heinzel

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Author name code: heinzel
ADS astronomy entries on 2022-09-14
author:"Heinzel, Petr"

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Title: Coronal mass ejection followed by a prominence eruption and
a plasma blob as observed by Solar Orbiter
Authors: Bemporad, A.; Andretta, V.; Susino, R.; Mancuso, S.; Spadaro,
D.; Mierla, M.; Berghmans, D.; D'Huys, E.; Zhukov, A. N.; Talpeanu,
D. -C.; Colaninno, R.; Hess, P.; Koza, J.; Jejčič, S.; Heinzel,
P.; Antonucci, E.; Da Deppo, V.; Fineschi, S.; Frassati, F.; Jerse,
G.; Landini, F.; Naletto, G.; Nicolini, G.; Pancrazzi, M.; Romoli,
M.; Sasso, C.; Slemer, A.; Stangalini, M.; Teriaca, L.
2022A&A...665A...7B Altcode: 2022arXiv220210294B
Context. On 2021 February 12, two subsequent eruptions occurred above
the western limb of the Sun, as seen along the Sun-Earth line. The
first event was a typical slow coronal mass ejection (CME), followed
∼7 h later by a smaller and collimated prominence eruption,
originating south of the CME, followed by a plasma blob. These
events were observed not only by the SOHO and STEREO-A missions,
but also by the suite of remote-sensing instruments on board Solar
Orbiter. Aims: We show how data acquired by the Full Sun
Imager (FSI), the Metis coronagraph, and the Heliospheric Imager
(HI) from the Solar Orbiter perspective can be combined to study
the eruptions and different source regions. Moreover, we show how
Metis data can be analyzed to provide new information about solar
eruptions. Methods: Different 3D reconstruction methods were
applied to the data acquired by different spacecraft, including
remote-sensing instruments on board Solar Orbiter. Images acquired
by the two Metis channels in the visible light (VL) and H I Ly-α
line (UV) were combined to derive physical information about the
expanding plasma. The polarization ratio technique was also applied
for the first time to Metis images acquired in the VL channel. Results: The two eruptions were followed in 3D from their source
region to their expansion in the intermediate corona. By combining
VL and UV Metis data, the formation of a post-CME current sheet (CS)
was followed for the first time in the intermediate corona. The
plasma temperature gradient across a post-CME blob propagating
along the CS was also measured for the first time. Application
of the polarization ratio technique to Metis data shows that by
combining four different polarization measurements, the errors are
reduced by ∼5 − 7%. This constrains the 3D plasma distribution
better. Movies associated to Figs. 4-7 are available at <A
href="https://www.aanda.org/10.1051/0004-6361/202243162/olm">https://www.aanda.org</A>

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Title: Linking Small-scale Solar Wind Properties with Large-scale
Coronal Source Regions through Joint Parker Solar Probe-Metis/Solar
Orbiter Observations
Authors: Telloni, Daniele; Zank, Gary P.; Sorriso-Valvo, Luca;
D'Amicis, Raffaella; Panasenco, Olga; Susino, Roberto; Bruno, Roberto;
Perrone, Denise; Adhikari, Laxman; Liang, Haoming; Nakanotani, Masaru;
Zhao, Lingling; Hadid, Lina Z.; Sánchez-Cano, Beatriz; Verscharen,
Daniel; Velli, Marco; Grimani, Catia; Marino, Raffaele; Carbone,
Francesco; Mancuso, Salvatore; Biondo, Ruggero; Pagano, Paolo; Reale,
Fabio; Bale, Stuart D.; Kasper, Justin C.; Case, Anthony W.; de Wit,
Thierry Dudok; Goetz, Keith; Harvey, Peter R.; Korreck, Kelly E.;
Larson, Davin; Livi, Roberto; MacDowall, Robert J.; Malaspina, David
M.; Pulupa, Marc; Stevens, Michael L.; Whittlesey, Phyllis; Romoli,
Marco; Andretta, Vincenzo; Deppo, Vania Da; Fineschi, Silvano; Heinzel,
Petr; Moses, John D.; Naletto, Giampiero; Nicolini, Gianalfredo;
Spadaro, Daniele; Stangalini, Marco; Teriaca, Luca; Capobianco,
Gerardo; Capuano, Giuseppe E.; Casini, Chiara; Casti, Marta; Chioetto,
Paolo; Corso, Alain J.; Leo, Yara De; Fabi, Michele; Frassati,
Federica; Frassetto, Fabio; Giordano, Silvio; Guglielmino, Salvo L.;
Jerse, Giovanna; Landini, Federico; Liberatore, Alessandro; Magli,
Enrico; Massone, Giuseppe; Messerotti, Mauro; Pancrazzi, Maurizio;
Pelizzo, Maria G.; Romano, Paolo; Sasso, Clementina; Schühle, Udo;
Slemer, Alessandra; Straus, Thomas; Uslenghi, Michela; Volpicelli,
Cosimo A.; Zangrilli, Luca; Zuppella, Paola; Abbo, Lucia; Auchère,
Frédéric; Cuadrado, Regina Aznar; Berlicki, Arkadiusz; Ciaravella,
Angela; Lamy, Philippe; Lanzafame, Alessandro; Malvezzi, Marco;
Nicolosi, Piergiorgio; Nisticò, Giuseppe; Peter, Hardi; Solanki,
Sami K.; Strachan, Leonard; Tsinganos, Kanaris; Ventura, Rita; Vial,
Jean-Claude; Woch, Joachim; Zimbardo, Gaetano
2022ApJ...935..112T Altcode:
The solar wind measured in situ by Parker Solar Probe in the very
inner heliosphere is studied in combination with the remote-sensing
observation of the coronal source region provided by the METIS
coronagraph aboard Solar Orbiter. The coronal outflows observed near
the ecliptic by Metis on 2021 January 17 at 16:30 UT, between 3.5 and
6.3 R ⊙ above the eastern solar limb, can be associated
with the streams sampled by PSP at 0.11 and 0.26 au from the Sun,
in two time intervals almost 5 days apart. The two plasma flows
come from two distinct source regions, characterized by different
magnetic field polarity and intensity at the coronal base. It follows
that both the global and local properties of the two streams are
different. Specifically, the solar wind emanating from the stronger
magnetic field region has a lower bulk flux density, as expected,
and is in a state of well-developed Alfvénic turbulence, with low
intermittency. This is interpreted in terms of slab turbulence in the
context of nearly incompressible magnetohydrodynamics. Conversely,
the highly intermittent and poorly developed turbulent behavior of the
solar wind from the weaker magnetic field region is presumably due to
large magnetic deflections most likely attributed to the presence of
switchbacks of interchange reconnection origin.

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Title: Dark off-limb gap: manifestation of temperature minimum and
dynamic nature of the chromosphere
Authors: Kuridze, D.; Heinzel, P.; Koza, J.; Oliver, R.
2022arXiv220814134K Altcode:
We study off-limb emission of the lower solar atmosphere using
high-resolution imaging spectroscopy in the H$\beta$ and Ca II 8542 Å
lines obtained with the CHROMospheric Imaging Spectrometer (CHROMIS)
and the CRisp Imaging SpectroPolarimeter (CRISP) on the Swedish 1-m
Solar Telescope. The H$\beta$ line wing images show the dark intensity
gap between the photospheric limb and chromosphere which is absent
in the Ca II images. We calculate synthetic spectra of the off-limb
emissions with the RH code in the one-dimension spherical geometry and
find good agreement with the observations. The analysis of synthetic
line profiles shows that the gap in the H$\beta$ line wing images maps
the temperature minimum region between the photosphere and chromosphere
due to the well known opacity and emissivity gap of Balmer lines in this
layer. However, observed gap is detected farther from the line core
in the outer line wing positions than in the synthetic profiles. We
found that an increased microturbulence in the model chromosphere is
needed to reproduce the dark gap in the outer line wing, suggesting that
observed H$\beta$ gap is the manifestation of the temperature minimum
and the dynamic nature of the solar chromosphere. The temperature
minimum produces a small enhancement in synthetic Ca II line-wing
intensities. Observed off-limb Ca II line-wing emissions show similar
enhancement below temperature minimum layer near the edge of the
photospheric limb.

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Title: Data-driven Model of Temporal Evolution of Solar Mg II h and
k Profiles over the Solar Cycle
Authors: Koza, Július; Gunár, Stanislav; Schwartz, Pavol; Heinzel,
Petr; Liu, Wenjuan
2022ApJS..261...17K Altcode:
The solar radiation in the cores of the Mg II h and k spectral lines
plays a significant role in the illumination of prominences, coronal
mass ejections (CMEs), spicules, flare loops, and surges. Moreover,
the radiation in these lines strongly correlates with solar magnetic
activity and the ultraviolet solar spectral irradiance affecting
the photochemistry, especially of oxygen and nitrogen, in the middle
atmosphere of the Earth. This work provides a data-driven model of
temporal evolution of the solar full-disk Mg II h and k profiles over
the solar cycle. The capability of the model to reproduce the Mg II h
and k profiles for an arbitrary date is statistically assessed. Based
on selected 76 IRIS near-UV full-Sun mosaics covering almost the full
solar cycle 24, we find the parameters of double-Gaussian fits of the
disk-averaged Mg II h and k profiles and a model of their temporal
evolution parameterized by the Bremen composite Mg II index. The
model yields intensities within the uncertainties of the observed
data in more than 90% of the reconstructed profiles assuming a
statistically representative set of Bremen Mg II index values in the
range of 0.150-0.165. The relevant full-disk Mg II h and k calibrated
profiles with uncertainties and spectral irradiances are provided as an
online machine-readable table. The model yields Mg II h and k profiles
representing the disk incident radiation for the radiative-transfer
modeling of prominences, CMEs, spicules, flare loops, and surges
observed at arbitrary time.

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Title: Large Impact of the Mg II h and k Incident Radiation Change
on Results of Radiative Transfer Models and the Importance of Dynamics
Authors: Gunár, Stanislav; Heinzel, Petr; Koza, Július; Schwartz,
Pavol
2022ApJ...934..133G Altcode:
We demonstrate that changes in the incident radiation in Mg II h
and k lines have a significant impact on the results of radiative
transfer modeling of prominence-like plasmas. To uncover the extent
of this impact and allow easy comparison, here we study two cases,
one representing the minimum of the solar activity and the other
corresponding to the typical conditions during solar maxima. To
represent well the properties of the prominence plasma, we use the 2D
non-LTE (i.e., departures from local thermodynamic equilibrium) model
of prominence fine structures in both the single-thread configuration
and the multithread configuration incorporating prominence dynamics. We
show that in the modeled environment of prominence fine structures,
the change in the central, integrated, and peak intensities of the
synthetic Mg II h and k profiles can be as large as the change in the
incident radiation itself. This means that the Mg II h and k spectra
of observed prominences can be affected by tens of percent because the
illumination from the solar disk can change by such a degree over the
solar cycle. That makes the knowledge and use of event-specific incident
radiation data very important for the diagnostics of prominences
and other chromospheric and coronal structures when using Mg II h
and k spectral observations. In addition, the observed Mg II h and k
spectra are strongly influenced by the line-of-sight dynamics, as the
multithread configuration of the 2D model allows us to reveal. The
effect of dynamics is, unsurprisingly, most pronounced in the line
widths and integrated intensities.

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Title: A first comparison of FLARIX flare simulations with the MSDP
H-alpha spectral observations on very short time scales
Authors: Heinzel, Petr; Kasparova, Jana; Berlicki, Arkadiusz;
Radziszewski, Krzysztof; Rudawy, Pawel
2022cosp...44.2560H Altcode:
We present first results of a comparative analysis of high temporal
resolution MSDP H$\alpha$ observations of a compact solar flare with
results of radiation-hydrodynamical simulations performed using the
FLARIX code. X-ray spectral observations of a compact C1 GOES-class
flare obtained from RHESSI satellite were used to estimate physical
parameters of the electron beams transporting the energy from the
reconnection site down to the chromosphere. These parameters are then
used for data-driven FLARIX simulations. A small size of the flare
and its simple structure allowed us to assume a single-loop geometry
which significantly simplified the modelling and analysis of the
whole event. Using the MSDP imaging spectrograph at Bia{\l}k\'{o}w
observatory, it was possible to compare the recorded H$\alpha$
line emission with that obtained from FLARIX simulations, on short
time-scales down to 50 ms.

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Title: Geometry and dynamics of cool flare loops observed by IRIS
Authors: Mikuła, Katarzyna; Heinzel, Petr; Berlicki, Arkadiusz
2022cosp...44.2414M Altcode:
Flare loops represent a well-known, inseparable part of solar
flares. They are observed mainly during the gradual phase of the flares,
being rooted in flare ribbons. They can form an entire arcade which
evolves in the corona, sometimes for hours. The loops are visible
in a wide range of temperature bands, from X-rays (hot flare loops)
to temperatures of the cool chromospheric-type plasma seen in the
ultraviolet and optical spectrum (cool flare loops). We present
results of our analysis of cool flare loops observed during the gradual
phase of M6.5 solar flare on June 22, 2015 based on the ultraviolet
observations obtained by Interface Region Imaging Spectrograph
(IRIS). Detailed investigation of these loops, made on the basis of
Mg II line profiles, was presented in Mikuła et al. (2017). Mg II
line profiles were modelled using the standard cloud model method
that allowed us obtaining simultaneously the physical parameters
characteridsing the moving plasma inside selected loops, i.e. the
velocity along the line-of-sight, microturbulent velocity, optical
thickness, and the line source function. Here we present a next step
of the work — reconstruction of the true shape of flare loops based
on the geometric method of Loughhead, Wang and Blows (1983). Based
on two-dimensional images of a given loop structure located on
the solar disk or at the limb, we can obtain its true orientation
and its size. The shape of the analysed loops was determined mainly
from IRIS slit-jaw images at 1330, 1400 and 2796 \AA{}, supplemented
with SDO/AIA 171 \AA{} images in some cases. Using basic geometry,
we reconstructed the shape of selected loops in the three-dimensional
space. Based on the method presented in Loughhead and Bray (1984) we
were able to derive the so-called true velocity of the plasma flows,
i.e. the velocity along the loop axis. The results obtained for each
loop were then compared with the free fall velocities.

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Title: New Insight into UV Compact Bursts - Statistical Analysis of
IRIS Data
Authors: Berlicki, Arkadiusz; Heinzel, Petr; Schmieder, Brigitte;
Michalina Litwicka, M.
2022cosp...44.2532B Altcode:
UV small-scale brightenings have been frequently observed by IRIS in
both NUV and FUV channels. They appear as compact and intense, but short
lived bursts visible within the solar active regions. Some of them seem
to be closely connected with the well-known Ellerman bombs and so-called
IRIS bombs. Based on the IRIS observations of many compact bursts
obtained in chromospheric Mg II h and k lines, Mg II triplet and FUV
lines we present detailed statistical analysis of these phenomena. In
the work of Grubecka et al. (2016), five different compact bursts (CBs)
were selected and analysed in detail. NLTE semi-empirical models of
them were constructed based on their spectral characteristics in the
Mg II h and k lines. In addition, they were preliminarily categorised
into three types. In present work we extend previous analysis and
investigate statistical diversity of Mg II lines of UV bursts and
their visibility in FUV lines such as Si IV or C II. IRIS database
from 2013-2018 was searched for dense rasters of active and emerging
flux regions containing spectra in Mg II, C II and Si IV. A next step
was to reconstruct full rasters in which we were looking for compact
brightenings with size of the order of one arcsec. We found more than
two thousands CBs using criteria based on specific parameters of the
Mg II k line profile. In addition, we analysed also the emission of
Mg II UV triplet and some parameters of Si IV and C II lines. This
database allowed us to make a novel statistical analysis of all bursts
and we categorised them in previously defined three types, depending on
their Mg II line profiles shapes. We also investigated the correlations
between the emission of Mg II lines, "hotter" Si IV lines, and C II
lines in order to find which of these events are linked with IRIS bombs
(Peter et al. 2014). Finally, we analysed some observables of those
UV bursts, which can be defined as candidates for Ellerman bombs.

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Title: Diagnostics of The Prominence Plasma Based on IRIS, H-alpha
and ALMA Observations
Authors: Berlicki, Arkadiusz; Bárta, Miroslav; Gunár, Stanislav;
Heinzel, Petr; Jejcic, Sonja; Radziszewski, Krzysztof; Rudawy, Pawel
2022cosp...44.2543B Altcode:
Solar prominences are now commonly observed above the solar limb in
different spectral bands and recent developments of new observing
techniques allow us to detect them from radio to far-UV ranges. In
addition to often used spectral observations in optical and UV,
ALMA interferometer obtained high-resolution images of a quiescent
solar prominence at 3 millimeters (Band 3) during the coordinated
space and ground-based observing campaign. For the first time
high-resolution observations of such structures in the millimeter
radio domain are available. The fine structures of this prominence was
also observed in the UV with IRIS and in the H$\alpha$ line with the
MSDP of Wroc{\l}aw Observatory. Both UV and H$\alpha$ data contains
not only images, but also spectra which makes the available dataset
extremely valuable. Moreover, all UV, H$\alpha$ and ALMA observations
are co-temporal which gives an unprecedented opportunity for a novel
diagnostic, not available so far. In this work we present analysis
of the prominence spectral characteristics in H$\alpha$ and UV Mg
II lines, looking for the statistical dependence between different
parameters (metrics) in the line profiles. This combined data is
then used for determination of plasma parameters in the prominence
fine structures. In addition, UV and H$\alpha$ spectral maps are
compared with the brightness temperature mosaics from ALMA, providing
an additional constraint on the plasma kinetic temperature. Detailed
diagnostics is then based on extensive NLTE numerical simulations of
the radiative transfer inside heterogeneous prominence structures.

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Title: Spectral line asymmetries observed during stellar flares
Authors: Wollmann, Jiří; Heinzel, Petr; Kabath, Petr; Karjalainen,
Raine; Skarka, Marek; Špoková, Magdalena
2022cosp...44.2468W Altcode:
Stellar flares are highly energetic events occuring in stellar
atmospheres. This solar-like activity has been observed on G, K and M
stars. Red dwarfs usually have vast and strong magnetic fields which
often reconnect and produce strong flares, sometimes classified as the
so-called superflares. From spectroscopic observations we see, apart
from typical enhancements of the line intensities, clearly asymmetrical
line profiles. In analogy with solar flares, one would interpret them
as due to flows in the flaring chromosphere. However, some stellar
observations indicate a peculiar behaviour of such asymmetries and
their nature is not well understood. In this work we present recent
spectroscopic observations of flares on AD Leo star obtained with the
Ondrejov Echelle Spectrograph. We analyze detected asymmetries using
the non-LTE radiative-transfer modeling and demonstrate the importance
of flare dynamics. Our interpretation is based on a close analogy with
solar flares.

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Title: Mini solar flare and jet due to small scale surface motions
Authors: Joshi, Reetika; Vilmer, Nicole; Chandra, Ramesh; Heinzel,
Petr; Bommier, Veronique; Schmieder, Brigitte; Aulanier, Guillaume;
Tomin, James
2022cosp...44.2535J Altcode:
Here we present the study of the fine structure and dynamics of the
plasma at a jet base forming a mini-flare between two emerging magnetic
fluxes (EMFs) observed with Interface Region Imaging Spectrograph
(IRIS) and the Solar Dynamics Observatory instruments. This active
region is an outcome of the collapse of two EMFs overlaid by arch
filament systems. We observed that, before the jet an extension of
the flux rope was present and a part of it was detached and formed
a small bipole with a bald patch region, which dynamically became
an X-current sheet over the dome of one EMF where the reconnection
took place. At the time in the site of reconnection, the IRIS C II,
Si IV, and Mg II line profiles present bi directional flows in a tiny
region. These types of spectra are typically associated with twist,
rotation, or the presence of plasma in helical structures. The tilt
observed in our spectra can be explained by the presence of a helical
structure at the jet base during the reconnection process due to a
transfer of the twist from a flux rope in the vicinity of the jet. We
also combined the observations of the Balmer continuum obtained with
the IRIS (spectra and SJIs 2832 Å). The calibrated Balmer continuum
was compared to non-local thermodynamic equilibrium radiative transfer
flare models and the radiated energy was estimated. Assuming thick
target HXR emission, we calculated the energy of the non thermal
electrons detected by the Fermi/GBM and compared it to the radiated
energy. The electron-beam flux estimated from Fermi/GBM between 10$
^{9}$ and 10$ ^{10}$ erg s$ ^{-1}$ cm$ ^{-2}$ is consistent with the
beam flux required in non-LTE radiative transfer models to obtain the
excess of Balmer continuum emission observed in this IRIS spectra. We
conclude that the bombardment of electrons could be in a region smaller
than the IRIS spatial resolution.

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Title: Variability of solar Lyman-alpha and Mg II h&amp;k lines
throughout the solar cycle and its impact on the diagnostics of
chromospheric and coronal structures
Authors: Gunár, Stanislav; Schwartz, Pavol; Heinzel, Petr; Liu,
Wenjuan; Koza, Julius
2022cosp...44.1553G Altcode:
The solar radiation in the Lyman-alpha and Mg II h&amp;k spectral lines
plays a crucial role in the illumination of chromospheric and coronal
structures, such as prominences/filaments, spicules, chromospheric
fibrils, cores of coronal mass ejections, or solar wind. Moreover,
it is important for the investigation of the heliosphere, Earth
ionosphere, and the atmospheres of planets, moons, and comets. However,
the emissivity of the Sun is not constant in these lines but changes
considerably throughout the solar cycle. To study these changes
and their impact, we first had to set the baseline representing the
radiation from the solar disk during a minimum of solar activity. We
thus derived new sets of quiet-Sun reference profiles of Lyman-alpha
and Mg II h&amp;k lines. For the Lyman-alpha line, we used SOHO/SUMER
raster scans obtained without the use of the SUMER attenuator (Gunár et
al. 2020) and for the Mg II h&amp;k lines we used the broad catalogue of
IRIS full-Sun mosaics (Gunár et al. 2021). To quantify the variability
with the solar cycle, we used the LISIRD Composite Lyman-alpha index to
adapt the Lyman lines to any specific date (Gunár et al. 2020). For
the Mg II h&amp;k lines, we used a data-driven model based on the
Bremen Composite Mg II index (Koza et al. 2022). These long-term
measures then allowed us to investigate how the changing irradiation
from the solar surface influences the synthetic spectra produced by
the radiative transfer modelling. As we showed in Gunár et al. (2020,
2022), both changes in the Lyman lines and the Mg II h&amp;k lines
affect the resulting synthetic spectra significantly, even up to 50 %
depending on the strength of individual solar cycles. That, however,
has a strong impact on the diagnostics of the observed chromospheric
and coronal structures, making up-to-date information about the solar
activity a critical input for their precise modelling.

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Title: Doppler-velocity Drifts Detected in a Solar Prominence
Authors: Zapiór, Maciej; Heinzel, Petr; Khomenko, Elena
2022ApJ...934...16Z Altcode:
We analyzed multiline observations of a quiescent prominence from the
slit spectrograph located at the Ondřejov Observatory. Dopplergrams
and integrated intensity maps of the whole prominence were obtained
from observations in six spectral lines: Ca II H, Hϵ, Hβ, He I D3,
Hα, and Ca II IR. By combining integrated intensity maps with non-LTE
radiative-transfer modeling, we carefully identified areas in an
optically thin regime. The comparison of the Doppler-velocity maps and
scatterplots from different lines shows the existence of differences
in the velocity of ions and neutrals called velocity drift. The drift
is of a local nature, present mostly at prominence edges in the area
with a large velocity gradient, as can be tentatively expected based on
multifluid MHD models. We could not explore the time evolution of the
drift, since our data set consists of a single scan only. Our paper
brings another contribution to a rather controversial problem of the
detection of multifluid effects in solar prominences.

