does not require a pre-defined feature
space but instead learns the features that best separate flaring from
non-flaring regions. CNNs are computationally complex to train and
require large amounts of training data. However, recent work has shown
that networks trained for other applications can be adapted to new
problems with limited training data and computational overhead. In this
process of transfer learning, a CNN trained on a large image dataset
is used and only the final layers are retrained on a new data set. In
this work, we study the the performance of solar flare prediction
using transfer learning on CNNs and report on the high level features
defined by the CNN that may potentially identify underlying phenomenon
that lead active regions to flare.

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Title: The Slowly Varying Corona. I. Daily Differential Emission
Measure Distributions Derived from EVE Spectra
Authors: Schonfeld, S. J.; White, S. M.; Hock-Mysliwiec, R. A.;
McAteer, R. T. J.
2017ApJ...844..163S Altcode: 2017arXiv170609525S
Daily differential emission measure (DEM) distributions of the solar
corona are derived from spectra obtained by the Extreme-ultraviolet
Variability Experiment (EVE) over a 4 yr period starting in 2010 near
solar minimum and continuing through the maximum of solar cycle 24. The
DEMs are calculated using six strong emission features dominated by
Fe lines of charge states viii, ix, xi, xii, xiv, and xvi that sample
the nonflaring coronal temperature range 0.3-5 MK. A proxy for the
non-Fe xviii emission in the wavelength band around the 93.9 Å line
is demonstrated. There is little variability in the cool component
of the corona (T &lt; 1.3 MK) over the 4 yr, suggesting that the
quiet-Sun corona does not respond strongly to the solar cycle, whereas
the hotter component (T &gt; 2.0 MK) varies by more than an order of
magnitude. A discontinuity in the behavior of coronal diagnostics in
2011 February-March, around the time of the first X-class flare of cycle
24, suggests fundamentally different behavior in the corona under solar
minimum and maximum conditions. This global state transition occurs
over a period of several months. The DEMs are used to estimate the
thermal energy of the visible solar corona (of order 1031
erg), its radiative energy loss rate ((2.5-8) × {10}27
erg s-1), and the corresponding energy turnover timescale
(about an hour). The uncertainties associated with the DEMs and these
derived values are mostly due to the coronal Fe abundance and density
and the CHIANTI atomic line database.

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Title: Quasi-periodic oscillations in flare emission in the solar
chromosphere simultaneously observed with IRIS and SDO
Authors: Farris, Laurel Elizabeth; McAteer, R. T. James
2017shin.confE.164F Altcode:
Quasi-periodic pulsations (QPPs) appear in the emission spectrum of most
solar flares over all wavelength bands and, in some cases, multiple
periodicities. There is some ambiguity as to the type of emission in
which they occur (i.e. line or continuum), and the mechanism that drives
them. Current possibilities include magnetohydrodynamic oscillations and
plasma flows of non-thermal electrons after the magnetic reconnection
process. Here, we investigate the response of the chromosphere to solar
flares by inspecting the power of the 3-minute oscillations before,
during and after flares, in order to constrain both the start time
of this power and where it originates. For this preliminary study,
we present analysis of continuum images from the Helioseismic and
Magnetic Imager (HMI) and of 1600 and 1700 Angstrom UV images from
the Atmospheric Imaging Assembly (AIA), two of the instruments on
board the Solar Dynamics Observatory (SDO), of the 2011 February 15
X-class flare. Future work will involve the Interface Region Imaging
Spectrometer (IRIS) to show whether the oscillations are manifest
in the line or continuum emission, a distinction that can be lost in
integrated bandpass intensity images. Results from wavelet analysis
and Fourier transforms will be explored.

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Title: On the Non-Kolmogorov Nature of Flare-productive Solar
Active Regions
Authors: Mandage, Revati S.; McAteer, R. T. James
2016ApJ...833..237M Altcode: 2016arXiv161100830M
A magnetic power spectral analysis is performed on 53 solar active
regions, observed from 2011 August to 2012 July. Magnetic field data
obtained from the Helioseismic and Magnetic Imager, inverted as Active
Region Patches, are used to study the evolution of the magnetic power
index as each region rotates across the solar disk. Active regions
are classified based on the numbers and sizes of solar flares they
produce in order to study the relationship between flare productivity
and the magnetic power index. The choice of window size and inertial
range plays a key role in determining the correct magnetic power
index. The overall distribution of magnetic power indices has a
range of 1.0-2.5. Flare-quiet regions peak at a value of 1.6. However,
flare-productive regions peak at a value of 2.2. Overall, the histogram
of the distribution of power indices of flare-productive active
regions is well separated from flare-quiet active regions. Only 12%
of flare-quiet regions exhibit an index greater than 2, whereas 90% of
flare-productive regions exhibit an index greater than 2. Flare-quiet
regions exhibit a high temporal variance (I.e., the index fluctuates
between high and low values), whereas flare-productive regions maintain
an index greater than 2 for several days. This shows the importance of
including the temporal evolution of active regions in flare prediction
studies, and highlights the potential of a 2-3 day prediction window
for space weather applications.

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Title: Correcting F10.7 for use in Ionospheric Models
Authors: Schonfeld, S.; White, S.; Hock, R. A.; Henney, C. J.; Mcateer,
R. T. J.; Arge, C. N.
2016AGUFMSA53B2449S Altcode:
The F10.7 (10.7 cm, 2.8 GHZ) radio flux has been used as a proxy
for solar extreme ultraviolet (EUV) emission in ionospheric models
for decades. An often ignored complication when using F10.7 as an EUV
proxy is the fact that there are two different mechanisms in the solar
corona responsible for creating F10.7, bremsstrahlung that correlates
well with EUV, and gyroresonance that does not. We present an overview
of the issues caused by the F10.7 source ambiguity and new results
identifying the contribution from each generation mechanism over
a four year period during the rising phase of solar cycle 24. This
allows for an empirical correction that we compare with the F10.7
inputs traditionally used in ionospheric modelling and we discuss the
implications of these results for past and future models.

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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.

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Title: Segmentation of Coronal Holes Using Active Contours Without
Edges
Authors: Boucheron, L. E.; Valluri, M.; McAteer, R. T. J.
2016SoPh..291.2353B Altcode: 2016SoPh..tmp..154B; 2016arXiv161001023B
An application of active contours without edges is presented as an
efficient and effective means of extracting and characterizing coronal
holes. Coronal holes are regions of low-density plasma on the Sun
with open magnetic field lines. The detection and characterization
of these regions is important for testing theories of their formation
and evolution, and also from a space weather perspective because they
are the source of the fast solar wind. Coronal holes are detected in
full-disk extreme ultraviolet (EUV) images of the corona obtained
with the Solar Dynamics Observatory Atmospheric Imaging Assembly
(SDO/AIA). The proposed method detects coronal boundaries without
determining any fixed intensity value in the data. Instead, the
active contour segmentation employs an energy-minimization in which
coronal holes are assumed to have more homogeneous intensities than the
surrounding active regions and quiet Sun. The segmented coronal holes
tend to correspond to unipolar magnetic regions, are consistent with
concurrent solar wind observations, and qualitatively match the coronal
holes segmented by other methods. The means to identify a coronal hole
without specifying a final intensity threshold may allow this algorithm
to be more robust across multiple datasets, regardless of data type,
resolution, and quality.

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Title: Inferring Magnetic Fields and Electron Densities from Coronal
Seismology
Authors: McAteer, R. T. J.; Ireland, J.
2016usc..confE..54M Altcode:
The solar corona oscillates at many different spatial sizes and
temporal size scales. However, much remains unknown about many of
these oscillations: they are intermittent for unknown reasons; appear
on some coronal features and not on others; and may, or may not,
be magnetohydrodynamic (MHD) wave modes. Using a series of automated
oscillation detection routines, we extract space-time-density maps from
a quagmire of oscillating loops. From these data products, we extract
coronal magnetic fields and densities in order to to differentiate
between potential excitation mechanisms and between potential damping
mechanisms. The spread of periods, amplitudes, and damping times,
allow us to map the spatial distribution of these parameters. Initial
periods of P 300-500s, result in inferred coronal magnetic field of B
20G-50G. The decrease in the oscillation period of the loop position
corresponds to a drop in number density inside each coronal loop,
as predicted by MHD. As the the period drops below a threshold of P
300s, our MHD model cannot explain the sudden observed decrease in
both period and density and so a secondary dissipation mechanism must
occur at this point in time and space.

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Title: An overview of coronal seismology and application to data
from AIA/SDO
Authors: Farris, Laurel; McAteer, R. T. James
2016shin.confE.201F Altcode:
Coronal seismology involves the investigation of magnetohydrodynamic
(MHD) waves and oscillatory phenomena that arise in the solar
corona. Properties of the observed modes are largely dependent on their
environment, and therefore can be used to extract atmospheric parameters
that are otherwise difficult to observe. The general theory behind
MHD phenomena is investigated here, along with the characteristics of
different modes and the information that can be extracted from them. A
few methods are applied to data from the Atmospheric Imaging Assembly
(AIA) instrument on the Solar Dynamics Observatory (SDO).

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Title: F10.7 and the slowly varying corona from EVE DEMs
Authors: Schonfeld, Sam; White, S. M.; Hock, R. A.; McAteer, R. T. J.
2016shin.confE.193S Altcode:
We present a differential emission measure (DEM) analysis of the
slowly varying corona during the first half of solar cycle 24. Using
the Extreme ultraviolet Variability Experiment (EVE) and the CHIANTI
atomic line database we identify strong isolated iron emission lines
present in the non-flaring spectrum with peak emissions covering the
coronal temperature range of 5.7 &lt; log(T) &lt; 6.5. These lines
are used to generate daily DEMs from EVE spectra to observe the long
term variability of global coronal thermal properties. We discuss the
choice of emission lines and the implications of this data set for
the relationship between EUV and the F10.7 radio flux.

---------------------------------------------------------
Title: Observation of the Evolution of a Current Sheet in a Solar
Flare
Authors: Zhu, Chunming; Liu, Rui; Alexander, David; McAteer,
R. T. James
2016ApJ...821L..29Z Altcode: 2016arXiv160307062Z
We report multi-wavelength and multi-viewpoint observations of a solar
eruptive event that involves loop-loop interactions. During a C2.0
flare, motions associated with inflowing and outflowing plasma provide
evidence for ongoing magnetic reconnection. The flare loop top and a
rising “concave-up” feature are connected by a current-sheet-like
structure (CSLS). The physical properties (thickness, length,
temperature, and density) of the CSLS are evaluated. In regions adjacent
to the CSLS, the EUV emission (characteristic temperature at 1.6 MK)
begins to increase more than 10 minutes prior to the onset of the flare,
and steeply decreases during the decay phase. The reduction of the
emission resembles that expected from coronal dimming. The dynamics
of this event imply a magnetic reconnection rate in the range 0.01-0.05.

---------------------------------------------------------
Title: Solar flares, Ampere's Law, and the Search for Units in
Scale-Free Processes
Authors: McAteer, R. T. James
2016IAUFM..29B.732M Altcode:
One of the most powerful SOC tools - the wavelet transform modulus
maxima approach to calculating multifractality - is connected to one
of the most powerful equations in all of physics - Ampere's law. In
doing so, the multifractal spectra can be expressed in terms of current
density, and how current density can then be used for the prediction
of future energy release from such a system.

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Title: 25 Years of Self-organized Criticality: Numerical Detection
Methods
Authors: McAteer, R. T. James; Aschwanden, Markus J.; Dimitropoulou,
Michaila; Georgoulis, Manolis K.; Pruessner, Gunnar; Morales, Laura;
Ireland, Jack; Abramenko, Valentyna
2016SSRv..198..217M Altcode: 2015SSRv..tmp...31M; 2015arXiv150608142M
The detection and characterization of self-organized criticality
(SOC), in both real and simulated data, has undergone many
significant revisions over the past 25 years. The explosive
advances in the many numerical methods available for detecting,
discriminating, and ultimately testing, SOC have played a critical
role in developing our understanding of how systems experience and
exhibit SOC. In this article, methods of detecting SOC are reviewed;
from correlations to complexity to critical quantities. A description
of the basic autocorrelation method leads into a detailed analysis
of application-oriented methods developed in the last 25 years. In
the second half of this manuscript space-based, time-based and
spatial-temporal methods are reviewed and the prevalence of power
laws in nature is described, with an emphasis on event detection and
characterization. The search for numerical methods to clearly and
unambiguously detect SOC in data often leads us outside the comfort
zone of our own disciplines—the answers to these questions are often
obtained by studying the advances made in other fields of study. In
addition, numerical detection methods often provide the optimum link
between simulations and experiments in scientific research. We seek
to explore this boundary where the rubber meets the road, to review
this expanding field of research of numerical detection of SOC systems
over the past 25 years, and to iterate forwards so as to provide some
foresight and guidance into developing breakthroughs in this subject
over the next quarter of a century.

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Title: Spatial variation of AIA coronal Fourier power spectra
Authors: Ireland, J.; Mcateer, R. T. J.
2015AGUFMSH54B..01I Altcode:
We describe a study of the spatial distribution of the properties
of the Fourier power spectrum of time-series of AIA 171Å and 193Å
data. The area studied includes examples of physically different
components of the corona, such as coronal moss, a sunspot, quiet Sun
and fan loop footpoints. We show that a large fraction of the power
spectra are well modeled by a power spectrum that behaves like a power
law f-n (n&gt;0)at lower frequencies f, dropping to a constant value
at higher frequencies. We also show that there are areas where the
power spectra are better described by the above power spectrum model,
plus a narrow band oscillatory feature, centered in the 3-5 minute
oscillation range. These narrow-band spectral features are thought
to be due to the propagation of oscillations from lower down in solar
atmosphere to hotter. This allows us to produce maps of large areas of
the corona showing where the propagation from one waveband to another
does and does not occur. This is an important step in understanding
wave propagation in different layers in the corona. We also show the
171Å and 193Å power spectrum power law indices are correlated, with
171Å power law indices in the range n = 1.8 to 2.8, and 193Å power
law indices n = 2 to 3.5 approximately. Maps of the power law index
show that different ranges of values of the power law indices occur
in spatially contiguous parts of the corona, indicating that local
spatial structure may play a role in defining the power law index
value. Taken with our previous result from Ireland et al. (2015) that
physically different parts of the corona have different mean values of
the power law index, this new result strongly suggests that the same
mechanism producing the observed power law power spectrum is operating
everywhere across the corona. We discuss the nanoflare hypothesis as
a possible explanation of these observations.

