dudik

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Author name code: dudik
ADS astronomy entries on 2022-09-14
author:"Dudik, Jaroslav"

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Title: Filament Leg--Leg Reconnection as a Source of Prominent
Supra-Arcade Downflows
Authors: Dudik, Jaroslav; Aulanier, Guillaume; Kasparova, Jana;
Karlicky, Marian; Zemanova, Alena; Lorincik, Juraj; Druckmuller,
Miloslav
2022arXiv220900306D Altcode:
We report on interaction of the legs of the erupting filament
of 2012 August 31 and associated prominent supra-arcade downflows
(P-SADs) as observed by the Atmospheric Imaging Assembly onboard the
Solar Dynamics Observatory. We employ a number of image processing
techniques to enhance weak interacting features. As the filament erupts,
both legs stretch outwards. The positive-polarity leg also untwists
and splits into two parts. The first part runs into the conjugate
(negative-polarity) leg, tearing it apart. The second part then
converges into the remnant of the conjugate leg, after which both
weaken and finally disappear. All these episodes of interaction of
oppositely-oriented filament legs are followed by appearance of P-SADs,
seen in the on-disk projection to be shaped as loop-tops, along with
many weaker SADs. All SADs are preceded by hot supra-arcade downflowing
loops. This observed evolution is consistent with the three-dimensional
rr-rf (leg-leg) reconnection, where the erupting flux rope reconnects
with itself. In our observations, as well as in some models, the
reconnection in this geometry is found to be long-lasting. It plays
a substantial role in the evolution of the flux rope of the erupting
filament and leads to prominent supra-arcade downflows.

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Title: Diagnostics of non-Maxwellian electron distributions in solar
active regions from Fe XII lines observed by Hinode/EIS and IRIS
Authors: Del Zanna, G.; Polito, V.; Dudík, J.; Testa, P.; Mason,
H. E.; Dzifčáková, E.
2022arXiv220707026D Altcode:
We present joint Hinode/EIS and IRIS observations of Fe XII lines
in active regions, both on-disk and off-limb. We use an improved
calibration for the EIS data, and find that the 192.4 A / 1349 A
observed ratio is consistent with the values predicted by CHIANTI and
the coronal approximation in quiescent areas, but not in all active
region observations, where the ratio is often lower than expected
by up to a factor of about two. We investigate a number of physical
mechanisms that could affect this ratio, such as opacity and absorption
from cooler material. We find significant opacity in the EIS Fe XII
193 and 195 A lines, but not in the 192.4 A line, in agreement with
previous findings. As we cannot rule out possible EUV absorption by
H, He and He II in the on-disk observations, we focus on an off-limb
observation where such absorption is minimal. After considering these,
as well as possible non-equilibrium effects, we suggest that the most
likely explanation for the observed low Fe XII 192.4 A / 1349 A ratio
is the presence of non-Maxwellian electron distributions in the active
regions. This is in agreement with previous findings based on EIS and
IRIS observations independently.

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Title: Blueshifted Si IV 1402.77 Å Line Profiles in a Moving Flare
Kernel Observed by IRIS
Authors: Lörinčík, Juraj; Dudík, Jaroslav; Polito, Vanessa
2022ApJ...934...80L Altcode:
We analyze the spectra of a slipping flare kernel observed during
the 2015 June 22 M6.5-class flare by the Interface Region Imaging
Spectrograph (IRIS). During the impulsive and peak phases of the flare,
loops exhibiting an apparent slipping motion along the ribbons were
observed in the 131 Å channel of SDO/AIA. The IRIS spectrograph
slit observed a portion of the ribbons, including a moving kernel
corresponding to a flare loop footpoint in Si IV, C II, and Mg II at a
very-high 1 s cadence. The spectra observed in the kernel were mostly
redshifted and exhibited pronounced red wings, as typically observed
in large flares. However, in a small region in one of the ribbons, the
Si IV 1402.77 Å line was partially blueshifted, with the corresponding
Doppler velocity ∣v D∣ exceeding 50 km s-1. In
the same region, the C II 1334.53, 1335.66, and 1335.71 Å lines were
weakly blueshifted (∣v D∣ &lt; 20 km s-1)
and showed pronounced blue wings, which were also observed in the Mg
II k 2796.35 Å as well as the Mg II triplet 2798.75 and 2798.82 Å
lines. Using high-cadence AIA observations we found that the region
where the blueshifts occurred corresponds to the accelerating kernel
front as it moved through a weak field region. The IRIS observations
with high resolution allowed us to capture the acceleration of the
kernel under the slit for the first time. The unique observations of
blueshifted chromospheric and TR lines provide new constraints for
current models of flares.

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Title: KAPPA package and diagnostics of the kappa-distribution from
EUV solar spectra
Authors: Dzifcakova, Elena; Dudik, Jaroslav; Zemanova, Alena;
Lorincik, Juraj
2022cosp...44.1218D Altcode:
Many theoretical calculations and several diagnostics support an idea
of the presence of non-Maxwellian electron distributions in the solar
corona and transition region. The kappa-distributions as well as other
distributions exhibiting high-energy tails change individual ionization,
recombination and collisional excitation rates. These changes are
reflected in the changes ionization equilibrium, populations of energy
levels and therefore in line intensities. This enables diagnostics of
non-Maxwellian distributions from observations. Theoretical spectra
for different kappa-distributions, temperatures and electron densities
can be obtained using the latest version KAPPA package which provides
fast calculations of synthetic spectra for kappa-distributions. This
allows us to search for diagnostic opportunities and enables us to
study how kappa-distributions influence the observed temperature
distribution in emitting plasma. We showed that forbidden lines have
a great potential for non-thermal diagnostics. The Fe XVII and Fe
XVIII lines in soft X-ray spectral range observable by Marshall
Grazing-Incidence X-ray Spectrometer (MaGIXS) are also suitable
to diagnose kappa-distributions. Finally, the Fe XI - Fe XIII lines
observed by the Extreme-Ultraviolet Imaging Spectrometer (EIS) onboard
the Hinode spacecraft were used to diagnose kappa in the active region
and for the quiet Sun. It was found that the quiet Sun spectra are
consistent with a Maxwellian distribution but the spectrum of coronal
loops, moss, and for the transient loop observed within active region
are strongly non-Maxwellian with kappa as low as 2.

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Title: Blueshifted Si IV 1402.77Å line profiles in a moving flare
kernel observed by IRIS
Authors: Lörinčík, Juraj; Dudík, Jaroslav; Polito, Vanessa
2022arXiv220610114L Altcode:
We analyze spectra of a slipping flare kernel observed during the 2015
June 22 M6.5-class flare by the Interface Region Imaging Spectrograph
(IRIS). During the impulsive and peak phases of the flare, loops
exhibiting an apparent slipping motion along the ribbons were observed
in the 131Å channel of SDO/AIA. The IRIS spectrograph slit observed
a portion of the ribbons, including a moving kernel corresponding to
a flare loop footpoint in Si IV, C II, and Mg II at a very-high 1 s
cadence. The spectra observed in the kernel were mostly redshifted
and exhibited pronounced red wings, as typically observed in large
flares. However, in a small region in one of the ribbons, the Si IV
1402.77Å line was partially blueshifted, with the corresponding Doppler
velocity |v_{D}| exceeding 50 km s$^{-1}$. In the same region, the C
II 1334.53Å, 1335.66Å and 1335.71Å lines were weakly blueshifted
(|v_{D}| &lt; 20 km s$^{-1}$) and showed pronounced blue wings,
which were observed also in the Mg II k 2796.35Å as well as the
Mg II triplet 2798.75Å and 2798.82Å lines. Using high-cadence AIA
observations we found that the region where the blueshifts occurred
corresponds to the accelerating kernel front as it moved through a
weak-field region. The IRIS observations with high resolution allowed
us to capture the acceleration of the kernel under the slit for the
first time. The unique observations of blueshifted chromospheric and
TR lines provide new constrains for current models of flares.

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Title: Diagnostics of Non-Maxwellian Electron Distributions in
Solar Active Regions from Fe XII Lines Observed by the Hinode
Extreme Ultraviolet Imaging Spectrometer and Interface Region
Imaging Spectrograph
Authors: Del Zanna, G.; Polito, V.; Dudík, J.; Testa, P.; Mason,
H. E.; Dzifčáková, E.
2022ApJ...930...61D Altcode:
We present joint Hinode Extreme Ultraviolet Imaging Spectrometer
(EIS) and Interface Region Imaging Spectrograph (IRIS) observations
of Fe XII lines in active regions, both on-disk and off-limb. We use
an improved calibration for the EIS data, and find that the 192.4
Å/1349 Å observed ratio is consistent with the values predicted by
CHIANTI and the coronal approximation in quiescent areas, but not in
all active-region observations, where the ratio is often lower than
expected by up to a factor of about two. We investigate a number of
physical mechanisms that could affect this ratio, such as opacity and
absorption from cooler material. We find significant opacity in the EIS
Fe XII 193 and 195 Å lines, but not in the 192.4 Å line, in agreement
with previous findings. As we cannot rule out possible EUV absorption by
H, He, and He II in the on-disk observations, we focus on an off-limb
observation where such absorption is minimal. After considering these,
as well as possible nonequilibrium effects, we suggest that the most
likely explanation for the observed low Fe XII 192.4 Å/1349 Å ratio
is the presence of non-Maxwellian electron distributions in the active
regions. This is in agreement with previous findings based on EIS and
IRIS observations independently.

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Title: KAPPA: A Package for the Synthesis of Optically Thin Spectra
for the Non-Maxwellian κ-distributions. II. Major Update to
Compatibility with CHIANTI Version 10
Authors: Dzifčáková, Elena; Dudík, Jaroslav; Zemanová, Alena;
Lörinčík, Juraj; Karlický, Marian
2021ApJS..257...62D Altcode:
KAPPA is a database and software for the calculation of the
optically thin spectra for the non-Maxwellian κ-distributions
that were recently diagnosed in the plasma of solar coronal loops,
flares, as well as in the transition region. KAPPA is based on the
widely used CHIANTI database and reproduces many of its capabilities
for κ-distributions. Here we perform a major update of the KAPPA
database, including a near-complete recalculation of the ionization,
recombination, excitation, and deexcitation rates for all ions in
the database, as well as an implementation of the two-ion model
for calculations of relative-level populations (and intensities) if
these are modified by ionization and recombination from or to excited
levels. As an example of KAPPA usage, we explore novel diagnostics of
κ, and show that O III lines near 500 and 700 Å provide a strong
sensitivity to κ, with some line intensity ratios changing by a
factor of up to 2-4 compared to Maxwellian. This is much larger than
previously employed diagnostics of κ.

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Title: Saddle-shaped Solar Flare Arcades
Authors: Lörinčík, Juraj; Dudík, Jaroslav; Aulanier, Guillaume
2021ApJ...909L...4L Altcode: 2021arXiv210210858L
Arcades of flare loops form as a consequence of magnetic reconnection
powering solar flares and eruptions. We analyze the morphology and
evolution of flare arcades that formed during five well-known eruptive
flares. We show that the arcades have a common saddle-like shape. The
saddles occur despite the fact that the flares were of different classes
(C to X), occurred in different magnetic environments, and were observed
in various projections. The saddles are related to the presence of
longer, relatively higher, and inclined flare loops, consistently
observed at the ends of the arcades, which we term "cantles." Our
observations indicate that cantles typically join straight portions
of flare ribbons with hooked extensions of the conjugate ribbons. The
origin of the cantles is investigated in stereoscopic observations of
the 2011 May 9 eruptive flare carried out by the Atmospheric Imaging
Assembly and Extreme Ultraviolet Imager. The mutual separation of
the instruments led to ideal observational conditions allowing for
simultaneous analysis of the evolving cantle and the underlying ribbon
hook. Based on our analysis we suggest that the formation of one of the
cantles can be explained by magnetic reconnection between the erupting
structure and its overlying arcades. We propose that the morphology of
flare arcades can provide information about the reconnection geometries
in which the individual flare loops originate.

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Title: Electron Densities in the Solar Corona Measured Simultaneously
in the Extreme Ultraviolet and Infrared
Authors: Dudík, Jaroslav; Del Zanna, Giulio; Rybák, Ján;
Lörinčík, Juraj; Dzifčáková, Elena; Mason, Helen E.; Tomczyk,
Steven; Galloy, Michael
2021ApJ...906..118D Altcode: 2020arXiv201109175D
Accurate measurements of electron density are critical for
determination of the plasma properties in the solar corona. We compare
the electron densities diagnosed from Fe XIII lines observed by the
Extreme-Ultraviolet Imaging Spectrometer (EIS) onboard the Hinode
mission with the near-infrared (NIR) measurements provided by the
ground-based Coronal Multichannel Polarimeter (CoMP). To do that, the
emissivity-ratio method based on all available observed lines of Fe
XIII is used for both EIS and CoMP. The EIS diagnostics is further
supplemented by the results from Fe XII lines. We find excellent
agreement, within 10%, between the electron densities measured from both
extreme-ultraviolet and NIR lines. In the five regions selected for
detailed analysis, we obtain electron densities of log(Ne
[cm-3]) = 8.2-8.6. Where available, the background
subtraction has a significant impact on the diagnostics, especially on
the NIR lines, where the loop contributes less than a quarter of the
intensity measured along the line of sight. For the NIR lines, we find
that the line center intensities are not affected by stray light within
the instrument, and recommend using these for density diagnostics. The
measurements of the Fe XIII NIR lines represent a viable method for
density diagnostics using ground-based instrumentation.

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Title: Diagnostics of Kappa Distributions from Optically Thin
Solar Spectra
Authors: Dudík, Jaroslav; Dzifčáková, Elena
2021ASSL..464...53D Altcode:
We review the diagnostics of the non-Maxwellian Kappa distributions
from the remote-sensing spectroscopic observations of the optically
thin parts of the solar atmosphere. While the electron distributions are
typically diagnosed from ratios of emission line intensities alongside
other plasma parameters such as electron densities and temperature,
the ion distributions affect the shape of the line profiles and are
more readily seen. The electron Kappa distributions relies on accurate
calculations of synthetic spectra which in turn depend on evaluation of
the ionization, recombination, and collisional excitation rates. Even
though the observational uncertainties can be significant, recent
results point out to a possibly widespread presence of low κ-values,
typically κ = 2, in many regions of the solar atmosphere, including the
transition region, active region corona, and solar flares, especially
the reconnection region.

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Title: Magnetic support of the solar filaments
Authors: Schmieder, Brigitte; Aulanier, Guillaume; Gunár, Stanislav;
Dudik, Jaroslav; Heinzel, Petr
2021cosp...43E1766S Altcode:
The scale height in prominence is 500 km at maximum. However, non
activated prominences can reach an altitude of 50000 km or more. Hanging
filaments observed over the limb give the impression of quasi vertical
structures. It was already the view in the past but reactivated by the
movies of Hinode in Ca II line showing fuzzing vertical structures. In
the corona it is not possible to measure the magnetic field supporting
prominences. Only extrapolations of the photospheric magnetic field
explain how cool plasma embedded in the dips of the magnetic field
lines can be supported in the hot corona. I will review a few papers
showing the distribution of the cool plasma dips and the observations
of filaments on the disk visible in H$\alpha$ and in UV. A recent
paper shows how a 3D extrapolation model and a radiative-transfer
based H$\alpha$ visualization method leads to H$\alpha$ prominence
fine structures. Finally, I will discuss the perspective effects on
the perceived morphology of observed and modeled prominences.