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Title: Modeling Balmer line signatures of stellar CMEs
Authors: Leitzinger, M.; Odert, P.; Heinzel, P.
2022MNRAS.513.6058L Altcode: 2022MNRAS.tmp.1287L; 2022arXiv220503110L
From the Sun, we know that coronal mass ejections (CMEs) are a
transient phenomenon, often correlated with flares. They have an
impact on solar mass- and angular momentum loss, and therefore solar
evolution, and make a significant part of space weather. The same
is true for stars, but stellar CMEs are still not well constrained,
although new methodologies have been established, and new detections
presented in the recent past. So far, probable detections of stellar
CMEs have been presented, but their physical parameters which are
not directly accessible from observations, such as electron density,
optical thickness, temperature, etc., have been so far not determined
for the majority of known events. We apply cloud modeling, as commonly
used on the Sun, to a known event from the literature, detected on
the young dMe star V374 Peg. This event manifests itself in extra
emission on the blue side of the Balmer lines. By determining the line
source function from 1D NLTE modeling together with the cloud model
formulation, we present distributions of physical parameters of this
event. We find that except for temperature and area all parameters
are at the upper range of typical solar prominence parameters. The
temperature and the area of the event were found to be higher than
for typical solar prominences observed in Balmer lines. We find more
solutions for the filament than for the prominence geometry. Moreover,
we show that filaments can appear in emission on dMe stars contrary
to the solar case.

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Title: Prominence eruption observed in He II 304 Å up to &gt;6
R⊙ by EUI/FSI aboard Solar Orbiter
Authors: Mierla, M.; Zhukov, A. N.; Berghmans, D.; Parenti, S.;
Auchère, F.; Heinzel, P.; Seaton, D. B.; Palmerio, E.; Jejčič, S.;
Janssens, J.; Kraaikamp, E.; Nicula, B.; Long, D. M.; Hayes, L. A.;
Jebaraj, I. C.; Talpeanu, D. -C.; D'Huys, E.; Dolla, L.; Gissot, S.;
Magdalenić, J.; Rodriguez, L.; Shestov, S.; Stegen, K.; Verbeeck,
C.; Sasso, C.; Romoli, M.; Andretta, V.
2022A&A...662L...5M Altcode: 2022arXiv220515214M
 Aims: We report observations of a unique, large prominence
eruption that was observed in the He II 304 Å passband of the Extreme
Ultraviolet Imager/Full Sun Imager telescope aboard Solar Orbiter on
15-16 February 2022. Methods: Observations from several vantage
points - Solar Orbiter, the Solar-Terrestrial Relations Observatory,
the Solar and Heliospheric Observatory, and Earth-orbiting satellites -
were used to measure the kinematics of the erupting prominence and the
associated coronal mass ejection. Three-dimensional reconstruction was
used to calculate the deprojected positions and speeds of different
parts of the prominence. Observations in several passbands allowed us
to analyse the radiative properties of the erupting prominence. 
Results: The leading parts of the erupting prominence and the leading
edge of the corresponding coronal mass ejection propagate at speeds
of around 1700 km s−1 and 2200 km s−1,
respectively, while the trailing parts of the prominence are
significantly slower (around 500 km s−1). Parts of the
prominence are tracked up to heights of over 6 R⊙. The
He II emission is probably produced via collisional excitation rather
than scattering. Surprisingly, the brightness of a trailing feature
increases with height. Conclusions: The reported prominence
is the first observed in He II 304 Å emission at such a great
height (above 6 R⊙). Movies are available at <A
href="https://www.aanda.org/10.1051/0004-6361/202244020/olm">https://www.aanda.org</A>

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Title: Observation of Magnetic Switchback in the Solar Corona
Authors: Telloni, Daniele; Zank, Gary P.; Stangalini, Marco;
Downs, Cooper; Liang, Haoming; Nakanotani, Masaru; Andretta,
Vincenzo; Antonucci, Ester; Sorriso-Valvo, Luca; Adhikari, Laxman;
Zhao, Lingling; Marino, Raffaele; Susino, Roberto; Grimani, Catia;
Fabi, Michele; D'Amicis, Raffaella; Perrone, Denise; Bruno, Roberto;
Carbone, Francesco; Mancuso, Salvatore; Romoli, Marco; Da Deppo, Vania;
Fineschi, Silvano; Heinzel, Petr; Moses, John D.; Naletto, Giampiero;
Nicolini, Gianalfredo; Spadaro, Daniele; Teriaca, Luca; Frassati,
Federica; Jerse, Giovanna; Landini, Federico; Pancrazzi, Maurizio;
Russano, Giuliana; Sasso, Clementina; Berghmans, David; Auchère,
Frédéric; Aznar Cuadrado, Regina; Chitta, Lakshmi P.; Harra, Louise;
Kraaikamp, Emil; Long, David M.; Mandal, Sudip; Parenti, Susanna;
Pelouze, Gabriel; Peter, Hardi; Rodriguez, Luciano; Schühle, Udo;
Schwanitz, Conrad; Smith, Phil J.; Verbeeck, Cis; Zhukov, Andrei N.
2022arXiv220603090T Altcode:
Switchbacks are sudden, large radial deflections of the solar wind
magnetic field, widely revealed in interplanetary space by the Parker
Solar Probe. The switchbacks' formation mechanism and sources are still
unresolved, although candidate mechanisms include Alfvénic turbulence,
shear-driven Kelvin-Helmholtz instabilities, interchange reconnection,
and geometrical effects related to the Parker spiral. This Letter
presents observations from the Metis coronagraph onboard Solar Orbiter
of a single large propagating S-shaped vortex, interpreted as first
evidence of a switchback in the solar corona. It originated above
an active region with the related loop system bounded by open-field
regions to the East and West. Observations, modeling, and theory provide
strong arguments in favor of the interchange reconnection origin of
switchbacks. Metis measurements suggest that the initiation of the
switchback may also be an indicator of the origin of slow solar wind.

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Title: Non-LTE Inversion of Prominence Spectroscopic Observations
in Hα and Mg II h&amp;k lines
Authors: Jejčič, Sonja; Heinzel, Petr; Schmieder, Brigitte; Gunár,
Stanislav; Mein, Pierre; Mein, Nicole; Ruan, Guiping
2022ApJ...932....3J Altcode:
We continued our investigation of the plasma characteristics of a
quiescent prominence that occurred on 2017 March 30. The prominence
was observed simultaneously by several instruments, including the
Interface Region Imaging Spectrograph (IRIS) and the Multichannel
Subtractive Double Pass (MSDP) spectrograph operating at the Meudon
solar tower. We focused on IRIS Mg II h&amp;k and MSDP Hα spectra,
selecting 55 well-coaligned points within the prominence. We computed
an extensive grid of 63,000 isothermal and isobaric 1D-slab prominence
models with a non-LTE (i.e., departures from the local thermodynamic
equilibrium) radiative transfer code. We then performed a 1.5D
spectral inversion searching for an optimal model that best fits
five parameters of the observed profiles (observables), namely,
the integrated intensity of the Hα and Mg II k lines, the FWHM of
both lines, and the ratio of intensities of the Mg II k and Mg II h
lines. The latter is sensitive to temperature. Our results show that
the prominence is a low-temperature structure, mostly below 10,000
K, with some excursions to higher values (up to 18,000 K) but also
rather low temperatures (around 5000 K). The microturbulent velocity is
typically low, peaking around 8 km s-1, and electron density
values are of the order of 1010 cm-3. The peak
effective thickness is 500 km, although the values range up to 5000
km. The studied prominence is rather optically thin in the Hα line
and optically thick in the Mg II h&amp;k lines.

---------------------------------------------------------
Title: Subarcsecond Imaging of a Solar Active Region Filament With
ALMA and IRIS
Authors: da Silva Santos, J. M.; White, S. M.; Reardon, K.; Cauzzi,
G.; Gunár, S.; Heinzel, P.; Leenaarts, J.
2022FrASS...9.8115D Altcode: 2022arXiv220413178D
Quiescent filaments appear as absorption features on the solar disk
when observed in chromospheric lines and at continuum wavelengths
in the millimeter (mm) range. Active region (AR) filaments are their
small-scale, low-altitude analogues, but they could not be resolved
in previous mm observations. This spectral diagnostic can provide
insight into the details of the formation and physical properties of
their fine threads, which are still not fully understood. Here, we shed
light on the thermal structure of an AR filament using high-resolution
brightness temperature (Tb) maps taken with ALMA Band 6 complemented by
simultaneous IRIS near-UV spectra, Hinode/SOT photospheric magnetograms,
and SDO/AIA extreme-UV images. Some of the dark threads visible in the
AIA 304 Å passband and in the core of Mg ii resonance lines have dark
(Tb &lt; 5,000 K) counterparts in the 1.25 mm maps, but their visibility
significantly varies across the filament spine and in time. These
opacity changes are possibly related to variations in temperature and
electron density in filament fine structures. The coolest Tb values
(&lt; 5,000 K) coincide with regions of low integrated intensity in the
Mg ii h and k lines. ALMA Band 3 maps taken after the Band 6 ones do not
clearly show the filament structure, contrary to the expectation that
the contrast should increase at longer wavelengths based on previous
observations of quiescent filaments. The ALMA maps are not consistent
with isothermal conditions, but the temporal evolution of the filament
may partly account for this.

---------------------------------------------------------
Title: ALMA as a Prominence Thermometer: First Observations
Authors: Heinzel, Petr; Berlicki, Arkadiusz; Bárta, Miroslav; Rudawy,
Paweł; Gunár, Stanislav; Labrosse, Nicolas; Radziszewski, Krzysztof
2022ApJ...927L..29H Altcode: 2022arXiv220212761H
We present first prominence observations obtained with Atacama
Large Millimeter Array (ALMA) in Band 3 at the wavelength of
3 mm. High-resolution observations have been coaligned with the
MSDP Hα data from Wrocław-Białków large coronagraph at similar
spatial resolution. We analyze one particular cotemporal snapshot,
first calibrating both ALMA and MSDP data and then demonstrating a
reasonable correlation between both. In particular, we can see quite
similar fine-structure patterns in both ALMA brightness-temperature maps
and MSDP maps of Hα intensities. Using ALMA, we intend to derive the
prominence kinetic temperatures. However, having current observations
only in one band, we use an independent diagnostic constraint, which
is the Hα line integrated intensity. We develop an inversion code and
show that it can provide realistic temperatures for brighter parts of
the prominence where one gets a unique solution, while within faint
structures, such inversion is ill conditioned. In brighter parts,
ALMA serves as a prominence thermometer, provided that the optical
thickness in Band 3 is large enough. In order to find a relation between
brightness and kinetic temperatures for a given observed Hα intensity,
we constructed an extended grid of non-LTE prominence models covering
a broad range of prominence parameters. We also show the effect of
the plane-of-sky filling factor on our results.

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Title: Constraining stellar CMEs by solar observations
Authors: Leitzinger, Martin; Odert, Petra; Leka, K. D.; Heinzel,
Petr; Dissauer, Karin
2021AGUFM.U43B..06L Altcode:
Stellar coronal mass ejections (CMEs) may play an important role
in star-planet interactions, such as planetary atmospheric escape,
and in stellar mass- and angular momentum loss, influencing stellar
evolution. In the last decades much effort has been put into determining
parameters of stellar CMEs. New detection methods have been developed,
but still the number of convincing events is low and far from
enabling statistical analyses. So far the methods of detections
comprise the direct signature of ejected plasma, namely Doppler
shifted emission/absorption visible in spectra (optical, UV, X-ray),
absorptions seen during flares in X-rays interpreted as obscuring
events, and CME-associated signatures known from the Sun, like radio
type II bursts and coronal dimmings, the latter being only recently
established. The first method (Doppler shifted emission/absorption
lines) has been used since decades on stars (especially in H which
well probes the eruptive filament/prominence in the CME core) and
provides a few convincing detections and a large number of candidate
events with projected velocities significantly below the stars' escape
velocities. Such events could be CMEs seen in projection but it has
been proposed that these signatures could be caused by flare related
plasma dynamics. As there is a large pool of candidate events which
cannot be unambiguously interpreted as CMEs, we propose a new approach
to distinguish between flare and CME related signtures to increase the
number of convincing CME events. What we observe from stars are disk
integrated signals, in contrast to solar observations. To constrain
stellar CMEs by solar observations, solar 2D imaging spectroscopy is
required from which spatially integrated spectra can be created for a
sufficiently large number of events (flares and CMEs). These aspects
are fulfilled by MEES CCD (MCCD) optical observations at Mees Solar
Observatory (MSO). Therefore we propose the analysis of a sample of
solar flares and filaments/prominences from MCCD/MSO and their spatially
integrated spectra which allows to separate contributions from flares
and filaments/prominences. We present preliminary results of a few
selected solar events from MCCD demonstrating how to characterize
flare and CME related signatures in stellar observations.

---------------------------------------------------------
Title: Empirical atmosphere model in a mini flare during magnetic
reconnection
Authors: Schmieder, Brigitte; Joshi, Reetika; Chandra, Ramesh;
Aulanier, Guillaume; Tei, Akiko; Heinzel, Petr; Tomin, James; Vilmer,
Nicole; Bommier, Veronique
2021arXiv211206790S Altcode:
A spatio-temporal analysis of IRIS spectra of MgII, CII, and SiIV ions
allows us to study the dynamics and the stratification of the flare
atmosphere along the line of sight during the magnetic reconnection
phase at the jet base. Strong asymmetric MgII and CII line profiles with
extended blue wings observed at the reconnection site are interpreted
by the presence of two chromospheric temperature clouds: one explosive
cloud with blueshifts at 290 km/s and one cloud with smaller Doppler
shift (around 36 km/s). Simultaneously at the same location a mini
flare was observed with strong emission in multi temperatures (AIA),
in several spectral IRIS lines (e.g. Oiv and Siiv, Mgii), absorption
of identified chromospheric lines in Siiv line profile, enhancement
of the Balmer continuum and X-ray emission by FERMI/GBM. With the
standard thick-target flare model we calculate the energy of non thermal
electrons observed by FERMI and compare it to the energy radiated by
the Balmer continuum emission. We show that the low energy input by
non thermal electrons above 20 keV was still sufficient to produce
the excess of Balmer continuum.

---------------------------------------------------------
Title: The first coronal mass ejection observed in both visible-light
and UV H I Ly-α channels of the Metis coronagraph on board Solar
Orbiter
Authors: Andretta, V.; Bemporad, A.; De Leo, Y.; Jerse, G.; Landini,
F.; Mierla, M.; Naletto, G.; Romoli, M.; Sasso, C.; Slemer, A.;
Spadaro, D.; Susino, R.; Talpeanu, D. -C.; Telloni, D.; Teriaca, L.;
Uslenghi, M.; Antonucci, E.; Auchère, F.; Berghmans, D.; Berlicki,
A.; Capobianco, G.; Capuano, G. E.; Casini, C.; Casti, M.; Chioetto,
P.; Da Deppo, V.; Fabi, M.; Fineschi, S.; Frassati, F.; Frassetto,
F.; Giordano, S.; Grimani, C.; Heinzel, P.; Liberatore, A.; Magli, E.;
Massone, G.; Messerotti, M.; Moses, D.; Nicolini, G.; Pancrazzi, M.;
Pelizzo, M. -G.; Romano, P.; Schühle, U.; Stangalini, M.; Straus,
Th.; Volpicelli, C. A.; Zangrilli, L.; Zuppella, P.; Abbo, L.; Aznar
Cuadrado, R.; Bruno, R.; Ciaravella, A.; D'Amicis, R.; Lamy, P.;
Lanzafame, A.; Malvezzi, A. M.; Nicolosi, P.; Nisticò, G.; Peter,
H.; Plainaki, C.; Poletto, L.; Reale, F.; Solanki, S. K.; Strachan,
L.; Tondello, G.; Tsinganos, K.; Velli, M.; Ventura, R.; Vial, J. -C.;
Woch, J.; Zimbardo, G.
2021A&A...656L..14A Altcode:
Context. The Metis coronagraph on board Solar Orbiter offers a new
view of coronal mass ejections (CMEs), observing them for the first
time with simultaneous images acquired with a broad-band filter in
the visible-light interval and with a narrow-band filter around the
H I Ly-α line at 121.567 nm, the so-called Metis UV channel. 
Aims: We show the first Metis observations of a CME, obtained on 16
and 17 January 2021. The event was also observed by the EUI/FSI imager
on board Solar Orbiter, as well as by other space-based coronagraphs,
such as STEREO-A/COR2 and SOHO/LASCO/C2, whose images are combined here
with Metis data. Methods: Different images are analysed here
to reconstruct the 3D orientation of the expanding CME flux rope using
the graduated cylindrical shell model. This also allows us to identify
the possible location of the source region. Measurements of the CME
kinematics allow us to quantify the expected Doppler dimming in the
Ly-α channel. Results: Observations show that most CME features
seen in the visible-light images are also seen in the Ly-α images,
although some features in the latter channel appear more structured
than their visible-light counterparts. We estimated the expansion
velocity of this event to be below 140 km s−1. Hence,
these observations can be understood by assuming that Doppler dimming
effects do not strongly reduce the Ly-α emission from the CME. These
velocities are comparable with or smaller than the radial velocities
inferred from the same data in a similar coronal structure on the
east side of the Sun. Conclusions: The first observations by
Metis of a CME demonstrate the capability of the instrument to provide
valuable and novel information on the structure and dynamics of these
coronal events. Considering also its diagnostics capabilities regarding
the conditions of the ambient corona, Metis promises to significantly
advance our knowledge of such phenomena. Movies are available at <A
href="https://www.aanda.org/10.1051/0004-6361/202142407/olm">https://www.aanda.org</A>

---------------------------------------------------------
Title: Cosmic-ray flux predictions and observations for and with
Metis on board Solar Orbiter
Authors: Grimani, C.; Andretta, V.; Chioetto, P.; Da Deppo, V.; Fabi,
M.; Gissot, S.; Naletto, G.; Persici, A.; Plainaki, C.; Romoli, M.;
Sabbatini, F.; Spadaro, D.; Stangalini, M.; Telloni, D.; Uslenghi, M.;
Antonucci, E.; Bemporad, A.; Capobianco, G.; Capuano, G.; Casti, M.;
De Leo, Y.; Fineschi, S.; Frassati, F.; Frassetto, F.; Heinzel, P.;
Jerse, G.; Landini, F.; Liberatore, A.; Magli, E.; Messerotti, M.;
Moses, D.; Nicolini, G.; Pancrazzi, M.; Pelizzo, M. G.; Romano, P.;
Sasso, C.; Schühle, U.; Slemer, A.; Straus, T.; Susino, R.; Teriaca,
L.; Volpicelli, C. A.; Freiherr von Forstner, J. L.; Zuppella, P.
2021A&A...656A..15G Altcode: 2021arXiv210413700G
Context. The Metis coronagraph is one of the remote sensing instruments
hosted on board the ESA/NASA Solar Orbiter mission. Metis is devoted
to carry out the first simultaneous imaging of the solar corona in
both visible light (VL) and ultraviolet (UV). High-energy particles
can penetrate spacecraft materials and may limit the performance of
the on-board instruments. A study of the galactic cosmic-ray (GCR)
tracks observed in the first VL images gathered by Metis during the
commissioning phase is presented here. A similar analysis is planned
for the UV channel. Aims: We aim to formulate a prediction of
the GCR flux up to hundreds of GeV for the first part of the Solar
Orbiter mission to study the performance of the Metis coronagraph. Methods: The GCR model predictions are compared to observations
gathered on board Solar Orbiter by the High-Energy Telescope in the
range between 10 MeV and 100 MeV in the summer of 2020 as well as with
the previous measurements. Estimated cosmic-ray fluxes above 70 MeV
n−1 have been also parameterized and used for Monte Carlo
simulations aimed at reproducing the cosmic-ray track observations in
the Metis coronagraph VL images. The same parameterizations can also
be used to study the performance of other detectors. Results:
By comparing observations of cosmic-ray tracks in the Metis VL images
with FLUKA Monte Carlo simulations of cosmic-ray interactions in
the VL detector, we find that cosmic rays fire only a fraction, on
the order of 10−4, of the whole image pixel sample. We
also find that the overall efficiency for cosmic-ray identification
in the Metis VL images is approximately equal to the contribution
of Z ≥ 2 GCR particles. A similar study will be carried out during
the whole of the Solar Orbiter's mission duration for the purposes of
instrument diagnostics and to verify whether the Metis data and Monte
Carlo simulations would allow for a long-term monitoring of the GCR
proton flux.

---------------------------------------------------------
Title: First light observations of the solar wind in the outer corona
with the Metis coronagraph
Authors: Romoli, M.; Antonucci, E.; Andretta, V.; Capuano, G. E.; Da
Deppo, V.; De Leo, Y.; Downs, C.; Fineschi, S.; Heinzel, P.; Landini,
F.; Liberatore, A.; Naletto, G.; Nicolini, G.; Pancrazzi, M.; Sasso,
C.; Spadaro, D.; Susino, R.; Telloni, D.; Teriaca, L.; Uslenghi,
M.; Wang, Y. -M.; Bemporad, A.; Capobianco, G.; Casti, M.; Fabi, M.;
Frassati, F.; Frassetto, F.; Giordano, S.; Grimani, C.; Jerse, G.;
Magli, E.; Massone, G.; Messerotti, M.; Moses, D.; Pelizzo, M. -G.;
Romano, P.; Schühle, U.; Slemer, A.; Stangalini, M.; Straus, T.;
Volpicelli, C. A.; Zangrilli, L.; Zuppella, P.; Abbo, L.; Auchère,
F.; Aznar Cuadrado, R.; Berlicki, A.; Bruno, R.; Ciaravella, A.;
D'Amicis, R.; Lamy, P.; Lanzafame, A.; Malvezzi, A. M.; Nicolosi,
P.; Nisticò, G.; Peter, H.; Plainaki, C.; Poletto, L.; Reale, F.;
Solanki, S. K.; Strachan, L.; Tondello, G.; Tsinganos, K.; Velli,
M.; Ventura, R.; Vial, J. -C.; Woch, J.; Zimbardo, G.
2021A&A...656A..32R Altcode: 2021arXiv210613344R
In this work, we present an investigation of the wind in the solar
corona that has been initiated by observations of the resonantly
scattered ultraviolet emission of the coronal plasma obtained with
UVCS-SOHO, designed to measure the wind outflow speed by applying
Doppler dimming diagnostics. Metis on Solar Orbiter complements the
UVCS spectroscopic observations that were performed during solar
activity cycle 23 by simultaneously imaging the polarized visible
light and the H I Lyman-α corona in order to obtain high spatial and
temporal resolution maps of the outward velocity of the continuously
expanding solar atmosphere. The Metis observations, taken on May 15,
2020, provide the first H I Lyman-α images of the extended corona
and the first instantaneous map of the speed of the coronal plasma
outflows during the minimum of solar activity and allow us to identify
the layer where the slow wind flow is observed. The polarized visible
light (580-640 nm) and the ultraviolet H I Lyα (121.6 nm) coronal
emissions, obtained with the two Metis channels, were combined in
order to measure the dimming of the UV emission relative to a static
corona. This effect is caused by the outward motion of the coronal
plasma along the direction of incidence of the chromospheric photons
on the coronal neutral hydrogen. The plasma outflow velocity was then
derived as a function of the measured Doppler dimming. The static
corona UV emission was simulated on the basis of the plasma electron
density inferred from the polarized visible light. This study leads
to the identification, in the velocity maps of the solar corona, of
the high-density layer about ±10° wide, centered on the extension
of a quiet equatorial streamer present at the east limb - the coronal
origin of the heliospheric current sheet - where the slowest wind
flows at about 160 ± 18 km s−1 from 4 R⊙
to 6 R⊙. Beyond the boundaries of the high-density layer,
the wind velocity rapidly increases, marking the transition between
slow and fast wind in the corona.