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Title: Complex Flare Dynamics Initiated by a Filament-Filament
Interaction
Authors: Zhu, Chunming; Liu, Rui; Alexander, David; Sun, Xudong;
McAteer, R. T. James
2015ApJ...813...60Z Altcode: 2015arXiv150705889Z
We report on an eruption involving a relatively rare filament-filament
interaction on 2013 June 21, observed by SDO and STEREO-B. The
two filaments were separated in height with a “double-decker”
configuration. The eruption of the lower filament began simultaneously
with a descent of the upper filament, resulting in a convergence
and direct interaction of the two filaments. The interaction was
accompanied by the heating of surrounding plasma and an apparent
crossing of a loop-like structure through the upper filament. The
subsequent coalescence of the filaments drove a bright front ahead
of the erupting structures. The whole process was associated with a
C3.0 flare followed immediately by an M2.9 flare. Shrinking loops and
descending dark voids were observed during the M2.9 flare at different
locations above a C-shaped flare arcade as part of the energy release,
giving us unique insight into the flare dynamics.

---------------------------------------------------------
Title: Prediction of Solar Flare Size and Time-to-Flare Using Support
Vector Machine Regression
Authors: Boucheron, Laura E.; Al-Ghraibah, Amani; McAteer, R. T. James
2015ApJ...812...51B Altcode: 2015arXiv151101941B
We study the prediction of solar flare size and time-to-flare using 38
features describing magnetic complexity of the photospheric magnetic
field. This work uses support vector regression to formulate a mapping
from the 38-dimensional feature space to a continuous-valued label
vector representing flare size or time-to-flare. When we consider
flaring regions only, we find an average error in estimating flare
size of approximately half a geostationary operational environmental
satellite (GOES) class. When we additionally consider non-flaring
regions, we find an increased average error of approximately
three-fourths a GOES class. We also consider thresholding the regressed
flare size for the experiment containing both flaring and non-flaring
regions and find a true positive rate of 0.69 and a true negative
rate of 0.86 for flare prediction. The results for both of these size
regression experiments are consistent across a wide range of predictive
time windows, indicating that the magnetic complexity features may be
persistent in appearance long before flare activity. This is supported
by our larger error rates of some 40 hr in the time-to-flare regression
problem. The 38 magnetic complexity features considered here appear
to have discriminative potential for flare size, but their persistence
in time makes them less discriminative for the time-to-flare problem.

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Title: Too big to fail: The role of magnetic structure and dynamics
in super active regions, on the Sun and Sun-like stars
Authors: McAteer, R. T. James
2015IAUGA..2257122M Altcode:
Accurate and timely solar activity forecasting has proved to be
illusive. Despite many decades of research, we are not much further
advanced in our forecasting efforts of the occurrence of solar activity
than we were two decades ago. However, one aspect has become clear -
big, complex magnetic active regions on the Sun inevitably produce
big, complex solar flares and coronal mass ejections. Here, I present
observations and models that show why these super active regions are
too big to fail.First I focus on studies of the largest active regions
of solar cycle 23 and 24, comparing proxies of non-potential magnetic
structure in these regions with similar proxies in less active regions
of the Sun. This shows that the necessary and sufficient conditions
exist in these super active regions to provide both the largest solar
flares and large, fast, coronal mass ejections.Second I show why these
conditions in super active regions differ so dramatically from the
conditions in smaller, less active, regions of the Sun. This uses
magnetic feature tracking to infer the Poynting flux injected into
the corona, and DEM analysis to provide radiative and conductive loss
estimates from the corona. The difference between energy injected,
and energy lost, is stored in the coronal magnetic field structure in
the super active regions.Finally, I apply this this research to Kepler
starspots , showing why these regions must differ in a fundamental way
in order to overcome the limitations that super granular flow places
on solar active regions formation and energy storage.

---------------------------------------------------------
Title: Coronal Seismology: Inferring Magnetic Fields and Exploring
Damping Mechanisms
Authors: McAteer, R. T. James; Ireland, Jack
2015IAUGA..2257620M Altcode:
Recent observations in extreme ultra-violet wavelengths have shown
that the solar corona oscillates at many different spatial sizes and
temporal size scales. However, much remains unknown about many of these
oscillations; they are intermittent for unknown reasons, appear on some
coronal features and not on other, similar, neighboring features, and
may (or may not) be magnetohydrodynamic (MHD) wave modes. Definitive
causes of the structure and origins of these oscillations are still
largely lacking. Here, we use automated oscillation detection routines
to study a large sample of oscillations, inferring physical mechanisms
as to how and why the corona varies.First, we measure the oscillation
content of different physical regions on the Sun in SDO AIA data, using
two different automated oscillation detection algorithms. This shows a
power-law distribution in oscillatory frequency, disagreeing with strong
historical assumptions about the nature of coronal heating and coronal
seismology. We show how such disagreements can be reconciled by using
a power-law background for oscillatory signals.Second we use coronal
seismology to provide a means to infer coronal plasma parameters and
to differentiate between potential damping mechanisms. Recent sets of
kink-mode observations (usually 5-8 loops) have come insights into how
the coronal is structured and how it evolves. We present a complex
set of flare-induced, off-limb, coronal kink-mode oscillations of
almost 100 loops. These display a spread of periods, amplitudes, and
damping times, allowing us to probe the spatial distribution of these
parameters for the first time. Both Fourier and Wavelet routines are
used to automatically extract and characterize these oscillations. An
initial period of P~500s, results in an inferred coronal magnetic field
of B~20G. The decrease in the oscillation period of the loop position
corresponds to a drop in number density inside the coronal loop, as
predicted by MHD. As the the period drops below a threshold of P~300s,
our MHD model cannot explain the sudden decrease in both period and
density. A secondary dissipation mechanism must occur at this point
in time and space.

---------------------------------------------------------
Title: Frozen Fractals all Around: Solar flares, Ampere’s Law,
and the Search for Units in Scale-Free Processes.
Authors: McAteer, R. T. James
2015IAUGA..2257411M Altcode:
My soul is spiraling in frozen fractals all around, And one thought
crystallizes like an icy blast, I'm never going back, the past
is in the past.Elsa, from Disney’s Frozen, characterizes two
fundamental aspects of scale-free processes in Nature: fractals
are everywhere in space; fractals can be used to probe changes in
time. Self-Organized Criticality provides a powerful set of tools
to study scale-free processes. It connects spatial fractals (more
generically, multifractals) to temporal evolution. The drawback is that
this usually results in scale-free, unit-less, indices, which can be
difficult to connect to everyday physics. Here, I show a novel method
that connects one of the most powerful SOC tools - the wavelet transform
modulus maxima approach to calculating multifractality - to one of the
most powerful equations in all of physics - Ampere’s law. In doing so
I show how the multifractal spectra can be expressed in terms of current
density, and how current density can then be used for the prediction of
future energy release from such a system.Our physical understanding of
the solar magnetic field structure, and hence our ability to predict
solar activity, is limited by the type of data currently available. I
show that the multifractal spectrum provides a powerful physical
connection between the details of photospheric magnetic gradients
of current data and the coronal magnetic structure. By decomposing
Ampere’s law and comparing it to the wavelet transform modulus maximum
method, I show how the scale-free Holder exponent provides a direct
measure of current density across all relevant sizes. The prevalence of
this current density across various scales is connected to its stability
in time, and hence to the ability of the magnetic structure to store
and then release energy. Hence (spatial) multifractals inform us of
(future) solar activity.Finally I discuss how such an approach can be
used in any study of scale-free processes, and highlight the necessary
key steps in identifying the nature of the mother wavelet to ensuring
the viability of this powerful connection.

---------------------------------------------------------
Title: Active Region Morphologies Selected from Near-side Helioseismic
Data
Authors: MacDonald, G. A.; Henney, C. J.; Díaz Alfaro, M.; González
Hernández, I.; Arge, C. N.; Lindsey, C.; McAteer, R. T. J.
2015ApJ...807...21M Altcode:
We estimate the morphology of near-side active regions using near-side
helioseismology. Active regions from two data sets, Air Force Data
Assimilative Photospheric flux Transport synchronic maps and Global
Oscillation Network Group near-side helioseismic maps, were matched and
their morphologies compared. Our algorithm recognizes 382 helioseismic
active regions between 2002 April 25 and 2005 December 31 and matches
them to their corresponding magnetic active regions with 100% success. A
magnetic active region occupies 30% of the area of its helioseismic
signature. Recovered helioseismic tilt angles are in good agreement with
magnetic tilt angles. Approximately 20% of helioseismic active regions
can be decomposed into leading and trailing polarity. Leading polarity
components show no discernible scaling relationship, but trailing
magnetic polarity components occupy approximately 25% of the area of the
trailing helioseismic component. A nearside phase-magnetic calibration
is in close agreement with a previous far-side helioseismic calibration
and provides confidence that these morphological relationships can
be used with far-side helioseismic data. Including far-side active
region morphology in synchronic maps will have implications for coronal
magnetic topology predictions and solar wind forecasts.

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Title: An automated classification approach to ranking photospheric
proxies of magnetic energy build-up
Authors: Al-Ghraibah, A.; Boucheron, L. E.; McAteer, R. T. J.
2015A&A...579A..64A Altcode: 2015arXiv150608717A
 Aims: We study the photospheric magnetic field of ~2000
active regions over solar cycle 23 to search for parameters that
may be indicative of energy build-up and its subsequent release as
a solar flare in the corona. Methods: We extract three sets
of parameters: (1) snapshots in space and time: total flux, magnetic
gradients, and neutral lines; (2) evolution in time: flux evolution;
and (3) structures at multiple size scales: wavelet analysis. This work
combines standard pattern recognition and classification techniques
via a relevance vector machine to determine (i.e., classify) whether
a region is expected to flare (≥C1.0 according to GOES). We consider
classification performance using all 38 extracted features and several
feature subsets. Classification performance is quantified using both
the true positive rate (the proportion of flares correctly predicted)
and the true negative rate (the proportion of non-flares correctly
classified). Additionally, we compute the true skill score which
provides an equal weighting to true positive rate and true negative
rate and the Heidke skill score to allow comparison to other flare
forecasting work. Results: We obtain a true skill score of ~0.5
for any predictive time window in the range 2 to 24 h, with a true
positive rate of ~0.8 and a true negative rate of ~0.7. These values
do not appear to depend on the predictive time window, although the
Heidke skill score (&lt;0.5) does. Features relating to snapshots of
the distribution of magnetic gradients show the best predictive ability
over all predictive time windows. Other gradient-related features
and the instantaneous power at various wavelet scales also feature
in the top five (of 38) ranked features in predictive power. It has
always been clear that while the photospheric magnetic field governs
the coronal non-potentiality (and hence likelihood of producing
a solar flare), photospheric magnetic field information alone is
not sufficient to determine this in a unique manner. Furthermore we
are only measuring proxies of the magnetic energy build up. We are
still lacking observational details on why energy is released at any
particular point in time. We may have discovered the natural limit of
the accuracy of flare predictions from these large scale studies.

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Title: Coronal Sources of the Solar F10.7 Radio Flux
Authors: Schonfeld, S. J.; White, S. M.; Henney, C. J.; Arge, C. N.;
McAteer, R. T. J.
2015ApJ...808...29S Altcode: 2015arXiv150800599S
We present results from the first solar full-disk {{{F}}}10.7
(the radio flux at 10.7 cm, 2.8 GHz) image taken with the S-band
receivers on the recently upgraded Karl G. Jansky Very Large Array in
order to assess the relationship between the {{{F}}}10.7
index and solar extreme ultraviolet (EUV) emission. To identify the
sources of the observed 2.8 GHz emission, we calculate differential
emission measures from EUV images collected by the Atmospheric Imaging
Assembly and use them to predict the bremsstrahlung component of the
radio emission. By comparing the bremsstrahlung prediction and radio
observation we find that 8.1% ± 0.5% of the variable component of
the {{{F}}}10.7 flux is associated with the gyroresonance
emission mechanism. Additionally, we identify optical depth effects on
the radio limb which may complicate the use of {{{F}}}10.7
time series as an EUV proxy. Our analysis is consistent with a coronal
iron abundance that is four times the photospheric level.

---------------------------------------------------------
Title: Frozen-in Fractals All Around: Inferring the Large-Scale
Effects of Small-Scale Magnetic Structure
Authors: McAteer, R. T. James
2015SoPh..290.1897M Altcode: 2015SoPh..tmp...87M; 2015arXiv150607914M
The large-scale structure of the magnetic field in the solar corona
provides the energy to power large-scale solar eruptive events. Our
physical understanding of this structure, and hence our ability
to predict these events, is limited by the type of data currently
available. It is shown that the multifractal spectrum is a powerful tool
to study this structure, by providing a physical connection between
the details of photospheric magnetic gradients and current density at
all size scales. This uses concepts associated with geometric measure
theory and the theory of weakly differentiable functions to compare
Ampère's law to the wavelet-transform modulus maximum method. The
Hölder exponent provides a direct measure of the rate of change
of current density across spatial size scales. As this measure is
independent of many features of the data (pixel resolution, data size,
data type, presence of quiet-Sun data), it provides a unique approach to
studying magnetic-field complexity and hence a potentially powerful tool
for a statistical prediction of solar-flare activity. Three specific
predictions are provided to test this theory: the multifractal spectra
will not be dependent on the data type or quality; quiet-Sun gradients
will not persist with time; structures with high current densities
at large size scales will be the source of energy storage for solar
eruptive events.

---------------------------------------------------------
Title: Performance Testing of an Off-Limb Solar Adaptive Optics System
Authors: Taylor, G. E.; Schmidt, D.; Marino, J.; Rimmele, T. R.;
McAteer, R. T. J.
2015SoPh..290.1871T Altcode: 2015arXiv150801826T; 2015SoPh..tmp...54T
Long-exposure spectro-polarimetry in the near-infrared is a preferred
method to measure the magnetic field and other physical properties of
solar prominences. In the past, it has been very difficult to observe
prominences in this way with sufficient spatial resolution to fully
understand their dynamical properties. Solar prominences contain
highly transient structures, visible only at small spatial scales;
hence they must be observed at sub-arcsecond resolution, with a high
temporal cadence. An adaptive optics (AO) system capable of directly
locking on to prominence structure away from the solar limb has the
potential to allow for diffraction-limited spectro-polarimetry of solar
prominences. We show the performance of the off-limb AO system and its
expected performance at the desired science wavelength Ca II 8542 Å.

---------------------------------------------------------
Title: Coronal Fourier Power Spectra: Implications for Coronal
Seismology and Coronal Heating
Authors: Ireland, J.; McAteer, R. T. J.; Inglis, A. R.
2015ApJ...798....1I Altcode: 2014arXiv1410.2171I
The dynamics of regions of the solar corona are investigated using
Atmospheric Imaging Assembly 171 Å and 193 Å data. The coronal
emission from the quiet Sun, coronal loop footprints, coronal moss,
and from above a sunspot is studied. It is shown that the mean Fourier
power spectra in these regions can be described by a power law at lower
frequencies that tails to a flat spectrum at higher frequencies, plus
a Gaussian-shaped contribution that varies depending on the region
studied. This Fourier spectral shape is in contrast to the commonly
held assumption that coronal time series are well described by the sum
of a long timescale background trend plus Gaussian-distributed noise,
with some specific locations also showing an oscillatory signal. The
implications of the observed spectral shape on the fields of coronal
seismology and the automated detection of oscillations in the corona
are discussed. The power-law contribution to the shape of the Fourier
power spectrum is interpreted as being due to the summation of a
distribution of exponentially decaying emission events along the line
of sight. This is consistent with the idea that the solar atmosphere
is heated everywhere by small energy deposition events.