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Title: Imaging Evidence for Solar Wind Outflows Originating from a
Coronal Mass Ejection Footpoint
Authors: Lörinčík, Juraj; Dudík, Jaroslav; Aulanier, Guillaume;
Schmieder, Brigitte; Golub, Leon
2021ApJ...906...62L Altcode: 2020arXiv201004250L
We report on Atmospheric Imaging Assembly observations of plasma
outflows originating in a coronal dimming during a 2015 April 28
filament eruption. After the filament started to erupt, two flare
ribbons formed, one of which had a well-visible hook enclosing a core
(twin) dimming region. Along multiple funnels located in this dimming,
a motion of plasma directed outward started to be visible in the
171 and 193 Å filter channels of the instrument. In time-distance
diagrams, this motion generated a strip-like pattern, which lasted
for more than 5 hr and whose characteristics did not change along
the funnel. We therefore suggest the motion is a signature of
outflows corresponding to velocities ranging between ≍70 and 140
km s-1. Interestingly, the pattern of the outflows and
their velocities were found to be similar to those we observed in a
neighboring ordinary coronal hole. Therefore, the outflows were most
likely a signature of a coronal mass ejection-induced solar wind flowing
along the open-field structures rooted in the dimming region. Further,
the evolution of the hook encircling the dimming region was examined
in the context of the latest predictions imposed for 3D magnetic
reconnection. The observations indicate that the filament's footpoints
were, during their transformation to the dimming region, reconnecting
with surrounding canopies. To our knowledge, our observations present
the first imaging evidence for outflows of plasma from a dimming region.

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Title: Links between prominence/filament magnetic field and plasma:
What can 3D WPFS models teach us?
Authors: Gunár, Stanislav; Schmieder, Brigitte; Aulanier, Guillaume;
Heinzel, Petr; Mackay, Duncan; Dudik, Jaroslav
2021cosp...43E1769G Altcode:
The magnetic field constitutes the skeleton and the driving force of
prominences/filaments. It supports the dense prominence plasma against
gravity and insulates it from the hot, coronal environment. The
magnetic field is also responsible for the prominence stability,
evolution and eruptions which affect the heliosphere and ultimately
the Earth. However, a strong imbalance exists between the numerous
efforts in detailed modelling of prominence magnetic field and its
understanding from observations. That is due to the complex nature of
the direct (and indirect) observations of solar magnetic fields which
are challenging at the best of times and even more so in prominences
or filaments. The direct observations of the prominence magnetic
field require high-precision spectro-polarimetric measurements and
realistic assumptions about the plasma structure which allow us to
infer the field configuration from its effect on the polarized light
emergent from the observed structures. The indirect observations rely
on the perceived location, shape and dynamics of the prominence or
filament plasma, often using moving small-scale plasma structures
as tracers guided by the field lines. Both methods thus rely on the
presence of observable plasma in the magnetic field configuration,
and on the radiation which carries the information about the in-situ
conditions to the observer. No prominence/filament magnetic field
measurements are made without these two additional components,
which are sometimes an afterthought in the magnetic field models. We
have developed 3D Whole-Prominence Fine Structure (WPFS) models to
illuminate the links between the prominence magnetic field, its plasma
distributed among numerous fine structures and the radiation which
carries the information about the prominence physical conditions to
the observer. What can we learn from these 3D models? For example,
we can see that a small change of the magnetic field configuration
can have a large effect on the perceived structure of prominences and
filaments visible in the H-alpha line. Consequently, this means that
significant changes observed in prominences or filaments do not need
to suggest that equally large changes in the underlying magnetic field
configuration had to occur. In another example, we see that seemingly
incomparable differences in the morphological look of prominences (long
horizontal fine structures versus small blobs of plasma arranged into
more-less vertical features) may not need to imply the existence of
radically different magnetic field configurations. Rather, they might
simply be manifestations of projection effects that can differ greatly
depending on the viewing angle under which we observe the naturally
three-dimensional prominences/filaments.

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Title: Lyrids 2020 observations by AMOS, spectral, visual and
photographic methods
Authors: Toth, Juraj; Matlovic, Pavol; Zigo, Pavol; Kornos, Leonard;
Simon, Jaroslav; Paulech, Tomas; Balaz, Martin; Polcic, Ludovit;
Pisarcikova, Adriana; Zilkova, Danica; Bartkova, Daniela; Dudik,
Jaroslav; Licandro, Javier; Masiar, Jan; Kaniansky, Stanislav; Barsa,
Robert; Veres, Peter
2020JIMO...48..199T Altcode:
We present observations of the 2020 Lyrid meteor shower by different
techniques from Slovakia and the Canary Islands. The visual observations
have been supported by video observations using the AMOS systems and are
in good agreement with IMO visual data. We also present data of a Lyrid
fireball observed on 2020 April 21 at 23h53m20s UTC by multiple stations
of AMOS, AMOS-Spec and by a digital photographer. The fireball was about
-4.5 magnitude and left a dust trail photographically visible for about
22 minutes. Just several minutes before, very long fireball was observed
at 23h45m29s UTC by AMOS stations as well as another photographer from
Kosice. The images illustrate the beauty of the night sky.

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Title: Flare Expansion to a Magnetic Rope Accompanied by Rare
Radio Bursts
Authors: Zemanová, Alena; Karlický, Marian; Kašparová, Jana;
Dudík, Jaroslav
2020ApJ...905..111Z Altcode: 2021arXiv210108633Z
We present multispectral analysis (radio, Hα, ultraviolet (UV)/extreme
ultraviolet (EUV), and hard X-ray) of a confined flare from 2015 March
12. This flare started within the active region NOAA 12 297 and then it
expanded into a large preexisting magnetic rope embedded with a cold
filament. The expansion started with several brightenings located
along the rope. This process was accompanied by a group of slowly
positively drifting bursts in the 0.8-2 GHz range. The frequency drift
of these bursts was 45-100 MHz s-1. One of the bursts had an
S-like form. During the brightening of the rope we observed a unique
bright EUV structure transverse to the rope axis. The structure was
observed in a broad range of temperatures and it moved along the rope
with the velocity of about 240 km s-1. When the structure
dissipated, we saw a plasma further following twisted threads in the
rope. The observed slowly positively drifting bursts were interpreted
considering particle beams and we show that one with the S-like
form could be explained by the beam propagating through the helical
structure of the magnetic rope. The bright structure transverse to
the rope axis was interpreted considering line-of-sight effects and
the dissipation-spreading process, which we found to be more likely.

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Title: Plasma Diagnostics from Active Region and Quiet-Sun Spectra
Observed by Hinode/EIS: Quantifying the Departures from a Maxwellian
Distribution
Authors: Lörinčík, Juraj; Dudík, Jaroslav; del Zanna, Giulio;
Dzifčáková, Elena; Mason, Helen E.
2020ApJ...893...34L Altcode: 2020arXiv200307091L
We perform plasma diagnostics, including that of the non-Maxwellian
κ-distributions, in several structures observed in the solar corona
by the Extreme-Ultraviolet Imaging Spectrometer (EIS) on board the
Hinode spacecraft. To prevent uncertainties due to the in-flight
calibration of EIS, we selected spectral atlases observed shortly
after the launch of the mission. One spectral atlas contains an
observation of an active region, while the other is an off-limb
quiet-Sun region. To minimize the uncertainties of the diagnostics,
we rely only on strong lines and average the signal over a spatial
area within selected structures. Multiple plasma parameters are
diagnosed, such as the electron density, the differential emission
measure, and the non-Maxwellian parameter κ. To do that, we use
a simple, well-converging iterative scheme based on refining the
initial density estimates via the differential emission measure
(DEM) and κ. We find that while the quiet-Sun spectra are consistent
with a Maxwellian distribution, the coronal loops and moss observed
within the active region are strongly non-Maxwellian with κ ⪅
3. These results were checked by calculating synthetic ratios using
DEMs obtained as a function of κ. Ratios predicted using the DEMs
assuming κ-distributions converged to the ratios observed in the
quiet Sun and coronal loops. To our knowledge, this work presents a
strong evidence of the presence of different electron distributions
between two physically distinct parts of the solar corona.

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Title: Diagnostics of non-thermal-distributions from solar flare
EUV line spectra
Authors: Dzifčáková, Elena; Zemanová, Alena; Dudík, Jaroslav;
Lörinčík, Juraj
2020IAUS..354..414D Altcode:
Spectral line intensities observed by the Extreme Ultraviolet
Variability Experiment (EVE) on board the Solar Dynamics
Observatory (SDO) during 2012 March 9 M6.3 flare were used
to diagnose a presence of a non-thermal electron distribution
represented by a κ-distribution. The diagnosed electron densities
($≈ 2 × {10^{11}}{{c}}{{{m}}^{ - 3}}$) are affected only a
little by the presence of the non-thermal distribution, and are
within the uncertainties of observation. On the other hand, the
temperature diagnostics based on the line ratios involving different
ionization degrees is strongly affected by the type of the electron
distribution. The distribution functions diagnosed from relative Fe
line intensities demonstrate the presence of strongly non-thermal
distributions during the impulsive phase of the flare and later their
gradual thermalization.

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Title: Observation of All Pre- and Post-reconnection Structures
Involved in Three-dimensional Reconnection Geometries in Solar
Eruptions
Authors: Dudík, Jaroslav; Lörinčík, Juraj; Aulanier, Guillaume;
Zemanová, Alena; Schmieder, Brigitte
2019ApJ...887...71D Altcode: 2019arXiv191008620D
We report on observations of the two newly identified reconnection
geometries involving erupting flux ropes. In 3D, a flux rope can
reconnect either with a surrounding coronal arcade (recently named
“ar-rf” reconnection) or with itself (“rr-rf” reconnection),
and both kinds of reconnection create a new flux-rope field line and a
flare loop. For the first time, we identify all four constituents of
both reconnections in a solar eruptive event, the filament eruption
of 2011 June 7 observed by Solar Dynamics Observatory/Atmospheric
Imaging Assembly. The ar-rf reconnection manifests itself as shift of
one leg of the filament by more than 25″ northward. At its previous
location, a flare arcade is formed, while the new location of the
filament leg previously corresponded to a footpoint of a coronal loop
in 171 Å. In addition, the evolution of the flare ribbon hooks is
also consistent with the occurrence of ar-rf reconnection as predicted
by MHD simulations. Specifically, the growing hook sweeps footpoints
of preeruptive coronal arcades, and these locations become inside the
hook. Furthermore, the rr-rf reconnection occurs during the peak phase
above the flare arcade, in an apparently X-type geometry involving a
pair of converging bright filament strands in the erupting filament. A
new flare loop forms near the leg of one of the strands, while a bright
blob, representing a remnant of the same strand, is seen ascending
into the erupting filament. All together, these observations vindicate
recent predictions of the 3D standard solar-flare model.

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Title: Manifestations of Three-dimensional Magnetic Reconnection
in an Eruption of a Quiescent Filament: Filament Strands Turning to
Flare Loops
Authors: Lörinčík, Juraj; Dudík, Jaroslav; Aulanier, Guillaume
2019ApJ...885...83L Altcode: 2019arXiv190903825L
We report on observations of the conversion of bright filament strands
into flare loops during the 2012 August 31 filament eruption. Prior
to the eruption, individual bright strands composing one of the legs
of the filament were observed in the 171 Å filter channel data of
the Atmospheric Imaging Assembly. After the onset of the eruption,
one of the hooked ribbons started to propagate and contract, sweeping
footpoints of the bright filament strands as well as coronal loops
located close by. Later on, hot flare loops appeared in regions
swept by the hook, where the filament strands were rooted. Timing
and localization of these phenomena suggest that they are caused by
reconnection of field lines composing the filament at the hook, which,
to our knowledge, has not been observed before. This process is not
included in the standard flare model (CSHKP), as it does not address
footpoints of erupting flux ropes and ribbon hooks. It has, however,
been predicted using the recent three-dimensional extensions to the
standard flare model. There, the erupting flux rope can reconnect with
surrounding coronal arcades as the hooked extensions of current ribbons
sweep its footpoints. This process results in formation of flare loops
rooted in previous footpoints of the flux rope. Our observations of
sweeping of filament footpoints are well described by this scenario. In
all observed cases, all of the footpoints of the erupting filament
became footpoints of flare loops. This process was observed to last
for about 150 minutes, throughout the whole eruption.

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Title: Observations of a Footpoint Drift of an Erupting Flux Rope
Authors: Zemanová, Alena; Dudík, Jaroslav; Aulanier, Guillaume;
Thalmann, Julia K.; Gömöry, Peter
2019ApJ...883...96Z Altcode: 2019arXiv190802082Z
We analyze the imaging observations of an M-class eruptive flare of 2015
November 4. The pre-eruptive Hα filament was modeled by the nonlinear
force-free field model, which showed that it consisted of two helical
systems. Tether-cutting reconnection involving these two systems led
to the formation of a hot sigmoidal loop structure rooted in a small
hook that formed at the end of the flare ribbon. Subsequently, the hot
loops started to slip away from the small hook until it disappeared. The
loops continued slipping and the ribbon elongated itself by several
tens of arcseconds. A new and larger hook then appeared at the end of
the elongated ribbon with hot and twisted loops rooted there. After
the eruption of these hot loops, the ribbon hook expanded and later
contracted. We interpret these observations in the framework of
the recent three-dimensional (3D) extensions to the standard solar
flare model predicting the drift of the flux rope footpoints. The hot
sigmoidal loop is interpreted as the flux rope, whose footpoints drift
during the eruption. While the deformation and drift of the new hook can
be described by the model, the displacement of the flux rope footpoint
from the filament to that of the erupting flux rope indicate that the
hook evolution can be more complex than those captured by the model.

---------------------------------------------------------
Title: Velocities of Flare Kernels and the Mapping Norm of Field
Line Connectivity
Authors: Lörinčík, Juraj; Aulanier, Guillaume; Dudík, Jaroslav;
Zemanová, Alena; Dzifčáková, Elena
2019ApJ...881...68L Altcode: 2019arXiv190601880L
We report on observations of flare ribbon kernels during the 2012
August 31 filament eruption. In the 1600 and 304 Å channels of
the Atmospheric Imaging Assembly, flare kernels were observed to
move along flare ribbons at velocities v ∥ of up to
450 km s-1. Kernel velocities were found to be roughly
anticorrelated with strength of the magnetic field. An apparent
slipping motion of the flare loops was observed in the 131 Å only
for the slowest kernels moving through the strong-B region. In order
to interpret the observed relation between B LOS and v
∥, we examined the distribution of the norm N, a quantity
closely related to the slippage velocity. We calculated the norm N of
the quasi-separatrix layers (QSLs) in MHD model of a solar eruption
adapted to the magnetic environment that qualitatively agrees to that
of the observed event. We found that both the modeled N and velocities
of kernels reach their highest values in the same weak-field regions,
one located in the curved part of the ribbon hook and the other in
the straight part of the conjugate ribbon located close to a parasitic
polarity. Contrariwise, lower values of the kernel velocities are seen
at the tip of the ribbon hook, where the modeled N is low. Because the
modeled distribution of N matches the observed dynamics of kernels,
this supports the notion that the kernel motions can be interpreted
as a signature of QSL reconnection during the eruption.