---------------------------------------------------------
Title: Analysis and modeling of the dynamics of the glow of calcium
and hydrogen lines in solar and stellar flares
Authors: Kupryakov, Yurij Alekseevich; Bychkov, Konstantin
Veniaminovich; Belova, Oksana Mikhailovna; Gorshkov, Alexey Borisovich;
Heinzel, Petr; Kotrč, Pavel
2021OAst...30...91K Altcode:
We present intensity curves of solar flares obtained in the Hα hydrogen
line and CaII H, CaIR 8542Å lines using multichannel spectrographs of
Ondřejov Observatory (Czech Republic) for the period 2000-2012. The
general behavior of observed intensity curves is practically the same
for all flares and is consistent with temporal variations of X-ray
emission. However, our results differ significantly from those obtained
by other authors for selected flare stars, for example, AD Leo; EV Lac;
YZ CMi. We tried to explain the difference in the behavior of Ca II
and Hα radiation flux by appearance of a shock wave during a flare
and slow heating of the plasma.

---------------------------------------------------------
Title: Balmer continuum enhancement detected in a mini flare observed
with IRIS
Authors: Joshi, Reetika; Schmieder, Brigitte; Heinzel, Petr; Tomin,
James; Chandra, Ramesh; Vilmer, Nicole
2021A&A...654A..31J Altcode: 2021arXiv210711651J
Context. Optical and near-UV continuum emissions in flares contribute
substantially to the flare energy budget. Two mechanisms play an
important role for continuum emission in flares: hydrogen recombination
after sudden ionization at chromospheric layers, and transportation of
the energy radiatively from the chromosphere to lower layers in the
atmosphere, the so-called back-warming. Aims: The aim of the
paper is to distinguish between these two mechanisms for the excess of
the Balmer continuum observed in a flare. Methods: We combined
the observations of the Balmer continuum obtained with the Interface
Region Imaging Spectrograph (IRIS) (spectra and slit-jaw images (SJIs)
2832 Å) and hard X-ray (HXR) emission detected by the Fermi/Gamma Burst
Monitor (GBM) during a mini flare. The calibrated Balmer continuum
was compared to non-local thermodynamic equilibrium (LTE) radiative
transfer flare models, and the radiated energy was estimated. Assuming
thick target HXR emission, we calculated the energy of the nonthermal
electrons detected by the Fermi/GBM and compared it to the radiated
energy. Results: The favorable argument of a relation between
the Balmer continuum excess and the HXR emission is that there is
a good time coincidence between them. In addition, the shape of the
maximum brightness in the 2832 SJIs, which is mainly due to this Balmer
continuum excess, is similar to that of the Fermi/GBM light curve. The
electron-beam flux estimated from Fermi/GBM between 109 and
1010 erg s−1 cm−2 is consistent
with the beam flux required in non-LTE radiative transfer models
to obtain the excess of Balmer continuum emission observed in this
IRIS spectra. Conclusions: The low-energy input by nonthermal
electrons above 20 keV is sufficient to produce the enhancement in the
Balmer continuum emission. This could be explained by the topology of
the reconnection site. The reconnection starts in a tiny bald-patch
region, which is transformed dynamically into an X-point current
sheet. The size of the interacting region would be below the spatial
resolution of the instrument.

---------------------------------------------------------
Title: On the importance of Ca II photoionization by the hydrogen
lyman transitions in solar flare models
Authors: Osborne, C. M. J.; Heinzel, P.; Kašparová, J.; Fletcher, L.
2021MNRAS.507.1972O Altcode: 2021MNRAS.tmp.1947O; 2021arXiv210711145O
The forward fitting of solar flare observations with
radiation-hydrodynamic simulations is a common technique for learning
about energy deposition and atmospheric evolution during these explosive
events. A frequent spectral line choice for this process is Ca II
854.2 nm due to its formation in the chromosphere and substantial
variability. It is important to ensure that this line is accurately
modelled to obtain the correct interpretation of observations. Here,
we investigate the importance of photoionization of Ca II to Ca III by
the hydrogen Lyman transitions, whilst the Lyman continuum is typically
considered in this context in simulations, the associated bound-bound
transitions are not. This investigation uses two RADYN flare simulations
and reprocesses the radiative transfer using the Lightweaver framework
which accounts for the overlapping of all active transitions. The
Ca II 854.2 nm line profiles are found to vary significantly due to
photoionization by the Lyman lines, showing notably different shapes
and even reversed asymmetries. Finally, we investigate to what extent
these effects modify the energy balance of the simulation and the
implications on future radiation-hydrodynamic simulations. There
is found to be a 10-15 per cent change in detailed optically thick
radiative losses from considering these photoionization effects on
the calcium lines in the two simulations presented, demonstrating the
importance of considering these effects in a self-consistent way.

---------------------------------------------------------
Title: VizieR Online Data Catalog: Quiet-Sun MgII h &amp; k line
profiles from IRIS (Gunar+, 2021)
Authors: Gunar, S.; Koza, J.; Schwartz, P.; Heinzel, P.; Liu, W.
2021yCat..22550016G Altcode:
Since its launch, the Interface Region Imaging Spectrograph (IRIS)
commenced a quasi-regular acquisition of maps of the entire solar
disk in both NUV and FUV spectral ranges. At the time of writing,
the archive of the IRIS full-Sun mosaics contained 91 observations
spanning the period from 2013 September 30 to 2020 October 19 which
cover two spectral windows of +/-1.75Å centered at 2803.53Å (MgII h)
and 2796.35Å (MgII k). (4 data files).

---------------------------------------------------------
Title: Exploring the Solar Wind from Its Source on the Corona into
the Inner Heliosphere during the First Solar Orbiter-Parker Solar
Probe Quadrature
Authors: Telloni, Daniele; Andretta, Vincenzo; Antonucci, Ester;
Bemporad, Alessandro; Capuano, Giuseppe E.; Fineschi, Silvano;
Giordano, Silvio; Habbal, Shadia; Perrone, Denise; Pinto, Rui F.;
Sorriso-Valvo, Luca; Spadaro, Daniele; Susino, Roberto; Woodham, Lloyd
D.; Zank, Gary P.; Romoli, Marco; Bale, Stuart D.; Kasper, Justin C.;
Auchère, Frédéric; Bruno, Roberto; Capobianco, Gerardo; Case,
Anthony W.; Casini, Chiara; Casti, Marta; Chioetto, Paolo; Corso,
Alain J.; Da Deppo, Vania; De Leo, Yara; Dudok de Wit, Thierry;
Frassati, Federica; Frassetto, Fabio; Goetz, Keith; Guglielmino,
Salvo L.; Harvey, Peter R.; Heinzel, Petr; Jerse, Giovanna; Korreck,
Kelly E.; Landini, Federico; Larson, Davin; Liberatore, Alessandro;
Livi, Roberto; MacDowall, Robert J.; Magli, Enrico; Malaspina, David
M.; Massone, Giuseppe; Messerotti, Mauro; Moses, John D.; Naletto,
Giampiero; Nicolini, Gianalfredo; Nisticò, Giuseppe; Panasenco,
Olga; Pancrazzi, Maurizio; Pelizzo, Maria G.; Pulupa, Marc; Reale,
Fabio; Romano, Paolo; Sasso, Clementina; Schühle, Udo; Stangalini,
Marco; Stevens, Michael L.; Strachan, Leonard; Straus, Thomas; Teriaca,
Luca; Uslenghi, Michela; Velli, Marco; Verscharen, Daniel; Volpicelli,
Cosimo A.; Whittlesey, Phyllis; Zangrilli, Luca; Zimbardo, Gaetano;
Zuppella, Paola
2021ApJ...920L..14T Altcode: 2021arXiv211011031T
This Letter addresses the first Solar Orbiter (SO)-Parker Solar
Probe (PSP) quadrature, occurring on 2021 January 18 to investigate
the evolution of solar wind from the extended corona to the inner
heliosphere. Assuming ballistic propagation, the same plasma volume
observed remotely in the corona at altitudes between 3.5 and 6.3
solar radii above the solar limb with the Metis coronagraph on SO
can be tracked to PSP, orbiting at 0.1 au, thus allowing the local
properties of the solar wind to be linked to the coronal source region
from where it originated. Thanks to the close approach of PSP to the
Sun and the simultaneous Metis observation of the solar corona, the
flow-aligned magnetic field and the bulk kinetic energy flux density
can be empirically inferred along the coronal current sheet with an
unprecedented accuracy, allowing in particular estimation of the Alfvén
radius at 8.7 solar radii during the time of this event. This is thus
the very first study of the same solar wind plasma as it expands from
the sub-Alfvénic solar corona to just above the Alfvén surface.

---------------------------------------------------------
Title: Quiet-Sun Mg II h and k Line Profiles Derived from IRIS
Full-Sun Mosaics. I. Reference Profiles and Center-to-limb Variation
Authors: Gunár, Stanislav; Koza, Július; Schwartz, Pavol; Heinzel,
Petr; Liu, Wenjuan
2021ApJS..255...16G Altcode:
We derived high-precision reference profiles of the Mg II h and k
lines that represent the quiet Sun during a minimum of the solar
activity. To do so, we used the broad catalog of full-Sun mosaics
obtained by the Interface Region Imaging Spectrograph (IRIS). To
minimize the influence of the local variations due to the on-disk
solar features and to achieve low levels of uncertainties, we used
12 IRIS full-Sun mosaics without sunspots or other significant signs
of solar activity. These mosaics were obtained between 2019 April and
2020 September in the near-ultraviolet spectral range. In this paper,
we present the disk-averaged reference profiles of Mg II h and Mg II
k lines, together with a series of reference profiles spanning the
distance between the disk center and the solar limb. These series of
profiles offer a detailed representation of the center-to-limb variation
of both Mg II h and Mg II k lines. The reference Mg II h and k line
profiles provided in this paper can be used as the incident radiation
boundary condition for radiative-transfer modeling of prominences,
spicules, and other coronal and chromospheric structures.

---------------------------------------------------------
Title: In-flight optical performance assessment for the Metis solar
coronagraph
Authors: Da Deppo, Vania; Chioetto, Paolo; Andretta, Vincenzo; Casini,
Chiara; Frassetto, Fabio; Slemer, Alessandra; Zuppella, Paola; Romoli,
Marco; Fineschi, Silvano; Heinzel, Petr; Naletto, Giampiero; Nicolini,
Gianalfredo; Spadaro, Daniele; Stangalini, Marco; Teriaca, Luca;
Bemporad, Alessandro; Casti, Marta; Fabi, Michele; Grimani, Catia;
Heerlein, Klaus; Jerse, Giovanna; Landini, Federico; Liberatore,
Alessandro; Magli, Enrico; Melich, Radek; Pancrazzi, Maurizio; Pelizzo,
Maria-G.; Romano, Paolo; Sasso, Clementina; Straus, Thomas; Susino,
Roberto; Uslenghi, Michela; Volpicelli, Cosimo Antonio
2021SPIE11852E..10D Altcode:
Metis is a multi-wavelength coronagraph onboard the European Space
Agency (ESA) Solar Orbiter mission. The instrument features an
innovative instrument design conceived for simultaneously imaging the
Sun's corona in the visible and ultraviolet range. The Metis visible
channel employs broad-band, polarized imaging of the visible K-corona,
while the UV one uses narrow-band imaging at the HI Ly 􀄮, i.e. 121.6
nm. During the commissioning different acquisitions and activities,
performed with both the Metis channels, have been carried out with the
aim to check the functioning and the performance of the instrument. In
particular, specific observations of stars have been devised to assess
the optical alignment of the telescope and to derive the instrument
optical parameters such as focal length, PSF and possibly check the
optical distortion and the vignetting function. In this paper, the
preliminary results obtained for the PSF of both channels and the
determination of the scale for the visible channel will be described
and discussed. The in-flight obtained data will be compared to those
obtained on-ground during the calibration campaign.

---------------------------------------------------------
Title: On-ground flat-field calibration of the Metis coronagraph
onboard the Solar Orbiter ESA mission
Authors: Casini, C.; Da Deppo, V.; Zuppella, P.; Chioetto, P.; Slemer,
A.; Frassetto, F.; Romoli, M.; Landini, F.; Pancrazzi, M.; Andretta,
V.; De Leo, Y.; Bemporad, A.; Fabi, M.; Fineschi, S.; Frassati, F.;
Grimani, C.; Jerse, G.; Heerlein, K.; Liberatore, A.; Magli, E.;
Naletto, G.; Nicolini, G.; Pelizzo, M. G.; Romano, P.; Sasso, C.;
Spadaro, D.; Stangalini, M.; Straus, T.; Susino, R.; Teriaca, L.;
Uslenghi, M.; Casti, M.; Heinzel, P.; Volpicelli, A.
2021SPIE11852E..5BC Altcode:
Solar Orbiter, launched on February 9th 2020, is an
ESA/NASA mission conceived to study the Sun. This work presents
the embedded Metis coronagraph and its on-ground calibration in the
580-640 nm wavelength range using a flat field panel. It provides
a uniform illumination to evaluate the response of each pixel of
the detector; and to characterize the Field of View (FoV) of the
coronagraph. Different images with different exposure times were
acquired during the on-ground calibration campaign. They were analyzed
to verify the linearity response of the instrument and the requirements
for the FoV: the maximum area of the sky that Metis can acquire.

---------------------------------------------------------
Title: Challenges during Metis-Solar Orbiter commissioning phase
Authors: Romoli, Marco; Andretta, Vincenzo; Bemporad, Alessandro;
Casti, Marta; Da Deppo, Vania; De Leo, Yara; Fabi, Michele; Fineschi,
Silvano; Frassetto, Fabio; Grimani, Catia; Heerlein, Klaus; Heinzel,
Petr; Jerse, Giovanna; Landini, Federico; Liberatore, Alessandro;
Magli, Enrico; Naletto, Giampiero; Nicolini, Gianalfredo; Pancrazzi,
Maurizio; Pelizzo, Maria Guglielmina; Romano, Paolo; Sasso, Clementina;
Schühle, Udo; Slemer, Alessandra; Spadaro, Daniele; Straus, Thomas;
Susino, Roberto; Teriaca, Luca; Uslenghi, Michela; Volpicelli, Cosimo
Antonio; Zupella, Paola
2021SPIE11852E..5AR Altcode:
Metis is the visible light and UV light imaging coronagraph on board
the ESA-NASA mission Solar Orbiter that has been launched February 10th,
2020, from Cape Canaveral. Scope of the mission is to study the Sun up
close, taking high-resolution images of the Sun's poles for the first
time, and understanding the Sun-Earth connection. Metis coronagraph
will image the solar corona in the linearly polarized broadband visible
radiation and in the UV HI Ly-α line from 1.6 to 3 solar radii when at
Solar Orbiter perihelion, providing a diagnostics, with unprecedented
temporal coverage and spatial resolution, of the structures and dynamics
of the full corona. Solar Orbiter commissioning phase big challenge was
Covid-19 social distancing phase that affected the way commissioning
of a spacecraft and its payload is typically done. Metis coronagraph
on-board Solar Orbiter had its additional challenges: to wake up and
check the performance of the optical, electrical and thermal subsystems,
most of them unchecked since Metis delivery to spacecraft prime, Airbus,
in May 2017. The roadmap to the fully commissioned coronagraph is here
described throughout the steps from the software functional test,
the switch on of the detectors of the two channels, UV and visible,
to the optimization of the occulting system and the characterization
of the instrumental stray light, one of the most challenging features
in a coronagraph.

---------------------------------------------------------
Title: In-flight calibration of Metis coronagraph on board of
Solar Orbiter
Authors: Liberatore, A.; Fineschi, S.; Casti, M.; Capobianco, G.;
Romoli, M.; Andretta, V.; Bemporad, A.; Da Deppo, V.; De Leo, Y.; Fabi,
M.; Frassetto, F.; Grimani, C.; Heerlein, K.; Heinzel, P.; Jerse,
G.; Landini, F.; Magli, E.; Naletto, G.; Nicolini, G.; Pancrazzi,
M.; Pelizzo, M. G.; Romano, P.; Sasso, C.; Slemer, A.; Spadaro, D.;
Straus, T.; Susino, R.; Teriaca, L.; Uslenghi, M.; Volpicelli, C. A.;
Zuppella, P.
2021SPIE11852E..48L Altcode:
Metis coronagraph is one of the remote-sensing instruments of the Solar
Orbiter mission launched at the begin of 2020. The mission profile will
allow for the first time the remote-sensing observation of the Sun
from a very close distance and increasing the latitude with respect
to the ecliptic plane. In particular, Metis is aimed at the overall
characterization and study of the solar corona and solar wind. Metis
instrument acquires images of the solar corona in two different
wavelengths simultaneously; ultraviolet (UV) and visible-light (VL). The
VL channel includes a polarimeter with an electro-optically modulating
Liquid Crystal Variable Retarder (LCVR) to measure the linearly
polarized brighness pB) of the K-corona. This paper presents part of
the in-flight calibration results for both wavelength channels together
with a comparison with on-ground calibrations. The orientation of the
K-corona linear polarization was used for the in-flight calibration
of the Metis polarimeter. This paper describes the correction of the
on-ground VL vignetting function after the in-flight adjustment of
the internal occulter. The same vignetting function was adaptated to
the UV channel.

---------------------------------------------------------
Title: IRIS observations of chromospheric heating by acoustic waves
in solar quiet and active regions
Authors: Abbasvand, V.; Sobotka, M.; Švanda, M.; Heinzel, P.; Liu,
W.; Mravcová, L.
2021A&A...648A..28A Altcode: 2021arXiv210208678A
 Aims: To study the heating of solar chromospheric magnetic and
nonmagnetic regions by acoustic and magnetoacoustic waves, the deposited
acoustic-energy flux derived from observations of strong chromospheric
lines is compared with the total integrated radiative losses. 
Methods: A set of 23 quiet-Sun and weak-plage regions were observed in
the Mg II k and h lines with the Interface Region Imaging Spectrograph
(IRIS). The deposited acoustic-energy flux was derived from Doppler
velocities observed at two different geometrical heights corresponding
to the middle and upper chromosphere. A set of scaled nonlocal
thermodynamic equilibrium 1D hydrostatic semi-empirical models -
obtained by fitting synthetic to observed line profiles - was applied
to compute the radiative losses. The characteristics of observed waves
were studied by means of a wavelet analysis. Results: Observed
waves propagate upward at supersonic speed. In the quiet chromosphere,
the deposited acoustic flux is sufficient to balance the radiative
losses and maintain the semi-empirical temperatures in the layers under
study. In the active-region chromosphere, the comparison shows that
the contribution of acoustic-energy flux to the radiative losses is
only 10−30%. Conclusions: Acoustic and magnetoacoustic waves
play an important role in the chromospheric heating, depositing a main
part of their energy in the chromosphere. Acoustic waves compensate
for a substantial fraction of the chromospheric radiative losses in
quiet regions. In active regions, their contribution is too small to
balance the radiative losses and the chromosphere has to be heated by
other mechanisms.

---------------------------------------------------------
Title: Constraining stellar CME occurrence with optical spectroscopy
Authors: Odert, Petra; Leitzinger, Martin; Guenther, Eike W.;
Heinzel, Petr
2021csss.confE..96O Altcode:
Our knowledge on coronal mass ejections (CMEs) on stars other than the
Sun is still sparse. Spectroscopic observations in the optical sometimes
show asymmetrically broadened wings and/or transient extra-emissions in
chromospheric lines during or shortly after flare events. These may be
interpreted as signatures of prominence eruptions, which are closely
related to CMEs on the Sun. Dedicated searches for these signatures
have, however, mostly yielded non-detections. Here we present a
semi-empirical model which combines predictions of intrinsic stellar
CME rates with simple radiative transfer calculations in the Balmer
lines. We find that typical observations have most likely been too
short and/or they had a too low signal-to-noise ratio to detect CMEs. We
predict the minimum observing time needed to detect CMEs in the Balmer
lines for stars with different spectral types and activity levels.

---------------------------------------------------------
Title: Multi-thermal atmosphere of a mini-solar flare during magnetic
reconnection observed with IRIS
Authors: Joshi, Reetika; Schmieder, Brigitte; Tei, Akiko; Aulanier,
Guillaume; Lörinčík, Juraj; Chandra, Ramesh; Heinzel, Petr
2021A&A...645A..80J Altcode: 2020arXiv201015401J
Context. The Interface Region Imaging Spectrograph (IRIS) with its
high spatial and temporal resolution facilitates exceptional plasma
diagnostics of solar chromospheric and coronal activity during magnetic
reconnection. Aims: The aim of this work is to study the fine
structure and dynamics of the plasma at a jet base forming a mini-flare
between two emerging magnetic fluxes (EMFs) observed with IRIS and the
Solar Dynamics Observatory instruments. Methods: We proceed to
a spatio-temporal analysis of IRIS spectra observed in the spectral
ranges of Mg II, C II, and Si IV ions. Doppler velocities from Mg II
lines were computed using a cloud model technique. Results:
Strong asymmetric Mg II and C II line profiles with extended blue
wings observed at the reconnection site (jet base) are interpreted by
the presence of two chromospheric temperature clouds: one explosive
cloud with blueshifts at 290 km s-1 and one cloud with
smaller Doppler shift (around 36 km s-1). Simultaneously at
the same location (jet base), strong emission of several transition
region lines (e.g. O IV and Si IV), emission of the Mg II triplet
lines, and absorption of identified chromospheric lines in Si IV
broad profiles have been observed and analysed. Conclusions:
Such observations of IRIS line and continuum emissions allow us
to propose a stratification model for the white light, mini-flare
atmosphere with multiple layers of different temperatures along the
line of sight in a reconnection current sheet. It is the first time
that we could quantify the fast speed (possibly Alfvénic flows)
of cool clouds ejected perpendicularly to the jet direction via the
cloud model technique. We conjecture that the ejected clouds come from
plasma which was trapped between the two EMFs before reconnection or
be caused by chromospheric-temperature (cool) upflow material similar
to a surge during reconnection. Movies are available at <A
href="https://www.aanda.org/10.1051/0004-6361/202039229/olm">https://www.aanda.org</A>

---------------------------------------------------------
Title: Spectral inversion of H-alpha and MgII lines in quiescent
prominences
Authors: Heinzel, Petr; Schmieder, Brigitte; Ruan, Guiping; Mein,
Pierre; Gunár, Stanislav; Jejcic, Sonja; Mein, Nicole
2021cosp...43E1764H Altcode:
Recent spectral analysis of simultaneous H-alpha (MSDP) and MgII
lines (IRIS) (Guiping et al. 2019) has revealed certain bifurcation
in resulting models. Two solutions were found from the line inversions
using the non-LTE modeling: relatively high kinetic temperature and low
non-thermal motions or temperatures mostly compatible with standard ones
plus non-thermal motions of the order of 16 km/sec. Here we will present
an improved spectral line inversion technique which clearly prefers
the latter solution. Strong non-thermal motions are then interpreted
as a mixture of microturbulence and the line-of-sight dynamics of
prominence fine-structure threads. A detailed multithread modeling with
the 2D non-LTE code and stochastic distributions of threads (position,
dynamics) is now in progress and we will show our preliminary results.