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Title: Qualities of Sequential Chromospheric Brightenings Observed
in Hα and UV Images
Authors: Kirk, Michael S.; Balasubramaniam, K. S.; Jackiewicz, Jason;
McAteer, R. T. James
2014ApJ...796...78K Altcode: 2014arXiv1411.4069K
Chromospheric flare ribbons observed in Hα appear well-organized
when first examined: ribbons impulsively brighten, morphologically
evolve, and exponentially decay back to pre-flare levels. Upon closer
inspection of the Hα flares, there is often a significant number
of compact areas brightening in concert with the flare eruption but
are spatially separated from the evolving flare ribbon. One class of
these brightenings is known as sequential chromospheric brightenings
(SCBs). SCBs are often observed in the immediate vicinity of erupting
flares and are associated with coronal mass ejections. In the past
decade there have been several previous investigations of SCBs. These
studies have exclusively relied upon Hα images to discover and analyze
these ephemeral brightenings. This work employs the automated detection
algorithm of Kirk et al. to extract the physical qualities of SCBs in
observations of ground-based Hα images and complementary Atmospheric
Imaging Assembly images in He II, C IV, and 1700 Å. The metadata
produced in this tracking process are then culled using complementary
Doppler velocities to isolate three distinguishable types of SCBs. From
a statistical analysis, we find that the SCBs at the chromospheric
Hα layer appear earlier and last longer than their corresponding
signatures measured in AIA. From this multi-layer analysis, we infer
that SCBs are spatially constrained to the mid-chromosphere. We also
derive an energy budget to explain SCBs which have a postulated energy
of not more than 0.01% of the total flare energy.

---------------------------------------------------------
Title: Coronal Fourier power spectra: implications for coronal
heating and coronal seismology
Authors: Ireland, J.; Mcateer, R. T. J.; Inglis, A. R.
2014AGUFMSH13C4128I Altcode:
The dynamics of regions of the solar corona are investigated using
AIA 171 and 193 Angstrom data. It is shown that the mean Fourier
power spectra of emission from active region cores, above sunspots, in
loop footpoints and in the quiet Sun, follow an approximate power-law
behaviour. We show that power-law power-spectra can be formed by summing
a distribution of exponentially decaying emission events along the line
of sight, consistent with the idea that the corona is heated everywhere
by small energy deposition events. We also examine changes in Fourier
power spectrum as a function of coronal loop height to look for evidence
of a preferred location to coronal heating. The observed power-law
power spectra also have implications for coronal seismology, as all
existing observational studies do not take into account the power-law
power spectrum of the coronal emission and its attendant statistical
properties. We show that random fluctuations in the emission can be
mis-identified as oscillatory signal, and give suggestions on how to
detect oscillatory motions above a background power-law power spectrum.

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Title: The Sources of F10.7 Emission
Authors: Schonfeld, Samuel Joseph; White, S. M.; Henney, C. J.;
McAteer, R. T. J.; Arge, C. N.
2014shin.confE..62S Altcode:
The solar radio flux at a wavelength of 10.7 cm, F10.7, serves as
a proxy for the Sun"s ionizing flux striking the Earth and is a
heavily used index for space weather studies. In principal both the
coronal sources of ionizing flux and strong coronal magnetic fields
contribute to F10.7 via different emission mechanisms. Recently the
Karl G. Jansky Very Large Array (VLA) has added the capability to make
high-spatial-resolution images of the Sun at 10.7 cm. In this work
we compare a trial F10.7 image from the VLA with the radio emission
predicted to be present from EUV images of the Sun acquired by the
AIA telescope on the Solar Dynamics Observatory at 6 wavelengths
covering the coronal temperature range. Photospheric magnetograms
are used to identify likely regions of strong coronal magnetic field,
and the circular polarization measured by the VLA is used as a tracer
of gyroresonance contributions to F10.7. We discuss the conversion
of the EUV data to bremsstrahlung radio fluxes via the construction
of differential emission measure images, and analyze the relative
contributions of the different sources of F10.7 flux.

---------------------------------------------------------
Title: Power Spectra in AIA 171 and 193 and Their Implications for
Coronal Seismology
Authors: Ireland, Jack; Mcateer, Robert TJ; Inglis, Andrew
2014AAS...22432321I Altcode:
We examine Fourier power spectra of time-series of AIA 171 and
193 waveband data. We show that these power spectra exhibit a
red-noise like power-law behaviour on time-scales of interest to
coronal seismology. We show that assuming a white noise background
power spectrum when a red-noise power spectrum is present can lead
to the mistaken identification of narrow-band oscillatory power
when none is present. Thisimplies that a background power-law power
spectrum must be taken in to account when determining the presence
of narrow-band oscillations that may be due to MHD wave processes
in the solar corona. We also show that the red-noise power spectrum
is consistent with the expected power spectrum from large number of
exponentially decaying emission events with event size taken from a
power law distribution.

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Title: On the Sensitivity of the GOES Flare Classification to
Properties of the Electron Beam in the Thick-target Model
Authors: Reep, J. W.; Bradshaw, S. J.; McAteer, R. T. J.
2013ApJ...778...76R Altcode: 2013arXiv1310.3242R
The collisional thick-target model, wherein a large number of electrons
are accelerated down a flaring loop, can be used to explain many
observed properties of solar flares. In this study, we focus on the
sensitivity of (GOES) flare classification to the properties of the
thick-target model. Using a hydrodynamic model with RHESSI-derived
electron beam parameters, we explore the effects of the beam energy flux
(or total non-thermal energy), the cut-off energy, and the spectral
index of the electron distribution on the soft X-rays observed by
GOES. We conclude that (1) the GOES class is proportional to the
non-thermal energy E α for α ≈ 1.7 in the low-energy
passband (1-8 Å) and ≈1.6 in the high-energy passband (0.5-4 Å)
(2) the GOES class is only weakly dependent on the spectral index in
both passbands; (3) increases in the cut-off will increase the flux in
the 0.5-4 Å passband but decrease the flux in the 1-8 Å passband,
while decreases in the cut-off will cause a decrease in the 0.5-4 Å
passband and a slight increase in the 1-8 Å passband.

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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 sensitivity of GOES flare classification to the
thick-target model
Authors: Reep, Jeffrey; Bradshaw, S.; Mcateer, R. T.
2013SPD....44...59R Altcode:
The collisional thick-target model has been used to explain many
spectral features of solar flares. Flare classification, based on
soft X-rays observed by GOES, should then depend on the model. Using a
combination of numerical simulations and observed features of flares,
we explore the sensitivity of flare classification to the parameters of
the thick-target model. We vary the total non-thermal energy, spectral
index, and the cut-off energy of the electron beam one at a time for
two sets of parameters derived from flares observed with RHESSI. We
find that the classification depends strongly on non-thermal energy,
only weakly on spectral index, and that the cut-off energy can either
increase or decrease the GOES class, depending upon how it varies.

---------------------------------------------------------
Title: On the sensitivity of GOES flare classification to the
collisional thick-target model
Authors: Reep, Jeffrey; Bradshaw, S.; Mcateer, R. T.
2013SPD....44...62R Altcode:
The collisional thick-target model has been used to explain many
spectral features of solar flares. Flare classification, based on
soft X-rays observed by GOES, should then depend on the model. Using a
combination of numerical simulations and observed features of flares,
we explore the sensitivity of flare classification to the parameters of
the thick-target model. We vary the total non-thermal energy, spectral
index, and the cut-off energy of the electron beam one at a time for
two sets of parameters derived from flares observed with RHESSI. We
find that the classification depends strongly on non-thermal energy,
only weakly on spectral index, and that the cut-off energy can either
increase or decrease the GOES class, depending upon how it varies.

---------------------------------------------------------
Title: Remote Oscillatory Responses to a Solar Flare
Authors: And¯ić, A.; McAteer, R. T. J.
2013ApJ...772...54A Altcode:
The processes governing energy storage and release in the Sun are both
related to the solar magnetic field. We demonstrate the existence of a
magnetic connection between the energy released by a flare and increased
oscillatory power in the lower solar atmosphere. The oscillatory
power in active regions tends to increase in response to explosive
events at other locations, but not in the active region itself. We
carry out timing studies and show that this effect is probably caused
by a large-scale magnetic connection between the regions, instead of
a globally-propagating wave. We show that oscillations tend to exist
in longer-lived wave trains with short periods (P &lt; 200 s) at the
time of a flare. These wave trains may be mechanisms by which flare
energy can be redistributed throughout the solar atmosphere.

---------------------------------------------------------
Title: Remote Oscillatory responses to a solar flare
Authors: Andic, Aleksandra; McAteer, R. T. James
2013arXiv1306.3475A Altcode:
The processes governing energy storage and release in the Sun are both
related to the solar magnetic field. We demonstrate the existence
of a magnetic connection between energy released caused by a flare
and increased oscillatory power in the lower solar atmosphere. The
oscillatory power in active regions tends to increase in response
to explosive events at a different location, but not in the region
itself. We carry out timing studies and show that this is probably
caused by a large scale magnetic connection between the regions,
and not a globally propagating wave. We show that oscillations tend
to exist in longer lived wave trains at short periods (P&lt; 200s)
at the time of a flare. This may be a mechanism by which flare energy
can be redistributed throughout the solar atmosphere.

---------------------------------------------------------
Title: SOC and Fractal Geometry
Authors: McAteer, R. T. J.
2013socs.book...73M Altcode:
When Mandelbrot, the father of modern fractal geometry, made this
seemingly obvious statement he was trying to show that we should move
out of our comfortable Euclidean space and adopt a fractal approach
to geometry. The concepts and mathematical tools of fractal geometry
provides insight into natural physical systems that Euclidean tools
cannot do. The benet from applying fractal geometry to studies of
Self-Organized Criticality (SOC) are even greater. SOC and fractal
geometry share concepts of dynamic n-body interactions, apparent
non-predictability, self-similarity, and an approach to global
statistics in space and time that make these two areas into naturally
paired research techniques. Further, the iterative generation techniques
used in both SOC models and in fractals mean they share common features
and common problems. This chapter explores the strong historical
connections between fractal geometry and SOC from both a mathematical
and conceptual understanding, explores modern day interactions between
these two topics, and discusses how this is likely to evolve into an
even stronger link in the near future.

---------------------------------------------------------
Title: Flares, waves, and energy
Authors: Andic, A.; McAteer, R. T. J.; McNamara, B.
2013enss.confE...2A Altcode:
Solar energy storage and release events are interconnected. This
research addresses one aspect of the interconnection of those energetic
solar events. Addressed aspect emerged in recent research that showed
a movement of a flux tubes generates oscillations. Analysis was
performed using six C class and one M class flares during Dec. 25,
2011. Using AIA and HMI data, we investigated the connection between
flare induced disturbance and changes in the flux of photospheric
oscillations. Results showed significant increase of oscillatory flux
following the flare itself. This increase was detected outside of
flare location. Results show a need for deeper statistical analysis
of the oscillatory response at flare induced disturbance. This kind
of analysis might reveal energy distributions when this aspect of
interconnection is in question.

---------------------------------------------------------
Title: An Automated Algorithm to Distinguish and Characterize Solar
Flares and Associated Sequential Chromospheric Brightenings
Authors: Kirk, M. S.; Balasubramaniam, K. S.; Jackiewicz, J.; McNamara,
B. J.; McAteer, R. T. J.
2013SoPh..283...97K Altcode: 2011arXiv1108.1384K; 2011SoPh..tmp..345K
We present a new automated algorithm to identify, track, and
characterize small-scale brightening associated with solar eruptive
phenomena observed in Hα. The temporal, spatially localized changes in
chromospheric intensities can be separated into two categories: flare
ribbons and sequential chromospheric brightenings (SCBs). Within each
category of brightening we determine the smallest resolvable locus of
pixels, a kernel, and track the temporal evolution of the position and
intensity of each kernel. This tracking is accomplished by isolating
the eruptive features, identifying kernels, and linking detections
between frames into trajectories of kernels. We fully characterize the
evolving intensity and morphology of the flare ribbons by observing
the tracked flare kernels in aggregate. With the location of SCB and
flare kernels identified, they can easily be overlaid on complementary
data sets to extract Doppler velocities and magnetic-field intensities
underlying the kernels. This algorithm is adaptable to any dataset to
identify and track solar features.

---------------------------------------------------------
Title: Solar Limb Adaptive Optics: A Test of Wavefront Sensors
and Algorithms
Authors: Taylor, G. E.; Rimmele, T. R.; Marino, J.; Tritschler, A.;
McAteer, R. T. J.
2012ASPC..463..321T Altcode:
In order to advance our understanding of solar prominences, we need
to be able to observe them at high spatial, spectral and temporal
resolution. In order to determine physical properties of these cool
and faint coronal structures, however, one is forced to use long
exposure times, particularly in spectroscopic and spectropolarimetric
applications. It is thus crucial that image stabilization is provided,
preferrably in form of an adaptive optics (AO) system that is capable
to lock onto the off-limb prominence structure, potentially providing
diffraction limited imaging. We investigate the preliminary design
of such a solar-limb AO system based on a correlating Shack-Hartmann
sensor. As an alternative we also studied a solar-limb AO wavefront
sensor using a phase-diverse approach.

---------------------------------------------------------
Title: Sequential Chomospheric Brightening: An Automated Approach
to Extracting Physics from Ephemeral Brightening
Authors: Kirk, M. S.; Balasubramaniam, K. S.; Jackiewicz, J.; McAteer,
R. T. J.; McNamara, B. J.
2012ASPC..463..267K Altcode: 2012arXiv1203.1277K
We make a comparison between small scale chromospheric brightenings
and energy release processes through examining the temporal evolution
of sequential chromospheric brightenings (SCBs), derive propagation
velocities, and propose a connection of the small-scale features to
solar flares. Our automated routine detects and distinguishes three
separate types of brightening regularly observed in the chromosphere:
plage, flare ribbon, and point brightenings. By studying their distinct
dynamics, we separate out the flare-associated bright points commonly
known as SCBs and identify a propagating Moreton wave. Superimposing
our detections on complementary off-band images, we extract a Doppler
velocity measurement beneath the point brightening locations. Using
these dynamic measurements, we put forward a connection between point
brightenings, the erupting flare, and overarching magnetic loops. A
destabilization of the pre-flare loop topology by the erupting flare
directly leads to the SCBs observed.