---------------------------------------------------------
Title: Signatures of the non-Maxwellian κ-distributions in optically
thin line spectra. II. Synthetic Fe XVII-XVIII X-ray coronal spectra
and predictions for the Marshall Grazing-Incidence X-ray Spectrometer
(MaGIXS)
Authors: Dudík, Jaroslav; Dzifčáková, Elena; Del Zanna, Giulio;
Mason, Helen E.; Golub, Leon L.; Winebarger, Amy R.; Savage, Sabrina L.
2019A&A...626A..88D Altcode: 2019arXiv190510356D
 Aims: We investigated the possibility of diagnosing the degree of
departure from the Maxwellian distribution using the Fe XVII-Fe XVIII
spectra originating in plasmas in collisional ionization equilibrium,
such as in the cores of solar active regions or microflares. 
Methods: The original collision strengths for excitation are integrated
over the non-Maxwellian electron κ-distributions characterized by a
high-energy tail. Synthetic X-ray emission line spectra were calculated
for a range of temperatures and κ. We focus on the 6-24 Å spectral
range to be observed by the upcoming Marshall Grazing-Incidence X-ray
Spectrometer MaGIXS. Results: We find that many line intensity
ratios are sensitive to both T and κ. Best diagnostic options are
provided if a ratio involving both Fe XVII and Fe XVIII is combined
with another ratio involving lines formed within a single ion. The
sensitivity of such diagnostics to κ is typically a few tens of per
cent. Much larger sensitivity, of about a factor of two to three, can
be obtained if the Fe XVIII 93.93 Å line observed by SDO/AIA is used
in conjuction with the X-ray lines. Conclusions: We conclude
that the MaGIXS instrument is well-suited for detection of departures
from the Maxwellian distribution, especially in active region cores.

---------------------------------------------------------
Title: Drifting of the line-tied footpoints of CME flux-ropes
Authors: Aulanier, Guillaume; Dudík, Jaroslav
2019A&A...621A..72A Altcode: 2018arXiv181104253A
Context. Bridging the gap between heliospheric and solar observations
of eruptions requires the mapping of interplanetary coronal mass
ejection (CME) footpoints down to the Sun's surface. But this not
straightforward. Improving the understanding of the spatio-temporal
evolutions of eruptive flares requires a comprehensive standard
model. But the current model is only two-dimensional and cannot
address the question of interplanetary CME footpoints. Aims:
Existing 3D extensions to the standard model show that flux-rope
footpoints are surrounded by curved-shaped quasi-separatrix layer (QSL)
footprints that can be related with hook-shaped flare-ribbons. We
build upon this finding and further address the joint questions of
their time-evolution, and of the formation of flare loops at the
ends of the flaring polarity inversion line (PIL) of the erupting
bipole, which are both relevant for flare understanding in general
and for interplanetary CME studies in particular. Methods:
We calculated QSLs and relevant field lines in an MHD simulation of a
torus-unstable flux-rope. The evolving QSL footprints are used to define
the outer edge of the flux rope at different times, and to identify and
characterize new 3D reconnection geometries and sequences that occur
above the ends of the flaring PIL. We also analyzed flare-ribbons as
observed in the extreme ultraviolet by SDO/AIA and IRIS during two
X-class flares. Results: The flux-rope footpoints are drifting
during the eruption, which is unexpected due to line-tying. This
drifting is due to a series of coronal reconnections that erode the
flux rope on one side and enlarge it on the other side. Other changes
in the flux-rope footpoint-area are due to multiple reconnections
of individual field lines whose topology can evolve sequentially from
arcade to flux rope and finally to flare loop. These are associated with
deformations and displacements of QSL footprints, which resemble those
of the studied flare ribbons. Conclusions: Our model predicts
continuous deformations and a drifting of interplanetary CME flux-rope
footpoints whose areas are surrounded by equally evolving hooked-shaped
flare-ribbons, as well as the formation of flare loops at the ends of
flaring PILs which originate from the flux-rope itself, both of which
being due to purely three-dimensional reconnection geometries. The
observed evolution of flare-ribbons in two events supports the model,
but more observations are required to test all its predictions.

---------------------------------------------------------
Title: Fast velocities of flare ribbon kernels and ribbon elongation
in a quescent filament eruption of 2012 August 31 observed by SDO/AIA
Authors: Lörinčík, Juraj; Dudík, Jaroslav; Kašparová, Jana;
Aulanier, Guillaume; Zemanová, Alena; Dzifčáková, Elena
2018csc..confE..63L Altcode:
We report on SDO observations of an eruption of a quiescent filament
from 2012 August 31. In the 1600 Å filter channel of AIA, flare
ribbons were observed to elongate at velocities up to 480 km s^{-1}
and flare kernels move along a ribbon at velocity of ≈ 260 km
s^{-1}. In order to investigate the emission observed in the 1600 Å
channel, we used synthetic spectra modeled using CHIANTI and RADYN
models of flare atmospheres with beam parameters constrained using
fits of RHESSI spectra. We found out that depending on parameters of
heating of a flare model, thickness of a region where the emission
of the 1600 Å filter channel originates ranges between 10^{-2} and
10^{2} km. Information on dimensions of the formation region were
then utilized to estimate densities in flare ribbons using inversions
of the emission measure. These were found to range between 10^{10} -
4.10^{12} cm^{-3} for flare atmospheres heated by beams of different
parameters. Together with B_{LOS} data from SDO/HMI, diagnosed densities
were used to calculate Alfvén velocities in observed ribbons. These
can be as small as 17 km s^{-1} for flare ribbons observed in region of
weak magnetic field at latter stages of heating. This finding suggests
that elongation of ribbons and motion of kernels might not be related
to waves. Motions along the PIL are well-described in the 3D model of
solar eruptions of Aulanier et al. 2013 (A&amp;A, 543, 110). However,
EUV observations of flare loops revealed that velocity of their apparent
slipping motion is much lower than velocity of elongation of a ribbon,
which is observed in a close vicinity. Therefore, observed phenomena can
not be directly related to super-Alvénic regime of magnetic slipping
reconnection introduced in the 3D model.

---------------------------------------------------------
Title: The nature of imploding loops during solar eruptions as
revealed by MHD simulations and AIA observations
Authors: Aulanier, Guillaume; Dudik, Jaroslav; Zucarello, F. P.;
Demoulin, Pascal; Schmieder, Brigitte
2018csc..confE..19A Altcode:
Over the last years AIA revealed the frequent occurence of contracting
loops at the flanks of erupting active regions. Those have often
been interpreted as an evidence of the implosion conjecture that
relates magnetic energy decreases with volume contractions in the Sun's
corona. So as to unveil the physical nature of these features we carried
out observational analyses of two solar eruptions observed with AIA with
different projection angles, which we coupled with new analyses of a
generic zero-beta MHD simulation of an asymmetric eruption driven by the
torus instability, that was not designed for this particular study. The
simulation does display contracting loops in general. And the synthetic
time-slices of the simulation, when rotated to the right projections,
do match the observed ones. But in the simulation these inward motions
are not due to any volume contraction. Instead they are associated
with two large-scale quasi-incompressible coronal-vortices. Those
develop at the flanks of the erupting flux ropes, as most of the
compressive component of the flow is evacuated away by an Alfven wave
in the early stages of the eruption. We argue that this behavior is
merely a magnetic version of the usual pressure-driven formation of
vortex rings in hydrodyanmics. This result implies that during a solar
eruption, the free magnetic-energy from the pre-erupting active-region
is converted not only in the flare and the CME, but is also "lost"
in the generation of these two large-scale coronal vortices.

---------------------------------------------------------
Title: Importance of the Hα Visibility and Projection Effects for
the Interpretation of Prominence Fine-structure Observations
Authors: Gunár, Stanislav; Dudík, Jaroslav; Aulanier, Guillaume;
Schmieder, Brigitte; Heinzel, Petr
2018ApJ...867..115G Altcode:
We construct a new 3D Whole-prominence Fine-structure (WPFS) model based
on a prominence magnetic field configuration designed to qualitatively
approximate the morphology of a quiescent prominence observed on 2010
June 22. The model represents an entire prominence with its numerous
fine structures formed by a prominence plasma located in dips in
the prominence magnetic field. We use the constructed 3D model and
employ a radiative-transfer-based Hα visualization method to analyze
the Hα visibility of prominence fine structures and its effect
on the perceived morphology of observed and modeled prominences. We
qualitatively compare three techniques used for visualization of modeled
prominences—visualizations drawing magnetic dips up to a height of
1 pressure scale height, drawing the full extent of magnetic dips,
and the synthetic Hα visualization—and discuss their suitability
for direct comparison between models and observations of prominences
and filaments. We also discuss the role of visibility of the prominence
fine structures in the estimation of the total height of prominences,
which may indicate the height of pre-erupting flux ropes. This
parameter is critical for the observational determination of the
flux-rope stability. In addition, we employ the WPFS model to assess
the effects caused by a projection of the naturally three-dimensional
and heterogeneous prominences onto a two-dimensional plane of the
sky. We discuss here how the morphological structures of prominences
differ when observed in projections from different viewing angles. We
also discuss the shapes of the dipped magnetic field lines and the
perceived projection of motions of prominence fine structures along
such field lines.

---------------------------------------------------------
Title: Broad Non-Gaussian Fe XXIV Line Profiles in the Impulsive
Phase of the 2017 September 10 X8.3-class Flare Observed by Hinode/EIS
Authors: Polito, Vanessa; Dudík, Jaroslav; Kašparová, Jana;
Dzifčáková, Elena; Reeves, Katharine K.; Testa, Paola; Chen, Bin
2018ApJ...864...63P Altcode: 2018arXiv180709361P
We analyze the spectra of high-temperature Fe XXIV lines observed by
the Hinode/Extreme-Ultraviolet Imaging Spectrometer (EIS) during the
impulsive phase of the X8.3-class flare on 2017 September 10. The
line profiles are broad, show pronounced wings, and clearly depart
from a single-Gaussian shape. The lines can be well fitted with κ
distributions, with values of κ varying between ≈1.7 and 3. The
regions where we observe the non-Gaussian profiles coincide with
the location of high-energy (≈100-300 keV) hard X-ray (HXR) sources
observed by RHESSI, suggesting the presence of particle acceleration or
turbulence, also confirmed by the observations of nonthermal microwave
sources with the Expanded Owens Valley Solar Array at and above the HXR
loop-top source. We also investigate the effect of taking into account
κ distributions in the temperature diagnostics based on the ratio of
the Fe XXIII λ263.76 and Fe XXIV λ255.1 EIS lines. We found that
these lines can be formed at much higher temperatures than expected
(up to log(T[K]) ≈ 7.8) if departures from Maxwellian distributions
are taken into account. Although larger line widths are expected because
of these higher formation temperatures, the observed line widths still
imply nonthermal broadening in excess of 200 km s-1. The
nonthermal broadening related to HXR emission is better interpreted
by turbulence than by chromospheric evaporation.

---------------------------------------------------------
Title: Signature of flux ropes before and after eruptions: electric
currents in active regions
Authors: Schmieder, Brigitte; Aulanier, Guillaume; Dalmasse, Kévin;
Janvier, Miho; Gilchrist, Stuart; Zhao, Jie; Dudik, Jaroslav
2018cosp...42E3026S Altcode:
Solar observations, nonlinear force-free field extrapolations relying
on these observations, and three-dimensional magnetohydrodynamic (MHD)
models indicate the presence of electric currents in the pre-eruption
state and in the course of eruptions of solar magnetic structures which
are interpreted as flux ropes (sigmoids, filaments, cavities).The MHD
models are able to explain the net currents in active regions by the
existence of strong magnetic shear along the polarity inversion lines,
thus confirming previous observations. The models have also captured
the essence of the behavior of electric currents in active regions
during solar eruptions, predicting current-density increases and
decreases inside flare ribbons and in the interior of expanding flux
ropes, respectively.The observed photospheric current-density maps,
inferred from vector magnetic field observations, exhibit whirling
ribbon patterns similar to the MHD model results, which are interpreted
as the signatures of flux ropes and of quasi-separatrix layers (QSLs)
between the magnetic systems in active regions. We will show how
observations can confirm enhancement of the total current in these
QSLs during the eruptions, and how these observations can be used
to investigate whether current density decrease can be seen at the
footpoints of erupting flux ropes

---------------------------------------------------------
Title: Can 3D whole-prominence fine structure models be used for
assessment of the prominence plasma mass and distribution prior to
the onset of CMEs?
Authors: Gunár, Stanislav; Schmieder, Brigitte; Aulanier, Guillaume;
Anzer, Ulrich; Heinzel, Petr; Mackay, Duncan; Dudik, Jaroslav
2018cosp...42E1316G Altcode:
Two complex 3D models of entire prominences including their numerous
fine structures were recently developed. The first 3D Whole-Prominence
Fine Structure (WPFS) model was developed by Gunár and Mackay. The
second 3D WPFS model was put forward by Gunár, Aulanier, Dudík,
Heinzel, and Schmieder. These 3D prominence models combine simulations
of the 3D magnetic field configuration of an entire prominence with a
detailed description of the prominence plasma. The plasma is located
in magnetic dips in hydrostatic equilibrium and is distributed
along hundreds of fine structures. The assumed prominence plasma
has realistic density and temperature distributions including the
prominence-corona transition region.These 3D WPFS models allow us
to study the distribution and the mass of the prominence plasma
contained in prominence magnetic field configurations. These can
be crucial during the onset and early evolution of CMEs. Moreover,
prominence plasma represents a bulk of the material ejected by CMEs
into the interplanetary space. Here, we investigate the potential of
using the 3D WPFS models for assessment of the role the prominence
plasma plays in the initiation and evolution of CMEs.

---------------------------------------------------------
Title: Broad Non-Gaussian fe XXIV Line Profiles in the Impulsive
Phase of the 2017 September 10 X8.3-CLASS Flare Observed by Hinode/eis
Authors: Polito, Vanessa; Dudik, Jaroslav; Kasparova, Jana; Dzifcakova,
Elena; Reeves, Katharine K.; Testa, Paola; Chen, Bin
2018shin.confE.212P Altcode:
We analyze the spectra of high temperature Fe XXIV lines observed by
Hinode/EIS during the impulsive phase the X8.3-class flare on September
10, 2017. The line profiles are broad, show pronounced wings, and
clearly depart from a single Gaussian shape. The lines can be well
fitted with the ? distributions, with values of ? varying between
?1.7 to 3. The region where we observe the non-Gaussian profiles
coincides with the location of high-energy (?100-300 keV) HXR sources
observed by RHESSI, suggesting the presence of particle acceleration
or turbulence, also confirmed by the observations of a non-thermal
microwave sources with EOVSA at and above the HXR looptop source. We
also investigate the effect of taking into account ? distributions in
the temperature diagnostics based on the ratio of the Fe XXIII 263.76
?A and Fe XXIV 255.1 ?A EIS lines. We found that these lines can be
formed at much higher temperatures than expected (up to log(T [K])
? 7.8), if departures from Maxwellian distributions are taken into
account. Although larger line widths are expected because of these
higher formation temperatures, the observed line widths still imply
non-thermal broadening in excess of 200kms?1.