---------------------------------------------------------
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.

---------------------------------------------------------
Title: Cool flare loops in solar and stellar coronae
Authors: Heinzel, Petr
2021cosp...43E.969H Altcode:
Cool structures in solar and stellar coronae may take various forms
like prominences, cores of CMEs or cool flare loops which often exhibit
the so-called coronal rain. In this talk we will focus on the latter
structures which recently attracted a great attention in relation with
largest solar flares observed during the 24th solar cycle. We will
summarise the multi-wavelength observations of giant off-limb post-flare
loops from September 10, 2017 and show the principally new results
concerning their magnetic fields and overall densities. High densities
obtained certainly require a strong magnetic field to keep the loops
stably confined in the corona. Downflows consistent with the coronal
rain and high non-thermal motions (the so-called microturbulence) have
been detected. Moreover, SDO/HMI data also indicate high densities
which would be compatible with those predicted in loops expected on
other cool stars. These conditions are favourable for explanation of
the continuum emission enhancements during superflares, in terms of
the loop-arcade component. However, in order to explain the superflare
behaviour, large loop-arcade areas are required as suggested in Heinzel
and Shibata 2018. Finally, we will show the effect of cool stellar
loops on the spectral line emission variations during a flare which
seems to be an unresolved mixture of ribbon and loop emission.

---------------------------------------------------------
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.

---------------------------------------------------------
Title: Quiet-Sun hydrogen Lyman-α line profile derived from
SOHO/SUMER solar-disk observations
Authors: Gunár, S.; Schwartz, P.; Koza, J.; Heinzel, P.
2020A&A...644A.109G Altcode: 2020arXiv201101299G
Context. The solar radiation in the Lyman-α spectral line of hydrogen
plays a significant role in the illumination of chromospheric and
coronal structures, such as prominences, spicules, chromospheric
fibrils, cores of coronal mass ejections, and solar wind. Moreover,
it is important for the investigation of the heliosphere, Earth's
ionosphere, and the atmospheres of planets, moons, and comets. 
Aims: We derive a reference quiet-Sun Lyman-α spectral profile that
is representative of the Lyman-α radiation from the solar disk during
a minimum of solar activity. This profile can serve as an incident
radiation boundary condition for the radiative transfer modelling of
chromospheric and coronal structures. Because the solar radiation in
the Lyman lines is not constant over time but varies significantly
with the solar cycle, we provide a method for the adaptation of
the incident radiation Lyman line profiles (Lyman-α and higher
lines) to a specific date. Moreover, we analyse how the change in
the incident radiation influences the synthetic spectra produced by
the radiative transfer modelling. Methods: We used SOHO/SUMER
Lyman-α raster scans obtained without the use of the attenuator in
various quiet-Sun regions on the solar disk. The observations were
performed on three consecutive days (June 24, 25, and 26, 2008) during
a period of minimum solar activity. The reference Lyman-α profile was
obtained as a spatial average over eight available raster scans. To
take into account the Lyman-α variation with the solar cycle, we
used the LISIRD composite Lyman-α index. To estimate the influence
of the change in the incident radiation in the Lyman lines on the
results of radiative transfer models, we used a 2D prominence fine
structure model. Results: We present the reference quiet-Sun
Lyman-α profile and a table of coefficients describing the variation
of the Lyman lines with the solar cycle throughout the lifetime of
SOHO. The analysis of the influence of the change in the incident
radiation shows that the synthetic spectra are strongly affected by
the modification of the incident radiation boundary condition. The
most pronounced impact is on the central and integrated intensities
of the Lyman lines. There, the change in the synthetic spectra can
often have the same amplitude as the change in the incident radiation
itself. The impact on the specific intensities in the peaks of reversed
Lyman-line profiles is smaller but still significant. The hydrogen
Hα line can also be considerably affected, despite the fact that
the Hα radiation from the solar disk does not vary with the solar
cycle. Data are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr/">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/644/A109">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/644/A109</A>

---------------------------------------------------------
Title: IRIS Mg II Observations and Non-LTE Modeling of Off-limb
Spicules
Authors: Tei, A.; Gunár, S.; Heinzel, P.; Okamoto, T. J.; Štěpán,
J.; Jejčič, S.; Shibata, K.
2020AGUFMSH0010008T Altcode:
We investigated the off-limb spicules observed in the Mg II h and k
spectral lines by Interface Region Imaging Spectrograph (IRIS) in a
solar polar coronal hole. We analyzed the large data set of obtained
spectra to extract quantitative information about the line intensities,
line shifts, and line widths. The observed Mg II line profiles are
broad and double peaked at lower altitudes, broad but flat topped
at middle altitudes, and narrow and single peaked with the largest
Doppler shifts at higher altitudes. We used one-dimensional non-LTE
vertical slab models (i.e., models that consider departures from local
thermodynamic equilibrium) in single-slab and multi-slab configurations
to interpret the observations and to investigate how a superposition
of spicules along a line of sight (LOS) affects the synthetic Mg II
line profiles. The employed multi-slab models are either static,
i.e., without any LOS velocities, or assume randomly assigned LOS
velocities of individual slabs, representing the spicule dynamics. We
performed such single-slab and multi-slab modeling for a broad set of
model input parameters and examined the dependence of the Mg II line
profiles on these parameters. In this presentation, we demonstrate that
the observed line widths of the Mg h and k line profiles are strongly
affected by the presence of multiple spicules along the LOS. We also
show that the profiles obtained at higher altitudes can be reproduced
by single-slab models representing individual spicules. We found that
the multi-slab model with a random distribution of the LOS velocities
ranging from −25 to 25 km/s can well reproduce the width and the
shape of the Mg II profiles observed at middle altitudes.

---------------------------------------------------------
Title: Metis - Solar Orbiter Topical Team on "Modelling of CME
propagation/evolution in corona and solar wind in connection with
Space Weather"
Authors: Bemporad, A.; Banerjee, D.; Berlicki, A.; Biondo, R.; Boe,
B.; Calchetti, D.; Capuano, G.; De Leo, Y.; Del Moro, D.; Feng, L.;
Foldes, R.; Frassati, F.; Frazin, R. A.; Giovannelli, L.; Giunta,
A. S.; Heinzel, P.; Ippolito, A.; Janvier, M.; Jerse, G.; Kilpua,
K. E. J.; Laurenza, M.; Lloveras, D.; Magdalenic, J.; Mancuso, S.;
Messerotti, M.; Mierla, M.; Nandy, D.; Napoletano, G.; Nuevo, F.;
Pagano, P.; Pinto, R.; Plainaki, C.; Reale, F.; Romoli, M.; Rodriguez,
L.; Slemer, A.; Spadaro, D.; Susino, R.; Stangalini, M.; Vainio,
R. O.; Valori, G.; Vásquez, A. M.; West, M. J.
2020AGUFMSH0360027B Altcode:
Despite the current availability of multi-spacecraft observations of
Coronal Mass Ejections (CMEs) and their interplanetary counterpart
(ICMEs), at present we still don't understand which physical phenomena
are driving their expansion and propagation phases. This also limits
our understanding on how CMEs (observed with remote sensing data)
become ICMEs (observed in situ), how they interact with the background
solar wind, and how their final geo-effectiveness can be modified
during their interplanetary evolution. Such problems match some of
the scientific objectives of the Solar Orbiter Science Activity Plan
and of the Metis coronagraph. Thanks to its multi-channel capability,
Metis (acquiring images in the visible light and at the same time in
the UV HI Lyman-alpha emission) will really provide an unprecedented
view of CMEs and in particular of their thermodynamic evolution. At
closest approaches to the Sun (in the nominal mission), Metis will
acquire high spatial resolution and/or temporal cadence multi-channel
images of CMEs. Farther from the Sun, Metis will shed light on the
early Interplanetary propagation of CMEs. Later on (in the extended
mission) Metis will observe for the first time the CME/ICME propagation
out-of-ecliptic. These novelties will be combined with the unique
vantage point that will be offered by the Solar Orbiter spacecraft,
and supported with valuable data acquired by other on-board remote
sensing (e.g. SPICE, EUI, SoloHI) and in situ (e.g. EPD, MAG,
SWA, RPW) instruments. In this contribution we present the ongoing
activities of the Metis Topical Team on "CME/ICME propagation", (<A
href="http://metis.oato.inaf.it/topical_teams.html">http://metis.oato.inaf.it/topical_teams.html</A>),
an international working group recently established and gathering
scientists from different countries, experts of both in-situ and remote
sensing observations, as well as numerical simulations, and we summarize
the main science objectives discussed during the last months.

---------------------------------------------------------
Title: Solar Orbiter: connecting remote sensing and in situ
measurements
Authors: Horbury, T. S.; Auchere, F.; Antonucci, E.; Berghmans, D.;
Bruno, R.; Carlsson, M.; del Toro Iniesta, J. C.; Fludra, A.; Harra,
L.; Hassler, D.; Heinzel, P.; Howard, R. A.; Krucker, S.; Livi, S. A.;
Long, D.; Louarn, P.; Maksimovic, M.; Mueller, D.; Owen, C. J.; Peter,
H.; Rochus, P. L.; Rodriguez-Pacheco, J.; Romoli, M.; Schühle, U.;
Solanki, S. K.; Teriaca, L.; Wimmer-Schweingruber, R. F.; Zouganelis,
Y.; Laker, R.
2020AGUFMSH038..10H Altcode:
A key science goal of the Solar Orbiter mission is to make connections
between phenomena on the Sun and their manifestations in interplanetary
space. To that end, the spacecraft carries a carefully tailored
payload of six remote sensing instruments and four making in situ
measurements. During June 2020, while the spacecraft was around 0.5
AU from the Sun, the remote sensing instruments operated for several
days. While this was primarily an engineering activity, the resulting
observations provided outstanding measurements and represent the ideal
first opportunity to investigate the potential for making connections
between the remote sensing and in situ payloads on Solar Orbiter. We present a preliminary analysis of the available remote sensing and
in situ observations, showing how connections can be made, and discuss
the potential for further, more precise mapping to be performed as
the mission progresses.

---------------------------------------------------------
Title: Observational study of chromospheric heating by acoustic waves
Authors: Abbasvand, V.; Sobotka, M.; Švanda, M.; Heinzel, P.;
García-Rivas, M.; Denker, C.; Balthasar, H.; Verma, M.; Kontogiannis,
I.; Koza, J.; Korda, D.; Kuckein, C.
2020A&A...642A..52A Altcode: 2020arXiv200802688A
 Aims: Our aim is to investigate the role of acoustic and
magneto-acoustic waves in heating the solar chromosphere. Observations
in strong chromospheric lines are analyzed by comparing the deposited
acoustic-energy flux with the total integrated radiative losses. Methods: Quiet-Sun and weak-plage regions were observed in the Ca
II 854.2 nm and Hα lines with the Fast Imaging Solar Spectrograph
(FISS) at the 1.6-m Goode Solar Telescope on 2019 October 3 and
in the Hα and Hβ lines with the echelle spectrograph attached
to the Vacuum Tower Telescope on 2018 December 11 and 2019 June
6. The deposited acoustic energy flux at frequencies up to 20 mHz
was derived from Doppler velocities observed in line centers and
wings. Radiative losses were computed by means of a set of scaled
non-local thermodynamic equilibrium 1D hydrostatic semi-empirical
models obtained by fitting synthetic to observed line profiles. 
Results: In the middle chromosphere (h = 1000-1400 km), the radiative
losses can be fully balanced by the deposited acoustic energy flux in
a quiet-Sun region. In the upper chromosphere (h &gt; 1400 km), the
deposited acoustic flux is small compared to the radiative losses in
quiet as well as in plage regions. The crucial parameter determining
the amount of deposited acoustic flux is the gas density at a given
height. Conclusions: The acoustic energy flux is efficiently
deposited in the middle chromosphere, where the density of gas is
sufficiently high. About 90% of the available acoustic energy flux in
the quiet-Sun region is deposited in these layers, and thus it is a
major contributor to the radiative losses of the middle chromosphere. In
the upper chromosphere, the deposited acoustic flux is too low, so that
other heating mechanisms have to act to balance the radiative cooling.

---------------------------------------------------------
Title: VizieR Online Data Catalog: Quiet-sun hydrogen Lyman-alpha
line profile (Gunar+, 2020)
Authors: Gunar, S.; Schwartz, P.; Koza, J.; Heinzel, P.
2020yCat..36440109G Altcode:
The reference quiet-Sun Lyman-alpha profile obtained as an average
over eight SOHO/SUMER raster scans obtained between 2008/06/24
and 2008/06/26. The central wavelength lambda0 of the
Lyman-alpha line is 1215.67Å (121.567nm). The symmetrized
reference quiet-Sun Lyman-alpha profile obtained by symmetrization of
the full profile from Table A1. Only the right half of the profile
is provided. The central wavelength lambda0 of the
Lyman-alpha line is 1215.67Å (121.567nm). table B1 ~List of
coefficients describing the variation of the solar radiation in the
Lyman-alpha and higher Lyman lines. The coefficients were derived from
400-day averaged LISIRD Lyman-alpha composite index (Machol et al.,
2019E&amp;SS....6.2263M). We provide coefficients for selected dates
throughout the lifetime of SOHO. Coefficients for the Lyman-alpha line
are computed with respect to the date 2008/06/25. Coefficients for the
higher Lyman lines are computed with respect to the date 1996/05/15
used in Warren et al. (1998ApJS..119..105W). (3 data files).

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Title: Metis: the Solar Orbiter visible light and ultraviolet
coronal imager
Authors: Antonucci, Ester; Romoli, Marco; Andretta, Vincenzo; Fineschi,
Silvano; Heinzel, Petr; Moses, J. Daniel; Naletto, Giampiero; Nicolini,
Gianalfredo; Spadaro, Daniele; Teriaca, Luca; Berlicki, Arkadiusz;
Capobianco, Gerardo; Crescenzio, Giuseppe; Da Deppo, Vania; Focardi,
Mauro; Frassetto, Fabio; Heerlein, Klaus; Landini, Federico; Magli,
Enrico; Marco Malvezzi, Andrea; Massone, Giuseppe; Melich, Radek;
Nicolosi, Piergiorgio; Noci, Giancarlo; Pancrazzi, Maurizio; Pelizzo,
Maria G.; Poletto, Luca; Sasso, Clementina; Schühle, Udo; Solanki,
Sami K.; Strachan, Leonard; Susino, Roberto; Tondello, Giuseppe;
Uslenghi, Michela; Woch, Joachim; Abbo, Lucia; Bemporad, Alessandro;
Casti, Marta; Dolei, Sergio; Grimani, Catia; Messerotti, Mauro;
Ricci, Marco; Straus, Thomas; Telloni, Daniele; Zuppella, Paola;
Auchère, Frederic; Bruno, Roberto; Ciaravella, Angela; Corso,
Alain J.; Alvarez Copano, Miguel; Aznar Cuadrado, Regina; D'Amicis,
Raffaella; Enge, Reiner; Gravina, Alessio; Jejčič, Sonja; Lamy,
Philippe; Lanzafame, Alessandro; Meierdierks, Thimo; Papagiannaki,
Ioanna; Peter, Hardi; Fernandez Rico, German; Giday Sertsu, Mewael;
Staub, Jan; Tsinganos, Kanaris; Velli, Marco; Ventura, Rita; Verroi,
Enrico; Vial, Jean-Claude; Vives, Sebastien; Volpicelli, Antonio;
Werner, Stephan; Zerr, Andreas; Negri, Barbara; Castronuovo, Marco;
Gabrielli, Alessandro; Bertacin, Roberto; Carpentiero, Rita; Natalucci,
Silvia; Marliani, Filippo; Cesa, Marco; Laget, Philippe; Morea, Danilo;
Pieraccini, Stefano; Radaelli, Paolo; Sandri, Paolo; Sarra, Paolo;
Cesare, Stefano; Del Forno, Felice; Massa, Ernesto; Montabone, Mauro;
Mottini, Sergio; Quattropani, Daniele; Schillaci, Tiziano; Boccardo,
Roberto; Brando, Rosario; Pandi, Arianna; Baietto, Cristian; Bertone,
Riccardo; Alvarez-Herrero, Alberto; García Parejo, Pilar; Cebollero,
María; Amoruso, Mauro; Centonze, Vito
2020A&A...642A..10A Altcode: 2019arXiv191108462A
 Aims: Metis is the first solar coronagraph designed for a
space mission and is capable of performing simultaneous imaging of the
off-limb solar corona in both visible and UV light. The observations
obtained with Metis aboard the Solar Orbiter ESA-NASA observatory
will enable us to diagnose, with unprecedented temporal coverage and
spatial resolution, the structures and dynamics of the full corona
in a square field of view (FoV) of ±2.9° in width, with an inner
circular FoV at 1.6°, thus spanning the solar atmosphere from 1.7
R⊙ to about 9 R⊙, owing to the eccentricity
of the spacecraft orbit. Due to the uniqueness of the Solar Orbiter
mission profile, Metis will be able to observe the solar corona
from a close (0.28 AU, at the closest perihelion) vantage point,
achieving increasing out-of-ecliptic views with the increase of the
orbit inclination over time. Moreover, observations near perihelion,
during the phase of lower rotational velocity of the solar surface
relative to the spacecraft, allow longer-term studies of the off-limb
coronal features, thus finally disentangling their intrinsic evolution
from effects due to solar rotation. Methods: Thanks to a novel
occultation design and a combination of a UV interference coating of
the mirrors and a spectral bandpass filter, Metis images the solar
corona simultaneously in the visible light band, between 580 and 640
nm, and in the UV H I Lyman-α line at 121.6 nm. The visible light
channel also includes a broadband polarimeter able to observe the
linearly polarised component of the K corona. The coronal images in
both the UV H I Lyman-α and polarised visible light are obtained at
high spatial resolution with a spatial scale down to about 2000 km
and 15 000 km at perihelion, in the cases of the visible and UV light,
respectively. A temporal resolution down to 1 s can be achieved when
observing coronal fluctuations in visible light. Results: The
Metis measurements, obtained from different latitudes, will allow for
complete characterisation of the main physical parameters and dynamics
of the electron and neutral hydrogen/proton plasma components of the
corona in the region where the solar wind undergoes the acceleration
process and where the onset and initial propagation of coronal mass
ejections (CMEs) take place. The near-Sun multi-wavelength coronal
imaging performed with Metis, combined with the unique opportunities
offered by the Solar Orbiter mission, can effectively address crucial
issues of solar physics such as: the origin and heating/acceleration
of the fast and slow solar wind streams; the origin, acceleration,
and transport of the solar energetic particles; and the transient
ejection of coronal mass and its evolution in the inner heliosphere,
thus significantly improving our understanding of the region connecting
the Sun to the heliosphere and of the processes generating and driving
the solar wind and coronal mass ejections. Conclusions: This
paper presents the scientific objectives and requirements, the overall
optical design of the Metis instrument, the thermo-mechanical design,
and the processing and power unit; reports on the results of the
campaigns dedicated to integration, alignment, and tests, and to
the characterisation of the instrument performance; describes the
operation concept, data handling, and software tools; and, finally,
the diagnostic techniques to be applied to the data, as well as a brief
description of the expected scientific products. The performance of the
instrument measured during calibrations ensures that the scientific
objectives of Metis can be pursued with success. Metis website:
<A href="http://metis.oato.inaf.it">http://metis.oato.inaf.it</A>

---------------------------------------------------------
Title: On the Possibility of Detecting Helium D3 Line Polarization
with Metis
Authors: Heinzel, Petr; Štěpán, Jiři; Bemporad, Alessandro;
Fineschi, Silvano; Jejčič, Sonja; Labrosse, Nicolas; Susino, Roberto
2020ApJ...900....8H Altcode: 2020arXiv200708940H
Metis, the space coronagraph on board the Solar Orbiter, offers us
new capabilities for studying eruptive prominences and coronal mass
ejections (CMEs). Its two spectral channels, hydrogen Lα and visible
light (VL), will provide for the first time coaligned and cotemporal
images to study dynamics and plasma properties of CMEs. Moreover,
with the VL channel (580-640 nm) we find an exciting possibility
to detect the helium D3 line (587.73 nm) and its linear
polarization. The aim of this study is to predict the diagnostic
potential of this line regarding the CME thermal and magnetic
structure. For a grid of models we first compute the intensity of the
D3 line together with VL continuum intensity due to Thomson
scattering on core electrons. We show that the Metis VL channel will
detect a mixture of both, with predominance of the helium emission at
intermediate temperatures between 30 and 50,000 K. Then we use the
code HAZEL to compute the degree of linear polarization detectable
in the VL channel. This is a mixture of D3 scattering
polarization and continuum polarization. The former one is lowered in
the presence of a magnetic field and the polarization axis is rotated
(Hanle effect). Metis has the capability of measuring Q/I and U/I
polarization degrees and we show their dependence on temperature and
magnetic field. At T = 30,000 K we find a significant lowering of
Q/I which is due to strongly enhanced D3 line emission,
while depolarization at 10 G amounts roughly to 10%.

---------------------------------------------------------
Title: Spectral Characteristics and Formation Height of Off-limb
Flare Ribbons
Authors: Kuridze, David; Mathioudakis, Mihalis; Heinzel, Petr; Koza,
Július; Morgan, Huw; Oliver, Ramon; Kowalski, Adam F.; Allred, Joel C.
2020ApJ...896..120K Altcode: 2020arXiv200510924K
Flare ribbons are bright manifestations of flare energy dissipation
in the lower solar atmosphere. For the first time, we report on
high-resolution imaging spectroscopy observations of flare ribbons
situated off limb in the Hβ and Ca II 8542 Å lines and make a detailed
comparison with radiative hydrodynamic simulations. Observations of
the X8.2 class solar flare SOL 2017-09-10T16:06 UT obtained with the
Swedish Solar Telescope reveal bright horizontal emission layers
in Hβ line-wing images located near the footpoints of the flare
loops. The apparent separation between the ribbon observed in the Hβ
wing and the nominal photospheric limb is about 300-500 km. The Ca II
8542 Å line-wing images show much fainter ribbon emissions located
right on the edge of the limb, without clear separation from the
limb. RADYN models are used to investigate synthetic spectral line
profiles for the flaring atmosphere, and good agreement is found
with the observations. The simulations show that, toward the limb,
where the line of sight is substantially oblique with respect to the
vertical direction, the flaring atmosphere model reproduces the high
contrast of the off-limb Hβ ribbons and their significant elevation
above the photosphere. The ribbons in the Ca II 8542 Å line-wing
images are located deeper in the lower solar atmosphere with a lower
contrast. A comparison of the height deposition of electron beam energy
and the intensity contribution function shows that the Hβ line-wing
intensities can be a useful tracer of flare energy deposition in the
lower solar atmosphere.

---------------------------------------------------------
Title: Signatures of Helium Continuum in Cool Flare Loops Observed
by SDO/AIA
Authors: Heinzel, Petr; Schwartz, Pavol; Lörinčík, Juraj; Koza,
Július; Jejčič, Sonja; Kuridze, David
2020ApJ...896L..35H Altcode: 2020arXiv200600574H
We present an analysis of off-limb cool flare loops observed by the
Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA)
during the gradual phase of SOL2017-09-10T16:06 X8.2-class flare. In the
extreme-ultraviolet (EUV) channels starting from the 335 Å one, cool
loops appear as dark structures against the bright loop arcade. These
dark structures were precisely coaligned (spatially and temporally)
with loops observed by Swedish Solar Telescope (SST) in emission lines
of hydrogen and ionized calcium. A recently published semi-empirical
model of cool loops based on SST observations serves to predict the
level of hydrogen and helium recombination continua. The continua were
synthesized using an approximate non-LTE (I.e., departures from local
thermodynamic equilibrium) approach and theoretical spectra were then
transformed to AIA signals. Comparison with signals detected inside
the dark loops shows that only in AIA 211 Å channel the computed
level of recombination continua is consistent with observations for
some models, while in all other channels that are more distant from
the continua edges the synthetic continuum is far too low. In analogy
with on-disk observations of flares we interpret the surplus emission
as due to numerous EUV lines emitted from hot but faint loops in front
of the cool ones. Finally we briefly comment on failure of the standard
absorption model when used for analysis of the dark-loop brightness.