---------------------------------------------------------
Title: Observations of Low Frequency Solar Radio Bursts from the
Rosse Solar-Terrestrial Observatory
Authors: Zucca, P.; Carley, E. P.; McCauley, J.; Gallagher, P. T.;
Monstein, C.; McAteer, R. T. J.
2012SoPh..280..591Z Altcode: 2012SoPh..tmp...94Z; 2012arXiv1204.0943Z
The Rosse Solar-Terrestrial Observatory (RSTO; www.rosseobservatory.ie)
was established at Birr Castle, Co. Offaly, Ireland (53°05'38.9″,
7°55'12.7″) in 2010 to study solar radio bursts and the response of
the Earth's ionosphere and geomagnetic field. To date, three Compound
Astronomical Low-cost Low-frequency Instrument for Spectroscopy in
Transportable Observatory (CALLISTO) spectrometers have been installed,
with the capability of observing in the frequency range of 10 - 870
MHz. The receivers are fed simultaneously by biconical and log-periodic
antennas. Nominally, frequency spectra in the range of 10 - 400 MHz
are obtained with four sweeps per second over 600 channels. Here, we
describe the RSTO solar radio spectrometer set-up, and present dynamic
spectra of samples of type II, III and IV radio bursts. In particular,
we describe the fine-scale structure observed in type II bursts,
including band splitting and rapidly varying herringbone features.

---------------------------------------------------------
Title: Coronal Mass Ejection Mass, Energy, and Force Estimates
Using STEREO
Authors: Carley, Eoin P.; McAteer, R. T. James; Gallagher, Peter T.
2012ApJ...752...36C Altcode: 2012arXiv1204.4601C
Understanding coronal mass ejection (CME) energetics and dynamics has
been a long-standing problem, and although previous observational
estimates have been made, such studies have been hindered by large
uncertainties in CME mass. Here, the two vantage points of the Solar
Terrestrial Relations Observatory (STEREO) COR1 and COR2 coronagraphs
were used to accurately estimate the mass of the 2008 December 12
CME. Acceleration estimates derived from the position of the CME front
in three dimensions were combined with the mass estimates to calculate
the magnitude of the kinetic energy and driving force at different
stages of the CME evolution. The CME asymptotically approaches a mass of
3.4 ± 1.0 × 1015 g beyond ~10 R ⊙. The kinetic
energy shows an initial rise toward 6.3 ± 3.7 × 1029
erg at ~3 R ⊙, beyond which it rises steadily to 4.2 ±
2.5 × 1030 erg at ~18 R ⊙. The dynamics are
described by an early phase of strong acceleration, dominated by a
force of peak magnitude of 3.4 ± 2.2 × 1014 N at ~3 R
⊙, after which a force of 3.8 ± 5.4 × 1013
N takes effect between ~7 and 18 R ⊙. These results are
consistent with magnetic (Lorentz) forces acting at heliocentric
distances of lsim7 R ⊙, while solar wind drag forces
dominate at larger distances (gsim7 R ⊙).

---------------------------------------------------------
Title: Properties of Sequential Chromospheric Brightenings and
Associated Flare Ribbons
Authors: Kirk, Michael S.; Balasubramaniam, K. S.; Jackiewicz, Jason;
McAteer, R. T. James; Milligan, Ryan O.
2012ApJ...750..145K Altcode: 2012arXiv1203.1271K
We report on the physical properties of solar sequential chromospheric
brightenings (SCBs) observed in conjunction with moderate-sized
chromospheric flares with associated Coronal mass ejections. To
characterize these ephemeral events, we developed automated procedures
to identify and track subsections (kernels) of solar flares and
associated SCBs using high-resolution Hα images. Following the
algorithmic identification and a statistical analysis, we compare
and find the following: SCBs are distinctly different from flare
kernels in their temporal characteristics of intensity, Doppler
structure, duration, and location properties. We demonstrate that
flare ribbons are themselves made up of subsections exhibiting
differing characteristics. Flare kernels are measured to have a mean
propagation speed of 0.2 km s-1 and a maximum speed of 2.3 km
s-1 over a mean distance of 5 × 103 km. Within
the studied population of SCBs, different classes of characteristics
are observed with coincident negative, positive, or both negative and
positive Doppler shifts of a few km s-1. The appearance of
SCBs precedes peak flare intensity by ≈12 minutes and decay ≈1 hr
later. They are also found to propagate laterally away from flare center
in clusters at 45 km s-1 or 117 km s-1. Given
SCBs' distinctive nature compared to flares, we suggest a different
physical mechanism relating to their origin than the associated
flare. We present a heuristic model of the origin of SCBs.

---------------------------------------------------------
Title: An Insight Into Atmospheric Structure Through Compact
Chromospheric Brightenings
Authors: Kirk, Michael S.; Balasubramaniam, K.; Jackiewicz, J.;
McAteer, R.
2012AAS...22012406K Altcode:
Compact chromospheric brightenings have a range of intensities,
Doppler velocities, and magnetic field strength each giving clues to
their physical origin. One type of compact brightening, sequential
chromospheric brightening (SCB), has several properties of small-scale
chromospheric evaporation. SCBs appear adjacent to two ribbon flares
with associated halo CMEs. This work presents a definition of SCBs
constrained by a statistical analysis of several chromospheric flaring
events. From this definition of SCBs, we extract physical qualities of
SCBs and correlate these qualities with data gathered from additional
layers of the solar atmosphere. Using these dynamic measurements, we
suggest a connection between compact brightenings, the erupting flare,
and overarching magnetic loops.

---------------------------------------------------------
Title: Waves and Flares
Authors: Andic, Aleksandra; McAteer, R.; Jackiewicz, J.; Boucheron,
L.; Cao, H.; McNamara, B.
2012AAS...22052109A Altcode:
It has been demonstrated that movement of the flux tube can cause
oscillations (Andic et al. 2010). In this work we present preliminary
research that shows what happens with the oscillations before, during,
and after magnetic field reconfigurations caused by explosive events. We
detect oscillations at locations where the magnetic field touches the
photosphere. However, we plan to analyze a larger statistical sample
of flaring active region to better quantify the relation between these
oscillations and movement of flux tubes caused by disturbances in the
magnetic field.

---------------------------------------------------------
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: Computer Vision for the Solar Dynamics Observatory (SDO)
Authors: Martens, P. C. H.; Attrill, G. D. R.; Davey, A. R.; Engell,
A.; Farid, S.; Grigis, P. C.; Kasper, J.; Korreck, K.; Saar, S. H.;
Savcheva, A.; Su, Y.; Testa, P.; Wills-Davey, M.; Bernasconi, P. N.;
Raouafi, N. -E.; Delouille, V. A.; Hochedez, J. F.; Cirtain, J. W.;
DeForest, C. E.; Angryk, R. A.; De Moortel, I.; Wiegelmann, T.;
Georgoulis, M. K.; McAteer, R. T. J.; Timmons, R. P.
2012SoPh..275...79M Altcode: 2011SoPh..tmp..144M; 2011SoPh..tmp..213M; 2011SoPh..tmp....8M
In Fall 2008 NASA selected a large international consortium to produce
a comprehensive automated feature-recognition system for the Solar
Dynamics Observatory (SDO). The SDO data that we consider are all of the
Atmospheric Imaging Assembly (AIA) images plus surface magnetic-field
images from the Helioseismic and Magnetic Imager (HMI). We produce
robust, very efficient, professionally coded software modules that
can keep up with the SDO data stream and detect, trace, and analyze
numerous phenomena, including flares, sigmoids, filaments, coronal
dimmings, polarity inversion lines, sunspots, X-ray bright points,
active regions, coronal holes, EIT waves, coronal mass ejections
(CMEs), coronal oscillations, and jets. We also track the emergence and
evolution of magnetic elements down to the smallest detectable features
and will provide at least four full-disk, nonlinear, force-free magnetic
field extrapolations per day. The detection of CMEs and filaments is
accomplished with Solar and Heliospheric Observatory (SOHO)/Large
Angle and Spectrometric Coronagraph (LASCO) and ground-based Hα
data, respectively. A completely new software element is a trainable
feature-detection module based on a generalized image-classification
algorithm. Such a trainable module can be used to find features that
have not yet been discovered (as, for example, sigmoids were in the
pre-Yohkoh era). Our codes will produce entries in the Heliophysics
Events Knowledgebase (HEK) as well as produce complete catalogs for
results that are too numerous for inclusion in the HEK, such as the
X-ray bright-point metadata. This will permit users to locate data on
individual events as well as carry out statistical studies on large
numbers of events, using the interface provided by the Virtual Solar
Observatory. The operations concept for our computer vision system is
that the data will be analyzed in near real time as soon as they arrive
at the SDO Joint Science Operations Center and have undergone basic
processing. This will allow the system to produce timely space-weather
alerts and to guide the selection and production of quicklook images and
movies, in addition to its prime mission of enabling solar science. We
briefly describe the complex and unique data-processing pipeline,
consisting of the hardware and control software required to handle
the SDO data stream and accommodate the computer-vision modules, which
has been set up at the Lockheed-Martin Space Astrophysics Laboratory
(LMSAL), with an identical copy at the Smithsonian Astrophysical
Observatory (SAO).

---------------------------------------------------------
Title: Chromospheric Explosions: Linking Observations Toward a
Physical Model
Authors: Kirk, Michael S.; Balasubramaniam, K. S.; Jackiewicz, J.;
McAteer, R. T. J.; McNamara, B. J.
2012AAS...21922408K Altcode:
Bright points are observed routinely in every layer of the Sun. One type
of bright point, called sequential chromospheric brightening (SCB),
is coincident with flares and is thought to represent a chromospheric
foot-point of a magnetic field line that extends into the corona. These
field lines are energized during a CME-causing eruption leading
to the brightening we observe. We extract physical measurements of
chromospheric flares and SCBs using an automated feature detection
suite. Correlating these results with complementary data from the
corona, we identify the spatio-temporal relationship between coronal
loops and SCBs. We explore a coronal origin for SCBs and put forth an
explicatory model.

---------------------------------------------------------
Title: Automated Classification of Flaring Behavior in Solar Active
Regions: Preliminary Results
Authors: Al-Ghraibah, Amani; Boucheron, L. E.; McAteer, R.; Cao, H.;
Jackiewicz, J.; McNamara, B.; Voelz, D.; Calabro, B.; DeGrave, K.;
Hao, Y.; Kirk, M.; Pevtsov, A.; Mckeever, J.; Taylor, G.
2012AAS...21914516A Altcode:
Solar active events are the source of many energetic and
geo-effective events such as solar flares and coronal mass ejections
(CMEs). Understanding how these complex source regions evolve and
produce these events is of fundamental importance, not only to solar
physics but also the demands of space weather forecasting. In this
poster, we present preliminary results from our analysis of the physical
properties of active region magnetic fields using fractal-, gradient-,
neutral line-, emerging flux-, and wavelet-based techniques. These
analyses look to use the defined physical measures to form a predictive
model for flaring behavior in active regions.

---------------------------------------------------------
Title: Coronal Loop Detection and Seismology
Authors: Pevtsov, Alexander; McAteer, R. T. J.; Jackiewicz, J.;
McNamara, B.; Kirk, M.; Degrave, K.; Boucheron, L.; Calabro, B.
2012AAS...21914405P Altcode:
We study the spatial distribution and temporal evolution of coronal
loops using data from the Solar Dynamics Observatory (SDO) Atmospheric
Imaging Assembly (AIA). We apply an automated coronal loop detection
algorithm that is maximized for accuracy and completeness, and
reconnects orphaned segments of coronal loops, to extreme ultraviolet
images of the solar corona. We quantify the loop size distribution
with a scaling index in each of the SDO AIA passbands, and show how
this changes with time. This provides new insights into the physical
mechanisms that create coronal structure.

---------------------------------------------------------
Title: Multifractality, magnetic fields, and solar eruptive events
Authors: Mcateer, R.
2011AGUFMSH43E..04M Altcode:
Solar flares and coronal mass ejections are among the most energetic
events in the solar system. These events occur in active regions in
the solar corona, formed through the convective action of subsurface
fluid motions pushing magnetic flux tubes through the Sun's surface,
the photosphere. It has long been recognized that through characterizing
active region magnetic field complexity we can begin to understand
which active region properties are important indicators of solar
eruptive events. We show that two such complexity measures, the
multifractal spectrum and the multiscale turbulence spectrum, have
enormous potential for the prediction of these events in a accurate
and timely manner. Furthermore we show that they are directly related
to physical measurements of field gradients and flux emergence,
thereby allowing a cross calibration of unitless SOC measures to the
distribution of measures with physical units.

---------------------------------------------------------
Title: Mapping the Dynamics of Chromospheric Flares
Authors: Kirk, M. S.; Balasubramaniam, K. S.; Jackiewicz, J.;
Mcateer, R.
2011AGUFMSH51B2003K Altcode:
Brightening in the chromosphere comes in three different flavors:
plage, flare ribbon, and point. These types of brightening are all
characterized by intensity above the background but have different
dynamics causing the increased intensity. We have developed an automated
software suite to identify and track both ribbon and point brightening
associated with moderate sized flares observed in H alpha. Superposing
our detections on complementary datasets, we produce a three-dimensional
velocity map of flare ribbons, and a Doppler velocity measurement
beneath the point brightening detections. These dynamic measurements
allow us to postulate a physical connection between point brightening,
the erupting flare, and coronal loops.

---------------------------------------------------------
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: Coronal mass ejection detection using wavelets, curvelets
and ridgelets: Applications for space weather monitoring
Authors: Gallagher, P. T.; Young, C. A.; Byrne, J. P.; McAteer,
R. T. J.
2011AdSpR..47.2118G Altcode: 2010arXiv1012.1901G
Coronal mass ejections (CMEs) are large-scale eruptions of plasma and
magnetic field that can produce adverse space weather at Earth and
other locations in the Heliosphere. Due to the intrinsic multiscale
nature of features in coronagraph images, wavelet and multiscale image
processing techniques are well suited to enhancing the visibility of
CMEs and suppressing noise. However, wavelets are better suited to
identifying point-like features, such as noise or background stars,
than to enhancing the visibility of the curved form of a typical CME
front. Higher order multiscale techniques, such as ridgelets and
curvelets, were therefore explored to characterise the morphology
(width, curvature) and kinematics (position, velocity, acceleration)
of CMEs. Curvelets in particular were found to be well suited to
characterising CME properties in a self-consistent manner. Curvelets
are thus likely to be of benefit to autonomous monitoring of CME
properties for space weather applications.