---------------------------------------------------------
Title: Non-equilibrium ionization by a periodic electron
beam. II. Synthetic Si IV and O IV transition region spectra
Authors: Dzifčáková, Elena; Dudík, Jaroslav
2018A&A...610A..67D Altcode: 2017arXiv171106653D
Context. Transition region (TR) spectra typically show the Si IV
1402.8 Å line to be enhanced by a factor of 5 or more compared
to the neighboring O IV 1401.2 Å, contrary to predictions of
ionization equilibrium models and the Maxwellian distribution
of particle energies. Non-equilibrium effects in TR spectra are
therefore expected. Aims: To investigate the combination of
non-equilibrium ionization and high-energy particles, we apply the
model of the periodic electron beam, represented by a κ-distribution
that recurs at periods of several seconds, to plasma at chromospheric
temperatures of 104 K. This simple model can approximate
a burst of energy release involving accelerated particles. 
Methods: Instantaneous time-dependent charge states of silicon and
oxygen were calculated and used to synthesize the instantaneous and
period-averaged spectra of Si IV and O IV. Results: The electron
beam drives the plasma out of equilibrium. At electron densities of
Ne = 1010 cm-3, the plasma is out
of ionization equilibrium at all times in all cases we considered,
while for a higher density of Ne = 1011
cm-3, ionization equilibrium can be reached toward the end
of each period, depending on the conditions. In turn, the character of
the period-averaged synthetic spectra also depends on the properties
of the beam. While the case of κ = 2 results in spectra with strong
or even dominant O IV, higher values of κ can approximate a range of
observed TR spectra. Spectra similar to typically observed spectra,
with the Si IV 1402.8 Å line about a factor 5 higher than O IV 1401.2
Å, are obtained for κ = 3. An even higher value of κ = 5 results
in spectra that are exclusively dominated by Si IV, with negligible
O IV emission. This is a possible interpretation of the TR spectra
of UV (Ellerman) bursts, although an interpretation that requires a
density that is 1-3 orders of magnitude lower than for equilibrium
estimates. Movies associated to Fig. A.1 are available at <A
href="https://www.aanda.org/10.1051/0004-6361/201731744/olm">https://www.aanda.org</A>

---------------------------------------------------------
Title: Solar Radio Burst Associated with the Falling Bright EUV Blob
Authors: Karlický, Marian; Zemanová, Alena; Dudík, Jaroslav;
Radziszewski, Krzysztof
2018ApJ...854L..29K Altcode: 2018arXiv180406206K
At the beginning of the 2015 November 4 flare, in the 1300-2000 MHz
frequency range, we observed a very rare slow positively drifting
burst. We searched for associated phenomena in simultaneous EUV
observations made by IRIS, SDO/AIA, and Hinode/XRT, as well as in H
α observations. We found that this radio burst was accompanied
with the bright blob, visible at transition region, coronal, and flare
temperatures, falling down to the chromosphere along the dark loop with
a velocity of about 280 km s-1. The dark loop was visible
in H α but disappeared afterward. Furthermore, we found
that the falling blob interacted with the chromosphere as expressed
by a sudden change of the H α spectra at the location
of this interaction. Considering different possibilities, we propose
that the observed slow positively drifting burst is generated by the
thermal conduction front formed in front of the falling hot EUV blob.

---------------------------------------------------------
Title: Spectroscopic Diagnostics of the Non-Maxwellian
κ-distributions Using SDO/EVE Observations of the 2012 March 7
X-class Flare
Authors: Dzifčáková, Elena; Zemanová, Alena; Dudík, Jaroslav;
Mackovjak, Šimon
2018ApJ...853..158D Altcode: 2018arXiv180102936D
Spectroscopic observations made by the Extreme Ultraviolet Variability
Experiment (EVE) on board the Solar Dynamics Observatory (SDO) during
the 2012 March 7 X5.4-class flare (SOL2012-03-07T00:07) are analyzed for
signatures of the non-Maxwellian κ-distributions. Observed spectra were
averaged over 1 minute to increase photon statistics in weaker lines
and the pre-flare spectrum was subtracted. Synthetic line intensities
for the κ-distributions are calculated using the KAPPA database. We
find strong departures (κ ≲ 2) during the early and impulsive phases
of the flare, with subsequent thermalization of the flare plasma during
the gradual phase. If the temperatures are diagnosed from a single line
ratio, the results are strongly dependent on the value of κ. For κ =
2, we find temperatures about a factor of two higher than the commonly
used Maxwellian ones. The non-Maxwellian effects could also cause the
temperatures diagnosed from line ratios and from the ratio of GOES X-ray
channels to be different. Multithermal analysis reveals the plasma to
be strongly multithermal at all times with flat DEMs. For lower κ,
the {{DEM}}κ are shifted toward higher temperatures. The
only parameter that is nearly independent of κ is electron density,
where we find log({n}{{e}} [{{cm}}-3]) ≈ 11.5
almost independently of time. We conclude that the non-Maxwellian
effects are important and should be taken into account when analyzing
solar flare observations, including spectroscopic and imaging ones.

---------------------------------------------------------
Title: Nonequilibrium Processes in the Solar Corona, Transition
Region, Flares, and Solar Wind (Invited Review)
Authors: Dudík, Jaroslav; Dzifčáková, Elena; Meyer-Vernet, Nicole;
Del Zanna, Giulio; Young, Peter R.; Giunta, Alessandra; Sylwester,
Barbara; Sylwester, Janusz; Oka, Mitsuo; Mason, Helen E.; Vocks,
Christian; Matteini, Lorenzo; Krucker, Säm; Williams, David R.;
Mackovjak, Šimon
2017SoPh..292..100D Altcode: 2017arXiv170603396D
We review the presence and signatures of the non-equilibrium processes,
both non-Maxwellian distributions and non-equilibrium ionization, in
the solar transition region, corona, solar wind, and flares. Basic
properties of the non-Maxwellian distributions are described
together with their influence on the heat flux as well as on the
rates of individual collisional processes and the resulting optically
thin synthetic spectra. Constraints on the presence of high-energy
electrons from observations are reviewed, including positive detection
of non-Maxwellian distributions in the solar corona, transition
region, flares, and wind. Occurrence of non-equilibrium ionization
is reviewed as well, especially in connection to hydrodynamic and
generalized collisional-radiative modeling. Predicted spectroscopic
signatures of non-equilibrium ionization depending on the assumed
plasma conditions are summarized. Finally, we discuss the future
remote-sensing instrumentation that can be used for the detection of
these non-equilibrium phenomena in various spectral ranges.

---------------------------------------------------------
Title: Expanding and Contracting Coronal Loops as Evidence of Vortex
Flows Induced by Solar Eruptions
Authors: Dudík, J.; Zuccarello, F. P.; Aulanier, G.; Schmieder, B.;
Démoulin, P.
2017ApJ...844...54D Altcode: 2017arXiv170604783D
Eruptive solar flares were predicted to generate large-scale vortex
flows at both sides of the erupting magnetic flux rope. This process
is analogous to a well-known hydrodynamic process creating vortex
rings. The vortices lead to advection of closed coronal loops located
at the peripheries of the flaring active region. Outward flows are
expected in the upper part and returning flows in the lower part of the
vortex. Here, we examine two eruptive solar flares, the X1.1-class flare
SOL2012-03-05T03:20 and the C3.5-class SOL2013-06-19T07:29. In both
flares, we find that the coronal loops observed by the Atmospheric
Imaging Assembly in its 171 Å, 193 Å, or 211 Å passbands show
coexistence of expanding and contracting motions, in accordance with
the model prediction. In the X-class flare, multiple expanding and
contracting loops coexist for more than 35 minutes, while in the C-class
flare, an expanding loop in 193 Å appears to be close by and cotemporal
with an apparently imploding loop arcade seen in 171 Å. Later, the 193
Å loop also switches to contraction. These observations are naturally
explained by vortex flows present in a model of eruptive solar flares.

---------------------------------------------------------
Title: Synthetic IRIS spectra of the solar transition region: Effect
of high-energy tails
Authors: Dzifčáková, E.; Vocks, C.; Dudík, J.
2017A&A...603A..14D Altcode: 2017arXiv170508728D
 Aims: The solar transition region satisfies the conditions
for presence of non-Maxwellian electron energy distributions with
high-energy tails at energies corresponding to the ionization
potentials of many ions emitting in the extreme-ultraviolet and
ultraviolet portions of the spectrum. Methods: We calculate the
synthetic Si iv, O iv, and S iv spectra in the far ultraviolet channel
of the Interface Region Imaging Spectrograph (IRIS). Ionization,
recombination, and excitation rates are obtained by integration of
the cross-sections or their approximations over the model electron
distributions considering particle propagation from the hotter
corona. Results: The ionization rates are significantly affected
by the presence of high-energy tails. This leads to the peaks of the
relative abundance of individual ions to be broadened with pronounced
low-temperature shoulders. As a result, the contribution functions
of individual lines observable by IRIS also exhibit low-temperature
shoulders, or their peaks are shifted to temperatures an order of
magnitude lower than for the Maxwellian distribution. The integrated
emergent spectra can show enhancements of Si iv compared to O iv by more
than a factor of two. Conclusions: The high-energy particles can
have significant impact on the emergent spectra and their presence needs
to be considered even in situations without strong local acceleration.

---------------------------------------------------------
Title: Non-Maxwellian Analysis of the Transition-region Line Profiles
Observed by the Interface Region Imaging Spectrograph
Authors: Dudík, Jaroslav; Polito, Vanessa; Dzifčáková, Elena;
Del Zanna, Giulio; Testa, Paola
2017ApJ...842...19D Altcode: 2017arXiv170502104D
We investigate the nature of the spectral line profiles for
transition-region (TR) ions observed with the Interface Region Imaging
Spectrograph (IRIS). In this context, we analyzed an active-region
observation performed by IRIS in its 1400 Å spectral window. The TR
lines are found to exhibit significant wings in their spectral profiles,
which can be well fitted with a non-Maxwellian κ distribution. The fit
with a κ distribution can perform better than a double-Gaussian fit,
especially for the strongest line, Si IV 1402.8 Å. Typical values of κ
found are about 2, occurring in a majority of spatial pixels where the
TR lines are symmetric, I.e., the fit can be performed. Furthermore,
all five spectral lines studied (from Si IV, O IV, and S IV) appear
to have the same full-width at half-maximum irrespective of whether
the line is an allowed or an intercombination transition. A similar
value of κ is obtained for the electron distribution by the fitting
of the line intensities relative to Si IV 1402.8 Å, if photospheric
abundances are assumed. The κ distributions, however, do not remove
the presence of non-thermal broadening. Instead, they actually increase
the non-thermal width. This is because, for κ distributions, TR ions
are formed at lower temperatures. The large observed non-thermal width
lowers the opacity of the Si IV line sufficiently enough for this line
to become optically thin.

---------------------------------------------------------
Title: Analysis and modelling of recurrent solar flares observed
with Hinode/EIS on March 9, 2012
Authors: Polito, V.; Del Zanna, G.; Valori, G.; Pariat, E.; Mason,
H. E.; Dudík, J.; Janvier, M.
2017A&A...601A..39P Altcode: 2016arXiv161203504P
Three homologous C-class flares and one last M-class flare were observed
by both the Solar Dynamics Observatory (SDO) and the Hinode EUV Imaging
Spectrometer (EIS) in the AR 11429 on March 9, 2012. All the recurrent
flares occurred within a short interval of time (less than 4 h),
showed very similar plasma morphology and were all confined, until the
last one when a large-scale eruption occurred. The C-class flares are
characterized by the appearance, at approximatively the same locations,
of two bright and compact footpoint sources of ≈3-10 MK evaporating
plasma, and a semi-circular ribbon. During all the flares, the
continuous brightening of a spine-like hot plasma (≈10 MK) structure
is also observed. Spectroscopic observations with Hinode/EIS are used to
measure and compare the blueshift velocities in the Fe xxiii emission
line and the electron number density at the flare footpoints for each
flare. Similar velocities, of the order of 150-200 km s-1,
are observed during the C2.0 and C4.7 confined flares, in agreement
with the values reported by other authors in the study of the last M1.8
class flare. On the other hand, lower electron number densities and
temperatures tend to be observed in flares with lower peak soft X-ray
flux. In order to investigate the homologous nature of the flares, we
performed a non-linear force-free field (NLFFF) extrapolation of the 3D
magnetic field configuration in the corona. The NLFFF extrapolation and
the Quasi-Separatrix Layers (QSLs) provide the magnetic field context
which explains the location of the kernels, spine-like hot plasma and
semi-circular brightenings observed in the (non-eruptive) flares. Given
the absence of a coronal null point, we argue that the homologous
flares were all generated by the continuous recurrence of bald patch
reconnection. The movie associated to Fig. 2 is available at <A
href="http://www.aanda.org/10.1051/0004-6361/201629703/olm">http://www.aanda.org</A>

---------------------------------------------------------
Title: Vortex and Sink Flows in Eruptive Flares as a Model for
Coronal Implosions
Authors: Zuccarello, F. P.; Aulanier, G.; Dudík, J.; Démoulin, P.;
Schmieder, B.; Gilchrist, S. A.
2017ApJ...837..115Z Altcode: 2017arXiv170200199Z
Eruptive flares are sudden releases of magnetic energy that
involve many phenomena, several of which can be explained by the
standard 2D flare model and its realizations in 3D. We analyze a 3D
magnetohydrodynamics simulation, in the framework of this model, that
naturally explains the contraction of coronal loops in the proximity
of the flare sites, as well as the inflow toward the region above the
cusp-shaped loops. We find that two vorticity arcs located along the
flanks of the erupting magnetic flux rope are generated as soon as the
eruption begins. The magnetic arcades above the flux rope legs are then
subjected to expansion, rotation, or contraction depending on which
part of the vortex flow advects them. In addition to the vortices,
an inward-directed magnetic pressure gradient exists in the current
sheet below the magnetic flux rope. It results in the formation of a
sink that is maintained by reconnection. We conclude that coronal loop
apparent implosions observed during eruptive flares are the result
of hydromagnetic effects related to the generation of vortex and sink
flows when a flux rope moves in a magnetized environment.

---------------------------------------------------------
Title: Can the non-Maxwellian kappa-distributions be diagnosed in
the solar corona?
Authors: Dudík, J.; Dzifcakova, E.; Del Zanna, G.; Mackovjak, Š.;
Mason, H. E.
2016AGUFMSH21D2555D Altcode:
We report on the search of signatures of the non-Maxwellian
kappa-distributions in the emission line spectra of the solar
corona. A survey of coronal lines is performed for single-ion and
multi-ion diagnostics using ions spanning the temperature range of
0.5 - 6 MK. State-of-art excitation cross-sections are integrated
directly to obtain the corresponding non-Maxwellian excitation and
deexcitation rates. Ionization and recombination rates are obtained by
approximative methods. We find that there are only a few good diagnostic
options. This is due to majority of lines being formed from similar
energy levels. The best diagnostic options rely on lines formed at
different excitation tresholds, i.e., at different wavelengths. This
highlights the importance of absolute intensity calibration of
space-borne spectrometers. The applicability of these methods is
demonstrated on analysis of a dedicated extreme-ultraviolet observations
made in the Fe XI-XIII lines by the Hinode/EIS satellite during HOP
226. The observations are performed in an active region containing a
filament and several coronal loops. A transient coronal loop appears
at the foot of a filament and is preceded by activity within this
filament. EIS spectra are used to diagnose the electron density,
but also reveal that the transient loop is highly non-Maxwellian,
characterized by a kappa=2 distribution. We discuss the methods for
separation the non-Maxwellian effects from the effects of plasma
multi-thermality arising due to finite spatial resolution, as well
as the effect of kappa-distributions on the degree of multithermality
diagnosed in various observed coronal features.