---------------------------------------------------------
Title: Optical design of the multi-wavelength imaging coronagraph
Metis for the solar orbiter mission
Authors: Fineschi, S.; Naletto, G.; Romoli, M.; Da Deppo, V.;
Antonucci, E.; Moses, D.; Malvezzi, A. M.; Nicolini, G.; Spadaro,
D.; Teriaca, L.; Andretta, V.; Capobianco, G.; Crescenzio, G.;
Focardi, M.; Frassetto, F.; Landini, F.; Massone, G.; Melich, R.;
Nicolosi, P.; Pancrazzi, M.; Pelizzo, M. G.; Poletto, L.; Schühle,
U.; Uslenghi, M.; Vives, S.; Solanki, S. K.; Heinzel, P.; Berlicki,
A.; Cesare, S.; Morea, D.; Mottini, S.; Sandri, P.; Alvarez-Herrero,
A.; Castronuovo, M.
2020ExA....49..239F Altcode: 2020ExA...tmp...14F
This paper describes the innovative optical design of the Metis
coronagraph for the Solar Orbiter ESA-NASA mission. Metis is a
multi-wavelength, externally occulted telescope for the imaging
of the solar corona in both the visible and ultraviolet wavelength
ranges. Metis adopts a novel occultation scheme for the solar disk,
that we named "inverse external occulter", for reducing the extremely
high thermal load on the instrument at the spacecraft perihelion. The
core of the Metis optical design is an aplanatic Gregorian telescope
common to both the visible and ultraviolet channels. A suitable
dichroic beam-splitter, optimized for transmitting a narrow-band in
the ultraviolet (121.6 nm, HI Lyman-α) and reflecting a broadband
in the visible (580-640 nm) spectral range, is used to separate the
two optical paths. Along the visible light optical path, a liquid
crystal electro-optical modulator, used for the first time in space,
allows making polarimetric measurements.

---------------------------------------------------------
Title: Stellar coronal mass ejections - II. Constraints from
spectroscopic observations
Authors: Odert, P.; Leitzinger, M.; Guenther, E. W.; Heinzel, P.
2020MNRAS.494.3766O Altcode: 2020MNRAS.tmp.1176O; 2020arXiv200404063O
Detections of stellar coronal mass ejections (CMEs) are still
rare. Observations of strong Balmer line asymmetries during flare
events have been interpreted as being caused by CMEs. Here, we aim to
estimate the maximum possible Balmer line fluxes expected from CMEs
to infer their detectability in spectroscopic observations. Moreover,
we use these results together with a model of intrinsic CME rates to
infer the potentially observable CME rates for stars of different
spectral types under various observing conditions, as well as the
minimum required observing time to detect stellar CMEs in Balmer
lines. We find that generally CME detection is favoured for mid-
to late-type M dwarfs, as they require the lowest signal-to-noise
ratio for CME detection, and the fraction of observable-to-intrinsic
CMEs is largest. They may require, however, longer observing times
than stars of earlier spectral types at the same activity level,
as their predicted intrinsic CME rates are lower. CME detections
are generally favoured for stars close to the saturation regime,
because they are expected to have the highest intrinsic rates; the
predicted minimum observing time to detect CMEs on just moderately
active stars is already &gt;100 h. By comparison with spectroscopic
data sets including detections as well as non-detections of CMEs,
we find that our modelled maximum observable CME rates are generally
consistent with these observations on adopting parameters within the
ranges determined by observations of solar and stellar prominences.

---------------------------------------------------------
Title: Chromospheric Heating by Acoustic Waves Compared to Radiative
Cooling. II. Revised Grid of Models
Authors: Abbasvand, Vahid; Sobotka, Michal; Heinzel, Petr; Švanda,
Michal; Jurčák, Jan; del Moro, Dario; Berrilli, Francesco
2020ApJ...890...22A Altcode: 2020arXiv200103413A
Acoustic and magnetoacoustic waves are considered to be possible
agents of chromospheric heating. We present a comparison of deposited
acoustic energy flux with total integrated radiative losses in the
middle chromosphere of the quiet Sun and a weak plage. The comparison
is based on a consistent set of high-resolution observations acquired
by the Interferometric Bidimensional Spectrometer instrument in the
Ca II 854.2 nm line. The deposited acoustic-flux energy is derived
from Doppler velocities observed in the line core and a set of 1737
non-local thermodynamic equilibrium 1D hydrostatic semi-empirical
models, which also provide the radiative losses. The models are obtained
by scaling the temperature and column mass of five initial models by
Vernazza et al. (1981; VAL) B-F to get the best fit of synthetic to
observed profiles. We find that the deposited acoustic-flux energy in
the quiet-Sun chromosphere balances 30%-50% of the energy released by
radiation. In the plage, it contributes by 50%-60% in locations with
vertical magnetic field and 70%-90% in regions where the magnetic
field is inclined more than 50° to the solar surface normal.

---------------------------------------------------------
Title: IRIS Mg II Observations and Non-LTE Modeling of Off-limb
Spicules in a Solar Polar Coronal Hole
Authors: Tei, Akiko; Gunár, Stanislav; Heinzel, Petr; Okamoto,
Takenori J.; Štěpán, Jiří; Jejčič, Sonja; Shibata, Kazunari
2020ApJ...888...42T Altcode: 2019arXiv191112243T
We investigated the off-limb spicules observed in the Mg II h and k
lines by IRIS in a solar polar coronal hole. We analyzed the large data
set of obtained spectra to extract quantitative information about the
line intensities, shifts, and widths. The observed Mg II line profiles
are broad and double peaked at lower altitudes, broad but flat topped
at middle altitudes, and narrow and single peaked with the largest
Doppler shifts at higher altitudes. We use one-dimensional non-LTE
vertical slab models (I.e., models that consider departures from local
thermodynamic equilibrium) in single-slab and multi-slab configurations
to interpret the observations and to investigate how a superposition
of spicules along the line of sight (LOS) affects the synthetic Mg
II line profiles. The used multi-slab models either are static, I.e.,
without any LOS velocities, or assume randomly assigned LOS velocities
of individual slabs, representing the spicule dynamics. We conducted
such single-slab and multi-slab modeling for a broad set of model
input parameters and showed the dependence of the Mg II line profiles
on these parameters. We demonstrated that the observed line widths
of the h and k line profiles are strongly affected by the presence
of multiple spicules along the LOS. We later showed that the profiles
obtained at higher altitudes can be reproduced by single-slab models
representing individual spicules. We found that the multi-slab model
with a random distribution of the LOS velocities ranging from -25 to
25 km s-1 can well reproduce the width and the shape of Mg
II profiles observed at middle altitudes.

---------------------------------------------------------
Title: Analysis of the Quasi-Periodic Pulsations in the X9.3 and X8.3
Flares on 6 and 10 September 2017 Observed by SDO/EVE, PROBA2/LYRA
and MAVEN/EUVM
Authors: Dominique, M.; Zhukov, A.; Thiemann, E.; Dolla, L.; Heinzel,
P.; Wauters, L.; Dammasch, I. E.
2019AGUFMSH13D3422D Altcode:
Quasi-periodic pulsations (QPPs) refer to nearly-periodic oscillations
that are often observed in irradiance time series during most solar
flares and have also been reported in several stellar flares. Two
families of mechanisms are usually invoked to explain QPPs: MHD
waves and quasi-periodic particle acceleration. In both cases, QPPs
could inform us on the conditions in which flares happen. The two
strongest flares of the current solar cycle, i.e. the X9.3 flare on
6 September 2017 and the off-limb X8.3 flare that occurred four days
later, have been observed by two SXR-to-UV radiometers: SDO/EVE and
PROBA2/LYRA. These two flares were produced in similar conditions by
the same active region. However, if QPPs with periods between 1 and
100 s were clearly detected in the LYRA and EVE time series during
the first event, this was not the case during the second event. To
understand what causes this difference between the two flares, we
involve the observations by a third instrument: MAVEN/EUVM orbiting
Mars. We will compare the observations by the three instruments and
see how this can shed some light on the QPP phenomenon.

---------------------------------------------------------
Title: Diagnostics of the Prominence Plasma from Hα and Mg II
Spectral Observations
Authors: Ruan, Guiping; Jejčič, Sonja; Schmieder, Brigitte; Mein,
Pierre; Mein, Nicole; Heinzel, Petr; Gunár, Stanislav; Chen, Yao
2019ApJ...886..134R Altcode:
The goal of this paper is to derive the physical conditions of the
prominence observed on 2017 March 30. To do so, we use a unique set
of data in Mg II lines obtained with the space-borne Interface Region
Imaging Spectrograph (IRIS) and in Hα line with the ground-based
Multi-Channel Subtractive Double Pass spectrograph operating at the
Meudon solar tower. Here, we analyze the prominence spectra of Mg
II h and k lines, and the Hα line in the part of the prominence
which is visible in both sets of lines. We compute a grid of 1D
NLTE (i.e., departures from the local thermodynamical equilibrium)
models providing synthetic spectra of Mg II k and h, and Hα lines
in a large space of model input parameters (temperature, density,
pressure, and microturbulent velocity). We compare Mg II and Hα
line profiles observed in 75 positions of the prominence with the
synthetic profiles from the grid of models. These models allow us
to compute the relationships between the integrated intensities
and between the optical thickness in Hα and Mg II k lines. The
optical thickness τ Hα is between 0.05 and 2, and
{τ }Mg{{II}}{{k}}} is between 3 and 200. We show that
the relationship of the observed integrated intensities agrees well
with the synthetic integrated intensities for models with a higher
microturbulence (16 km s-1) and T around 8000 K, ne =
1.5 × 1010 cm-3, p = 0.05 dyne. In this case,
large microturbulence values could be a way to take into account the
large mixed velocities existing in the observed prominence.

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Title: 2D non-LTE modelling of a filament observed in the Hα line
with the DST/IBIS spectropolarimeter
Authors: Schwartz, P.; Gunár, S.; Jenkins, J. M.; Long, D. M.;
Heinzel, P.; Choudhary, D. P.
2019A&A...631A.146S Altcode: 2019arXiv191003607S
Context. We study a fragment of a large quiescent filament observed on
May 29, 2017 by the Interferometric BIdimensional Spectropolarimeter
(IBIS) mounted at the Dunn Solar Telescope. We focus on its quiescent
stage prior to its eruption. Aims: We analyse the spectral
observations obtained in the Hα line to derive the thermodynamic
properties of the plasma of the observed fragment of the filament. Methods: We used a 2D filament model employing radiative transfer
computations under conditions that depart from the local thermodynamic
equilibrium. We employed a forward modelling technique in which we
used the 2D model to produce synthetic Hα line profiles that we
compared with the observations. We then found the set of model input
parameters, which produces synthetic spectra with the best agreement
with observations. Results: Our analysis shows that one part
of the observed fragment of the filament is cooler, denser, and
more dynamic than its other part that is hotter, less dense, and more
quiescent. The derived temperatures in the first part range from 6000 K
to 10 000 K and in the latter part from 11 000 K to 14 000 K. The gas
pressure is 0.2-0.4 dyn cm-2 in the first part and around
0.15 dyn cm-2 in the latter part. The more dynamic nature
of the first part is characterised by the line-of-sight velocities with
absolute values of 6-7 km s-1 and microturbulent velocities
of 8-9 km s-1. On the other hand, the latter part exhibits
line-of-sight velocities with absolute values 0-2.5 km s-1
and microturbulent velocities of 4-6 km s-1.

---------------------------------------------------------
Title: Spectral Diagnostics of Cool Flare Loops Observed by the
SST. I. Inversion of the Ca II 8542 Å and Hβ Lines
Authors: Koza, Július; Kuridze, David; Heinzel, Petr; Jejčič,
Sonja; Morgan, Huw; Zapiór, Maciej
2019ApJ...885..154K Altcode: 2019arXiv190907356K
Flare loops form an integral part of eruptive events, being detected in
the range of temperatures from X-rays down to cool chromospheric-like
plasmas. While hot loops are routinely observed by the Solar Dynamics
Observatory’s Atmospheric Imaging Assembly, cool loops seen
off-limb are rare. In this paper we employ unique observations of
the SOL2017-09-10T16:06 X8.2-class flare which produced an extended
arcade of loops. The Swedish 1 m Solar Telescope made a series of
spectral images of the cool off-limb loops in the Ca II 8542 Å and
the hydrogen Hβ lines. Our focus is on the loop apices. Non-local
thermal equilibrium (non-LTE; i.e., departures from LTE) spectral
inversion is achieved through the construction of extended grids of
models covering a realistic range of plasma parameters. The Multilevel
Accelerated Lambda Iterations code solves the non-LTE radiative-transfer
problem in a 1D externally illuminated slab, approximating the studied
loop segment. Inversion of the Ca II 8542 Å and Hβ lines yields two
similar solutions, both indicating high electron densities around 2 ×
1012 cm-3 and relatively large microturbulence
around 25 km s-1. These are in reasonable agreement with
other independent studies of the same or similar events. In particular,
the high electron densities in the range 1012-1013
cm-3 are consistent with those derived from the Solar
Dynamics Observatory’s Helioseismic and Magnetic Imager white-light
observations. The presence of such high densities in solar eruptive
flares supports the loop interpretation of the optical continuum
emission of stars which manifest superflares.

---------------------------------------------------------
Title: Modelling of Flare Processes: A Comparison of the Two RHD
Codes FLARIX and RADYN
Authors: Kašparová, Jana; Carlsson, Mats; Heinzel, Petr; Varady,
Michal
2019ASPC..519..141K Altcode:
We present a comparison of two autonomous, methodologically different
radiation hydrodynamic codes, FLARIX and RADYN, and their use to model
the solar flare processes. Both codes can model the time evolution
of a 1D atmosphere heated by a specified process, e.g. by electron
beams propagating from the injection site in the corona down to the
lower atmosphere. In such a scenario time scales can be rather short
and lead to fast heating on even sub-second time scales. Our aim is
to compare the FLARIX and RADYN codes using exactly the same setup
and model conditions. Although such a comparison has never been done
successfully before for this type of codes, we will present a close
agreement between the time evolution of the modelled atmospheric
structure for a test case of electron beam heating.

---------------------------------------------------------
Title: Solar and Stellar Chromospheres
Authors: Heinzel, Petr; Štěpán, Jiří
2019ASPC..519...59H Altcode:
RADCOSMOS conference was largely devoted to many aspects of stellar
photospheric modeling, and namely a great success of Ivan's code
&lt;tt&gt;TLUSTY&lt;/tt&gt; was emphasized. In this short contribution
we focus on models of solar and stellar chromospheres which are not
in radiative equilibrium and thus require the knowledge of various
non-radiative heating mechanisms. We desrcibe both semiempirical,
as well as fully 3D RMHD models and mention the importance of partial
redistribution for a proper line diagnostics. Finally, since RADCOSMOS
was also covering topic of the polarized line transfer, we present
here some of the latests achievements related to the solar chromosphere.

---------------------------------------------------------
Title: Modeling the Scattering Polarization of the Hydrogen Lyα
Line Observed by CLASP in a Filament Channel
Authors: Štěpán, J.; Trujillo Bueno, J.; Gunár, S.; Heinzel, P.;
del Pino Alemán, T.; Kano, R.; Ishikawa, R.; Narukage, N.; Bando,
T.; Winebarger, A.; Kobayashi, K.; Auchère, F.
2019ASPC..526..165S Altcode:
The 400 arcsec spectrograph slit of CLASP crossed mainly quiet
regions of the solar chromosphere, from the limb towards the solar
disk center. Interestingly, in the CLASP slit-jaw images and in the
SDO images of the He II line at 304 Å, we can identify a filament
channel (FC) extending over more than 60 arcsec crossing the slit of
the spectrograph. In order to interpret the peculiar spatial variation
of the Q/I and U/I signals observed by CLASP in the hydrogen Lyα line
(1216 Å), we perform multi-dimensional radiative transfer modeling
in given filament models. In this contribution, we show the first
results of the two-dimensional calculations we have carried out, with
the aim of determining the filament thermal and magnetic structure by
comparing the theoretical and the observed polarization signals. Our
results suggest that the temperature gradients in the filament observed
by CLASP are significantly larger than previously thought.

---------------------------------------------------------
Title: 3D Whole-Prominence Fine Structure Model as a Test Case for
Verification and Development of Magnetic Field Inversion Techniques
Authors: Gunár, S.; Mackay, D. H.; Štěpán, J.; Heinzel, P.;
Trujillo Bueno, J.
2019ASPC..526..159G Altcode:
We show the potential of a new 3D whole-prominence fine structure
model to serve as a well-controlled yet complex environment for testing
inversion techniques for the magnetic field inference. The realistic
3D magnetic field and plasma environment provided by the model can
be used for the direct synthesis of spectro-polarimetric data. Such
synthetic data can be analyzed by advanced inversion tools and their
results compared with the known properties provided by the model.

---------------------------------------------------------
Title: Determination of the physical properties of an erupting
prominence from SOHO/LASCO and UVCS observations
Authors: Susino, R.; Bemporad, A.; Heinzel, P.; Jejčič, S.; Anzer,
, U.; Dzifčáková, E.
2019NCimC..42...37S Altcode:
We studied the physical conditions of an erupting prominence
observed in the core of a coronal mass ejection, using combination
of SOHO/LASCO-C2 visible-light images and SOHO/UVCS ultraviolet
data. Measured intensities and profiles of the neutral-hydrogen
Lyman- α and Lyman- β lines and the 977 Å C III line were
used together with the visible-light brightness to derive the
geometrical and physical parameters of the prominence, such as the
line-of-sight apparent thickness, electron column density, kinetic
temperature, and microturbolent velocity. These parameters were used
to constrain a non-LTE ( i.e., out of local thermodynamic equilibrium)
radiative-transfer model of the prominence that provides the effective
thickness, electron density, and flow velocity, in a sample of points
selected along the prominence. The prominence can be described as a hot
structure with low electron density and very low gas pressure compared
to typical quiescent prominences. Intensities of the hydrogen lines
were also used for a detailed determination of the plasma line-of-sight
filling factor, in the two prominence points where simultaneous and
cospatial LASCO-C2 and UVCS observations were available.

---------------------------------------------------------
Title: Chapter 5.2 - Models of Solar and Stellar Atmospheres
Authors: Heinzel, Petr
2019sgsp.book..157H Altcode:
This chapter addresses the basic principles of the radiative transfer
theory and nonequilibrium plasma physics, which were developed during
the past century and are now widely used to model solar and stellar
atmospheres. Many key results have been obtained and new numerical
methods developed by solar physicists; they serve as a guide for
stellar astrophysics. We start with the basics of radiation transport
and demonstrate the classical ideas of the nonequilibrium line formation
using a two-level atom example. Then we summarize the equations used to
construct standard plane-parallel models of atmospheres in hydrostatic
and radiative equilibrium and show examples of models with different
levels of complexity. Although such models are well-suited for modeling
photospheres, solar and stellar chromospheres require even more advanced
approaches. The simplest is represented by so-called semiempirical
models; we show some classical examples for the Sun and cool stars. A
specific class of problems concerns isolated atmospheric structures
illuminated by solar or stellar disk radiation. Based on various
atmospheric models, we discuss how model spectra are synthesized and
spectral lines are actually formed. Finally, we briefly introduce the
topic of radiation hydrodynamics as the most sophisticated tool for
solar and stellar atmospheric modeling.

---------------------------------------------------------
Title: Blue-wing enhancement of the chromospheric Mg II h and k
lines in a solar flare
Authors: Tei, Akiko; Sakaue, Takahito; Okamoto, Takenori J.; Kawate,
Tomoko; Heinzel, Petr; UeNo, Satoru; Asai, Ayumi; Ichimoto, Kiyoshi;
Shibata, Kazunari
2018PASJ...70..100T Altcode: 2018PASJ..tmp...61T; 2018arXiv180305237T
We performed coordinated observations of AR 12205, which showed a
C-class flare on 2014 November 11, with the Interface Region Imaging
Spectrograph (IRIS) and the Domeless Solar Telescope (DST) at Hida
Observatory. Using spectral data in the Si IV 1403 Å, C II 1335 Å,
and Mg II h and k lines from IRIS and the Ca II K, Ca II 8542 Å, and
Hα lines from DST, we investigated a moving flare kernel during the
flare. In the Mg II h line, the leading edge of the flare kernel showed
an intensity enhancement in the blue wing and a smaller intensity of the
blue-side peak (h2v) than that of the red-side one (h2r). The blueshift
lasted for 9-48 s with a typical speed of 10.1 ± 2.6 km s-1,
which was followed by a high intensity and a large redshift with a speed
of up to 51 km s-1 detected in the Mg II h line. The large
redshift was a common property for all six lines, but the blueshift
prior to it was found only in the Mg II lines. Cloud modeling of the
Mg II h line suggests that the blue-wing enhancement with such a peak
difference could have been caused by a chromospheric-temperature (cool)
upflow. We discuss a scenario in which an upflow of cool plasma is
lifted up by expanding hot plasma owing to the deep penetration of
non-thermal electrons into the chromosphere. Furthermore, we found
that the blueshift persisted without any subsequent redshift in the
leading edge of the flare kernel during its decaying phase. The cause
of such a long-lasting blueshift is also discussed.

---------------------------------------------------------
Title: Solar Ultraviolet Bursts
Authors: Young, Peter R.; Tian, Hui; Peter, Hardi; Rutten, Robert J.;
Nelson, Chris J.; Huang, Zhenghua; Schmieder, Brigitte; Vissers, Gregal
J. M.; Toriumi, Shin; Rouppe van der Voort, Luc H. M.; Madjarska, Maria
S.; Danilovic, Sanja; Berlicki, Arkadiusz; Chitta, L. P.; Cheung, Mark
C. M.; Madsen, Chad; Reardon, Kevin P.; Katsukawa, Yukio; Heinzel, Petr
2018SSRv..214..120Y Altcode: 2018arXiv180505850Y
The term "ultraviolet (UV) burst" is introduced to describe small,
intense, transient brightenings in ultraviolet images of solar active
regions. We inventorize their properties and provide a definition
based on image sequences in transition-region lines. Coronal signatures
are rare, and most bursts are associated with small-scale, canceling
opposite-polarity fields in the photosphere that occur in emerging flux
regions, moving magnetic features in sunspot moats, and sunspot light
bridges. We also compare UV bursts with similar transition-region
phenomena found previously in solar ultraviolet spectrometry and
with similar phenomena at optical wavelengths, in particular Ellerman
bombs. Akin to the latter, UV bursts are probably small-scale magnetic
reconnection events occurring in the low atmosphere, at photospheric
and/or chromospheric heights. Their intense emission in lines with
optically thin formation gives unique diagnostic opportunities
for studying the physics of magnetic reconnection in the low solar
atmosphere. This paper is a review report from an International Space
Science Institute team that met in 2016-2017.