---------------------------------------------------------
Title: Solar Oscillations And Acoustic Power Measured In H-alpha
Authors: Jackiewicz, Jason; Balasubramaniam, K.; McAteer, R.;
Jefferies, S. M.
2011SPD....42.1731J Altcode: 2011BAAS..43S.1731J
We present initial studies of the evidence of acoustic power in H alpha
data observed with the ISOON telescope. Uninterrupted times series
were obtained at 1-minute cadence of the H alpha intensity and Doppler
velocity signals of both quiet and active regions on the Sun. Spatial
and temporal power maps show enhanced contributions from a flaring
active region that is a strong function of frequency. Cross-correlations
and wave travel times are computed and give indications of the presence
of running waves below the acoustic cut-off frequency.

---------------------------------------------------------
Title: Coronal Loop detection and seismology
Authors: Pevtsov, Alexander; McAteer, R. T. J.; Jackiewicz, J.; Kirk,
M.; McNamara, B.; DeGrave, K.; Amani Al-Ghraibah, A.; Boucheron, L.;
Voelz, D.; Cao, H.; Taylor, G.
2011SPD....42.1822P Altcode: 2011BAAS..43S.1822P
Using a TRACE image with a bipolar active region and over one hundred
distinguishable loops, we examine several current methods for automated
coronal loop detection. Using the same TRACE image, several new
approaches are also taken in an attempt to increase accuracy and
completeness rates for the automated detection process. By means
of these new methods the expectation is to achieve a higher degree
of completeness while maintaining a high level of accuracy in the
detection process. To increase completeness, an automated attempt for
the reconnection between orphaned loop segments will also be tested. In
the future, an approach to reconstruction of three-dimensional images
from several two-dimensional images can be devised by using the detected
coronal loops and a known 3D offset of each image. However this process
heavily depends on the ability to accurately and completely detect
the coronal loops.

---------------------------------------------------------
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: Solar flare prediction: A worthy goal, or a foolish
pursuit? (Invited)
Authors: McAteer, R.; "All Clear Workshop", "Solarmonitor. Org Team"
2010AGUFMSH54D..02M Altcode:
The solar physics community has made a number of progressive
breakthroughs in the field of solar flare prediction within the last
few years. Although we still do not have a means of predicting the
size, timing, and geo-effectiveness of any individual event, we can
now predict two ends of the spectrum - the 'all-clear' and the 'big
storm'. I will highlight these recent advances, and discuss the major
problems associated with this aspect of solar physics. By identifying
common features and problems across a number of solar flare prediction
techniques, I will propose how this field can advance and show how
our lessons learned can be applied to other aspects of solar physics
(e.g., nanoflare occurrence, short timescale precursors)

---------------------------------------------------------
Title: Quantifying the Evolving Magnetic Structure of Active Regions
Authors: Conlon, Paul A.; McAteer, R. T. James; Gallagher, Peter T.;
Fennell, Linda
2010ApJ...722..577C Altcode:
The topical and controversial issue of parameterizing the magnetic
structure of solar active regions has vital implications in the
understanding of how these structures form, evolve, produce solar
flares, and decay. This interdisciplinary and ill-constrained problem of
quantifying complexity is addressed by using a two-dimensional wavelet
transform modulus maxima (WTMM) method to study the multifractal
properties of active region photospheric magnetic fields. The
WTMM method provides an adaptive space-scale partition of a fractal
distribution, from which one can extract the multifractal spectra. The
use of a novel segmentation procedure allows us to remove the quiet Sun
component and reliably study the evolution of active region multifractal
parameters. It is shown that prior to the onset of solar flares, the
magnetic field undergoes restructuring as Dirac-like features (with a
Hölder exponent, h = -1) coalesce to form step functions (where h =
0). The resulting configuration has a higher concentration of gradients
along neutral line features. We propose that when sufficient flux is
present in an active region for a period of time, it must be structured
with a fractal dimension greater than 1.2, and a Hölder exponent
greater than -0.7, in order to produce M- and X-class flares. This
result has immediate applications in the study of the underlying
physics of active region evolution and space weather forecasting.

---------------------------------------------------------
Title: Evidence for Internal Tether-cutting in a Flare/Coronal Mass
Ejection Observed by MESSENGER, RHESSI, and STEREO
Authors: Raftery, Claire L.; Gallagher, Peter T.; McAteer, R. T. James;
Lin, Chia-Hsien; Delahunt, Gareth
2010ApJ...721.1579R Altcode:
The relationship between eruptive flares and coronal mass ejections
(CMEs) is a topic of ongoing debate, especially regarding the
possibility of a common initiation mechanism. We studied the kinematic
and hydrodynamic properties of a well-observed event that occurred
on 2007 December 31 using data from MESSENGER, RHESSI, and STEREO
in order to gain new physical insight into the evolution of the
flare and CME. The initiation mechanism was determined by comparing
observations to the internal tether-cutting, breakout, and ideal
magnetohydrodynamic (MHD) models. Evidence of pre-eruption reconnection
immediately eliminated the ideal MHD model. The timing and location of
the soft and hard X-ray sources led to the conclusion that the event
was initiated by the internal tether-cutting mechanism. In addition,
a thermal source was observed to move in a downward direction during
the impulsive phase of the event, followed by upward motion during the
decay phase, providing evidence for X- to Y-type magnetic reconnection.

---------------------------------------------------------
Title: Propagation of an Earth-directed coronal mass ejection in
three dimensions
Authors: Byrne, Jason P.; Maloney, Shane A.; McAteer, R. T. James;
Refojo, Jose M.; Gallagher, Peter T.
2010NatCo...1...74B Altcode: 2010NatCo...1E..74B; 2010arXiv1010.0643B
Solar coronal mass ejections (CMEs) are the most significant drivers
of adverse space weather on Earth, but the physics governing their
propagation through the heliosphere is not well understood. Although
stereoscopic imaging of CMEs with NASA's Solar Terrestrial
Relations Observatory (STEREO) has provided some insight into their
three-dimensional (3D) propagation, the mechanisms governing their
evolution remain unclear because of difficulties in reconstructing their
true 3D structure. In this paper, we use a new elliptical tie-pointing
technique to reconstruct a full CME front in 3D, enabling us to quantify
its deflected trajectory from high latitudes along the ecliptic, and
measure its increasing angular width and propagation from 2 to 46
(~0.2 AU). Beyond 7 , we show that its motion is determined by an
aerodynamic drag in the solar wind and, using our reconstruction as
input for a 3D magnetohydrodynamic simulation, we determine an accurate
arrival time at the Lagrangian L1 point near Earth.

---------------------------------------------------------
Title: Advanced image processing for solar physics
Authors: McAteer, R. T. James
2010ada..confE..26M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Characterizing Complexity in Solar Magnetogram Data Using a
Wavelet-based Segmentation Method
Authors: Kestener, P.; Conlon, P. A.; Khalil, A.; Fennell, L.; McAteer,
R. T. J.; Gallagher, P. T.; Arneodo, A.
2010ApJ...717..995K Altcode:
The multifractal nature of solar photospheric magnetic structures is
studied using the two-dimensional wavelet transform modulus maxima
(WTMM) method. This relies on computing partition functions from
the wavelet transform skeleton defined by the WTMM method. This
skeleton provides an adaptive space-scale partition of the fractal
distribution under study, from which one can extract the multifractal
singularity spectrum. We describe the implementation of a multiscale
image processing segmentation procedure based on the partitioning of
the WT skeleton, which allows the disentangling of the information
concerning the multifractal properties of active regions from the
surrounding quiet-Sun field. The quiet Sun exhibits an average Hölder
exponent ~-0.75, with observed multifractal properties due to the
supergranular structure. On the other hand, active region multifractal
spectra exhibit an average Hölder exponent ~0.38, similar to those
found when studying experimental data from turbulent flows.

---------------------------------------------------------
Title: Turbulence, complexity, and solar flares
Authors: McAteer, R. T. James; Gallagher, Peter T.; Conlon, Paul A.
2010AdSpR..45.1067M Altcode: 2009arXiv0909.5636M
The issue of predicting solar flares is one of the most fundamental in
physics, addressing issues of plasma physics, high-energy physics, and
modelling of complex systems. It also poses societal consequences, with
our ever-increasing need for accurate space weather forecasts. Solar
flares arise naturally as a competition between an input (flux emergence
and rearrangement) in the photosphere and an output (electrical
current build up and resistive dissipation) in the corona. Although
initially localised, this redistribution affects neighbouring regions
and an avalanche occurs resulting in large scale eruptions of plasma,
particles, and magnetic field. As flares are powered from the stressed
field rooted in the photosphere, a study of the photospheric magnetic
complexity can be used to both predict activity and understand the
physics of the magnetic field. The magnetic energy spectrum and
multifractal spectrum are highlighted as two possible approaches
to this.

---------------------------------------------------------
Title: Computer Vision for SDO: First Results from the SDO Feature
Finding Algorithms
Authors: Martens, Petrus C.; Attrill, G.; Davey, A.; Engell, A.;
Farid, S.; Grigis, P.; Kasper, J.; Korreck, K.; Saar, S.; Su, Y.;
Testa, P.; Wills-Davey, M.; Bernasconi, P.; Raouafi, N.; Georgoulis,
M.; Deforest, C.; Peterson, J.; Berghoff, T.; Delouille, V.; Hochedez,
J.; Mampaey, B.; Verbeek, C.; Cirtain, J.; Green, S.; Timmons, R.;
Savcheva, A.; Angryk, R.; Wiegelmann, T.; McAteer, R.
2010AAS...21630804M Altcode:
The SDO Feature Finding Team produces robust and very efficient
software modules that can keep up with the relentless SDO data stream,
and detect, trace, and analyze a large number of phenomena including:
flares, sigmoids, filaments, coronal dimmings, polarity inversion
lines, sunspots, X-ray bright points, active regions, coronal holes,
EIT waves, CME's, coronal oscillations, and jets. In addition we track
the emergence and evolution of magnetic elements down to the smallest
features that are detectable, and we will also provide at least four
full disk nonlinear force-free magnetic field extrapolations per day. During SDO commissioning we will install in the near-real time data
pipeline the modules that provide alerts for flares, coronal dimmings,
and emerging flux, as well as those that trace filaments, sigmoids,
polarity inversion lines, and active regions. We will demonstrate
the performance of these modules and illustrate their use for science
investigations.

---------------------------------------------------------
Title: Evidence of Enhanced Particle Acceleration During a
Plasmoid-Looptop Collision Observed with RHESSI
Authors: Milligan, Ryan; McAteer, R. T. J.; Dennis, B. R.; Young, C. A.
2010AAS...21640426M Altcode: 2010BAAS...41..904M
Rare observations are presented of a downward-propagating
plasmoid (formed in the wake of an erupting CME) merging with an
underlying looptop kernel during an occulted limb event observed with
RHESSI. RHESSI lightcurves in the 9-18 keV energy range, as well as that
of the 245 MHz channel of the Learmonth Solar Observatory, show enhanced
nonthermal emission in the corona at the time of the merging suggesting
that additional particle acceleration took place. This was attributed
to a secondary episode of magnetic reconnection in the current sheet
that formed between the two merging sources. Complimentary observations
from the SECCHI suite of instruments onboard STEREO-Behind showed
that this process was concurrent with the acceleration phase of the
associated CME. From wavelet-enhanced EUVI images evidence of inflowing
magnetic field lines prior to the CME eruption is also presented. This
combination of observations supports a recent numerical simulation of
plasmoid formation, propagation and subsequent particle acceleration
due to the tearing mode instability during current sheet formation.

---------------------------------------------------------
Title: Evidence For Internal Tether-cutting in a Flare/CME Event.
Authors: Raftery, Claire; Gallagher, P. T.; McAteer, R. T. J.; Lin,
C. H.; Delahunt, G.
2010AAS...21631403R Altcode: 2010BAAS...41..894R
The relationship between eruptive flares and CMEs is a topic of ongoing
debate, especially regarding the possibility of a common initiation
mechanism. In order to gain new physical insight into this problem,
the kinematic and hydrodynamic properties of a well-observed event were
studied using data from MESSENGER, RHESSI and STEREO/Secchi. These data
were compared to three theoretical models to determine the event's
initiation mechanism. The timing and positioning of EUV and X-ray
sources along with evidence for pre-eruption particle acceleration
led to the conclusion that the event was initiated by the internal
tether-cutting mechanism and was followed by breakout reconnection
some 10 minutes after launch.

---------------------------------------------------------
Title: Evidence of a Plasmoid-Looptop Interaction and Magnetic
Inflows During a Solar Flare/Coronal Mass Ejection Eruptive Event
Authors: Milligan, Ryan O.; McAteer, R. T. James; Dennis, Brian R.;
Young, C. Alex
2010ApJ...713.1292M Altcode: 2010arXiv1003.0665M
Observational evidence is presented for the merging of a
downward-propagating plasmoid with a looptop kernel during an occulted
limb event on 2007 January 25. RHESSI light curves in the 9-18 keV
energy range, as well as that of the 245 MHz channel of the Learmonth
Solar Observatory, show enhanced nonthermal emission in the corona at
the time of the merging suggesting that additional particle acceleration
took place. This was attributed to a secondary episode of reconnection
in the current sheet that formed between the two merging sources. RHESSI
images were used to establish a mean downward velocity of the plasmoid
of 12 km s-1. Complementary observations from the SECCHI
suite of instruments on board STEREO-B showed that this process occurred
during the acceleration phase of the associated coronal mass ejection
(CME). From wavelet-enhanced EUV Imager, image evidence of inflowing
magnetic field lines prior to the CME eruption is also presented. The
derived inflow velocity was found to be 1.5 km s-1. This
combination of observations supports a recent numerical simulation of
plasmoid formation, propagation, and subsequent particle acceleration
due to the tearing mode instability during current sheet formation.

---------------------------------------------------------
Title: Automated Detection of Coronal Loops Using a Wavelet Transform
Modulus Maxima Method
Authors: McAteer, R. T. James; Kestener, Pierre; Arneodo, Alain;
Khalil, Andre
2010SoPh..262..387M Altcode: 2010SoPh..tmp...56M; 2010SoPh..tmp...44M; 2010arXiv1002.3107M
We propose and test a wavelet transform modulus maxima method for
the automated detection and extraction of coronal loops in extreme
ultraviolet images of the solar corona. This method decomposes an
image into a number of size scales and tracks enhanced power along
each ridge corresponding to a coronal loop at each scale. We compare
the results across scales and suggest the optimum set of parameters to
maximize completeness, while minimizing detection of noise. For a test
coronal image, we compare the global statistics (e.g. number of loops
at each length) to previous automated coronal-loop detection algorithms.