---------------------------------------------------------
Title: Slipping reconnection in a solar flare observed in high
resolution with the GREGOR solar telescope
Authors: Sobotka, M.; Dudík, J.; Denker, C.; Balthasar, H.; Jurčák,
J.; Liu, W.; Berkefeld, T.; Collados Vera, M.; Feller, A.; Hofmann,
A.; Kneer, F.; Kuckein, C.; Lagg, A.; Louis, R. E.; von der Lühe, O.;
Nicklas, H.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Sigwarth,
M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier, K. G.;
Volkmer, R.; Waldmann, T.
2016A&A...596A...1S Altcode: 2016arXiv160500464S
A small flare ribbon above a sunspot umbra in active region 12205 was
observed on November 7, 2014, at 12:00 UT in the blue imaging channel
of the 1.5 m GREGOR telescope, using a 1 Å Ca II H interference
filter. Context observations from the Atmospheric Imaging Assembly
(AIA) onboard the Solar Dynamics Observatory (SDO), the Solar Optical
Telescope (SOT) onboard Hinode, and the Interface Region Imaging
Spectrograph (IRIS) show that this ribbon is part of a larger one
that extends through the neighboring positive polarities and also
participates in several other flares within the active region. We
reconstructed a time series of 140 s of Ca II H images by means of the
multiframe blind deconvolution method, which resulted in spatial and
temporal resolutions of 0.1″ and 1 s. Light curves and horizontal
velocities of small-scale bright knots in the observed flare ribbon
were measured. Some knots are stationary, but three move along the
ribbon with speeds of 7-11 km s-1. Two of them move in the
opposite direction and exhibit highly correlated intensity changes,
which provides evidence of a slipping reconnection at small spatial
scales. Movies associated to Figs. 1 and 2 are available at <A
href="http://www.aanda.org/10.1051/0004-6361/201527966/olm">http://www.aanda.org</A>

---------------------------------------------------------
Title: Density diagnostics derived from the O iv and S iv
intercombination lines observed by IRIS
Authors: Polito, V.; Del Zanna, G.; Dudík, J.; Mason, H. E.; Giunta,
A.; Reeves, K. K.
2016A&A...594A..64P Altcode: 2016arXiv160705072P
The intensity of the O iv 2s2 2p
2P-2s2p24P and S iv 3 s2
3p 2P-3s 3p24 P intercombination lines
around 1400 Å observed with the Interface Region Imaging Spectrograph
(IRIS) provide a useful tool to diagnose the electron number density
(Ne) in the solar transition region plasma. We measure the
electron number density in a variety of solar features observed by
IRIS, including an active region (AR) loop, plage and brightening,
and the ribbon of the 22-June-2015 M 6.5 class flare. By using the
emissivity ratios of O iv and S iv lines, we find that our observations
are consistent with the emitting plasma being near isothermal
(logT[K] ≈ 5) and iso-density (Ne ≈ 1010.6
cm-3) in the AR loop. Moreover, high electron number
densities (Ne ≈ 1013 cm-3) are
obtained during the impulsive phase of the flare by using the S iv line
ratio. We note that the S iv lines provide a higher range of density
sensitivity than the O iv lines. Finally, we investigate the effects
of high densities (Ne ≳ 1011 cm-3)
on the ionization balance. In particular, the fractional ion
abundances are found to be shifted towards lower temperatures for
high densities compared to the low density case. We also explored the
effects of a non-Maxwellian electron distribution on our diagnostic
method. The movie associated to Fig. 3 is available at <A
href="http://www.aanda.org/10.1051/0004-6361/201628965/olm">http://www.aanda.org</A>

---------------------------------------------------------
Title: Evidence of flux rope and sigmoid in Active Regions prior
eruptions
Authors: Schmieder, Brigitte; Aulanier, Guillaume; Janvier, Miho;
Bommier, Veronique; Dudik, Jaroslav; Gilchrist, Stuart; Zhao, Jie
2016cosp...41E1750S Altcode:
In the solar corona, the magnetic field is dominant, and the current
density vector is nearly aligned with the magnetic field lines
for strong and stressed field regions. Stressed and highly twisted
flux ropes are at the origin of eruptive events such as flares and
coronal mass ejections, which inject material into the interplanetary
medium. The standard three dimensional (3D) flare model predicts
the complex evolution of flare loops and the flux rope before
the eruption. Flux ropes are not directly observed in the corona,
however it has started to be possible to detect their footprints
in the photosphere. Recent high spatial and temporal resolution
spectro-polarimeters have allowed us to compute the photospheric
electric currents and follow their evolution. Characteristics pattern
like J-shaped ribbons indicate the presence of a flux rope before
the flare. The results confirm the predictions of the 3D MHD standard
model of eruptive flares. It is interesting to compare the magnetic
helicity of the ejected flux rope with the in situ measurements of the
corresponding ICME at L1. We will show some examples (February 15 2011,
July 12 2012, Sept 10 2014).

---------------------------------------------------------
Title: Slipping Magnetic Reconnection, Chromospheric Evaporation,
Implosion, and Precursors in the 2014 September 10 X1.6-Class
Solar Flare
Authors: Dudík, Jaroslav; Polito, Vanessa; Janvier, Miho; Mulay,
Sargam M.; Karlický, Marian; Aulanier, Guillaume; Del Zanna, Giulio;
Dzifčáková, Elena; Mason, Helen E.; Schmieder, Brigitte
2016ApJ...823...41D Altcode: 2016arXiv160306092D
We investigate the occurrence of slipping magnetic reconnection,
chromospheric evaporation, and coronal loop dynamics in the 2014
September 10 X-class flare. Slipping reconnection is found to be present
throughout the flare from its early phase. Flare loops are seen to slip
in opposite directions toward both ends of the ribbons. Velocities
of 20-40 km s-1 are found within time windows where the
slipping is well resolved. The warm coronal loops exhibit expanding and
contracting motions that are interpreted as displacements due to the
growing flux rope that subsequently erupts. This flux rope existed and
erupted before the onset of apparent coronal implosion. This indicates
that the energy release proceeds by slipping reconnection and not via
coronal implosion. The slipping reconnection leads to changes in the
geometry of the observed structures at the Interface Region Imaging
Spectrograph slit position, from flare loop top to the footpoints in
the ribbons. This results in variations of the observed velocities of
chromospheric evaporation in the early flare phase. Finally, it is found
that the precursor signatures, including localized EUV brightenings as
well as nonthermal X-ray emission, are signatures of the flare itself,
progressing from the early phase toward the impulsive phase, with
the tether-cutting being provided by the slipping reconnection. The
dynamics of both the flare and outlying coronal loops is found to be
consistent with the predictions of the standard solar flare model in
three dimensions.

---------------------------------------------------------
Title: Non-equilibrium ionization by a periodic electron
beam. I. Synthetic coronal spectra and implications for interpretation
of observations
Authors: Dzifčáková, E.; Dudík, J.; Mackovjak, Š.
2016A&A...589A..68D Altcode: 2016arXiv160304256D
Context. Coronal heating is currently thought to proceed via the
mechanism of nanoflares, small-scale and possibly recurring heating
events that release magnetic energy. Aims: We investigate
the effects of a periodic high-energy electron beam on the synthetic
spectra of coronal Fe ions. Methods: Initially, the coronal
plasma is assumed to be Maxwellian with a temperature of 1 MK. The
high-energy beam, described by a κ-distribution, is then switched
on every period P for the duration of P/ 2. The periods are on
the order of several tens of seconds, similar to exposure times or
cadences of space-borne spectrometers. Ionization, recombination,
and excitation rates for the respective distributions are used
to calculate the resulting non-equilibrium ionization state of Fe
and the instantaneous and period-averaged synthetic spectra. Results: Under the presence of the periodic electron beam, the
plasma is out of ionization equilibrium at all times. The resulting
spectra averaged over one period are almost always multithermal if
interpreted in terms of ionization equilibrium for either a Maxwellian
or a κ-distribution. Exceptions occur, however; the EM-loci curves
appear to have a nearly isothermal crossing-point for some values
of κs. The instantaneous spectra show fast changes in
intensities of some lines, especially those formed outside of the peak
of the respective EM(T) distributions if the ionization equilibrium
is assumed. Movies 1-5 are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201527557/olm">http://www.aanda.org</A>

---------------------------------------------------------
Title: Erratum: Erratum to: Ionisation Equilibrium for the
Non-Maxwellian Electron n-Distributions in Solar Flares: Updated
Calculations
Authors: Dzifčáková, Elena; Dudík, Jaroslav
2016SoPh..291..729D Altcode: 2016SoPh..tmp...11D
No abstract at ADS

---------------------------------------------------------
Title: GREGOR observations of a small flare above a sunspot
Authors: Sobotka, M.; Dudík, J.; Denker, C.; Balthasar, H.; Jurčák,
J.; Liu, W.
2016IAUS..320...68S Altcode:
A small flare ribbon above a sunspot umbra in active region 12205 was
observed on November 7, 2014, at 12:00 UT in the blue imaging channel
of the 1.5-m GREGOR telescope, using a 0.1 nm Ca II H interference
filter. Context observations from SDO/AIA, Hinode/SOT, and IRIS show
that the ribbon is a part of a larger one that extends through the
neighboring positive polarities and also participates in several
other flares within the active region. A 140 second long time series
of Ca II H images was reconstructed by means of the Multi-Frame
Blind Deconvolution method, giving the respective spatial and
temporal resolutions of 0”.1 and 1 s. Light curves and horizontal
velocities of small-scale bright knots in the observed flare ribbon
were measured. Some knots are stationary but three move along the
ribbon with speeds of 7-11 km s-1. Two of them move in the
opposite direction and exhibit highly correlated intensity changes,
providing evidence for the presence of slipping reconnection at small
spatial scales.

---------------------------------------------------------
Title: Updated calculations of the ionization equilibrium for the
non-Maxwellian electron n-distributions in solar flares
Authors: Dzifčáková, Elena; Dudík, Jaroslav
2016IAUS..320..243D Altcode:
The assumption of an equilibrium (Maxwellian) distribution of
electron energies cannot explain observed high intensities of the Si
XIId satellite lines relative to the Si XIII allowed lines during
the flares. However, the presence of n-distribution with a higher
and narrower shape than the Maxwellian one is able to explain this
behavior. We calculated the ionization equilibrium for the non-thermal
n-distributions using the latest atomic data for each element up to
the proton number of 30. Significant changes in the shape and maxima of
the ion abundance peak occur and can strongly influence the temperature
diagnostics.

---------------------------------------------------------
Title: Simultaneous IRIS and Hinode/EIS Observations and Modelling
of the 2014 October 27 X2.0 Class Flare
Authors: Polito, V.; Reep, J. W.; Reeves, K. K.; Simões, P. J. A.;
Dudík, J.; Del Zanna, G.; Mason, H. E.; Golub, L.
2016ApJ...816...89P Altcode: 2015arXiv151206378P
We present a study of the X2-class flare which occurred on 2014 October
27 and was observed with the Interface Region Imaging Spectrograph
(IRIS) and the EUV Imaging Spectrometer (EIS) on board the Hinode
satellite. Thanks to the high cadence and spatial resolution of the IRIS
and EIS instruments, we are able to compare simultaneous observations
of the Fe xxi 1354.08 Å and Fe xxiii 263.77 Å high-temperature
emission (≳10 MK) in the flare ribbon during the chromospheric
evaporation phase. We find that IRIS observes completely blueshifted
Fe xxi line profiles, up to 200 km s-1 during the rise
phase of the flare, indicating that the site of the plasma upflows is
resolved by IRIS. In contrast, the Fe xxiii line is often asymmetric,
which we interpret as being due to the lower spatial resolution of
EIS. Temperature estimates from SDO/AIA and Hinode/XRT show that hot
emission (log(T[K]) &gt; 7.2) is first concentrated at the footpoints
before filling the loops. Density-sensitive lines from IRIS and
EIS give estimates of electron number density of ≳1012
cm-3 in the transition region lines and 1010
cm-3 in the coronal lines during the impulsive phase. In
order to compare the observational results against theoretical
predictions, we have run a simulation of a flare loop undergoing
heating using the HYDRAD 1D hydro code. We find that the simulated
plasma parameters are close to the observed values that are obtained
with IRIS, Hinode, and AIA. These results support an electron beam
heating model rather than a purely thermal conduction model as the
driving mechanism for this flare.

---------------------------------------------------------
Title: Ionisation Equilibrium for the Non-Maxwellian Electron n
-Distributions in Solar Flares: Updated Calculations
Authors: Dzifčáková, Elena; Dudík, Jaroslav
2015SoPh..290.3545D Altcode: 2015SoPh..tmp..104D
We use the latest available atomic data to calculate the ionisation
and recombination rates for the non-Maxwellian n -distributions,
which were shown previously to provide a good fit to the enhanced
intensities of dielectronic satellite lines during solar flares. The
ionisation and recombination coefficients are subsequently used
to derive the ionisation equilibrium. To do so, we consider odd
values of n ranging from 1 to 19, i.e., from Maxwellian to strongly
non-Maxwellian cases. These calculations involve all elements with
proton number up to 30, i.e., H to Zn. The n -distributions modify
both the ionisation and the recombination rates. The ionisation
rates decrease more steeply at lower pseudo-temperatures, while the
radiative recombination rate is reduced due to a lower number of
low-energy electrons. The peaks of the dielectronic recombination
rates become narrower. These changes are reflected in the ionisation
equilibrium. Ion abundance peaks become narrower and can also be
shifted, mostly towards higher temperatures. The He-like ions are
an important exception, as they are formed in a larger temperature
range than that for the Maxwellian distribution. The ions Si XIII -
XIV used previously for the diagnostics of the n -distributions are
affected only weakly, confirming the determination of n . The ionisation
equilibria are available as the electronic supplementary material in
a format compatible with the CHIANTI database.

---------------------------------------------------------
Title: On the possibility to diagnose a kappa-distribution from EVE
flare spectra
Authors: Dzifcakova, Elena; Dudík, Jaroslav
2015IAUGA..2254765D Altcode:
X-ray flare emission is strongly affected by the non-thermal part
of the electron distribution. RHESSI observations and also recent
theoretical derivations showed that the electron distribution function
in coronal X-ray sources could be a kappa-distribution. An effect of
kappa-distribution on the relative intensities of spectral lines of
Fe XVIII - Fe XXIV observed in SDO/EVE flare spectra was calculated
using KAPPA package based on the CHIANTI. Together with CHIANTI,
this allows us to estimate the influence of the kappa-distributions
on the diagnostics of electron density and temperature from
the flare spectra. The possibility to diagnose parameters of the
kappa-distribution from EVE flare spectra is discussed. The synthetic
spectra for the kappa-distribution are compared with the observed
flare spectra.

---------------------------------------------------------
Title: Updated calculations of the ionization equilibrium for the
non-Maxwellian electron n-distributions in solar flares
Authors: Dzifcakova, Elena; Dudík, Jaroslav
2015IAUGA..2254777D Altcode:
Observed flare high intensities of the Si XIId satellite lines in
comparison with the Si XIII allowed lines cannot be interpreted
under the assumption of a Maxwellian distribution. This behavior of
the relative line intensities can be explained by the presence of
n-distribution with a higher and narrower shape than the Maxwellian
one. This distribution can be formed in flaring plasma in the electric
double layers and its presence is associated with type III radio
bursts.The latest atomic data to calculate the ionization equilibrium
for the non-thermal n-distributions with n ranging from 1 to 19
were used. These calculations involve each of elements with atomic
number up to 30. The n-distributions influence both the ionization and
recombination rates and make the ion abundance peaks narrower. They can
also shift the maxima of the ion abundance peaks in comparison with the
Maxwellian distribution and can influence the temperature diagnostics.

---------------------------------------------------------
Title: Slipping reconnection and chromospheric evaporation in the
10 September 2014 flare
Authors: Dudík, Jaroslav; Janvier, Miho; Polito, Vanessa; Mulay,
Sargam; Del Zanna, Giulio; Mason, Helen; Aulanier, Guillaume
2015IAUGA..2252237D Altcode:
We study the occurrence of slipping reconnection in the long-duration
X-class flare of 2014 September 10. From the start, the flare shows
apparent slippage of hot Fe XXI flare loops observed in the 131A
channel of SDO/AIA. Using the time-distance plots, we show that the
slipping motion of the flare loops proceeds in counter directions in
both flare ribbons. Simultaneous IRIS Fe XXI observations show the
occurrence of chromospheric evaporation at brightening kernels that are
involved in the slipping reconnection of AIA loops. This happens also
during a flux-rope breakout accompanied by a faint 'magnetic implosion'
of a coronal loop. Based on the 3D MHD flare model, we argue that the
'implosion' is caused by the erupting flux rope pushing the neighbouring
loops aside, with the low-lying loops being squeezed.