---------------------------------------------------------
Title: High-density Off-limb Flare Loops Observed by SDO
Authors: Jejčič, S.; Kleint, L.; Heinzel, P.
2018ApJ...867..134J Altcode: 2018arXiv181002431J
The density distribution of flare loops and the mechanisms of their
emission in the continuum are still open questions. On 2017 September
10, a prominent loop system appeared during the gradual phase of an X8.2
flare (SOL2017-09-10), visible in all passbands of SDO/AIA and in the
white-light continuum of SDO/HMI. We investigate its electron density
by taking into account all radiation processes in the flare loops,
i.e., the Thomson continuum, hydrogen Paschen and Brackett recombination
continua, as well as free-free continuum emission. We derive a quadratic
function of the electron density for a given temperature and effective
loop thickness. By absolutely calibrating SDO/HMI intensities,
we convert the measured intensities into electron density at each
pixel in the loops. For a grid of plausible temperatures between cool
(6000 K) and hot (106 K) structures, the electron density
is computed for representative effective thicknesses between 200 and
20,000 km. We obtain a relatively high maximum electron density, about
1013 cm-3. At such high electron densities, the
Thomson continuum is negligible and therefore one would not expect a
significant polarization degree in dense loops. We conclude that the
Paschen and Brackett recombination continua are dominant in cool flare
loops, while the free-free continuum emission is dominant for warmer
and hot loops.

---------------------------------------------------------
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: First Detection of Solar Flare Emission in Mid-ultraviolet
Balmer Continuum
Authors: Dominique, Marie; Zhukov, Andrei N.; Heinzel, Petr;
Dammasch, Ingolf E.; Wauters, Laurence; Dolla, Laurent; Shestov,
Sergei; Kretzschmar, Matthieu; Machol, Janet; Lapenta, Giovanni;
Schmutz, Werner
2018ApJ...867L..24D Altcode: 2018arXiv181009835D
We present the first detection of solar flare emission at
mid-ultraviolet wavelengths around 2000 Å by the channel 2 of the
Large-Yield RAdiometer (LYRA) on board the PRoject for OnBoard Autonomy
2 mission. The flare (SOL20170906) was also observed in the channel
1 of LYRA centered at the H I Lyα line at 1216 Å, showing a clear
non-thermal profile in both channels. The flare radiation in channel 2
is consistent with the hydrogen Balmer continuum emission produced by an
optically thin chromospheric slab heated up to 10,000 K. Simultaneous
observations in channels 1 and 2 allow the separation of the line
emission (primarily from the Lyα line) from the Balmer continuum
emission. Together with the recent detection of the Balmer continuum
emission in the near-ultraviolet by the Interface Region Imaging
Spectrometer, the LYRA observations strengthen the interpretation
of broadband flare emission as the hydrogen recombination continua
originating in the chromosphere.

---------------------------------------------------------
Title: Statistical analysis of UV spectra of a quiescent prominence
observed by IRIS
Authors: Jejčič, S.; Schwartz, P.; Heinzel, P.; Zapiór, M.;
Gunár, S.
2018A&A...618A..88J Altcode: 2018arXiv180705767J
Context. The paper analyzes the structure and dynamics of a quiescent
prominence that occurred on October 22, 2013 and was observed by
several instruments including the Interface Region Imaging Spectrograph
(IRIS). Aims: We aim to determine the physical characteristics
of the observed prominence using Mg II k and h (2796 and 2803 Å), C
II (1334 and 1336 Å), and Si IV (1394 Å) lines observed by IRIS. In
addition we study the dynamical behavior of the prominence. 
Methods: We employed the one-dimensional non-LTE (departures from the
local thermodynamic equilibrium - LTE) modeling of Mg II lines assuming
static isothermal-isobaric slabs. We selected a large grid of models
with realistic input parameters expected for quiescent prominences
(temperature, gas pressure, effective thickness, microturbulent
velocity, height above the solar surface) and computed synthetic Mg II
lines. The method of Scargle periodograms was used to detect possible
prominence oscillations. Results: We analyzed 2160 points of the
observed prominence in five different sections along the slit averaged
over ten pixels due to low signal to noise ratio in the C II and Si IV
lines. We computed the integrated intensity for all studied lines, while
the central intensity and reversal ratio was determined only for both Mg
II and C II 1334 lines. We plotted several correlations: time evolution
of the integrated intensities and central intensities, scatter plots
between all combinations of line integrated intensities, and reversal
ratio as a function of integrated intensity. We also compared Mg II
observations with the models. Results show that more than two-thirds
of Mg II profiles and about one-half of C II 1334 profiles are
reversed. Profiles of Si IV are generally unreversed. The Mg II and C II
lines are optically thick, while the Si IV line is optically thin. Conclusions: The studied prominence shows no global oscillations
in the Mg II and C II lines. Therefore, the observed time variations
are caused by random motions of fine structures with velocities up
to 10 km s-1. The observed average ratio of Mg II k to
Mg II h line intensities can be used to determine the prominence's
characteristic temperature. Certain disagreements between observed
and synthetic line intensities of Mg II lines point to the necessity
of using more complex two-dimensional multi-thread modeling in the
future. The movies associated to Figs. 1 and 7 are available at <A
href="https://www.aanda.org/10.1051/0004-6361/201833466/olm">https://www.aanda.org</A>

---------------------------------------------------------
Title: Hot prominence detected in the core of a coronal mass
ejection. III. Plasma filling factor from UVCS Lyman-α and Lyman-β
observations
Authors: Susino, R.; Bemporad, A.; Jejčič, S.; Heinzel, P.
2018A&A...617A..21S Altcode: 2018arXiv180512465S
Context. We study an erupting prominence embedded in the core of a
coronal mass ejection that occurred on August 2, 2000, and focus on
deriving the plasma filling factor of the prominence. Aims:
We explore two methods for measuring this factor along the line of
sight. They are based on a combination of visible-light and ultraviolet
spectroscopic observations. Methods: Theoretical relationships
for resonant scattering and collisional excitation were used to evaluate
the intensity of the neutral hydrogen Lyman-α and Lyman-β lines in
two prominence points where simultaneous and cospatial LASCO-C2 and
UVCS data were available. Thermodynamic and geometrical parameters
assumed for the calculation (i.e., electron column density, kinetic
temperature, flow velocity, chromospheric Lyα and Lyβ intensities
and profiles, and thickness of the prominence along the line of sight)
are provided by both observations and the results of a detailed 1D
non-local thermal equilibrium (non-LTE) radiative-transfer model
of the prominence, developed in our previous work. The geometrical
filling factor was derived from comparing the calculated and measured
intensities of the two lines. The results were then checked against the
non-LTE model in order to verify the reliability of the methods. 
Results: The resulting filling factors are consistent with the model in
both prominence points when the radiative and collisional components
of the total intensity of the hydrogen lines are separated using
the Lyα and Lyβ line intensities, which is required to estimate
the filling factor. The exploration of the parameter space shows
that the results are weakly sensitive to the plasma flow velocity,
but depend more strongly on the assumed kinetic temperatures. 
Conclusions: The combination of visible-light and ultraviolet Lyα
and Lyβ data can be used to approximately estimate the line-of-sight
geometrical filling factor in erupting prominences, but the proposed
technique, which is model dependent, is reliable only for emission
that is optically thin in the lines considered, a condition that is
not in general representative of prominence plasma.

---------------------------------------------------------
Title: 3D modelling of magnetic field and plasma structure of entire
prominences
Authors: Gunár, Stanislav; Anzer, Ulrich; Heinzel, Petr; Mackay,
Duncan
2018cosp...42E1315G Altcode:
The 3D Whole-Prominence Fine Structure (WPFS) model allows us for
the first time to simulate entire prominences/filaments including
their numerous fine structures. This model combines a 3D magnetic
field configuration of an entire prominence obtained from non-linear
force-free field simulations, 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
within the 3D magnetic model. The prominence plasma has realistic
density and temperature distributions including the prominence-corona
transition region. This allows us to produce synthetic H-alpha images
of simulated prominences both in emission on the solar limb and in
absorption against the solar disk (viewed as filaments) using a single
model.Such 3D WPFS model provides us with consistent information about
the prominence magnetic field configuration, prominence fine structure
plasma and its radiative output. Moreover, we are able to follow the
evolution of modeled prominences caused by changes of the underlying
photospheric magnetic flux distribution. Thanks to these capabilities we
can study links between the photospheric flux distribution, prominence
magnetic field configuration, distribution and composition of the
prominence plasma and its observable signatures. These relationships
are important for interpretation of the observed imaging and
spectral/spectropolarimetric data and for inference of the properties
of the prominence magnetic field.

---------------------------------------------------------
Title: Plasma physical parameters of a prominence embedded in the
core of a Coronal Mass Ejection
Authors: Bemporad, Alessandro; Anzer, Ulrich; Heinzel, Petr; Jejcic,
Sonja; Susino, Roberto
2018cosp...42E.267B Altcode:
We determine the plasma physical parameters of an erupting prominence
embedded in the core of a CME, combininging visible light coronagraphic
images from SOHO/LASCO with UV spectra acquired by SOHO/UVCS. Strong
UV emissions were detected in the hydrogen Lyman-α and Lyman-β
lines and C III line. Visible light and UV intensities have been used
to estimate the projected thickness and velocity of the prominence,
together with the effective plasma temperature, microturbolent velocity,
and column density. These parameters have been used to constrain
1D NLTE modeling of the erupting plasma, taking into account the
effects of large flow velocities (Doppler dimming). Roughly one-half
of considered points in the prominence body show a non-negligible
Lyman-α optical thickness. Comparison between the calculated and the
measured intensities of the two Lyman lines was also used to derive the
geometrical filling factor. Results show that the erupting prominence
plasma is relatively hot, with a low electron density, a wide range of
effective thicknesses, a rather narrow range of radial flow velocities,
and a microturbulence of about 25 km/s. This analysis provides a basis
for future diagnostics of prominences using the METIS coronagraph on
board the Solar Orbiter mission.

---------------------------------------------------------
Title: Dynamics in quiescent prominences observed by the IRIS and
MSDP spectrographs
Authors: Gunár, Stanislav; Schmieder, Brigitte; Ruan, Guiping; Mein,
Pierre; Heinzel, Petr
2018cosp...42E1314G Altcode:
Quiescent solar prominences are generally considered to
be stable. However, these prominences consist of a multitude of
small-scale structures or threads that are often significantly
dynamic. To understand the nature of the plasma dynamics we use the
high spatial, temporal and spectral resolution observations obtained
by IRIS during coordinated campaign with the MSDP spectrograph
at the Meudon Solar Tower. Mg II h and k lines observed by IRIS
represent a good diagnostic tool for investigation of the prominence
fine structure dynamics, as they are optically thick under the
prominence conditions. We will present detailed IRIS observations of
Mg II lines. We explain significant asymmetries in the observed Mg II
spectra by the presence of several threads located along the line of
sight with different velocities. In such a case, the decrease of the
intensity of individual components of the observed spectra with the
distance from the central wavelength can be explained by the Doppler
dimming effect. To interpret the observed Mg II profiles in terms
of dynamics we use 1D or 2D radiative transfer models including a
prominence-corona transition region. We also show that the H-alpha
line which is optically thinner than the Mg II doublet is an important
constrain for the radiative transfer radiation modelling.

---------------------------------------------------------
Title: Hot Erupting Prominences in Cores of Cme's
Authors: Heinzel, Petr; Bemporad, Alessandro; Anzer, Ulrich; Jejcic,
Sonja; Susino, Roberto; Dzifcakova, Elena
2018cosp...42E1421H Altcode:
Coronal mass ejections (CME) associated with prominence eruptions
exhibit relatively coolmaterial in their cores. Such prominence
plasmas were frequently detected in various spectrallines by SOHO/UVCS
coronagraph and in the visible light by SOHO/LASCO as well as bySTEREO
coronagraphs. UVCS provided excellent spectra of CME-core prominences
and anextended catalogue of these data is available. We will present
recent results of a hot prominence diagnostics using the hydrogen Lyman
lines and the CIII line . The erupting prominence parameters are further
constrained by the visible light observations from LASCO-C2. A novel
non-LTE modeling based on such observations will be presented and we
will highlight the diagnostic potential of the UV and visible light for
future space coronagraphs like Metis on board the ESA Solar Orbiter
mission. The plasma parameters of such hot prominences are compared
with those obtained from numerical MHD simulations of erupting flux
ropes surrounded by CMEs. Finally, we will also mention synergies with
stellar analogues.

---------------------------------------------------------
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: IRIS Observations and Modeling of MGII Flare Loops
Authors: Heinzel, Petr; Berlicki, Arkadiusz; Mikula, Katarzyna;
Liu, Wenjuan
2018cosp...42E1423H Altcode:
Solar chromospheric flares are often associated with cool loops which
are rooted in the ribbons. These loops extend into coronal altitudes
and usually are modelled as prominence-like structures illuminated from
the solar disk. The loops exhibit large down-flows (coronal rain) and
they evolve in time in accordance with the characteristic cooling times
of the loop plasmas. Cool loops are visible in various spectral lines
formed at chromospheric temperatures. We exploit novel observations
of such loops in MgII h and k lines obtained by the IRIS satellite,
analyse selected observations where the cool loops are well visible
and studytheir temporal evolution. Our spectroscopic diagnostics is
based on 2D non-LTE modelling ofMgII lines in flare loops taking into
account the flows along the loops. From these models wedetermine various
plasma parameters and the rates of radiation cooling. These results
allow usto better understand the structure, dynamics and evolution of
cool flare loops.

---------------------------------------------------------
Title: Blue wing enhancement of the chromospheric Mg II h and k
lines in a solar flare
Authors: Tei, Akiko; Shibata, Kazunari; Asai, Ayumi; Ichimoto,
Kiyoshi; Heinzel, Petr; Ueno, Satoru; Okamoto, Joten; Sakaue, Takahito;
Kawate, Tomoko
2018cosp...42E3350T Altcode:
We performed coordinated observations of NOAA AR 12205, which produced
a C-class flare on 2014 November 11, with the Interface Region Imaging
Spectrograph (IRIS) and the Domeless Solar Telescope (DST) at Hida
Observatory.Using spectral data in the Si IV 1403 Å, C II 1335 Å,
and Mg II h and k lines from IRIS and the Ca II K, Ca II 8542 Å,
and Hα lines from DST, we investigated the temporal and spatial
evolution around a moving flare kernel.In the Mg II h line, the leading
edge of the kernel showed intensity enhancement in the blue wing and
difference between the blue-side peak and red-side one (I_{h2v} &lt;
I_{h2r}).Then, the drastic change of the intensity in the red wing
occurred.The blueshift lasted for 9-48 s with a speed of 10.1 ± 2.6
km s^{-1} and it was followed by the strong redshift with a speed of
up to 51 km s^{-1} detected in the Mg II h line.The strong redshift
was a common property for all six lines but the blueshift prior to it
was found only in the Mg II lines.A cloud modeling of the Mg II h line
suggests that the blue wing enhancement with such peak difference can
be caused by a chromospheric-temperature (cool) upflow.We discuss a
scenario in which an upflow of cool plasma is lifted up by expanding
(hot) plasma owing to the deep penetration of non-thermal electrons
into the chromosphere.In addition, at the leading edge of the final
flare footpoints, the blueshift persisted in the Mg II h line, which
was not followed by any large redshift and intensity enhancement.Such
long-lasting blueshift can be explained by cool upflow caused by small
energy flux into the lower atmosphere.

---------------------------------------------------------
Title: Cool Loops on Cool Stars
Authors: Heinzel, Petr
2018cosp...42E1422H Altcode:
Recently a significant effort has been devoted to systematic modelling
of solar and stellar chromospheric flares which are typically manifested
by bright ribbons embedded in the lower atmospheric layers. However,
apart from ribbons detectable in a broad range of the electromagnetic
spectrum, overlying loops are also frequently observed on the Sun. They
appear in various spectral lines and can be well resolved in the
so-called eruptive flares. We will show how their appearance depends
on the loop plasma conditions and parameters. We will also briefly
review the efforts to model the radiation properties of such loops and
namely of those which cooled down to chromospheric temperatures. Light
curves of the flaring ribbons may differ from time evolution of the
loop brightness and this can be easily detected on the Sun. However,
on cool stars the measured light curves may contain an unresolved
information about the temporal evolution of both ribbons and cool
loops and we will demonstrate how this can be modelled.

---------------------------------------------------------
Title: Can Flare Loops Contribute to the White-light Emission of
Stellar Superflares?
Authors: Heinzel, P.; Shibata, K.
2018ApJ...859..143H Altcode: 2018arXiv180409656H
Since the discovery of stellar superflares by the Kepler satellite,
these extremely energetic events have been studied in analogy to
solar flares. Their white-light (WL) continuum emission has been
interpreted as being produced by heated ribbons. In this paper,
we compute the WL emission from overlying flare loops depending
on their density and temperature and show that, under conditions
expected during superflares, the continuum brightening due to
extended loop arcades can significantly contribute to stellar flux
detected by Kepler. This requires electron densities in the loops of
1012-1013 cm-3 or higher. We show
that such densities, exceeding those typically present in solar-flare
loops, can be reached on M-dwarf and solar-type superflare stars with
large starspots and much stronger magnetic fields. Quite importantly,
the WL radiation of loops is not very sensitive to their temperature
and thus both cool as well as hot loops may contribute. We show that
the WL intensity emergent from optically thin loops is lower than the
blackbody radiation from flare ribbons, but the contribution of loops
to total stellar flux can be quite important due to their significant
emitting areas. This new scenario for interpreting superflare emission
suggests that the observed WL flux is due to a mixture of the ribbon
and loop radiation and can be even loop-dominated during the gradual
phase of superflares.

---------------------------------------------------------
Title: Observation of the X9.3 flare of September 6 2017 in UV/EUV
by PROBA2/LYRA
Authors: Dominique, Marie; Zhukov, Andrei; Heinzel, Petr; Dammasch,
Ingolf E.; Wauters, Laurence; Dolla, Laurent; Shestov, Sergei
2018tess.conf31903D Altcode:
After several months of relative quietness, a sudden burst of solar
activity was observed starting on September 4 2017, when the NOAA AR
12673 started to develop quickly. This region remained active until it
disappeared behind the west limb on September 10. It produced multiple
strong flares (27 M-class flares and 4 X-class flares). Among them,
there were the two strongest flare observed so far during the solar
cycle 24: the X9.3 flare of September 6 and the off-limb X8.3 flare of
September 10. At the time of these two events, the Large-Yield
Radiometer (LYRA) onboard PROBA2 was performing a special flare
observation campaign, involving one of its spare units that is normally
only used for calibration purposes. As this unit was only sporadically
opened over the mission lifetime, it is relatively preserved from the
ageing processes that otherwise affect the instrument, and it delivered
very clear observations of both flares. In particular, the X9.3 flare
produced a signature in the four channels of the instrument, of which
two observe the EUV range, one the hydrogen Lyman-alpha line, and the
last one the continuum around 2000 Angstroms. As flare observations
are relatively rare in Lyman-alpha and almost non-existing in the
continuum around 2000 Angstroms, this constitutes a rather unique set
of observations. In contrast, the X8.3 flare only produced signatures
in the two EUV channels. This presentation will describe the
LYRA observations, compare both flares, and discuss the origin of the
emitted signal in the four channels.

---------------------------------------------------------
Title: Václav Bumba (1925 - 2018)
Authors: Kotrč, Pavel; Heinzel, Petr; Sobotka, Michal; Ambrož,
Pavel; van Driel-Gesztelyi, Lidia
2018SoPh..293...40K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Visibility of Prominences Using the He I D3 Line
Filter on the PROBA-3/ASPIICS Coronagraph
Authors: Jejčič, S.; Heinzel, P.; Labrosse, N.; Zhukov, A. N.;
Bemporad, A.; Fineschi, S.; Gunár, S.
2018SoPh..293...33J Altcode: 2018arXiv180700155J
We determine the optimal width and shape of the narrow-band filter
centered on the He I D3 line for prominence and coronal
mass ejection (CME) observations with the ASPIICS (Association of
Spacecraft for Polarimetric and Imaging Investigation of the Corona of
the Sun) coronagraph onboard the PROBA-3 (Project for On-board Autonomy)
satellite, to be launched in 2020. We analyze He I D3 line
intensities for three representative non-local thermal equilibrium
prominence models at temperatures 8, 30, and 100 kK computed with a
radiative transfer code and the prominence visible-light (VL) emission
due to Thomson scattering on the prominence electrons. We compute
various useful relations at prominence line-of-sight velocities of 0,
100, and 300 km s−1 for 20 Å wide flat filter and three
Gaussian filters with a full-width at half-maximum (FWHM) equal to 5,
10, and 20 Å to show the relative brightness contribution of the He I
D3 line and the prominence VL to the visibility in a given
narrow-band filter. We also discuss possible signal contamination by Na
I D1 and D2 lines, which otherwise may be useful
to detect comets. Our results mainly show that i) an optimal narrow-band
filter should be flat or somewhere between flat and Gaussian with an
FWHM of 20 Å in order to detect fast-moving prominence structures,
ii) the maximum emission in the He I D3 line is at 30 kK
and the minimal at 100 kK, and iii) the ratio of emission in the He I
D3 line to the VL emission can provide a useful diagnostic
for the temperature of prominence structures. This ratio is up to 10
for hot prominence structures, up to 100 for cool structures, and up
to 1000 for warm structures.

---------------------------------------------------------
Title: Quiescent Prominences in the Era of ALMA. II. Kinetic
Temperature Diagnostics
Authors: Gunár, Stanislav; Heinzel, Petr; Anzer, Ulrich; Mackay,
Duncan H.
2018ApJ...853...21G Altcode:
We provide the theoretical background for diagnostics of the thermal
properties of solar prominences observed by the Atacama Large
Millimeter/submillimeter Array (ALMA). To do this, we employ the 3D
Whole-Prominence Fine Structure (WPFS) model that produces synthetic
ALMA-like observations of a complex simulated prominence. We use
synthetic observations derived at two different submillimeter/millimeter
(SMM) wavelengths—one at a wavelength at which the simulated
prominence is completely optically thin and another at a wavelength at
which a significant portion of the simulated prominence is optically
thick—as if these were the actual ALMA observations. This allows
us to develop a technique for an analysis of the prominence plasma
thermal properties from such a pair of simultaneous high-resolution ALMA
observations. The 3D WPFS model also provides detailed information about
the distribution of the kinetic temperature and the optical thickness
along any line of sight. We can thus assess whether the measure of the
kinetic temperature derived from observations accurately represents
the actual kinetic temperature properties of the observed plasma. We
demonstrate here that in a given pixel the optical thickness at the
wavelength at which the prominence plasma is optically thick needs
to be above unity or even larger to achieve a sufficient accuracy of
the derived information about the kinetic temperature of the analyzed
plasma. Information about the optical thickness cannot be directly
discerned from observations at the SMM wavelengths alone. However,
we show that a criterion that can identify those pixels in which
the derived kinetic temperature values correspond well to the actual
thermal properties in which the observed prominence can be established.