---------------------------------------------------------
Title: Automated Feature and Event Detection with SDO AIA and HMI Data
Authors: Davey, Alisdair; Martens, P. C. H.; Attrill, G. D. R.;
Engell, A.; Farid, S.; Grigis, P. C.; Kasper, J.; Korreck, K.; Saar,
S. H.; Su, Y.; Testa, P.; Wills-Davey, M.; Savcheva, A.; Bernasconi,
P. N.; Raouafi, N. -E.; Delouille, V. A.; Hochedez, J. F. .; Cirtain,
J. W.; Deforest, C. E.; Angryk, R. A.; de Moortel, I.; Wiegelmann,
T.; Georgouli, M. K.; McAteer, R. T. J.; Hurlburt, N.; Timmons, R.
2010cosp...38.2878D Altcode: 2010cosp.meet.2878D
The Solar Dynamics Observatory (SDO) represents a new frontier in
quantity and quality of solar data. At about 1.5 TB/day, the data will
not be easily digestible by solar physicists using the same methods
that have been employed for images from previous missions. In order for
solar scientists to use the SDO data effectively they need meta-data
that will allow them to identify and retrieve data sets that address
their particular science questions. We are building a comprehensive
computer vision pipeline for SDO, abstracting complete metadata
on many of the features and events detectable on the Sun without
human intervention. Our project unites more than a dozen individual,
existing codes into a systematic tool that can be used by the entire
solar community. The feature finding codes will run as part of the SDO
Event Detection System (EDS) at the Joint Science Operations Center
(JSOC; joint between Stanford and LMSAL). The metadata produced will
be stored in the Heliophysics Event Knowledgebase (HEK), which will be
accessible on-line for the rest of the world directly or via the Virtual
Solar Observatory (VSO) . Solar scientists will be able to use the
HEK to select event and feature data to download for science studies.

---------------------------------------------------------
Title: The propagation of a CME front in 3D
Authors: Maloney, Shane; Byrne, Jason; Gallagher, Peter T.; McAteer,
R. T. James
2010cosp...38.1867M Altcode: 2010cosp.meet.1867M
We present a new three-dimensional (3D) reconstruction of an
Earth-directed coronal mass ejec-tion (CME), providing new insight into
the processes that control its evolution and propagation. Previously
limited fields-of-view and single vantage point observations made it
impossible to confidently describe CMEs in 3D. This uncertainty in a
CME's position and geometry made comparison to theory difficult and
hindered progress. Our 3D reconstruction unambiguously shows three
effects at play on the CME: deflection from a high latitude source
region, angular width expansion, and interplanetary drag. The CME
undergoes a deflection of ∼20° degrees below 10 RSun and slowly tends
towards the ecliptic throughout its subsequent propagation. We interpret
this deflection as a direct result of the interplay between the CME and
the drawn-out dipolar topology of the (solar minimum) coronal magnetic
field. The increasing angular width is in excess of that due to simple
spherical expansion in the diverging solar wind so an additional source
of expansion must be present. The additional source is inferred to be
a pressure gradient between the internal pressure (magnetic and gas)
of the flux rope relative to the ambient solar wind pressure. Low in the
corona there is rapid expansion due to a large pressure difference, but
further out the CME approaches equilibrium with the solar wind, and the
angular width tends to a constant. The 3D reconstruction allows us to
accurately determine the CME kinematics, and we show unambiguously that
the interplanetary acceleration is due to aerodynamic drag. Furthermore
we derive parameters from our reconstruction that act as inputs to an
ENLIL model of the CME's propagation to Earth. The results show the
CME undergoes a significant degrease in velocity where it encounters
a slow-speed solar wind stream ahead of it (&gt;50 RSun ). This lower
velocity agrees with the derived velocity from in-situ data at the
L1 point and predicts the correct arrival time, to within minutes. In
our ever-increasingly technological society, the accurate prediction
of adverse space weather is of paramount impor-tance and to achieve
this we must understand the basic processes that govern CMEs. Our
3D reconstruction has allowed us to gain some novel insights into
these processes, and emphasises the dynamic interplay between CMEs
and solar wind.

---------------------------------------------------------
Title: On the 3-D reconstruction of Coronal Mass Ejections using
coronagraph data
Authors: Mierla, M.; Inhester, B.; Antunes, A.; Boursier, Y.; Byrne,
J. P.; Colaninno, R.; Davila, J.; de Koning, C. A.; Gallagher, P. T.;
Gissot, S.; Howard, R. A.; Howard, T. A.; Kramar, M.; Lamy, P.;
Liewer, P. C.; Maloney, S.; Marqué, C.; McAteer, R. T. J.; Moran, T.;
Rodriguez, L.; Srivastava, N.; St. Cyr, O. C.; Stenborg, G.; Temmer,
M.; Thernisien, A.; Vourlidas, A.; West, M. J.; Wood, B. E.; Zhukov,
A. N.
2010AnGeo..28..203M Altcode:
Coronal Mass ejections (CMEs) are enormous eruptions of magnetized
plasma expelled from the Sun into the interplanetary space, over the
course of hours to days. They can create major disturbances in the
interplanetary medium and trigger severe magnetic storms when they
collide with the Earth's magnetosphere. It is important to know their
real speed, propagation direction and 3-D configuration in order to
accurately predict their arrival time at the Earth. Using data from
the SECCHI coronagraphs onboard the STEREO mission, which was launched
in October 2006, we can infer the propagation direction and the 3-D
structure of such events. In this review, we first describe different
techniques that were used to model the 3-D configuration of CMEs in
the coronagraph field of view (up to 15 R⊙). Then, we apply these
techniques to different CMEs observed by various coronagraphs. A
comparison of results obtained from the application of different
reconstruction algorithms is presented and discussed.

---------------------------------------------------------
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: Reconstructing the 3-D Trajectories of CMEs in the Inner
Heliosphere
Authors: Maloney, Shane A.; Gallagher, Peter T.; McAteer, R. T. James
2009SoPh..256..149M Altcode: 2009arXiv0905.2153M
A method for the full three-dimensional (3-D) reconstruction of the
trajectories of coronal mass ejections (CMEs) using Solar TErrestrial
RElations Observatory (STEREO) data is presented. Four CMEs that were
simultaneously observed by the inner and outer coronagraphs (COR1
and 2) of the Ahead and Behind STEREO satellites were analysed. These
observations were used to derive CME trajectories in 3-D out to ∼
15 R⊙. The reconstructions using COR1/2 data support a
radial propagation model. Assuming pseudo-radial propagation at large
distances from the Sun (15 - 240 R⊙), the CME positions
were extrapolated into the Heliospheric Imager (HI) field-of-view. We
estimated the CME velocities in the different fields-of-view. It was
found that CMEs slower than the solar wind were accelerated, while
CMEs faster than the solar wind were decelerated, with both tending
to the solar wind velocity.

---------------------------------------------------------
Title: Magnetic Fields, Flares &amp; Forecasts
Authors: Conlon, Paul A.; Kestener, P.; McAteer, R.; Gallagher, P.
2009SPD....40.1602C Altcode:
A 2D wavelet transform modulus maxima (WTMM) method is used to
characterise the complexity of the distribution of the photospheric
magnetic field of active regions. The WTMM method offers increased
accuracy and reliability over previous fractal and multifractal
methods. The multifractal spectrum of both quiet Sun and active region
magnetic features are presented. It is shown that the multifractal
nature of the quiet Sun is significantly different from that of
an active region. As such, a method is proposed to seperate the
information corresponding to the multifractal spectrum of an active
region from the surrounding quite Sun texture. The WTMM method and
segmentation procedure are shown to detect the internal restructuring
of active region magnetic features prior to flaring. We detect two
thresholds (Haussdorf dimension &gt; 1.2 and Holder Exponent &gt;
-0.7) as possible indicators for conditions favourable to flaring.

---------------------------------------------------------
Title: Observation Of Inflows And Collapsing X-point During CME
Initiation Using STEREO And RHESSI
Authors: Milligan, Ryan; McAteer, R. T. J.; Dennis, B.
2009SPD....40.2110M Altcode:
In the standard flare/CME model, converging magnetic field lines
in the corona reconnect to release vast amounts of energy. This
liberated energy is used in heating plasma, accelerating particles,
and driving coronal mass ejections (CMEs). This work presents tentative
observational evidence of converging magnetic field lines before the
initiation of a CME using the SECCHI suite of instruments onboard
STEREO. During a limb event on 25 January 2007, one 'leg' of the
CME is observed to propagate "inwards" at a rate of 1.5 km/s for 4
hours before reconnection occurs. As the CME begins to accelerate,
a (thermal) coronal X-ray source is observed by RHESSI in the 6-12
keV energy band. The downward motion of this source is temporally
correlated with the acceleration phase of the CME, and is therefore
interpreted as the collapsing X-point associated with the reconnection.

---------------------------------------------------------
Title: The kinematics of coronal mass ejections using multiscale
methods
Authors: Byrne, J. P.; Gallagher, P. T.; McAteer, R. T. J.; Young,
C. A.
2009A&A...495..325B Altcode: 2009arXiv0901.3392B
Aims: The diffuse morphology and transient nature of coronal mass
ejections (CMEs) make them difficult to identify and track using
traditional image processing techniques. We apply multiscale methods
to enhance the visibility of the faint CME front. This enables
an ellipse characterisation to objectively study the changing
morphology and kinematics of a sample of events imaged by the
Large Angle Spectrometric Coronagraph (LASCO) onboard the Solar
and Heliospheric Observatory (SOHO) and the Sun Earth Connection
Coronal and Heliospheric Investigation (SECCHI) onboard the Solar
Terrestrial Relations Observatory (STEREO). The accuracy of these
methods allows us to test the CMEs for non-constant acceleration and
expansion. Methods: We exploit the multiscale nature of CMEs
to extract structure with a multiscale decomposition, akin to a Canny
edge detector. Spatio-temporal filtering highlights the CME front as
it propagates in time. We apply an ellipse parameterisation of the
front to extract the kinematics (height, velocity, acceleration)
and changing morphology (width, orientation). Results: The
kinematic evolution of the CMEs discussed in this paper have been
shown to differ from existing catalogues. These catalogues are based
upon running-difference techniques that can lead to over-estimating
CME heights. Our resulting kinematic curves are not well-fitted with
the constant acceleration model. It is shown that some events have
high acceleration below ~5 R⊙. Furthermore, we find that
the CME angular widths measured by these catalogues are over-estimated,
and indeed for some events our analysis shows non-constant CME expansion
across the plane-of-sky.

---------------------------------------------------------
Title: EUV Wave Reflection from a Coronal Hole
Authors: Gopalswamy, N.; Yashiro, S.; Temmer, M.; Davila, J.; Thompson,
W. T.; Jones, S.; McAteer, R. T. J.; Wuelser, J. -P.; Freeland, S.;
Howard, R. A.
2009ApJ...691L.123G Altcode:
We report on the detection of EUV wave reflection from a coronal
hole, as observed by the Solar Terrestrial Relations Observatory
mission. The EUV wave was associated with a coronal mass ejection
(CME) erupting near the disk center. It was possible to measure the
kinematics of the reflected waves for the first time. The reflected
waves were generally slower than the direct wave. One of the important
implications of the wave reflection is that the EUV transients are
truly a wave phenomenon. The EUV wave reflection has implications for
CME propagation, especially during the declining phase of the solar
cycle when there are many low-latitude coronal holes.

---------------------------------------------------------
Title: Multiresolution Analysis of Active Region Magnetic Structure
and its Correlation with the Mount Wilson Classification and Flaring
Activity
Authors: Ireland, J.; Young, C. A.; McAteer, R. T. J.; Whelan, C.;
Hewett, R. J.; Gallagher, P. T.
2008SoPh..252..121I Altcode: 2008arXiv0805.0101I; 2008SoPh..tmp..134I
Two different multiresolution analyses are used to decompose the
structure of active-region magnetic flux into concentrations of
different size scales. Lines separating these opposite polarity
regions of flux at each size scale are found. These lines are used as
a mask on a map of the magnetic field gradient to sample the local
gradient between opposite polarity regions of given scale sizes. It
is shown that the maximum, average, and standard deviation of the
magnetic flux gradient for α,β,βγ, and βγδ active-regions
increase in the order listed, and that the order is maintained over
all length scales. Since magnetic flux gradient is strongly linked
to active-region activity, such as flares, this study demonstrates
that, on average, the Mt. Wilson classification encodes the notion
of activity over all length scales in the active-region, and not
just those length scales at which the strongest flux gradients are
found. Further, it is also shown that the average gradients in the
field, and the average length-scale at which they occur, also increase
in the same order. Finally, there are significant differences in the
gradient distribution, between flaring and non-flaring active regions,
which are maintained over all length scales. It is also shown that the
average gradient content of active-regions that have large flares (GOES
class "M" and above) is larger than that for active regions containing
flares of all flare sizes; this difference is also maintained at all
length scales. All of the reported results are independent of the
multiresolution transform used. The implications for the Mt. Wilson
classification of active-regions in relation to the multiresolution
gradient content and flaring activity are discussed.

---------------------------------------------------------
Title: Multiscale Characterization of Eruptive Events
Authors: Byrne, J. P.; Young, C. A.; Gallagher, P. T.; McAteer,
R. T. J.
2008ASPC..397..162B Altcode:
Image processing plays an important role in the analysis of data
from space-based instruments. With the large volumes of information
currently available from missions such as Hinode and STEREO, our aim
is to produce computationally fast methods for extracting features of
interest (e.g. loops, filaments, waves and eruptions). Multiscale image
processing methods enable us to study these features as a function
of scale. Here we describe these methods, and use them to study the
multiscale properties of a coronal mass ejection (CME) observed by
SOHO/LASCO, and briefly discuss the implications for Hinode.

---------------------------------------------------------
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: Discovery of Spatial Periodicities in a Coronal Loop Using
Automated Edge-Tracking Algorithms
Authors: Jess, D. B.; Mathioudakis, M.; Erdélyi, R.; Verth, G.;
McAteer, R. T. J.; Keenan, F. P.
2008ApJ...680.1523J Altcode: 2008arXiv0802.1971J
A new method for automated coronal loop tracking, in both spatial
and temporal domains, is presented. Applying this technique to TRACE
data, obtained using the 171 Å filter on 1998 July 14, we detect a
coronal loop undergoing a 270 s kink-mode oscillation, as previously
found by Aschwanden et al. However, we also detect flare-induced,
and previously unnoticed, spatial periodicities on a scale of 3500 km,
which occur along the coronal loop edge. Furthermore, we establish a
reduction in oscillatory power for these spatial periodicities of 45%
over a 222 s interval. We relate the reduction in detected oscillatory
power to the physical damping of these loop-top oscillations.

---------------------------------------------------------
Title: Solar feature tracking in both spatial and temporal domains
Authors: Jess, D. B.; Mathioudakis, M.; Erdélyi, R.; Verth, G.;
McAteer, R. T. J.; Keenan, F. P.
2008IAUS..247..288J Altcode: 2007IAUS..247..288J
A new method for automated coronal loop tracking, in both spatial and
temporal domains, is presented. The reliability of this technique
was tested with TRACE 171 Å observations. The application of this
technique to a flare-induced kink-mode oscillation, revealed a 3500
km spatial periodicity which occur along the loop edge. We establish
a reduction in oscillatory power, for these spatial periodicities,
of 45% over a 322 s interval. We relate the reduction in oscillatory
power to the physical damping of these loop-top oscillations.