---------------------------------------------------------
Title: GREGOR observations of a small flare above a sunspot
Authors: Sobotka, Michal; Dudik, Jaroslav; Denker, Carsten; Balthasar,
Horst; Jurcak, Jan; Liu, Wenjuan; GREGOR Team
2015IAUGA..2246841S Altcode:
A small flare ribbon above a sunspot with a light bridge was observed on
7 November 2014 around 12:00 UT in the blue imaging channel of GREGOR,
using a 0.1 nm Ca II H interference filter. Context observations from
SDO/AIA, Hinode/SOT and IRIS show that the ribbon is a part of a larger
ribbon extending through the neighbouring negative polarities that also
participates in several other flares within the active region. A 140
s long time series of Ca II H images was reconstructed by means of the
Multi Frame Blind Deconvolution method, giving the respective spatial
and temporal resolutions of 0.1" and 1 s. Light curves and horizontal
velocities of small-scale brightenings in the flare ribbon located
above an umbral core were measured. Some of them are stationary but
three brightenings move in opposite directions along the ribbon with
speeds of 7 - 11 km/s. Expecting that the brightenings correspond to
footpoints of flare loops, their motions can be interpreted in terms
of the slipping reconnection model.

---------------------------------------------------------
Title: Imaging and Spectroscopic Observations of a Transient Coronal
Loop: Evidence for the Non-Maxwellian K Distributions
Authors: Dudík, Jaroslav; Mackovjak, Šimon; Dzifčáková, Elena;
Del Zanna, Giulio; Williams, David R.; Karlický, Marian; Mason,
Helen E.; Lörinčík, Juraj; Kotrč, Pavel; Fárník, František;
Zemanová, Alena
2015ApJ...807..123D Altcode: 2015arXiv150504333D
We report on the Solar Dynamics Observatory/Atmospheric Imaging Assembly
(AIA) and Hinode/EUV Imaging Spectrograph (EIS) observations of a
transient coronal loop. The loop brightens up in the same location after
the disappearance of an arcade formed during a B8.9-class microflare
3 hr earlier. EIS captures this loop during its brightening phase,
as observed in most of the AIA filters. We use the AIA data to study
the evolution of the loop, as well as to perform the differential
emission measure (DEM) diagnostics as a function of κ. The Fe xi-Fe
xiii lines observed by EIS are used to perform the diagnostics of
electron density and subsequently the diagnostics of κ. Using ratios
involving the Fe xi 257.772 Å self-blend, we diagnose κ ≲ 2,
i.e., an extremely non-Maxwellian distribution. Using the predicted
Fe line intensities derived from the DEMs as a function of κ, we
show that, with decreasing κ, all combinations of ratios of line
intensities converge to the observed values, confirming the diagnosed
κ ≲ 2. These results represent the first positive diagnostics of
κ-distributions in the solar corona despite the limitations imposed
by calibration uncertainties.

---------------------------------------------------------
Title: Sunspot waves and flare energy release
Authors: Sych, R.; Karlický, M.; Altyntsev, A.; Dudík, J.;
Kashapova, L.
2015A&A...577A..43S Altcode: 2014arXiv1409.2947S
Context. We study the possibility of flare process triggering by
waves propagating from the sunspot along a magnetic loop (channel)
to a nearby flare site. Aims: We present a relationship between
the dynamics of ~3-min slow magnetoacoustic waves in the sunspot and
flare emergence process. Waves propagating in the magnetic channel
whose one foot is anchored in the umbra represent the disturbing agent
responsible for triggering the flare energy release. Methods:
We applied time-distance plots and pixel wavelet filtration methods
to obtain spatio-temporal distribution of wave power variations in
radio and SDO/AIA data. To find the magnetic channel, we used potential
magnetic field extrapolation of SDO/HMI magnetograms. The propagation
velocity of wave fronts was measured from wave locations at specific
times. Results: In the correlation curves of the 17 GHz (NoRH)
radio emission, we found a monotonous energy amplification of the
3-min waves in the sunspot umbra before the 2012 June 7 flare. This
amplification was associated with an increase in the length of the
oscillatory wakes in coronal loops (SDO/AIA, 171 Å) prior to the flare
onset. A peculiarity of the flare is the constant level of the flare
emission in soft X-rays (RHESSI, 3-25 keV) for ~10 min after the short
impulsive phase, which indicates continuing energy release. Throughout
this time, we found transverse oscillations of the flare loop with a
30 s period in the radio-frequency range (NoRH, 17 GHz). This period
appears to be related to the 3-min waves from the sunspot. The magnetic
field extrapolation based on SDO/HMI magnetograms shows the existence
of the magnetic channel (waveguide) connecting the sunspot with the
energy release region. Conclusions: We analysed the sunspot
3-min wave dynamics and found a correlation between the oscillation
power amplification and flare triggering in the region connected to the
sunspot through the magnetic channel. We propose that this amplified
wave flux triggered the flare. The flare occurred because of this
amplified flux, however, and because a sufficient amount of free
magnetic energy was accumulated in close vicinity to the magnetic
channel prior to the flare. Furthermore, because of loop heating,
the wave velocity (sound velocity) increased with the penetration of
waves into the energy release site. The heating is shown to be able to
proceed after the flare main peak owing to a further energy pumping
in the form of waves from the sunspot and additional reconnection
episodes in the flare region.

---------------------------------------------------------
Title: KAPPA: A Package for Synthesis of Optically Thin Spectra for
the Non-Maxwellian κ-distributions Based on the Chianti Database
Authors: Dzifčáková, Elena; Dudík, Jaroslav; Kotrč, Pavel;
Fárník, František; Zemanová, Alena
2015ApJS..217...14D Altcode: 2015arXiv150200853D
Non-Maxwellian κ-distributions have been detected in the solar
transition region and in flares. These distributions are characterized
by a high-energy tail and a near-Maxwellian core and are known to have
a significant impact on the resulting optically thin spectra arising
from collisionally dominated astrophysical plasmas. We developed the
KAPPA package for the synthesis of such line and continuum spectra. The
package is based on the freely available CHIANTI database and software,
and can be used in a similar manner. Ionization and recombination rates
together with the ionization equilibria are provided for a range of κ
values. Distribution-averaged collision strengths for excitation are
obtained using an approximate method for all transitions in all ions
available within CHIANTI. The validity of this approximate method is
tested through a comparison with direct calculations. Typical precisions
of better than 5% are found with all cases being within 10%. Tools
for the calculation of synthetic line and continuum intensities are
provided and described. Examples of the synthetic spectra and SDO/AIA
responses to emission for the κ-distributions are given.

---------------------------------------------------------
Title: KAPPA: Optically thin spectra synthesis for non-Maxwellian
kappa-distributions
Authors: Dzifcáková, Elena; Dudík, Jaroslav; Kotrc, Pavel; Fárník,
Frantisek; Zemanová, Alena
2015ascl.soft02008D Altcode:
Based on the freely available CHIANTI (ascl:9911.004) database and
software, KAPPA synthesizes line and continuum spectra from the
optically thin spectra that arise from collisionally dominated
astrophysical plasmas that are the result of non-Maxwellian
κ-distributions detected in the solar transition region and
flares. Ionization and recombination rates together with the ionization
equilibria are provided for a range of κ values. Distribution-averaged
collision strengths for excitation are obtained by an approximate method
for all transitions in all ions available within CHIANTI; KAPPA also
offers tools for calculating synthetic line and continuum intensities.

---------------------------------------------------------
Title: On the Area Expansion of Magnetic Flux Tubes in Solar Active
Regions
Authors: Dudík, Jaroslav; Dzifčáková, Elena; Cirtain, Jonathan W.
2014ApJ...796...20D Altcode: 2014arXiv1409.6947D
We calculated the three-dimensional (3D) distribution of the area
expansion factors in a potential magnetic field, extrapolated from the
high-resolution Hinode/SOT magnetogram of the quiescent active region
NOAA 11482. Retaining only closed loops within the computational box,
we show that the distribution of area expansion factors show significant
structure. Loop-like structures characterized by locally lower values
of the expansion factor are embedded in a smooth background. These
loop-like flux tubes have squashed cross-sections and expand with
height. The distribution of the expansion factors show an overall
increase with height, allowing an active region core characterized
by low values of the expansion factor to be distinguished. The
area expansion factors obtained from extrapolation of the Solar
Optical Telescope magnetogram are compared to those obtained from an
approximation of the observed magnetogram by a series of 134 submerged
charges. This approximation retains the general flux distribution in the
observed magnetogram, but removes the small-scale structure in both the
approximated magnetogram and the 3D distribution of the area expansion
factors. We argue that the structuring of the expansion factor can
be a significant ingredient in producing the observed structuring of
the solar corona. However, due to the potential approximation used,
these results may not be applicable to loops exhibiting twist or to
active regions producing significant flares.

---------------------------------------------------------
Title: Signatures of the non-Maxwellian κ-distributions in optically
thin line spectra. I. Theory and synthetic Fe IX-XIII spectra
Authors: Dudík, J.; Del Zanna, G.; Mason, H. E.; Dzifčáková, E.
2014A&A...570A.124D Altcode: 2014arXiv1408.0950D
 Aims: We investigate the possibility of diagnosing the degree of
departure from the Maxwellian distribution using single-ion spectra
originating in astrophysical plasmas in collisional ionization
equilibrium. Methods: New atomic data for excitation of Fe ix
- Fe xiii are integrated under the assumption of a κ-distribution
of electron energies. Diagnostic methods using lines of a single
ion formed at any wavelength are explored. Such methods minimize
uncertainties from the ionization and recombination rates, as well as
the possible presence of non-equilibrium ionization. Approximations
to the collision strengths are also investigated. Results: The
calculated intensities of most of the Fe ix - Fe xiii EUV lines show
consistent behaviour with κ at constant temperature. Intensities
of these lines decrease with κ, with the vast majority of ratios
of strong lines showing little or no sensitivity to κ. Several of
the line ratios, especially involving temperature-sensitive lines,
show a sensitivity to κ that is of the order of several tens of per
cent, or, in the case of Fe ix, up to a factor of two. Forbidden
lines in the near-ultraviolet, visible, or infrared parts of the
spectrum are an exception, with smaller intensity changes or even
a reverse behaviour with κ. The most conspicuous example is the Fe
x 6378.26 Å red line, whose intensity incerases with κ. This line
is a potentially strong indicator of departures from the Maxwellian
distribution. We find that it is possible to perform density diagnostics
independently of κ, with many Fe xi, Fe xii, and Fe xiii line ratios
showing strong density-sensitivity and negligible sensitivity to κ
and temperature. We also tested different averaging of the collision
strengths. It is found that averaging over 0.01 interval in log(E [ Ryd
]) is sufficient to produce accurate distribution-averaged collision
strengths Υ(T,κ) at temperatures of the ion formation in ionization
equilibrium. Appendices are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201424124/olm">http://www.aanda.org</A>

---------------------------------------------------------
Title: Magnetic field and radiative transfer modelling of a quiescent
prominence
Authors: Gunár, S.; Schwartz, P.; Dudík, J.; Schmieder, B.; Heinzel,
P.; Jurčák, J.
2014A&A...567A.123G Altcode:
 Aims: The aim of this work is to analyse the multi-instrument
observations of the June 22, 2010 prominence to study its structure in
detail, including the prominence-corona transition region and the dark
bubble located below the prominence body. Methods: We combined
results of the 3D magnetic field modelling with 2D prominence fine
structure radiative transfer models to fully exploit the available
observations. Results: The 3D linear force-free field model
with the unsheared bipole reproduces the morphology of the analysed
prominence reasonably well, thus providing useful information about
its magnetic field configuration and the location of the magnetic
dips. The 2D models of the prominence fine structures provide a good
representation of the local plasma configuration in the region dominated
by the quasi-vertical threads. However, the low observed Lyman-α
central intensities and the morphology of the analysed prominence
suggest that its upper central part is not directly illuminated from the
solar surface. Conclusions: This multi-disciplinary prominence
study allows us to argue that a large part of the prominence-corona
transition region plasma can be located inside the magnetic dips in
small-scale features that surround the cool prominence material located
in the dip centre. We also argue that the dark prominence bubbles
can be formed because of perturbations of the prominence magnetic
field by parasitic bipoles, causing them to be devoid of the magnetic
dips. Magnetic dips, however, form thin layers that surround these
bubbles, which might explain the occurrence of the cool prominence
material in the lines of sight intersecting the prominence bubbles. Movie and Appendix A are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201322777/olm">http://www.aanda.org</A>

---------------------------------------------------------
Title: Slipping Magnetic Reconnection during an X-class Solar Flare
Observed by SDO/AIA
Authors: Dudík, J.; Janvier, M.; Aulanier, G.; Del Zanna, G.;
Karlický, M.; Mason, H. E.; Schmieder, B.
2014ApJ...784..144D Altcode: 2014arXiv1401.7529D
We present SDO/AIA observations of an eruptive X-class flare of
2012 July 12, and compare its evolution with the predictions of a
three-dimensional (3D) numerical simulation. We focus on the dynamics of
flare loops that are seen to undergo slipping reconnection during the
flare. In the Atmospheric Imaging Assembly (AIA) 131 Å observations,
lower parts of 10 MK flare loops exhibit an apparent motion with
velocities of several tens of km s-1 along the developing
flare ribbons. In the early stages of the flare, flare ribbons consist
of compact, localized bright transition-region emission from the
footpoints of the flare loops. A differential emission measure analysis
shows that the flare loops have temperatures up to the formation of
Fe XXIV. A series of very long, S-shaped loops erupt, leading to a
coronal mass ejection observed by STEREO. The observed dynamics are
compared with the evolution of magnetic structures in the "standard
solar flare model in 3D." This model matches the observations well,
reproducing the apparently slipping flare loops, S-shaped erupting
loops, and the evolution of flare ribbons. All of these processes are
explained via 3D reconnection mechanisms resulting from the expansion
of a torus-unstable flux rope. The AIA observations and the numerical
model are complemented by radio observations showing a noise storm
in the metric range. Dm-drifting pulsation structures occurring
during the eruption indicate plasmoid ejection and enhancement of the
reconnection rate. The bursty nature of radio emission shows that the
slipping reconnection is still intermittent, although it is observed
to persist for more than an hour.

---------------------------------------------------------
Title: Differential emission measure analysis of active region cores
and quiet Sun for the non-Maxwellian κ-distributions
Authors: Mackovjak, Š.; Dzifčáková, E.; Dudík, J.
2014A&A...564A.130M Altcode:
Context. The non-Maxwellian κ-distributions have been detected in
the solar wind and can explain intensities of some transition region
lines. Presence of such distributions in the outer layers of the solar
atmosphere influences the ionization and excitation equilibrium and
widens the line contribution functions. This behavior may be reflected
on the reconstructed differential emission measure (DEM). 
Aims: We aim to investigate the influence of κ-distributions on the
reconstructed DEMs. Methods: We perform DEM reconstruction
for three active region cores and a quiet Sun region using the
Withbroe-Sylwester method and the regularization method. Results:
We find that the reconstructed DEMs depend on the value of κ. The DEMs
of the active region cores show similar behavior with decreasing κ,
or an increasing departure from the Maxwellian distribution. For lower
κ, the peaks of the DEMs are typically shifted to higher temperatures
and the DEMs themselves become more concave. This is caused by the less
steep high-temperature slopes for lower κ. However, the low-temperature
slopes do not change significantly even for extremely low κ. The
behavior of the quiet-Sun DEM distribution is different. It becomes
progressively less multithermal for lower κ with the EM-loci plots
that indicate near-isothermal plasma for κ = 2. Conclusions:
The κ-distributions can influence the reconstructed DEMs. The slopes
of the DEM, however, do not change with κ significantly enough to
produce different constraints on the heating mechanism in terms of
frequency of coronal heating events.