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Title: ASPIICS: a giant, white light and emission line coronagraph
for the ESA proba-3 formation flight mission
Authors: Lamy, P. L.; Vivès, S.; Curdt, W.; Damé, L.; Davila, J.;
Defise, J. -M.; Fineschi, S.; Heinzel, P.; Howard, Russel; Kuzin,
S.; Schmutz, W.; Tsinganos, K.; Zhukov, A.
2017SPIE10565E..0TL Altcode:
Classical externally-occulted coronagraphs are presently limited in
their performances by the distance between the external occulter and
the front objective. The diffraction fringe from the occulter and
the vignetted pupil which degrades the spatial resolution prevent
useful observations of the white light corona inside typically 2-2.5
solar radii (Rsun). Formation flying offers and elegant solution to
these limitations and allows conceiving giant, externally-occulted
coronagraphs using a two-component space system with the external
occulter on one spacecraft and the optical instrument on the
other spacecraft at a distance of hundred meters [1, 2]. Such
an instrument ASPIICS (Association de Satellites Pour l'Imagerie
et l'Interférométrie de la Couronne Solaire) has been selected
by the European Space Agency (ESA) to fly on its PROBA-3 mission
of formation flying demonstration which is presently in phase B
(Fig. 1). The classical design of an externally-occulted coronagraph is
adapted to the formation flying configuration allowing the detection
of the very inner corona as close as 0.04 solar radii from the solar
limb. By tuning the position of the occulter spacecraft, it may even be
possible to reach the chromosphere and the upper part of the spicules
[3]. ASPIICS will perform (i) high spatial resolution imaging of the
continuum K+F corona in photometric and polarimetric modes, (ii) high
spatial resolution imaging of the E-corona in two coronal emission lines
(CEL): Fe XIV and He I D3, and (iii) two-dimensional spectrophotometry
of the Fe XIV emission line. ASPIICS will address the question of the
coronal heating and the role of waves by characterizing propagating
fluctuations (waves and turbulence) in the solar wind acceleration
region and by looking for oscillations in the intensity and Doppler
shift of spectral lines. The combined imaging and spectral diagnostics
capabilities available with ASPIICS will allow mapping the velocity
field of the corona both in the sky plane (directly on the images)
and along the line-of-sight by measuring the Doppler shifts of
emission lines in an effort to determine how the different components
of the solar wind, slow and fast are accelerated. With a possible
launch in 2014, ASPIICS will observe the corona during the maximum of
solar activity, insuring the detection of many Coronal Mass Ejections
(CMEs). By rapidly alternating high-resolution imaging and spectroscopy,
CMEs will be thoroughly characterized.

---------------------------------------------------------
Title: Hot prominence detected in the core of a coronal mass
ejection. II. Analysis of the C III line detected by SOHO/UVCS
Authors: Jejčič, S.; Susino, R.; Heinzel, P.; Dzifčáková, E.;
Bemporad, A.; Anzer, U.
2017A&A...607A..80J Altcode:
Context. We study the physics of erupting prominences in the core
of coronal mass ejections (CMEs) and present a continuation of a
previous analysis. Aims: We determine the kinetic temperature
and microturbulent velocity of an erupting prominence embedded in the
core of a CME that occurred on August 2, 2000 using the Ultraviolet
Coronagraph and Spectrometer observations (UVCS) on board the Solar
and Heliospheric Observatory (SOHO) simultaneously in the hydrogen
Lα and C III lines. We develop the non-LTE (departures from the local
thermodynamic equilibrium - LTE) spectral diagnostics based on Lα and
Lβ measured integrated intensities to derive other physical quantities
of the hot erupting prominence. Based on this, we synthesize the C
III line intensity to compare it with observations. Methods:
Our method is based on non-LTE modeling of eruptive prominences. We
used a general non-LTE radiative-transfer code only for optically thin
prominence points because optically thick points do not allow the
direct determination of the kinetic temperature and microturbulence
from the line profiles. The input parameters of the code were the
kinetic temperature and microturbulent velocity derived from the Lα
and C III line widths, as well as the integrated intensity of the Lα
and Lβ lines. The code runs in three loops to compute the radial flow
velocity, electron density, and effective thickness as the best fit
to the Lα and Lβ integrated intensities within the accuracy defined
by the absolute radiometric calibration of UVCS data. Results:
We analyzed 39 observational points along the whole erupting prominence
because for these points we found a solution for the kinetic temperature
and microturbulent velocity. For these points we ran the non-LTE code to
determine best-fit models. All models with τ0(Lα) ≤ 0.3
and τ0(C III) ≤ 0.3 were analyzed further, for which we
computed the integrated intensity of the C III line using a two-level
atom. The best agreement between computed and observed integrated
intensity led to 30 optically thin points along the prominence. The
results are presented as histograms of the kinetic temperature,
microturbulent velocity, effective thickness, radial flow velocity,
electron density, and gas pressure. We also show the relation between
the microturbulence and kinetic temperature together with a scatter plot
of computed versus observed C III integrated intensities and the ratio
of the computed to observed C III integrated intensities versus kinetic
temperature. Conclusions: The erupting prominence embedded in
the CME is relatively hot with a low electron density, a wide range of
effective thicknesses, a rather narrow range of radial flow velocities,
and a microturbulence of about 25 km s-1. This analysis shows
a disagreement between observed and synthetic intensities of the C III
line, the reason for which most probably is that photoionization is
neglected in calculations of the ionization equilibrium. Alternatively,
the disagreement might be due to non-equilibrium processes.

---------------------------------------------------------
Title: On the Nature of Off-limb Flare Continuum Sources Detected
by SDO/HMI
Authors: Heinzel, P.; Kleint, L.; Kašparová, J.; Krucker, S.
2017ApJ...847...48H Altcode: 2017arXiv170906377H
The Helioseismic and Magnetic Imager on board the Solar Dynamics
Observatory has provided unique observations of off-limb flare
emission. White-light continuum enhancements were detected in the
“continuum” channel of the Fe 6173 Å line during the impulsive
phase of the observed flares. In this paper we aim to determine which
radiation mechanism is responsible for such enhancement being seen above
the limb, at chromospheric heights around or below 1000 km. Using a
simple analytical approach, we compare two candidate mechanisms, the
hydrogen recombination continuum (Paschen) and the Thomson continuum
due to scattering of disk radiation on flare electrons. Both mechanisms
depend on the electron density, which is typically enhanced during the
impulsive phase of a flare as the result of collisional ionization (both
thermal and also non-thermal due to electron beams). We conclude that
for electron densities higher than 1012 cm-3,
the Paschen recombination continuum significantly dominates the
Thomson scattering continuum and there is some contribution from the
hydrogen free-free emission. This is further supported by detailed
radiation-hydrodynamical (RHD) simulations of the flare chromosphere
heated by the electron beams. We use the RHD code FLARIX to compute the
temporal evolution of the flare-heating in a semi-circular loop. The
synthesized continuum structure above the limb resembles the off-limb
flare structures detected by HMI, namely their height above the limb,
as well as the radiation intensity. These results are consistent with
recent findings related to hydrogen Balmer continuum enhancements,
which were clearly detected in disk flares by the IRIS near-ultraviolet
spectrometer.

---------------------------------------------------------
Title: Structure and Dynamics of Cool Flare Loops Observed by the
Interface Region Imaging Spectrograph
Authors: Mikuła, K.; Heinzel, P.; Liu, W.; Berlicki, A.
2017ApJ...845...30M Altcode:
Flare loops were well observed with the Interface Region Imaging
Spectrograph (IRIS) during the gradual phase of two solar flares
on 2014 March 29 and 2015 June 22. Cool flare loops are visible in
various spectral lines formed at chromospheric and transition-region
temperatures and exhibit large downflows which correspond to the
standard scenario. The principal aim of this work is to analyze
the structure and dynamics of cool flare loops observed in Mg II
lines. Synthetic profiles of the Mg II h line are computed using the
classical cloud model and assuming a uniform background intensity. In
this paper, we study novel IRIS NUV observations of such loops in Mg II
h and k lines and also show the behavior of hotter lines detected in
the FUV channel. We obtained the spatial evolution of the velocities:
near the loop top, the flow velocities are small and they are increasing
toward the loop legs. Moreover, from slit-jaw image (SJI) movies, we
observe some plasma upflows into the loops, which are also detectable
in Mg II spectra. The brightness of the loops systematically decreases
with increasing flow velocity, and we ascribe this to the effect of
Doppler dimming, which works for Mg II lines. Emission profiles of Mg
II were found to be extremely broad, and we explain this through the
large unresolved non-thermal motions.

---------------------------------------------------------
Title: On the Origin of the Flare Emission in IRIS’ SJI 2832
Filter:Balmer Continuum or Spectral Lines?
Authors: Kleint, Lucia; Heinzel, Petr; Krucker, Säm
2017ApJ...837..160K Altcode: 2017arXiv170207167K
Continuum (“white-light,” WL) emission dominates the energetics of
flares. Filter-based observations, such as the IRIS SJI 2832 filter,
show WL-like brightenings during flares, but it is unclear whether
the emission arises from real continuum emission or enhanced spectral
lines, possibly turning into emission. The difficulty in filter-based
observations, contrary to spectral observations, is to determine which
processes contribute to the observed brightening during flares. Here
we determine the contribution of the Balmer continuum and the spectral
line emission to IRIS’ SJI 2832 emission by analyzing the appropriate
passband in simultaneous IRIS NUV spectra. We find that spectral line
emission can contribute up to 100% to the observed slitjaw images (SJI)
emission, that the relative contributions usually temporally vary,
and that the highest SJI enhancements that are observed are most likely
because of the Balmer continuum. We conclude that care should be taken
when calling SJI 2832 a continuum filter during flares, because the
influence of the lines on the emission can be significant.

---------------------------------------------------------
Title: Extreme Space Weather in Extra-Solar Systems - a Flare
Alert Program
Authors: Hanslmeier, A.; Leitzinger, M.; Greimel, R.; Odert, P.;
Ratzka, T.; Brajša, R.; Guenther, E. W.; Korhonen, H.; Pribulla, T.;
Šlechta, M.; Vida, K.; Güdel, M.; Heinzel, P.; Lammer, H.; Ribas, I.
2017CEAB...41...67H Altcode:
Highly energetic stellar activity phenomena, such as outbreaks of
radiations (flares) and mass expulsions into the helio-/astro-sphere
(coronal mass ejections/CMEs), may have a severe impact on
the atmospheric evolution of planets. Stellar flare have been
studied for decades now and their typical parameters are determined
statistically. However, observations of stellar CMEs are rare, yielding
only a handful of detections so far. The detection of CMEs on stars
demands more observational effort than the detection flares, because
the circumstellar environment cannot be spatially resolved like in the
Solar System. The most convincing detections up to now were found as
Doppler-shifted Balmer line extra-emission/absorption features emerging
close to flare events, indicating the rise end ejection of prominence
material embedded in the CME core. Dedicated programs aiming for a
statistical determination of occurrence rates and the parameters of
stellar CMEs are still lacking. Therefore, we propose an innovative
and efficient observational approach to search for and characterize
CMEs on Sun-like and late-type pre-main sequence and main sequence
stars to determine stellar CME parameters and their occurrence rates
as a function of stellar spectral type and age, as well as establish
a stellar flare/CME association rate, for the first time ever.

---------------------------------------------------------
Title: Quiescent Prominences in the Era of ALMA: Simulated
Observations Using the 3D Whole-prominence Fine Structure Model
Authors: Gunár, Stanislav; Heinzel, Petr; Mackay, Duncan H.; Anzer,
Ulrich
2016ApJ...833..141G Altcode:
We use the detailed 3D whole-prominence fine structure model to
produce the first simulated high-resolution ALMA observations
of a modeled quiescent solar prominence. The maps of synthetic
brightness temperature and optical thickness shown in the present
paper are produced using a visualization method for synthesis of the
submillimeter/millimeter radio continua. We have obtained the simulated
observations of both the prominence at the limb and the filament
on the disk at wavelengths covering a broad range that encompasses
the full potential of ALMA. We demonstrate here extent to which the
small-scale and large-scale prominence and filament structures will be
visible in the ALMA observations spanning both the optically thin and
thick regimes. We analyze the relationship between the brightness and
kinetic temperature of the prominence plasma. We also illustrate the
opportunities ALMA will provide for studying the thermal structure
of the prominence plasma from the cores of the cool prominence fine
structure to the prominence-corona transition region. In addition, we
show that detailed 3D modeling of entire prominences with their numerous
fine structures will be important for the correct interpretation of
future ALMA observations of prominences.

---------------------------------------------------------
Title: NLTE modeling of a small active region filament observed with
the VTT
Authors: Schwartz, P.; Balthasar, H.; Kuckein, C.; Koza, J.; Gömöry,
P.; Rybák, J.; Heinzel, P.; Kučera, A.
2016AN....337.1045S Altcode:
An active region mini-discretionary-filament was observed with the
Vacuum Tower Telescope (VTT) in Tenerife simultaneously in the He
I infrared triplet using the Tenerife Infrared Polarimeter 1 (TIP
1), in Hα with the TESOS Fabry-Pérot interferometer, and in Ca II
8542 Å with the VTT spectrograph. The spectropolarimetric data were
inverted using the HAZEL code and Hα profiles were modelled by solving
a NLTE radiative transfer in a simple isobaric and isothermal 2D slab
irradiated both from its bottom and sides from the solar surface. It was
found that the mini-discretionary-filament is composed of horizontal
fluxtubes, along which the cool plasma of T∼10 000 K can flow with
very large, even supersonic, velocities.

---------------------------------------------------------
Title: On measurements of the Balmer continuum flux in a solar flare:
Analysis of pre-flare and flare pulsations
Authors: Zapiór, M.; Kotrč, P.; Oliver, R.; Procházka, O.;
Heinzel, P.
2016AN....337.1078Z Altcode:
A new ground based device for the measurement of the Balmer continuum
flux in solar flares was recently developed and installed at the
Ondřejov Observatory. We observed an X1 solar flare on 2014 June 11
during its pre-flare and impulsive phases using a wide band spectrometer
with a cadence of 1 s. The Ensemble Empirical Mode Decomposition (EEMD)
of the registered signal was performed. We found damped oscillations
with a period of 609 s and damping time of 1478 s. Shorter periods of
about 30-120 s were found during the pre-flare and impulsive phases,
but they might be of non-flare origin.

---------------------------------------------------------
Title: Height formation of bright points observed by IRIS in Mg II
line wings during flux emergence
Authors: Grubecka, M.; Schmieder, B.; Berlicki, A.; Heinzel, P.;
Dalmasse, K.; Mein, P.
2016A&A...593A..32G Altcode:
Context. A flux emergence in the active region AR 111850 was observed
on September 24, 2013 with the Interface Region Imaging Spectrograph
(IRIS). Many bright points are associated with the new emerging flux
and show enhancement brightening in the UV spectra. Aims:
The aim of this work is to compute the altitude formation of the
compact bright points (CBs) observed in Mg II lines in the context
of searching Ellerman bombs (EBs). Methods: IRIS provided two
large dense rasters of spectra in Mg II h and k lines, Mg II triplet,
C II and Si IV lines covering all the active region and slit jaws in
the two bandpasses (1400 Å and 2796 Å) starting at 11:44 UT and
15:39 UT, and lasting 20 min each. Synthetic profiles of Mg II and
Hα lines are computed with non-local thermodynamic equlibrium (NLTE)
radiative transfer treatment in 1D solar atmosphere model including
a hotspot region defined by three parameters: temperature, altitude,
and width. Results: Within the two IRIS rasters, 74 CBs are
detected in the far wings of the Mg II lines (at +/-1 Å and 3.5
Å). Around 10% of CBs have a signature in Si IV and CII. NLTE models
with a hotspot located in the low atmosphere were found to fit a sample
of Mg II profiles in CBs. The Hα profiles computed with these Mg II
CB models are consistent with typical EB profiles observed from ground
based telescopes e.g. THEMIS. A 2D NLTE modelling of fibrils (canopy)
demonstrates that the Mg II line centres can be significantly affected
but not the peaks and the wings of Mg II lines. Conclusions:
We conclude that the bright points observed in Mg II lines can be
formed in an extended domain of altitudes in the photosphere and/or
the chromosphere (400 to 750 km). Our results are consistent with the
theory of heating by Joule dissipation in the atmosphere produced by
magnetic field reconnection during flux emergence.

---------------------------------------------------------
Title: Synthetic Hydrogen Spectra of Oscillating Prominence Slabs
Immersed in the Solar Corona
Authors: Zapiór, M.; Oliver, R.; Ballester, J. L.; Heinzel, P.
2016ApJ...827..131Z Altcode:
We study the behavior of Hα and Hβ spectral lines and their spectral
indicators in an oscillating solar prominence slab surrounded by the
solar corona, using an MHD model combined with a 1D radiative transfer
code taken in the line of sight perpendicular to the slab. We calculate
the time variation of the Doppler shift, half-width, and maximum
intensity of the Hα and Hβ spectral lines for different modes of
oscillation. We find a non-sinusoidal time dependence of some spectral
parameters with time. Because Hα and Hβ spectral indicators have
different behavior for different modes, caused by differing optical
depths of formation and different plasma parameter variations in
time and along the slab, they may be used for prominence seismology,
especially to derive the internal velocity field in prominences.

---------------------------------------------------------
Title: Flares In Time-Domain Surveys
Authors: Kowalski, Adam; Hawley, Suzanne; Davenport, James; Berlicki,
Arkadiusz; Cauzzi, Gianna; Fletcher, Lyndsay; Heinzel, Petr; Notsu,
Yuta; Loyd, Parke; Martinez Oliveros, Juan Carlos; Pugh, Chloe;
Schmidt, Sarah Jane; Karmakar, Subhajeet; Pye, John; Flaccomio, Ettore
2016csss.confE.126K Altcode:
Proceedings for the splinter session "Flares in Time-Domain Surveys"
convened at Cool Stars 19 on June 07, 2016 in Uppsala, Sweden. Contains
a two page summary of the splinter session, links to YouTube talks,
and a PDF copy of the slides from the presenters.

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Title: Chromospheric Heating by Acoustic Waves Compared to Radiative
Cooling
Authors: Sobotka, M.; Heinzel, P.; Švanda, M.; Jurčák, J.; del Moro,
D.; Berrilli, F.
2016ApJ...826...49S Altcode: 2016arXiv160504794S
Acoustic and magnetoacoustic waves are among the possible candidate
mechanisms that heat the upper layers of the solar atmosphere. A weak
chromospheric plage near the large solar pore NOAA 11005 was observed
on 2008 October 15, in the Fe I 617.3 nm and Ca II 853.2 nm lines of
the Interferometric Bidimemsional Spectrometer attached to the Dunn
Solar Telescope. In analyzing the Ca II observations (with spatial
and temporal resolutions of 0.″4 and 52 s) the energy deposited by
acoustic waves is compared to that released by radiative losses. The
deposited acoustic flux is estimated from the power spectra of Doppler
oscillations measured in the Ca II line core. The radiative losses
are calculated using a grid of seven one-dimensional hydrostatic
semi-empirical model atmospheres. The comparison shows that the
spatial correlation of the maps of radiative losses and acoustic flux
is 72%. In a quiet chromosphere, the contribution of acoustic energy
flux to radiative losses is small, only about 15%. In active areas
with a photospheric magnetic-field strength between 300 and 1300 G
and an inclination of 20°-60°, the contribution increases from 23%
(chromospheric network) to 54% (a plage). However, these values have
to be considered as lower limits and it might be possible that the
acoustic energy flux is the main contributor to the heating of bright
chromospheric network and plages.

---------------------------------------------------------
Title: Hot prominence detected in the core of a coronal mass ejection:
Analysis of SOHO/UVCS Lα and SOHO/LASCO visible-light observations
Authors: Heinzel, P.; Susino, R.; Jejčič, S.; Bemporad, A.; Anzer, U.
2016A&A...589A.128H Altcode:
Context. The paper deals with the physics of erupting prominences in
the core of coronal mass ejections (CME). Aims: We determine the
physical parameters of an erupting prominence embedded in the core of a
CME using SOHO/UVCS hydrogen Lα and Lβ lines and SOHO/LASCO visible
light observations. In particular we analyze the CME event observed
on August 2, 2000. We develop the non-LTE (NLTE; I.e. considering
departures from the local thermodynamic equilibrium - LTE) spectral
diagnostics based on Lα and visible light observations. Methods:
Our method is based on 1D NLTE modeling of eruptive prominences and
takes into account the effect of large flow velocities, which reach
up to 300 km s-1 for the studied event (the so-called
Doppler dimming). The NLTE radiative-transfer method can be used
for both optically thin and thick prominence structures. We combine
spectroscopic UVCS observations of an erupting prominence in the core
of a CME with visible light images from LASCO-C2 in order to derive the
geometrical parameters like projected thickness and velocity, together
with the effective temperature and column density of electrons. These
are then used to constrain our NLTE radiative transfer modeling which
provides the kinetic temperature, microturbulent velocity, gas pressure,
ionization degree, the line opacities, and the prominence effective
thickness (geometrical filling factor). Results: Analysis was
made for 69 observational points (spatial pixels) inside the whole
erupting prominence. Roughly one-half of them show a non-negligible Lα
optical thickness for flow velocity 300 km s-1 and about
one-third for flow velocity 150 km s-1. All pixels with
Lατ0 ≤ 0.3 have been considered for further analysis,
which is presented in the form of statistical distributions (histograms)
of various physical quantities such as the kinetic temperature, gas
pressure, and electron density for two representative flow velocities
(150 and 300 km s-1) and non-zero microturbulence. For
two pixels co-temporal LASCO visible-light data are also available,
which further constrains the diagnostics of the electron density and
effective thickness. Detailed NLTE modeling is presented for various
sets of input parameters. Conclusions: The studied CME event
shows that the erupting prominence expands to large volumes, meaning
that it is a low-pressure structure with low electron densities and
high temperatures. This analysis provides a basis for future diagnostics
using the METIS coronagraph on board the Solar Orbiter mission.

---------------------------------------------------------
Title: The dynamics and magnetism of the X1 flare on 2014-03-29
Authors: Kleint, Lucia; Heinzel, Petr; Philip, Judge; Krucker, Sam
2016SPD....47.0613K Altcode:
The X1 flare on 2014-03-29 was observed with an unprecedented number
of instruments including chromospheric polarimetry and spectroscopy
from the UV to the IR. By combining data from these instruments, we can
answer several open questions: Where is the observed continuum emission
during flares formed and through which physical processes? How does
the magnetic field structure in the photosphere and in the chromosphere
change during a flare? We discuss the implications of our findings on
standard flare models.

---------------------------------------------------------
Title: Is it Possible to Use the Green Coronal Line Instead of X rays
to Cancel an Effect of the Coronal Emissivity Deficit in Estimation of
the Prominence Total Mass from Decrease of the EUV-corona Intensities?
Authors: Schwartz, P.; Heinzel, P.; Jejčič, S.; Rybák, J.; Kotrč,
P.; Fárník, F.; Kupryakov, Yu. A.; Deluca, E. E.; Golub, L.; Jibben,
P. R.; Anzer, U.; Tlatov, A. G. .; Guseva, S. A.
2016ASPC..504...89S Altcode:
Total masses of six quiescent prominences observed from April through
June 2011 were estimated using multi-spectral observations (in EUV,
X-rays, Hα, and Ca &lt;small&gt;II&lt;/small&gt; H). The method for
the total mass estimation is based on the fact that the intensity
of the EUV solar corona at wavelengths below 912 Å is reduced at a
prominence by the absorption in resonance continua (photoionisation)
of hydrogen and possibly by helium and subsequently an amount of
absorbed radiation is proportional to the column density of hydrogen
and helium plasma. Moreover, the deficit of the coronal emissivity in
volume occupied by the cool prominence plasma also contributes to the
intensity decrease. The observations in X-rays which are not absorbed
by the prominence plasma, allow us to separate these two mechanisms
from each other. The X-ray observations of XRT onboard the Hinode
satellite made with the Al-mesh focal filter were used because the
X-ray coronal radiation formed in plasma of temperatures of the order
of 106 K was registered and EUV spectral lines occurring in
the 193, 211 and 335 Å channels of the Atmospheric Imaging Assembly
of the Solar Dynamics Observatory satellite are also formed at such
temperatures. Unfortunately, the Al-mesh filter has a secondary peak
of the transmittance at around 171 Å which causes a contribution
from the EUV corona to the measured data of up to 11 % in the quiet
corona. Thus, absorption in prominence plasma influences XRT X-ray
data when using the Al-mesh filter. On the other hand, other X-ray XRT
filters are more sensitive to plasma of much higher temperatures (log
T of the order of 7), thus observations using these filters cannot
be used together with the AIA observations in the method for mass
estimations. This problem could be solved using observations in the
green coronal line instead of X-rays. Absorption of the green coronal
line by a prominence plasma is negligible and this line is formed at
temperatures of the order of 106 K. We compare values of
the total mass of the prominence observed on 20 October 2012 on the
SE limb estimated when using XRT X-ray observations and observations
in the green coronal line obtained at Kislovodsk Mountain Astronomical
Station of the Pulkovo observatory (Russia).