---------------------------------------------------------
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: Multiscale Analysis of Active Region Evolution
Authors: Hewett, R. J.; Gallagher, P. T.; McAteer, R. T. J.; Young,
C. A.; Ireland, J.; Conlon, P. A.; Maguire, K.
2008SoPh..248..311H Altcode:
Flows in the photosphere of solar active regions are turbulent in
nature. Because magnetic fields are frozen into the plasma on the
solar surface, magnetograms can be used to investigate the processes
responsible for structuring active regions. Here, a continuous wavelet
technique is developed, analyzed, and used to investigate the multiscale
structure of an evolving active region using magnetograms obtained by
the Michelson Doppler Imager (MDI) onboard the Solar and Heliospheric
Observatory (SOHO). The multiscale structure was measured using a 2D
continuous wavelet technique to extract the energy spectrum of the
region over the time scale of 13 days. Preliminary evidence of an
inverse cascade in active region NOAA 10488 is presented as well as
a potential relationship between energy scaling and flare productivity.

---------------------------------------------------------
Title: Multifractal Properties of Evolving Active Regions
Authors: Conlon, P. A.; Gallagher, P. T.; McAteer, R. T. J.; Ireland,
J.; Young, C. A.; Kestener, P.; Hewett, R. J.; Maguire, K.
2008SoPh..248..297C Altcode:
Magnetohydrodynamic turbulence is thought to be responsible for
producing complex, multiscale magnetic field distributions in solar
active regions. Here we explore the multiscale properties of a number of
evolving active regions using magnetograms from the Michelson Doppler
Imager (MDI) on the Solar and Heliospheric Observatory (SOHO). The
multifractal spectrum was obtained by using a modified box-counting
method to study the relationship between magnetic-field multifractality
and region evolution and activity. The initial emergence of each
active region was found to be accompanied by characteristic changes
in the multifractal spectrum. Specifically, the range of multifractal
structures (Ddiv) was found to increase during emergence,
as was their significance or support (Cdiv). Following this,
a decrease in the range in multifractal structures occurred as the
regions evolved to become large-scale, coherent structures. From the
small sample considered, evidence was found for a direct relationship
between the multifractal properties of the flaring regions and their
flaring rate.

---------------------------------------------------------
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: Two contrasting events from multiple viewpoints
Authors: McAteer, R.; Davilla, J.; St. Cyr, C.
2007AGUFMSH41B..05M Altcode:
Two contrasting events are described by studying data from both
STEREO and earth-Sun line of sight instruments. In each case the
image registration and alignment issues are addressed and the specific
science benefits of the separation angles of the three viewpoints are
highlighted. In the first event (25-Jan-2007), a small flare in a slowly
evolving active region ejecting a fast moving CME is studied using
EUVI/COR1/COR2 from both STEREO spacecraft, with additional information
from EIT/LASCO and RHESSI.The benefits of small spacecraft separation
are exploited as pre-CME EUVI (behind) images show significant loop
'opening', with a RHESSI thermal energy source detected prior to the
post-flare loops cooling thru the EUVI passbands. The CME passes is
studied as it passes thru COR1/COR2 and LASCO, and is followed by a
slow moving thermal energy source in its wake. In the second event
(1-May-2007), a rapidly rotating (but non-erupting) filament as the
source of a slowly rising, non radial, feature is studied using both
STEREO spacecraft, SOHO and the Mk-IV coronagraph. The benefits of
larger spacecraft separation are exploited to give three plane of
sky height time plots to determine the 'actual' velocity profile of
the slow moving feature. The differences in EIT and EUVI are used to
study the filament rotational motion in detail

---------------------------------------------------------
Title: Multi-scale Tools for Solar Image Processing
Authors: Young, C.; Ireland, J.; McAteer, R.; Gallagher, P. T.;
Byrne, J.
2007AGUFMSH13A1093Y Altcode:
The important information contained in solar image data exists on many
different time and spatial scales. This makes multi-scale transforms
such as wavelets and curvelets very appropriate tools. These and other
multi- scale transforms are used in several different types of image
processing including image enhancement, feature detection, deconvolution
and noise reduction. We present an overview of multi-scale transforms
and show some of their applications to solar image data.

---------------------------------------------------------
Title: The Bursty Nature of Solar Flare X-Ray Emission
Authors: McAteer, R. T. James; Young, C. Alex; Ireland, Jack;
Gallagher, Peter T.
2007ApJ...662..691M Altcode:
The complex and highly varying temporal nature of emission from an X4.8
flare is studied across seven X-ray energy bands. A wavelet transform
modulus maxima method is used to obtain the multifractal spectra of
the temporal variation of the X-ray emission. As expected from the
Neupert effect, the time series of the emission at low energies (3-6,
6-12 keV; thermal) is smooth. The peak Hölder exponent, around 1.2,
for this low-energy emission is indicative of a signal with a high
degree of memory and suggestive of a smooth chromospheric evaporation
process. The more bursty emission at higher energies (100-300, 300-800
keV; nonthermal) is described by a multifractal spectrum that peaks at a
smaller Hölder exponent (less than 0.5 for the largest singularities),
indicative of a signal with a low degree of memory. This describes an
antipersistent walk and indicates an impulsive, incoherent driving
source. We suggest that this may arise from bursty reconnection,
with each reconnection event producing a different and uncorrelated
nonthermal particle source. The existence of a power-law scaling
of wavelet coefficients across timescales is in agreement with the
creation of a fractal current sheet diffusion region.

---------------------------------------------------------
Title: Wavelet Analysis of Active Region Magnetic Structure
Authors: Ireland, Jack; Young, C. A.; Gallagher, P. T.; McAteer,
R. T. James; Whelan, C.; Hewett, R. J.
2007AAS...210.9322I Altcode: 2007BAAS...39..214I
A wavelet analysis is used to decompose active region magnetic
fields into regions of different lengthscales, allowing one to
examine the structure of the active region field at different
lengthscales. Linesseparating opposite polarity groupings of flux
at different lengthscales are found; these lines can be seen as a
generalization of the notion of a magnetic neutral line. It is shown
that the average magnetic field gradient for alpha, beta, beta-gamma,
and beta-gamma-delta active regions increases in the order listed,
and that the order is maintained over all length-scales. Further,
the standard deviation and maximum of the magnetic field gradient,
as well as the length of these generalized neutral lines, all share
the same property. Since magnetic field gradient is strongly linked
to active region activity, such as flares, this study demonstrates
that, on average, the Mt. Wilson classification encodes the notion
of activity over all lengthscales in the active region, and not
just those lengthscales at which the strongest field gradients are
found. This study uses the multiscale analysis toolkit Mkit developed
by C. A. Young and presented elsewhere at this meeting.

---------------------------------------------------------
Title: Solar Activity Monitoring
Authors: Gallagher, Peter T.; McAteer, R. T. James; Young, C. Alex;
Ireland, Jack; Hewett, Russell J.; Conlon, Paul
2007ASSL..344...15G Altcode:
No abstract at ADS

---------------------------------------------------------
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: First results from SECIS observations of the 2001 total
Solar eclipse
Authors: Katsiyannis, A. C.; Williams, D. R.; Murtagh, F.; McAteer,
R. T. J.; Keenan, F. P.
2006AIPC..848...95K Altcode:
SECIS observations of the June 2001 total solar eclipse were taken
using an Fe XIV 5303 Å filter. Existing software was modified and new
code was developed for the reduction and analysis of these data. The
observations, data reduction, study of the atmospheric and instrumental
effects, together with some preliminary results are discussed. Emphasis
is given to the techniques used for the automated alignment of the
8000 images, the software developed for the automated detection of
intensity oscillations using wavelet analysis and the application of the
Monte Carlo randomisation test as a means of checking the reliability
of those detections. In line with findings from the 1999 SECIS total
eclipse observations, intensity oscillations with periods in the range
of 7-8 s, lying outside coronal loops were also detected.

---------------------------------------------------------
Title: The Complex Sun: Turbulence and Complexity of the Solar
atmosphere
Authors: McAteer, R. T. James; Gallagher, Peter T.; Ireland, J.;
Young, C Alex; Hewett, Russell J.; Conlon, P.
2006ESASP.617E.137M Altcode: 2006soho...17E.137M
No abstract at ADS

---------------------------------------------------------
Title: How Complex Are Solar Flare Hrx Lightcurves? A Multiscalar
Multifractal Approach.
Authors: McAteer, R. T. J.; Young, C.; Ireland, J.; Gallagher, P. T.
2006SPD....37.0824M Altcode: 2006BAAS...38..235M
A wavelet transform modulus maxima approach to the calculation of
the singularity spectrum is applied to hard X-ray (7 energy bands
from 3--800keV) lightcurves from an X4.8 flare on 23 July 2002. The
multifractality of each lightcurve is discussed in terms of the
Hausdorff dimension, D, of the Holder exponent, h, of each detected
singularity. In addition to a general discussion of the technique, we
show results showing a general increase in complexity of lightcurves
at higher energies

---------------------------------------------------------
Title: Multiscale Structure of Active Region Magnetic Fields
Authors: Hewett, Russell J.; Gallagher, P. T.; McAteer, R.; Young,
C.; Ireland, J.
2006SPD....37.0301H Altcode: 2006BAAS...38..222H
Flows in the photosphere of solar active regions are in a state ofhighly
developed turbulence. As magnetic fields are frozen into theplasma in
the solar surface, magnetograms can therefore be used toinvestigate
the processes responsible for structuring active regions.Here, the
multiscale structure of a large sample of active regionmagnetograms from
the Michelson Doppler Imager (MDI) onboard theSolar and Heliospheric
Observatory (SOHO) are investigated. Initialresults regarding the
relationship between multiscale structuring andactive region evolution
and flaring activity is discussed.

---------------------------------------------------------
Title: Multifractal Analysis of Solar Magnetograms
Authors: Conlon, Paul; McAteer, R. T.; Gallagher, P. T.; Ireland,
J.; Young, C. A.; Young, C. A.
2006SPD....37.0303C Altcode: 2006BAAS...38Q.222C
Magnetohydrodynamic turbulence is thought to be responsible for
structuring sunspot magnetic fields. Here we explore the selfsimilar
and multi-scaling properties of this turbulence using multi-fractal
methods. The multi-fractal spectrum was obtained from full disk
Michelos Doppler Imager magnetograms, to study the relationship
between magnetic field multifractality and flaring and non-flaring
regions. In particular, box counting and wavelet based techniques
where investigated. The discrete box counting method was found to
be inadequate for these purposes, primarily due to discretization
errors. Wavelet based methods, on the other hand, where found to be
more stable for diagnosing turbulence in active region magnetic fields.

---------------------------------------------------------
Title: Wavelet analysis of Active Region structure
Authors: Ireland, J.; Young, C. A.; Whelan, C.; Gallagher, P. T.;
McAteer, R. T. J.; Hewett, R. J.
2006cosp...36.2595I Altcode: 2006cosp.meet.2595I
Active regions are known to consist of complex magnetic fields as
evinced by both fractal and multifractal studies In contrast the Mt
Wilson classification of active regions is relatively simple yet is
useful in predicting the likelihood of flaring events since it considers
the overall geometrical structure of the active region In particular
neutral lines are especially important in evaluating the likelihood
of flare events occurring Wavelet analysis techniques in conjunction
with edge detection methods are applied to the problem of diagnosing
the gross geometrical structure of active region magnetic field Active
region fields are decomposed into their constituent parts using wavelet
techniques and edge detection methods are used to characterize the
neutral lines present A statistical analysis is presented outlining
the utility of this approach in automatically generating a Mt Wilson
classification for a given active region

---------------------------------------------------------
Title: Preliminary Results from Secis Observations of the 2001 Total
Solar Eclipse
Authors: Katsiyannis, A. C.; Williams, D. R.; Murtagh, F.; McAteer,
R. T. J.; Keenan, F. P.
2005ESASP.600E..86K Altcode: 2005ESPM...11...86K; 2005dysu.confE..86K
No abstract at ADS

---------------------------------------------------------
Title: First Results from Secis Observations of the 2001 Total
Solar Eclipse
Authors: Katsiyannis, A. C.; Williams, D. R.; Murtagh, F.; McAteer,
R. T. J.; Keenan, F. P.
2005ESASP.596E..45K Altcode: 2005ccmf.confE..45K
No abstract at ADS

---------------------------------------------------------
Title: Statistics of Active Region Complexity: A Large-Scale Fractal
Dimension Survey
Authors: McAteer, R. T. James; Gallagher, Peter T.; Ireland, Jack
2005ApJ...631..628M Altcode:
A quantification of the magnetic complexity of active regions using a
fractal dimension measure is presented. This fully automated approach
uses full-disk MDI magnetograms of active regions from a large data set
(2742 days of the SOHO mission, 9342 active region images) to compare
the calculated fractal dimension of each region to both its Mount
Wilson classification and flare rate. Each Mount Wilson class exhibits
a similar fractal dimension frequency distribution, possibly suggesting
a self-similar nature of all active regions. Solar flare productivity
exhibits an increase in both the frequency and GOES X-ray magnitude
of flares from regions with higher fractal dimension. Specifically, a
lower threshold fractal dimension of 1.2 and 1.25 exists as a necessary,
but not sufficient, requirement for an active region to produce M-
and X-class flares, respectively, within 24 hr of the observation.

---------------------------------------------------------
Title: Automated Boundary-extraction And Region-growing Techniques
Applied To Solar Magnetograms
Authors: McAteer, R. T. James; Gallagher, Peter T.; Ireland, Jack;
Young, C. Alex
2005SoPh..228...55M Altcode:
We present an automated approach to active region extraction from
full-disc MDI longitudinal magnetograms. This uses a region-growing
technique in conjunction with boundary-extraction to define a number
of enclosed contours as belonging to separate regions of magnetic
significance on the solar disc. This provides an objective definition
of active regions and areas of plage on the Sun. A number of parameters
relating to the flare potential of each region are discussed.

---------------------------------------------------------
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: From Raw Data to Flare Predictions: A Fully Automated Technique
Authors: McAteer, R. T.; Gallagher, P. T.; Ireland, J.; Young, A.
2005AGUSMSP42A..06M Altcode:
With the large volume of solar data which already exists, and expected
in the near future with SDO, automated techniques are becoming
increasingly vital. We present a fully automated active region
extraction routine based on boundary extraction and region growing
techniques applied to full disc MDI longitudinal magnetograms. Once
extracted, any number of image processing techniques can be applied to
the data leading to the possibility of automated classification. We
discuss a large scale (9 years of MDI data, ~10,000 active region
images) fractal survey of this data. This quantifies the meaning of
magnetic complexity, relating lower threshold fractal dimension to
the onset of large flares.