---------------------------------------------------------
Title: Diagnostics for the O IV and Si IV lines observed by IRIS
Authors: Dudik, Jaroslav; Mason, Helen; Del Zanna, Giulio; Golub,
Leon; Dzifcakova, Elena
2014cosp...40E.754D Altcode:
We investigate the formation of the IRIS O IV and Si IV lines under
non-Maxwellian conditions characterized by kappa-distributions. It is
found that the Si IV lines are always formed at lower temperatures
than the O IV lines. However, as the departure from the Maxwellian
increases, the peak formation temperatures are shifted progressively to
lower and lower temperatures. Coupled with the slope of the differential
emission measure (DEM), it is possible for the Si IV lines to be formed
very close to the solar chromosphere, with the majority of the O IV
intensities coming from a different, higher part of the transition
region. The predicted spectra for kappa-distributions exhibit very low O
IV intensities compared to Si IV, analogously to what is observed by the
IRIS spacecraft. Potential density diagnostics are discussed, as well
as the contribution of photoexcitation to the formation of these lines.

---------------------------------------------------------
Title: Chromospheric evaporation in recurrent flares
Authors: Polito, V.; Mason, Helen; Del Zanna, Giulio; Dudik, Jaroslav
2014cosp...40E2581P Altcode:
We present high-cadence (3 minutes) Hinode/EIS observations of small
recurrent flares and provide densities and velocities of the upflowing
plasma in the locations of the chromospheric evaporation. Lines formed
in the 2-10 MK range have significant blueshifts, of the order of
50 km/s or more. This upflowing plasma is the source of the 10 MK
plasma that emits strongly in EUV and X-ray lines after the impulsive
phases. We use the high-cadence and high-resolution SDO/AIA images
to describe the locations of the upflows, and magnetograms to locate
the ribbons. One interesting feature is that the recurrent flares are
confined, until the last one when a large-scale eruption occurs.

---------------------------------------------------------
Title: New calculations of the ionization equilibrium for the
non-Maxwellian electron distribution in solar flares
Authors: Dzifcakova, Elena; Dudik, Jaroslav
2014cosp...40E.772D Altcode:
It has been shown that observed flare high intensities of the Si XII
satellite lines in comparison with the Si XIII allowed lines cannot be
explained under the assumption of a Maxwellian distribution. The real
electron distribution function in the region of a formation of these
lines should decrease much faster than for the Maxwellian one. The
so-called n-distribution has been proposed for the explanation of
the observed line intensities. This distribution can be formed in
the electric double layers in flaring plasma and its presence is
associated with type III radio bursts. We used new atomic data to
calculate the ionization and recombination rates for the non-thermal
n-distributions with a higher and narrower shape than the Maxwellian
one. These calculations involve each of elements with atomic number
up to 30. The n-distributions influence both the ionization and
recombination rates and make the ion abundance peaks narrower. They
can also shift the maxima of the ion abundance peaks in comparison
with Maxwellian distribution and can influence the temperature
diagnostics. Synthetic spectra for n-distributions are compared with
the observed flare spectra.

---------------------------------------------------------
Title: Solar Transition Region Lines Observed by the Interface Region
Imaging Spectrograph: Diagnostics for the O IV and Si IV Lines
Authors: Dudík, J.; Del Zanna, G.; Dzifčáková, E.; Mason, H. E.;
Golub, L.
2014ApJ...780L..12D Altcode: 2013arXiv1311.6978D
The formation of the transition region O IV and Si IV lines observable
by the Interface Region Imaging Spectrograph (IRIS) is investigated
for both Maxwellian and non-Maxwellian conditions characterized by
a κ-distribution exhibiting a high-energy tail. The Si IV lines
are formed at lower temperatures than the O IV lines for all κ. In
non-Maxwellian situations with lower κ, the contribution functions
are shifted to lower temperatures. Combined with the slope of the
differential emission measure, it is possible for the Si IV lines to be
formed at very different regions of the solar transition region than the
O IV lines; possibly close to the solar chromosphere. Such situations
might be discernible by IRIS. It is found that photoexcitation can be
important for the Si IV lines, but is negligible for the O IV lines. The
usefulness of the O IV ratios for density diagnostics independently of
κ is investigated and it is found that the O IV 1404.78 Å/1399.77
Å ratio provides a good density diagnostics except for very low T
combined with extreme non-Maxwellian situations.

---------------------------------------------------------
Title: H to Zn Ionization Equilibrium for the Non-Maxwellian Electron
κ-distributions: Updated Calculations
Authors: Dzifčáková, E.; Dudík, J.
2013ApJS..206....6D Altcode: 2013arXiv1304.4064D
New data for the calculation of ionization and recombination rates have
been published in the past few years, most of which are included in the
CHIANTI database. We used these data to calculate collisional ionization
and recombination rates for the non-Maxwellian κ-distributions with an
enhanced number of particles in the high-energy tail, which have been
detected in the solar transition region and the solar wind. Ionization
equilibria for elements H to Zn are derived. The κ-distributions
significantly influence both the ionization and recombination rates
and widen the ion abundance peaks. In comparison with the Maxwellian
distribution, the ion abundance peaks can also be shifted to lower or
higher temperatures. The updated ionization equilibrium calculations
result in large changes for several ions, notably Fe VIII-Fe XIV. The
results are supplied in electronic form compatible with the CHIANTI
database.

---------------------------------------------------------
Title: Fast Magnetoacoustic Waves in a Fan Structure Above a Coronal
Magnetic Null Point
Authors: Mészárosová, H.; Dudík, J.; Karlický, M.; Madsen,
F. R. H.; Sawant, H. S.
2013SoPh..283..473M Altcode: 2013arXiv1301.2485M
We analyze the 26 November 2005 solar radio event observed
interferometrically at frequencies of 244 and 611 MHz by the Giant
Metrewave Radio Telescope (GMRT) in Pune, India. These observations
are used to make interferometric maps of the event at both frequencies
with the time cadence of 1 s from 06:50 to 07:12 UT. These maps reveal
several radio sources. The light curves of these sources show that only
two sources at 244 MHz and 611 MHz are well correlated in time. The
EUV flare is more localized with flare loops located rather away from
the radio sources. Using SoHO/MDI observations and potential magnetic
field extrapolation we demonstrate that both the correlated sources
are located in the fan structure of magnetic field lines starting from
a coronal magnetic null point. Wavelet analysis of the light curves of
the radio sources detects tadpoles with periods in the range P=10 - 83
s. These wavelet tadpoles indicate the presence of fast magnetoacoustic
waves that propagate in the fan structure of the coronal magnetic null
point. We estimate the plasma parameters in the studied radio sources
and find them consistent with the presented scenario involving the
coronal magnetic null point.

---------------------------------------------------------
Title: SDO/AIA Prominence physical conditions
Authors: Schmieder, B.; Parenti, S.; Dudik, J.; Aulanier, G.; Heinzel,
P.; Zapior, M.; Golub, L.
2013enss.confE..27S Altcode:
SDO/AIA has carried out continuous observations of prominences in
multiple wavelengths, with high spatial and temporal resolution. These
data provide us an opportunity to understand the physical conditions
and dynamics of prominences. The surprising brightness of prominences
in some coronal lines has been well explained by the presence of
transition region lines in the bandpass of the filters (171 A, 131 A),
a result that leads us to revise our model of the transition region
of prominences and to consider a relatively dense transition region in
some prominence evolutionary phases or in some viewing orientation. An
additional aspect of prominence dynamics will be presented with a new
quasi-static MHD model proposed for bubbles and plumes. We propose
an alternative to the interpretation that thermal instabilities are
responsible for the formation of bubbles. The bubbles are found to
correspond to magnetic separatrices formed by emerging magnetic field
close to prominence footpoints.

---------------------------------------------------------
Title: Dielectronic satellite lines and double layers in solar flares
Authors: Dzifčáková, E.; Karlický, M.; Dudík, J.
2013A&A...550A..60D Altcode:
Context. Particle acceleration during solar flares results
in departures of the distribution of particle energies from the
Maxwellian distribution. Apart from the high-energy tail, the bulk of
the distribution was recently also found to be significantly affected,
due, e.g., to the presence of double layers. Aims: We investigate
the influence of several proposed non-Maxwellian distribution functions
on the X-ray flare line spectra. The distribution functions considered
are sharply peaked and include the n-distribution, the moving Maxwellian
distribution, and the distribution formed in strong double layers in
the flaring plasma. Methods: Synthetic Si xiid-Si xiv spectra
involving allowed and dielectronic transitions at 5 - 6 Å are
calculated numerically. The parameters chosen for the calculations
correspond to the impulsive phase of solar flares, as inferred by
previous authors. Results: The Si xiid λ5.56/Si xiii λ5.68
and Si xiid λ5.82/Si xiii λ5.68 ratios depend on the relative number
of electrons at energies corresponding to the formation of the Si
xiid lines. Therefore, these ratios increase with the increasing
narrowness of the peak of the electron distribution function. The
highest ratios are achieved for the distribution formed in double
layers, while the moving Maxwellian distribution is less likely to
reproduce the observed enhancement of Si xiid intensities. However,
the ratio of the allowed Si xiv λ5.22/Si xiii λ5.68 transitions
depends on the ionization equilibrium. This ratio is very small for the
double-layer distribution. Combination of the double-layer distribution
with a Maxwellian distribution with the same mean energy significantly
enhances this ratio, while keeping the Si xiid intensities sufficiently
increased to explain the characteristics of the observed spectra. Conclusions: These results support the presence of double layers
in the plasma during impulsive phase of solar flares.

---------------------------------------------------------
Title: On the Possibility to Diagnose the Non-Maxwellian
κ-Distributions from the Hinode/EIS EUV Spectra
Authors: Mackovjak, Š.; Dzifčáková, E.; Dudík, J.
2013SoPh..282..263M Altcode: 2012SoPh..tmp..273M
We investigate the possibility to diagnose the κ-distributions from the
EUV spectra observed by the Hinode/EIS spectrometer. Observable lines of
the most abundant elements except Fe are considered. Synthetic spectra
for the κ-distributions with κ=2 - 10 and the Maxwellian distribution
were calculated for a range of temperatures and electron densities. We
find that only a small number of O, S, Ca, and Ni line ratios are
sensitive to κ. A list of the best diagnostic options using transition
region and coronal lines is provided. Usually, the line ratios sensitive
to κ are also sensitive to electron density. Weak O IV lines are a
notable exception. These lines offer greatest sensitivity to κ from
all the lines observed by Hinode/EIS. Density diagnostics using lines
of the non-Fe elements is discussed and the influence of κ on the
diagnostics of electron density is presented. The density diagnostics
using these non-Fe EIS lines are strongly affected by both known and
unknown blends. Therefore, we performed the density diagnostics using
the Fe XII - XIV lines. Subsequently, these proposed diagnostic methods
for κ-distributions are tested using the spectral atlas obtained by
Brown et al. (Astrophys. J. Suppl.176, 511, 2008). These data do not
provide conclusive evidence for the presence of κ-distributions due to
possible plasma multitermality, a low observed signal-to-noise ratio,
and unremovable or unknown blends.

---------------------------------------------------------
Title: Magnetic Topology of Bubbles in Quiescent Prominences
Authors: Dudík, J.; Aulanier, G.; Schmieder, B.; Zapiór, M.;
Heinzel, P.
2012ApJ...761....9D Altcode:
We study a polar-crown prominence with a bubble and its plume observed
in several coronal filters by the SDO/AIA and in Hα by the MSDP
spectrograph in Białków (Poland) to address the following questions:
what is the brightness of prominence bubbles in EUV with respect to the
corona outside of the prominence and the prominence coronal cavity? What
is the geometry and topology of the magnetic field in the bubble? What
is the nature of the vertical threads seen within prominences? We
find that the brightness of the bubble and plume is lower than the
brightness of the corona outside of the prominence, and is similar to
that of the coronal cavity. We constructed linear force-free models of
prominences with bubbles, where the flux rope is perturbed by inclusion
of parasitic bipoles. The arcade field lines of the bipole create the
bubble, which is thus devoid of magnetic dips. Shearing the bipole or
adding a second one can lead to cusp-shaped prominences with bubbles
similar to the observed ones. The bubbles have complex magnetic
topology, with a pair of coronal magnetic null points linked by a
separator outlining the boundary between the bubble and the prominence
body. We conjecture that plume formation involves magnetic reconnection
at the separator. Depending on the viewing angle, the prominence can
appear either anvil-shaped with predominantly horizontal structures,
or cusp-shaped with predominantly vertical structuring. The latter
is an artifact of the alignment of magnetic dips with respect to the
prominence axis and the line of sight.

---------------------------------------------------------
Title: Can bubbles in quiescent prominences be purely magnetic
phenomena?
Authors: Dudik, Jaroslav; Schmieder, Brigitte; Aulanier, Guillaume;
Zapior, Maciej; Heinzel, Petr
2012cosp...39..486D Altcode: 2012cosp.meet..486D
We present a model of the magnetic field constituting quiescent
prominences. The model assumes a linear force-free field with a
weakly twisted flux-tube in an OX/OF topology perturbed by presence
of parasitic polarities within the filament channel. The parasitic
polarities locally create the cusp-shaped prominences with bubbles
exactly as those observed by the SDO/AIA and Bialkow Observatory. We
find that the observations are best reproduced if the parasitic bipoles
are sheared with respect to the main inversion line. We show that
the bubbles are in fact constituted by the arcade-like field lines,
as opposed to that of the prominence, which is created by magnetic
dips. A pair of null points is always associated with the parasitic
bipole. These null points are connected by a separator passing through
the prominence bubble. We show how the presence of an additional
parasitic bipole moves the separator to the boundary between the bubble
and the rest of the prominence, producing a topology favorable for
reconnection and possibly for the formation of plumes.

---------------------------------------------------------
Title: X-ray and EUV Filter Responses for Nonthermal κ-Distributions
Authors: Dzifčáková, E.; Dudík, J.; Karlický, M.
2012ASPC..456..135D Altcode:
We calculate the XRT and AIA filter responses to emission for
nonthermal electron kappa-distributions. The filter responses are in
general wider and shifted to higher temperatures. This can affect
temperature diagnostic during flares. We analyze the effect of
nonthermal kappa-distributions on the resulting forward models of AR
emission and show that their influence is small except for the extreme
nonthermal cases.

---------------------------------------------------------
Title: Temperature Diagnostic of a Brightening Observed by Hinode/XRT
Authors: Dudík, J.; Reeves, K. K.; Schmieder, B.; Dzifčáková,
E.; Golub, L.
2012ASPC..456..137D Altcode:
We analyze the temperature distribution of the active region brightening
observed by HINODE/XRT. The temperature structure is derived using
various filter-ratio techniques and DEM analysis. The results are
compared and it is found that the filter-ratio techniques are accurate
only for relatively narrow DEMs.

---------------------------------------------------------
Title: The non-Maxwellian continuum in the X-ray, UV, and radio range
Authors: Dudík, J.; Kašparová, J.; Dzifčáková, E.; Karlický,
M.; Mackovjak, Š.
2012A&A...539A.107D Altcode:
 Aims: We investigate the X-ray, UV, and also the radio
continuum arising from plasmas with a non-Maxwellian distribution of
electron energies. The two investigated types of distributions are
the κ- and n-distributions. Methods: We derived analytical
expressions for the non-Maxwellian bremsstrahlung and free-bound
continuum spectra. The spectra were calculated using available
cross-sections. Then we compared the bremsstrahlung spectra arising from
the different bremsstrahlung cross-sections that are routinely used
in solar physics. Results: The behavior of the bremsstrahlung
spectra for the non-Maxwellian distributions is highly dependent
on the assumed type of the distribution. At flare temperatures and
hard X-ray energies, the bremsstrahlung is greatly increased for
κ-distributions and exhibits a strong high-energy tail. With decreasing
κ, the maximum of the bremsstrahlung spectrum decreases and moves
to higher wavelengths. In contrast, the maximum of the spectra for
n-distributions increases with increasing n, and the spectrum then
falls off very steeply with decreasing wavelength. In the millimeter
radio range, the non-Maxwellian bremsstrahlung spectra are almost
parallel to the thermal bremsstrahlung. Therefore, the non-Maxwellian
distributions cannot be detected by off-limb observations made by the
ALMA instrument. The free-bound continua are also highly dependent
on the assumed type of the distribution. For n-distributions, the
ionization edges disappear and a smooth continuum spectrum is formed
for n ≧ 5. Opposite behavior occurs for κ-distributions where
the ionization edges are in general significantly enhanced, with
details depending on κ and T through the ionization equilibrium. We
investigated how the non-Maxwellian κ-distributions can be
determined from the observations of the continuum and conclude that
one can sample the low-energy part of the distribution from the
continuum. Appendix A is available in electronic form at <A
href="http://www.aanda.org">http://www.aanda.org</A>

---------------------------------------------------------
Title: On the physical meaning of n-distributions in solar flares
Authors: Karlický, M.; Dzifčáková, E.; Dudík, J.
2012A&A...537A..36K Altcode:
 Aims: We investigate the physical meaning of the n-distributions
detected in solar flares. Methods: We consider a Maxwellian
velocity distribution with a velocity drift. This distribution is
analytically integrated to obtain the energy distribution, and its
stability is investigated numerically using a fully electromagnetic
particle-in-cell code. Results: It is shown that the
derived moving Maxwellian energy distribution is very similar to
the n-distribution, especially in their high-energy parts. Both
these distributions are mutually fitted and a relation between their
parameters found. Contrary to the n-distribution, the moving Maxwellian
distribution has a simple physical meaning, e.g., the electron component
of the return current in the beam-plasma system. However, for high drift
velocities of such a component, the moving Maxwellian distribution is
unstable. Therefore to keep the form of this distribution similar to
the n-distribution, some stabilization processes are necessary. If so,
then the high intensities of the Si xiid 5.56 Å and 5.82 Å satellite
lines and their evolution in solar flares can be explained by moving
Maxwellian distributions instead of the n-distributions. Thus, our
previous results connected with the n-distributions can be understood
in a new, physically profound way.

---------------------------------------------------------
Title: Is it possible to model observed active region coronal emission
simultaneously in EUV and X-ray filters?
Authors: Dudík, J.; Dzifčáková, E.; Karlický, M.; Kulinová, A.
2011A&A...531A.115D Altcode:
 Aims: We investigate the possibility of modeling the active
region coronal emission in the EUV and X-ray filters using one,
universal, steady heating function, tied to the properties of the
magnetic field. Methods: We employ a simple, static model to
compute the temperature and density distributions in the active region
corona. The model allows us to explore a wide range of parameters
of the heating function. The predicted EUV and X-ray emission in the
filters of EIT/SOHO and XRT/Hinode are calculated and compared with
observations. Using the combined improved filter-ratio (CIFR) method,
a temperature diagnostic is employed to compare the modeled temperature
structure of the active region with the temperature structure derived
from the observations. Results: The global properties of the
observations are most closely matched for heating functions scaling
as B_00.7-0.8/L_0^{0.5} that depend on the spatially
variable heating scale-length. The modeled X-ray emission originates
from locations where large heating scale-lengths are found. However,
the majority of the loops observed in the 171 and 195 filters can be
modeled only by loops with very short heating scale-lengths. These loops
are known to be thermally unstable. We are unable to find a model that
both matches the observations in all EUV and X-ray filters, and contains
only stable loops. As a result, although our model with a steady heating
function can explain some of the emission properties of the 171 and 195
loops, it cannot explain their observed lifetimes. Thus, the model does
not lead to a self-consistent solution. The performance of the CIFR
method is evaluated and we find that the diagnosed temperature can be
approximated with a geometric mean of the emission-measure weighted
and maximum temperature along the line of sight. Conclusions:
We conclude that if one universal heating function exists, it should
be at least partially time-dependent.

---------------------------------------------------------
Title: The ionization equilibrium and flare line spectra for the
electron distribution with a power-law tail
Authors: Dzifčáková, E.; Homola, M.; Dudík, J.
2011A&A...531A.111D Altcode:
Context. Electron energy spectra exhibiting a high-energy tail are
commonly observed during solar flares. Aims: We investigate the
influence of the high-energy tail and thermal or nonthermal plasma bulk
on the ionization equilibrium of Si and Si flare line spectra. Methods: We construct a realistically composed distribution that
reflects the fits to RHESSI observations. We describe the high-energy
tail by a power-law distribution and the bulk of the electron
distribution by either the Maxwellian or n-distribution. The shape of
this composed distribution is described by three parameters: the ratio
of the plasma bulk density to the density of the high-energy tail,
the power-law index of the high-energy tail, and the parameter n, which
describes the bulk of the distribution. Results: Both the plasma
bulk and the high-energy tail change the ionization equilibrium. The
relative ion abundances are sensitive to the shape of the plasma
bulk, but are much less sensitive to the high-energy tail. The
high-energy tail increases the ratio of temperature-sensitive lines
Si XIV λ5.22/Si XIII λ5.68. Because this ratio can be fitted with
a thermal distribution with higher temperature, the high-energy tail
influences the temperature diagnostics from flare lines. The high-energy
tail has only a small effect on the ratio of the satellite-to-allowed
Si XIId/Si XIII lines, which are dominantly sensitive on the shape of
the plasma bulk. This enables us to perform an accurate diagnostic of
the parameter n describing the plasma bulk. Conclusions: The
realistically composed distribution is able to explain the observed
features of the RESIK X-ray flare line spectra.

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Title: The bound-bound and free-free radiative losses for the
nonthermal distributions in solar and stellar coronae
Authors: Dudík, J.; Dzifčáková, E.; Karlický, M.; Kulinová, A.
2011A&A...529A.103D Altcode:
Context. The radiative-loss function is an important ingredient
in the physics of the solar corona, transition region, and
flares. Aims: We investigate the radiative losses due to the
bound-bound transitions and bremsstrahlung for nonthermal κ- and
n-distributions. Methods: The bound-bound radiative losses are
computed by integrating synthetic spectra. An analytical expression is
derived for nonthermal bremsstrahlung. The bremsstrahlung is computed
numerically using accurate values of the free-free Gaunt factor. Results: We find that the changes in radiative-loss functions
due to nonthermal distributions are several times greater than the
errors due to the missing contribution of the free-bound continuum
or errors in atomic data. For κ-distributions, the radiative-loss
functions are in general weaker than for Maxwellian distribution,
with a few exceptions caused by the behavior of Fe. The peaks of the
radiative-loss functions are in general flatter. The situation is
opposite for n-distributions, for which the radiative-loss functions
have higher and narrower peaks. Local minima and maxima of the
radiative-loss functions may also be shifted. The contribution
from bremsstrahlung only changes by a few percent except in the
extreme nonthermal case of κ = 2. Stability analysis reveals that
the X-ray loops are stable against the radiatively-driven thermal
instability. The calculated radiative losses for nonthermal
distributions are available as two electronic tables at the CDS
via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/529/A103">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/529/A103</A>

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Title: VizieR Online Data Catalog: Radiative losses in solar and
stellar coronae (Dudik+, 2011)
Authors: Dudik, J.; Dzifcakova, E.; Karlicky, M.; Kulinova, A.
2011yCat..35290103D Altcode: 2011yCat..35299103D
The radiative losses due to bound-bound and free-free transitions
calculated for plasma with nonthermal {kappa}- and n-distributions of
electron energies are presented. The radiative losses are calculated
for the values of {kappa}=2, 3, 5, and 10 (rloss_k.dat) and n=1
(Maxwellian), 3, 5, and 11 (rloss_n.dat) as function of temperature (T)
or pseudo-temperature (tau) for the assumed value of electron density
ne=1016m-3. The ne*nH
factor is not included in the calculations. (2 data files).

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Title: Emisia C IV a magnetická topológia

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Title: Emisia C IV a
magnetická topológia

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Title: C IV emission and magnetic topology.
Authors: Mackovjak, Š.; Dudík, J.; Dzifčáková, E.
2010nspm.conf...78M Altcode:
The contribution discusses a study of emissions of carbon ion C IV
during solar flares. Data on the emission of the "clean" C IV and
"clean" UV continuum were obtained from the emission observed in
three TRACE UV filters 1550, 1600 and 1700. Their correlation was
examined. We also studied the spatial correlation of flare nuclei
with images in the calcium ion Ca II line and mainly its relation
to quasiseparatrix positions calculated by extrapolation of the
photospheric magnetogram assuming linear force-free approximation of
the magnetic field. Perticular results were summarized and applied to
a selected flare.

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Title: Kappa-distribúcie a ohrev koróny

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Title: Kappa-distribúcie
a ohrev koróny

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Title: Kappa-distributions and coronal heating.
Authors: Dudík, J.; Dzifčáková, E.; Kulinová, A.; Karlický, M.
2010nspm.conf..161D Altcode:
Particle energy kappa-distributions (distributions with non-thermal
tails) have been diagnosed in plasma of the transition region and
also in solar flares. Theoretical models suggest a link between
kappa-distributions and dynamic heating of the corona. Since
the presence of non-thermal distributions leads to changes in
intensities of emission lines, we have examined their effect on the
total radiation losses of the corona as well as responses of the EUV
and X-ray filters. Temperature responses of the filters are wider for
kappa-distributions than in the case of the Maxwell distribution, and
their respective maxima are shifted towards higher temperatures. On
the other hand, the total radiation losses of the corona are lower
compared to the Maxwell distribution except for the extreme non-thermal
case. This means that lower heating energy is needed to reach the
same corona temperature in case of kappa-distributions. In this work
we discuss the effect of element abundances and specific ions on the
total radiation losses of the corona.

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Title: EUV filter responses to plasma emission for the nonthermal
κ-distributions
Authors: Dudík, J.; Kulinová, A.; Dzifčáková, E.; Karlický, M.
2009A&A...505.1255D Altcode:
The responses to plasma emission of the TRACE EUV filters are
computed by integrating their spectral responses over the synthetic
spectra obtained from the CHIANTI database. The filter responses
to emission are functions of temperature, electron density, and the
assumed electron distribution function. It is shown here that, for the
nonthermal κ-distributions, the resulting responses to emission are
more broadly dependent on T, and their maxima are flatter than for the
Maxwellian electron distribution. The positions of the maxima can also
be shifted. Filter reponses to T are density-dependent as well. The
influence of the nonthermal κ-distributions on the diagnostics of T
from the observations in all three EUV filters is discussed.

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Title: Analytical model of static coronal loops
Authors: Dudík, J.; Dzifčáková, E.; Karlický, M.; Kulinová, A.
2009A&A...502..957D Altcode:
By solving the energy-equilibrium equation in the stationary
case, we derive analytical formulae in the form of scaling laws
for non-uniformly heated and gravitationally stratified coronal
loops. The heating is assumed to be localized in the chromosphere
and to exponentially decrease with increasing distance along the loop
strand. This exponential behavior of the heating and pressure profiles
implies that we need to use the mean-value theorem, and in turn fit
the mean-value parameters of the scaling laws to the results of the
numerical simulations. The radiative-loss function is approximated by a
power-law function of the temperature, and its effect on the resulting
scaling laws for coronal loops is studied. We find that this effect
is more important than the effect of varying loop geometry. We also
find that the difference in lengths of the different loop strands in
a loop with expanding cross-section does not produce differences in
the EUV emission of these strands significant enough to explain the
observed narrowness of the coronal loops.

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Title: Hydrostatic Modelling of Active Region EUV and X-ray Emission
Authors: Dudik, J.; Dzifcakova, E.; Kulinova, A.; Karlicky, M.
2008ESPM...12.3.65D Altcode:
The hydrostatic modeling of active region NOAA 10963 coronal EUV and
X-ray emission is presented. The model considers three-dimensional
magnetic field structure obtained by the extraplation of
the longitudinal magnetogram in potential or linear force-free
approximation. We derived new scaling laws for loop apex temperature
and footpoint pressure as functions of loop length, volumetric
heating rate and heating scale height. These scaling laws assume a
power-law dependency of radiative loss function on the temperature,
a power-law dependency of the heating function on the loop length
and field strength at the loop base. The scaling laws are applied to
the results of the field extrapolations in AR NOAA 10963 in order to
calculate the temperature and density distributions in the active
region corona. The functions of filter response to emissivity has
been calculated by using the CHIANTI atomic database. Unlike previous
authors, we are able to get emitting loop structures in EUV. The results
show that the heating scale height plays important role in modeling
of the active region emission. The computed emission is compared with
observations and the implications on the heating function are discussed.

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Title: Topological Departures from Translational Invariance along
a Filament Observed by THEMIS
Authors: Dudík, J.; Aulanier, G.; Schmieder, B.; Bommier, V.;
Roudier, T.
2008SoPh..248...29D Altcode: 2008SoPh..tmp...53D
We study the topology of the 3D magnetic field in a filament channel
to address the following questions: Is a filament always formed in a
single flux tube? How does the photospheric magnetic field lead to
filament interruptions and to feet formation? What is the relation
between feet-related field lines and the parasitic polarities? What
can topological analyses teach us about EUV filament channels? To do
so, we consider a filament observed on 6 October 2004 with THEMIS/MTR,
in Hα with the full line profile simultaneously and cospatially with
its photospheric vector magnetic field. The coronal magnetic field
was calculated from a "linear magnetohydrostatic" extrapolation of a
composite THEMIS-MDI magnetogram. Its free parameters were adjusted
to get the best match possible between the distribution of modeled
plasma-supporting dips and the Hα filament morphology. The model
results in moderate plasma β≤1 at low altitudes in the filament,
in conjunction with non-negligible departures from force-freeness
measured by various metrics. The filament here is formed by a split
flux tube. One part of the flux tube is rooted in the photosphere aside
an observed interruption in the filament. This splitted topology is
due to strong network polarities on the edge of the filament channel,
not to flux concentrations closer to the filament. We focus our study
to the northwest portion of the filament. The related flux tube is
highly fragmented at low altitudes. This fragmentation is due to small
flux concentrations of two types. First, some locally distort the
tube, leading to noticeable thickness variations along the filament
body. Second, parasitic polarities, associated with filament feet,
result in secondary dips above the related local inversion line. These
dips belong to long field lines that pass below the flux tube. Many
of these field lines are not rooted near the related foot. Finally,
the present model shows that the coronal void interpretation cannot
be ruled out to interpret the wideness of EUV filament channels.

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Title: Simulation of Active Region Coronal Loops EUV Emission
Authors: Dudík, J.; Dzifčáková, E.; Karlický, M.; Wu, S. T.;
Wang, A. H.
2006ESASP.617E..57D Altcode: 2006soho...17E..71D
No abstract at ADS

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Title: C IV Enhanced Emission and the Non-Thermal Electron
Distribution
Authors: Dzifčáková, E.; Kulinová, A.; Tóthová, D.; Dudík, J.
2005ESASP.600E.120D Altcode: 2005ESPM...11..120D; 2005dysu.confE.120D
No abstract at ADS

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Title: Changes in Filament Connectivity and its Structure during
the C-Class Flare
Authors: Kulinová, A.; Dzifčáková, E.; Dudík, J.
2005ESASP.600E.129K Altcode: 2005ESPM...11..129K; 2005dysu.confE.129K
No abstract at ADS