---------------------------------------------------------
Title: Representation of Sun Spots with Shapelets
Authors: Young, C.; Gallagher, P. T.; Ireland, J.; McAteer, R.
2005AGUSMSP11A..07Y Altcode:
Shapelets are complete set of orthonormal functions that can be used to
represent most images. These functions are Gauss-Hermite polynomials and
are the eigenfunctions of the 2D harmonic oscillator. They were first
used in image processing to study the shape of galaxies. Shapelets have
properties that allow one to compute quantities such as chirality,
shear and asymmetry in images. We use these functions to represent
magnetograms of sunspots, allowing us to calculate a large set of
descriptive quantities including those previously mentioned. These
quantities are then correlated with the current classification schemes
used to type sunspots.

---------------------------------------------------------
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: Initial Results from Secis Observations of the 2001 Eclipse
Authors: Katsiyannis, A. C.; Williams, D. R.; Murtagh, F.; McAteer,
R. T. J.; Keenan, F. P.
2004ESASP.575..410K Altcode: 2004soho...15..410K; 2003astro.ph.11534K
SECIS observations of the June 2001 total solar eclipse were taken
using an Fe xiv 5303 A filter. Existing software was modified and new
code was developed for the reduction and analysis of these data. The
observations, data reduction, study of the atmospheric and instrumental
effects, together with some preliminary results are discussed. Emphasis
is given to the techniques used for the automated alignment of the 8000
images, the application of the a Trous algorithm for noise filtering
and the software developed for the automated detection of intensity
oscillations using wavelet analysis. In line with findings from the
1999 SECIS total eclipse observations, intensity oscillations with
periods in the range of 20-30 s, both inside and just outside coronal
loops are also presented.

---------------------------------------------------------
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: Waves and wavelets: An automated detection technique for
solar oscillations
Authors: De Moortel, I.; McAteer, R. T. J.
2004SoPh..223....1D Altcode: 2004SoPh..223....1M
This paper investigates the possibility of automating the detection
of propagating intensity perturbations in coronal loops using
wavelet analysis. Two different sets of TRACE 171 Å images are
studied using the automated wavelet routine presented by McAteer et
al. (2004). Both localised, short-lived periodicities and sustained,
periodic, oscillations are picked up by the routine, with the results
dependent to a large extent on the signal-to-noise ratio of the
dataset. At present, the automation is only partial; the relevance
of the detected periodicity and the identification of the coronal
structure supporting it still have to be determined by the user, as
does the judging of the accuracy of the results. Care has to be taken
when interpreting the results of the wavelet analysis, and a good
knowledge of all possible factors that might influence or distort the
results is a necessity. Despite these limitations, wavelet analysis
can play an important role in automatically identifying a variety of
phenomena and in the analysis of the ever-growing (observational or
simulated) datasets.

---------------------------------------------------------
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: Optical Observations of Flare-Induced Oscillations
Authors: McATeer, R. T. J.; Gallagher, P. T.; Brown, D. S.
2004AAS...204.9806M Altcode: 2004BAAS...36..985M
We present high-cadence H alpha blue wing observations of a C9.6
solar flare. Oscillations (period 40-80s) are shown to be present
in the post-flare section of lightcurves from a short-lived flare
ribbon. Wavelet analysis is used to show the excellent agreement of
oscillatory power at 52.4s with a distance-time plot along one half of
the ribbon. A best-fit of an oscillation to the curve shows oscillatory
amplitude ∼ 0.03% flare ampltiude, period ∼ 69s and decay time
∼ 500s. These parameters are in good agreement with the formation
of a second harmonic acoustic wave. A study of loop lengths along the
ribbon also agrees with the presence of a ∼ 50s period JMA is
funded by a NRC Research Associateship. Observations were carried out
via a Leverhulme Trust Fellowship.

---------------------------------------------------------
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: Low-frequency oscillations of the solar atmosphere
Authors: McAteer, Robert Thomas James
2004PhDT.........6M Altcode:
This thesis presents detections of oscillations in multi- wavelength
images of the quiet-Sun chromosphere, and interprets these oscillations
in terms of various chromospheric wave-heating theories. Oscillations
in network bright points (NBPs) are studied in the light of Ca II
K3 as a function of radial distance from the centre of
each NBP. It is shown that low-frequencies (1 4 mHz) tend to dominate,
especially in the central portions, suggesting a magnetic component in
any waves present. Correlations between wavelet power density maps of
light curves in four optical passbands is used to search for vertically
propagating wave packets. In each NBP studied, observational evidence is
found for transverse-mode magnetohydrodynamic (MHD) waves (1.3 mHz, 1.9
mHz) propagating upwards from the low- to mid-chromosphere, where they
couple to longitudinal-mode MHD waves at twice the originally frequency
(2.6 mHz, 3.8 mHz), which then shock in the high-chromosphere. There is
also further evidence of other upward- and downward-propagating waves
in the 1.3 4.6 mHz range. An automated wavelet analysis routine is
developed to provide a comparison, in frequency and duration, between
network and internetwork oscillations in ultraviolet images of the
quiet Sun. The tendency of the network to contain lower frequencies
(peak at 3.5 mHz, with an extended tail down to 1 mHz) is discussed
in terms of transverse-mode MHD waves. In contrast, the internetwork
contains frequencies around 4 mHz, with oscillations tending to contain
a higher degree of spatial memory. These are interpreted as persistent
flashers. The network tends to contain more oscillations below 3.3
mHz than the internetwork in the low-chromosphere, with this cross-
over frequency increasing to 4 mHz in the upper chromosphere. However,
below this cross-over frequency, the internetwork still contains a
larger number of oscillations, but with short lifetimes. Both regions
also contain a small number of non-recurring long-lived oscillations.

---------------------------------------------------------
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: Initial Results from SECIS Observations of the 2001 Eclipse
Authors: Katsiyannis, A. C.; McAteer, R. T. J.; Williams, D. R.;
Gallagher, P. T.; Keenan, F. P.
2004ESASP.547..459K Altcode: 2004astro.ph.11722K; 2004soho...13..459K
SECIS observations of the June 2001 total solar eclipse were taken
using an Fe XIV 5303 Å filter. Existing software was modified and new
code was developed for the reduction and analysis of these data. The
observations, data reduction, study of the atmospheric and instrumental
effects, together with some preliminary results are discussed. Emphasis
is given to the techniques used for the automated alignment of the 8000
images, the application of the `a Trous algorithm for noise filtering
and the software developed for the automated detection of intensity
oscillations using wavelet analysis. In line with findings from the
1999 SECIS total eclipse observations, intensity oscillations with
periods in the range of 20-30 s, both inside and just outside coronal
loops are also presented.

---------------------------------------------------------
Title: Low Frequency Oscillations of the Solar Atmosphere
Authors: McAteer, R. T. James
2003PhDT........15M Altcode:
This thesis presents detections of intensity oscillations in
multi-wavelength image sequences of the quiet-Sun chromosphere,
and interprets these oscillations in terms of various chromospheric
wave-heating theories. Oscillations in network bright points (NBPs) are
studied in the light of Ca II K3 as a function of radial distance from
the centre of each NBP. It is shown that low frequencies (1--4mHz) tend
to dominate, especially in the central portions, suggesting a magnetic
component in any waves present. Correlations between wavelet
power density maps of light curves in four optical passbands is used
to search for vertically propagating wave packets. In each NBP studied,
observational evidence is found for transverse-mode magnetohydrodynamic
(MHD) waves (1.3mHz, 1.9mHz) propagating upwards from the low- to
mid- chromosphere, where they couple to longitudinal-mode MHD waves
at twice the originally frequency (2.6mHz, 3.8mHz), which then shock
in the high-chromosphere. There is also further evidence of other
upward- and downward- propagating waves in the 1.3--4.6mHz range. An automated wavelet analysis routine is developed to compare,
in frequency and duration, network and internetwork oscillations,
in ultraviolet image sequences of the quiet Sun. The tendency of
the network to contain lower frequencies (peak at 3.5mHz, with an
extended tail down to 1mHz) is discussed in terms of transverse-mode
MHD waves. In contrast, the internetwork contains frequencies around
4mHz, with oscillations tending to contain a higher degree of spatial
memory. These are interpreted as persistent flashers. The network tends
to contain more oscillations below 3.3mHz than the internetwork in the
low-chromosphere, with this cross-over frequency increasing to 4mHz
in the upper chromosphere. However, below this cross-over frequency,
the internetwork still contains a larger number of oscillations,
but with short lifetimes. Both regions also contain a small number of
non-recurring long-lived oscillations.

---------------------------------------------------------
Title: Eclipse observations of high-frequency oscillations in active
region coronal loops
Authors: Katsiyannis, A. C.; Williams, D. R.; McAteer, R. T. J.;
Gallagher, P. T.; Keenan, F. P.; Murtagh, F.
2003A&A...406..709K Altcode: 2003astro.ph..5225K
One of the mechanisms proposed for heating the corona above solar active
regions is the damping of magnetohydrodynamic (MHD) waves. Continuing
on previous work, we provide observational evidence for the existence
of high-frequency MHD waves in coronal loops observed during the
August 1999 total solar eclipse. A wavelet analysis is used to identify
twenty 4x4 arcsec2 areas showing intensity oscillations. All
detections lie in the frequency range 0.15-0.25 Hz (7-4 s), last for
at least 3 periods at a confidence level of more than 99% and arise
just outside known coronal loops. This leads us to suggest that they
occur in low emission-measure or different temperature loops associated
with the active region.

---------------------------------------------------------
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: An observational study of a magneto-acoustic wave in the
solar corona
Authors: Williams, D. R.; Mathioudakis, M.; Gallagher, P. T.; Phillips,
K. J. H.; McAteer, R. T. J.; Keenan, F. P.; Rudawy, P.; Katsiyannis,
A. C.
2002MNRAS.336..747W Altcode:
The Solar Eclipse Corona Imaging System (SECIS) observed a strong 6-s
oscillation in an active region coronal loop, during the 1999 August 11
total solar eclipse. In the present paper we show that this oscillation
is associated with a fast-mode magneto-acoustic wave that travels
through the loop apex with a velocity of 2100 km s-1. We use
near-simultaneous SOHO observations to calculate the parameters of the
loop and its surroundings such as density, temperature and their spatial
variation. We find that the temporal evolution of the intensity is in
agreement with the model of an impulsively generated, fast-mode wave.

---------------------------------------------------------
Title: Detections of high-frequency oscillations in solar active
region coronal loops
Authors: Katsiyannis, Athanassios C.; Williams, David R.; McAteer,
R. T. James; Gallagher, Peter T.; Mathioudakis, Mihalis; Keenan,
Francis P.
2002ESASP.505..441K Altcode: 2002IAUCo.188..441K; 2002solm.conf..441K
One of the mechanisms proposed as a possible solution to the
Sun's coronal heating problem is the damping of energy carried by
magnetohydrodynamic (MHD) waves that are expected to be present
in active regions. Continuing previous work on total solar eclipse
data, we provide further obervational evidence for the existence of
high-frequency MHD waves in coronal loops. Wavelet analysis is used to
identify 21 areas of 4×4 arcsec2 with periodic intensity
oscillations. The frequency range of these detections was 0.2-0.3 Hz
and all last for at least 3 periods at a confidence level of more than
99%. All of the above detections are made just outside known coronal
loops, leading us to suggest a possible, unconventional mechanism.

---------------------------------------------------------
Title: Detection of propagating waves throughout the chromosphere
in network bright points
Authors: McAteer, R. T. James; Gallagher, Peter T.; Williams, David
R.; Mathioudakis, Mihalis; Phillips, Kenneth J. H.; Keenan, Francis P.
2002ESASP.505..305M Altcode: 2002IAUCo.188..305M; 2002solm.conf..305M
We analysed oscillations in individual Network Bright Points (NBPs)
in Ca II K3, Hα core, Mg I b2, and Mg I
b1-0.4 Å giving us a range of heights from the upper
to the lower chromosphere. Lightcurves, and hence power spectra,
were created by isolating distinct regions of the NBP via a simple
intensity thresholding technique. Using this technique, it was
possible to identify peaks in the power spectra with particular spatial
positions within the NBPs. This was extended into the time domain by
means of wavelet analysis. We track the temporal evolution of power
in particular frequency bands by creating power curves. These are
then cross-correlated across all observed wavelengths to search for
propagating waves. In particular, long-period waves with periods of
4-15 minutes (1-4 mHz) were found in the central portion of each NBP,
indicating that these waves are certainly not acoustic, but possibly
due to magneto-acoustic or magneto-gravity wave modes. We note the
possible existence of fast-mode MHD waves in the lower chromosphere,
coupling and transferring power top higher-frequency slow-mode MHD
waves in the upper chromosphere.

---------------------------------------------------------
Title: Observations of a high-frequency, fast-mode wave in a
coronal loop
Authors: Williams, David R.; Mathioudakis, Mihalis; Gallagher, Peter
T.; Phillips, Kenneth J. H.; McAteer, R. T. James; Keenan, Francis P.;
Katsiyannis, Athanassios C.
2002ESASP.505..615W Altcode: 2002IAUCo.188..615W; 2002solm.conf..615W
The high-cadence Solar Eclipse Corona Imaging System (SECIS) observed
a strong 6-second oscillation in an active region coronal loop, during
the 1999 August 11 total solar eclipse. In the present paper we show
that this oscillation is associated with a fast-mode wave that travels
through the loop apex with a velocity of ~2000 km s-1. We
use near-simultaneous SoHO/CDS obervations to calculate the parameters
of the loop and its surroundings such as density, temperature and their
spatial variation. We also calculate radiative losses from the loop in
the temperature range 105.8 - 106.4K, and compare
these losses with the wave energy density. Although the wave travels a
distance greater than λ/4π and therefore meets a necessary criterion
for slow dissipation, the dissipation length is well in excess of the
loop length. The temporal evolution of the intensity is found to be
in agreement with the model of an impulsively generated, fast-mode wave.

---------------------------------------------------------
Title: Long-Period Chromospheric Oscillations in Network Bright Points
Authors: McAteer, R. T. James; Gallagher, Peter T.; Williams, David
R.; Mathioudakis, Mihalis; Phillips, Kenneth J. H.; Keenan, Francis P.
2002ApJ...567L.165M Altcode:
The spatial variation of chromospheric oscillations in network bright
points (NBPs) is studied using high-resolution observations in Ca II
K3. Light curves and hence power spectra were created by isolating
distinct regions of the NBP via a simple intensity thresholding
technique. Using this technique, it was possible to identify peaks in
the power spectra with particular spatial positions within the NBPs. In
particular, long-period waves with periods of 4-15 minutes (1-4 mHz)
were found in the central portions of each NBP, indicating that these
waves are certainly not acoustic but possibly due to magnetoacoustic
or magnetogravity wave modes. We also show that spatially averaged
or low spatial resolution power spectra can lead to an inability to
detect such long-period waves.