---------------------------------------------------------
Title: Magnetic Field and Plasma Diagnostics from Coordinated
Prominence Observations
Authors: Schmieder, B.; Levens, P.; Dalmasse, K.; Mein, N.; Mein,
P.; Lopez-Ariste, A.; Labrosse, N.; Heinzel, P.
2016ASPC..504..119S Altcode:
We study the magnetic field in prominences from a statistical point of
view, by using THEMIS in the MTR mode, performing spectropolarimetry
of the He I D3 line. Combining these measurements with
spectroscopic data from IRIS, Hinode/EIS as well as ground-based
telescopes, such as the Meudon Solar Tower, we infer the temperature,
density, and flow velocities of the plasma. There are a number of
open questions that we aim to answer: - What is the general direction
of the magnetic field in prominences? Is the model using a single
orientation of magnetic field always valid for atypical prominences? %-
Does this depend on the location of the filament on the disk (visible
in Hα, in He II 304 Å) over an inversion line between weak or strong
network ? - Are prominences in a weak environment field dominated by
gas pressure? - Measuring the Doppler shifts in Mg II lines (with IRIS)
and in Hα can tell us if there are substantial velocities to maintain
vertical rotating structures, as has been suggested for tornado-like
prominences. We present here some results obtained with different
ground-based and space-based instruments in this framework.

---------------------------------------------------------
Title: Measurements of Continuum Flux in Solar Flares
Authors: Kotrč, P.; Heinzel, P.; Procházka, O.
2016ASPC..504...49K Altcode:
A broad-band diagnostics of chromospheric flare plasma needs to analyze
spectra covering many spectral lines and various continuum features. The
flare spectra are well detected on the background of the solar disk, but
the detection of flare line emission from the Sun-as-a-star in optical
is much more difficult due to a strong background radiation. When the
flare/background radiation contrast is strong enough to be detected,
we need a device for measuring the flux from a selected part of the
flaring region. Here we present technical demands for such an instrument
and its brief description. This device denoted as Image Selector is a
post-focus instrument installed at the horizontal solar telescope HSFA2
of the Ondřejov observatory, described by Kotrč (2009). Its core
consists of a system of diaphragms, imaging Hα telescope and a fast
spectrometer with dispersion of 3 px per Å but with cadency reaching
up to 50 frames per second. The first solar flares observed recently
by this novel technique provide quite interesting results. Our analysis
of the data proves that the described device is sufficiently sensitive
to detect variations in the Balmer continuum during solar flares.

---------------------------------------------------------
Title: Solar Science with the Atacama Large Millimeter/Submillimeter
Array—A New View of Our Sun
Authors: Wedemeyer, S.; Bastian, T.; Brajša, R.; Hudson, H.;
Fleishman, G.; Loukitcheva, M.; Fleck, B.; Kontar, E. P.; De Pontieu,
B.; Yagoubov, P.; Tiwari, S. K.; Soler, R.; Black, J. H.; Antolin,
P.; Scullion, E.; Gunár, S.; Labrosse, N.; Ludwig, H. -G.; Benz,
A. O.; White, S. M.; Hauschildt, P.; Doyle, J. G.; Nakariakov, V. M.;
Ayres, T.; Heinzel, P.; Karlicky, M.; Van Doorsselaere, T.; Gary,
D.; Alissandrakis, C. E.; Nindos, A.; Solanki, S. K.; Rouppe van
der Voort, L.; Shimojo, M.; Kato, Y.; Zaqarashvili, T.; Perez, E.;
Selhorst, C. L.; Barta, M.
2016SSRv..200....1W Altcode: 2015SSRv..tmp..118W; 2015arXiv150406887W
The Atacama Large Millimeter/submillimeter Array (ALMA) is a new
powerful tool for observing the Sun at high spatial, temporal, and
spectral resolution. These capabilities can address a broad range
of fundamental scientific questions in solar physics. The radiation
observed by ALMA originates mostly from the chromosphere—a complex
and dynamic region between the photosphere and corona, which plays a
crucial role in the transport of energy and matter and, ultimately,
the heating of the outer layers of the solar atmosphere. Based on
first solar test observations, strategies for regular solar campaigns
are currently being developed. State-of-the-art numerical simulations
of the solar atmosphere and modeling of instrumental effects can help
constrain and optimize future observing modes for ALMA. Here we present
a short technical description of ALMA and an overview of past efforts
and future possibilities for solar observations at submillimeter and
millimeter wavelengths. In addition, selected numerical simulations
and observations at other wavelengths demonstrate ALMA's scientific
potential for studying the Sun for a large range of science cases.

---------------------------------------------------------
Title: Non-LTE Inversion of Spectropolarimetric and Spectroscopic
Observations of a Small Active-region Filament Observed at the VTT
Authors: Schwartz, P.; Balthasar, H.; Kuckein, C.; Koza, J.; Gömöry,
P.; Rybák, J.; Kučera, A.; Heinzel, P.
2016ASPC..504..205S Altcode:
An active region mini-filament was observed by VTT simultaneously
in the He&lt;small&gt;I&lt;/small&gt; 10 830 Å triplet by the TIP 1
spectropolarimeter, in Hα by the TESOS Fabry-Pérot interferometer, and
in Ca &lt;small&gt;II&lt;/small&gt; 8542 Å by the VTT spectrograph. The
spectropolarimetric data were inverted using the HAZEL code and Hα
profiles were modelled solving a NLTE radiative transfer in a simple
isobaric and isothermal 2D slab irradiated both from bottom and
sides. It was found that the mini-filament is composed of horizontal
fluxtubes, along which the cool plasma of T∼10 000 K can flow by
very large - even supersonic - velocities.

---------------------------------------------------------
Title: New Observations of Balmer Continuum Flux in Solar
Flares. Instrument Description and First Results
Authors: Kotrč, P.; Procházka, O.; Heinzel, P.
2016SoPh..291..779K Altcode: 2016SoPh..tmp...17K; 2016arXiv160104610K
Increase in the Balmer continuum radiation during solar flares was
predicted by various authors, but has never been firmly confirmed
observationally using ground-based slit spectrographs. Here we
describe a new post-focal instrument, the image selector, with which
the Balmer continuum flux can be measured from the whole flare area,
in analogy to successful detections of flaring dMe stars. The system
was developed and put into operation at the horizontal solar telescope
HSFA2 of the Ondřejov Observatory. We measure the total flux by a
fast spectrometer from a limited but well-defined region on the solar
disk. Using a system of diaphragms, the disturbing contribution of a
bright solar disk can be eliminated as much as possible. Light curves
of the measured flux in the spectral range 350 - 440 nm are processed,
together with the H α images of the flaring area delimited by the
appropriate diaphragm. The spectral flux data are flat-fielded,
calibrated, and processed to be compared with model predictions. Our
analysis of the data proves that the described device is sufficiently
sensitive to detect variations in the Balmer continuum during solar
flares. Assuming that the Balmer-continuum kernels have at least a
similar size as those visible in H α , we find the flux increase in
the Balmer continuum to reach 230 - 550 % of the quiet continuum during
the observed X-class flare. We also found temporal changes in the Balmer
continuum flux starting well before the onset of the flare in H α.

---------------------------------------------------------
Title: Observations and modeling of the ultraviolet emission of
solar flares
Authors: Mikuła, Katarzyna; Berlicki, Arkadiusz; Heinzel, Petr
2016IAUS..320...57M Altcode:
In this paper we present the method of using far UV spectra of
the flare observed by Interface Region Imaging Spectrograph (IRIS)
for determination of the contribution of the continuum emission to
the total UV radiation observed e.g. by SDO in 1600 Å channel. In
our method the Si IV (1402.77 Å) line observed by IRIS is used as a
proxy of C IV line emission contained in SDO/AIA UV images. Determined
intensity of the flare continuum emission can be used to study the
physics of the flare heated chromosphere and for better understanding
of the emission mechanisms.

---------------------------------------------------------
Title: White-light continuum emission from a solar flare and plage
Authors: Berlicki, Arkadiusz; Awasthi, Arun Kumar; Heinzel, Petr;
Sobotka, Michal
2016IAUS..320..268B Altcode: 2016arXiv160404186B
Observations of flare emissions in the optical continuum are very
rare. Therefore, the analysis of such observations is useful and
may contribute to our understanding of the flaring chromosphere and
photosphere. We study the white light continuum emission observed
during the X6.9 flare. This emission comes not only from the flare
ribbons but also form the nearby plage area. The main aim of this work
is to disentangle the flare and plage (facula) emission. We analyzed
the spatial, spectral and temporal evolution of the flare and plage
properties by analyzing multi-wavelength observations. We study
the morphological correlation of the white-light continuum emission
observed with different instruments. We found that some active region
areas which produce the continuum emission correspond rather to plages
than to the flare kernels. We showed that in some cases the continuum
emission from the WL flare kernels is very similar to the continuum
emission of faculae.

---------------------------------------------------------
Title: Numerical RHD simulations of flaring chromosphere with Flarix
Authors: Heinzel, Petr; Kašparová, Jana; Varady, Michal; Karlický,
Marian; Moravec, Zdeněk
2016IAUS..320..233H Altcode: 2016arXiv160200016H
Flarix is a radiation-hydrodynamical (RHD) code for modeling of the
response of the chromosphere to a beam bombardment during solar
flares. It solves the set of hydrodynamic conservation equations
coupled with NLTE equations of radiative transfer. The simulations are
driven by high energy electron beams. We present results of the Flarix
simulations of a flaring loop relevant to the problem of continuum
radiation during flares. In particular we focus on properties of the
hydrogen Balmer continuum which was recently detected by IRIS.

---------------------------------------------------------
Title: Continuum Enhancements in the Ultraviolet, the Visible and
the Infrared during the X1 Flare on 2014 March 29
Authors: Kleint, Lucia; Heinzel, Petr; Judge, Phil; Krucker, Säm
2016ApJ...816...88K Altcode: 2015arXiv151104161K
Enhanced continuum brightness is observed in many flares (“white
light flares”), yet it is still unclear which processes contribute to
the emission. To understand the transport of energy needed to account
for this emission, we must first identify both the emission processes
and the emission source regions. Possibilities include heating in the
chromosphere causing optically thin or thick emission from free-bound
transitions of Hydrogen, and heating of the photosphere causing enhanced
H- continuum brightness. To investigate these possibilities,
we combine observations from Interface Region Imaging Spectrograph
(IRIS), SDO/Helioseismic and Magnetic Imager, and the ground-based
Facility Infrared Spectrometer instrument, covering wavelengths in
the far-UV, near-UV (NUV), visible, and infrared during the X1 flare
SOL20140329T17:48. Fits of blackbody spectra to infrared and visible
wavelengths are reasonable, yielding radiation temperatures ∼6000-6300
K. The NUV emission, formed in the upper photosphere under undisturbed
conditions, exceeds these simple fits during the flare, requiring
extra emission from the Balmer continuum in the chromosphere. Thus,
the continuum originates from enhanced radiation from photosphere
(visible-IR) and chromosphere (NUV). From the standard thick-target
flare model, we calculate the energy of the nonthermal electrons
observed by Reuven Ramaty High Energy Solar Spectroscope Imager (RHESSI)
and compare it to the energy radiated by the continuum emission. We
find that the energy contained in most electrons &gt;40 keV, or
alternatively, of ∼10%-20% of electrons &gt;20 keV is sufficient to
explain the extra continuum emission of ∼(4-8) × 1010
erg s-1 cm-2. Also, from the timing of the RHESSI
HXR and the IRIS observations, we conclude that the NUV continuum is
emitted nearly instantaneously when HXR emission is observed with a
time difference of no more than 15 s.

---------------------------------------------------------
Title: Lines of MgI Detected in Solar Prominences
Authors: Heinzel, P.; Kupryakov, Yu.; Schwartz, P.
2016CEAB...40...87H Altcode:
Using the flare spectrograph at Ondřejov observatory, we have observed
several prominences with the aim to detect the MgI lines. These lines
play an important diagnostic role, complementary to MgII resonance
lines now routinely observed by the IRIS satellite. Our preliminary
analysis shows that a rather weak MgI emission, e.g. in the 5172.7
Å line, is detectable and this correlates well with the presence of
extended bright regions on the solar disk visible in SDO/AIA 1600 Å
band. Physical reasons for such a correlation are discussed.

---------------------------------------------------------
Title: Observed IRIS Profiles of the h and k Doublet of Mg II and
Comparison with Profiles from Quiescent Prominence NLTE Models
Authors: Vial, Jean-Claude; Pelouze, Gabriel; Heinzel, Petr; Kleint,
Lucia; Anzer, Ulrich
2016SoPh..291...67V Altcode: 2015SoPh..tmp..173V
With the launch of the Interface Region Imaging Spectrograph (IRIS)
mission, it is now possible to obtain high-resolution solar prominence
spectra and to begin to distinguish the contributions of the many
(apparent or not) threads that structure prominences. We aim at
comparing unique observations obtained in the Mg II h and k lines of a
polar crown prominence with the radiative outputs from one-dimensional
models built with non-local-thermodynamic equilibrium codes (Heinzel et
al.Astron. Astrophys.564, A132, 2014). We characterize the profiles
obtained through thorough calibration procedures, with attention
paid to the absolute values, full-width at half-maximum, and the
ratio of k to h intensities. We also show that at the top of some
structures, line-of-sight velocities of about 9 kms−1 can
be detected. We find a range of static, low-pressure, low-thickness,
low-temperature models that could fit k or h observed values, but that
cannot satisfy the low observed k/h ratio. We investigate whether these
low values might be explained by the inclusion of horizontal flows in
small-scale threads. These flows are also necessary in another class
of models, where the pressure is kept low but thickness and temperature
are increased up to the observed thickness and up to 15 000 K.

---------------------------------------------------------
Title: Solar and Stellar Flares and their Effects on Planets
Authors: Kosovichev, A. G.; Hawley, S. L.; Heinzel, P.
2016IAUS..320.....K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: SSALMON - The Solar Simulations for the Atacama Large
Millimeter Observatory Network
Authors: Wedemeyer, S.; Bastian, T.; Brajša, R.; Barta, M.; Hudson,
H.; Fleishman, G.; Loukitcheva, M.; Fleck, B.; Kontar, E.; De Pontieu,
B.; Tiwari, S.; Kato, Y.; Soler, R.; Yagoubov, P.; Black, J. H.;
Antolin, P.; Gunár, S.; Labrosse, N.; Benz, A. O.; Nindos, A.;
Steffen, M.; Scullion, E.; Doyle, J. G.; Zaqarashvili, T.; Hanslmeier,
A.; Nakariakov, V. M.; Heinzel, P.; Ayres, T.; Karlicky, M.
2015AdSpR..56.2679W Altcode: 2015arXiv150205601W
The Solar Simulations for the Atacama Large Millimeter Observatory
Network (SSALMON) was initiated in 2014 in connection with two ALMA
development studies. The Atacama Large Millimeter/submillimeter Array
(ALMA) is a powerful new tool, which can also observe the Sun at
high spatial, temporal, and spectral resolution. The international
SSALMONetwork aims at co-ordinating the further development of solar
observing modes for ALMA and at promoting scientific opportunities
for solar physics with particular focus on numerical simulations,
which can provide important constraints for the observing modes and
can aid the interpretation of future observations. The radiation
detected by ALMA originates mostly in the solar chromosphere - a
complex and dynamic layer between the photosphere and corona, which
plays an important role in the transport of energy and matter and the
heating of the outer layers of the solar atmosphere. Potential targets
include active regions, prominences, quiet Sun regions, flares. Here,
we give a brief overview over the network and potential science cases
for future solar observations with ALMA.

---------------------------------------------------------
Title: Preface
Authors: Fletcher, L.; Heinzel, P.; van Driel-Gesztelyi, L.; Mandrini,
C. H.; Fárník, F.
2015SoPh..290.3379F Altcode: 2015SoPh..tmp..168F
No abstract at ADS

---------------------------------------------------------
Title: Mg II Lines Observed During the X-class Flare on 29 March
2014 by the Interface Region Imaging Spectrograph
Authors: Liu, W.; Heinzel, P.; Kleint, L.; Kašparová, J.
2015SoPh..290.3525L Altcode: 2015SoPh..tmp..166L; 2015arXiv151100480L
Mg II lines represent one of the strongest emissions from the
chromospheric plasma during solar flares. In this article, we
studied the Mg II lines observed during the X1 flare on 29 March 2014
(SOL2014-03-29T17:48) by the Interface Region Imaging Spectrograph
(IRIS). IRIS detected large intensity enhancements of the Mg II h and
k lines, subordinate triplet lines, and several other metallic lines
at the flare footpoints during this flare. We have used the advantage
of the slit-scanning mode (rastering) of IRIS and performed, for the
first time, a detailed analysis of spatial and temporal variations
of the spectra. Moreover, we were also able to identify positions
of strongest hard X-ray (HXR) emissions using the Reuven Ramaty
High Energy Solar Spectroscopic Imager (RHESSI) observations and to
correlate them with the spatial and temporal evolution of IRIS Mg
II spectra. The light curves of the Mg II lines increase and peak
contemporarily with the HXR emissions but decay more gradually. There
are large red asymmetries in the Mg IIh and k lines after the flare
peak. We see two spatially well-separated groups of Mg II line profiles,
non-reversed and reversed. In some cases, the Mg II footpoints with
reversed profiles are correlated with HXR sources. We show the spatial
and temporal behavior of several other line parameters (line metrics)
and briefly discuss them. Finally, we have synthesized the Mg IIk line
using our non-LTE code with the Multilevel Accelerated Lambda Iteration
(MALI) technique. Two kinds of models are considered, the flare model
F2 of Machado et al. (Astrophys. J.242, 336, 1980) and the models of
Ricchiazzi and Canfield (Astrophys. J.272, 739, 1983, RC models). Model
F2 reproduces the peak intensity of the non-reversed Mg IIk profile
at flare maximum, but does not account for high wing intensities. On
the other hand, the RC models show the sensitivity of Mg II line
intensities to various electron-beam parameters. Our simulations also
show that the microturbulence produces a broader line core, while the
intense line wings are caused by an enhanced line source function.

---------------------------------------------------------
Title: White-light continuum emission from solar flare and plages:
observations and modeling
Authors: Berlicki, Arkadiusz; Awasthi, Arun Kumar; Heinzel, Petr
2015IAUGA..2256469B Altcode:
Observations of flares in optical continuum emission are very
rare. Therefore, the analysis of such observations is very useful and
may contribute to our understanding of the flaring chromosphere. We
study the white-light continuum emission observed during the X6.9
flare observed on August 09, 2011. This emission comes not only from
the flare ribbons but also form the nearby plage area observed within
the active region. The main aim of this work is to disentangle the
flare and plage emission and to understand the physical mechanisms
responsible for the production of white-light continuum.There are two
main mechanisms which can be responsible for the optical continuum
emission of the solar atmosphere: enhanced photospheric H- continuum
due to the temperature increase below the temperature minimum region,
or hydrogen recombination continua (Balmer, Paschen) formed in solar
chromosphere. In our work we analyse the physical conditions in solar
active atmosphere in order to obtain the contribution from these two
mechanisms to the whole continuum emission of the flare and plage.We
analyzed the spatial, spectral and temporal evolution study of the
flare and plage parameters by analyzing multi-wavelength observations
obtained from ground and space based solar observatories. We study
the morphological correlation of the white-light continuum emission
observed with different instruments. Moreover, we also explore the
non-thermal electron beam properties by forward fitting the observed
X-ray spectra.The unique opportunity of an intense X6.9 flare occurrence
close to the limb enabled us to explore the origin of white-light
continuum with better visibility. The analysis of multi-wavelength
data revealed the origin of this emission from the foot-points of the
loops. Spatial association of HXR foot-points synthesized from RHESSI
observations confirmed this finding. In addition, we found a good
temporal correlation of hard (&gt;30 keV) X-ray with the white-light
emission. However, some active region areas which produce the continuum
emission correspond rather to plages than to the flare kernels.

---------------------------------------------------------
Title: Multi-wavelength diagnostics and modelling of the emission
during a B6.4 flare of August 20, 2005
Authors: Awasthi, Arun Kumar; Berlicki, Arkadiusz; Rudawy, Powel;
Heinzel, Petr
2015IAUGA..2256580A Altcode:
We study the temporal, spatial and spectral evolution of
multi-wavelength emission observed during a B6.4 flare occurred
on August 20, 2005 with the motivation to outline the thermal and
non-thermal processes during the precursor and gradual phase of the
flare. Precursor phase is designated as the gradual enhancement of
soft X-ray emission prior to onset of the impulsive phase. Observations
from several space and ground based observatories viz. RHESSI, TRACE,
GONG, SoHO/EIT and NoRP are included in this study. Temporal evolution
of X-ray emission does not show the presence of hard X-rays (&gt;12
keV) emission during the precursor phase of the flare. We synthesized
X-ray images in 6-12 keV from RHESSI observations, which show several
discrete sources during the precursor phase. Following to this, one
of these sources pronounced during the main phase of the flare. We
carry out in-depth analysis of chromospheric response in various
phases of the flare employing high temporal cadence images of the Sun
in Hα line centre as well as wings obtained from the Multi-channel
Subtractive Double Pass Spectrograph (MSDP) at the Bialkow Observatory
of the University of Wroclaw, Poland. Our analysis of Hα images
during the main phase of the flare suggests localized emission in
the form of kernels. On the contrary, we note extended and diffused
source morphology of emitting region during the precursor phase of
the flare. We also study various kinematic properties of different
structures visible in the Hα images in the line centre as well as
wings. In addition, the correlation of the relative timing of X-ray
and Hα emission profile is performed to estimate the delay in the
chromospheric response during different phases of flare. Further, we
employ thermal plasma parameters estimated during the precursor and
gradual phase to model the associated Hα emission. For the modeling we
employ NLTE numerical codes modified for flare conditions. The modeled
and observed flare emission parameters are then compared. Finally,
we propose a unified schematic scenario for the trigger and energy
release during this low-intensity class flare.

---------------------------------------------------------
Title: Observations and modeling of the ultraviolet emission of
solar flares
Authors: Berlicki, Arkadiusz; Heinzel, Petr; Mikula, Katarzyna
2015IAUGA..2257337B Altcode:
It is well known that during solar flares the heated chromospheric
plasma emits the ultraviolet (UV) radiation in spectral lines
and continua. UV space telescopes (e.g. TRACE, Solar Dynamic
Observatory/Atmospheric Imaging Assembly - SDO/AIA) provide images
of solar flares where the complicated fine structure of the flaring
atmosphere is well visible. However, these broadband images contain
the mixture of line and continuum UV emission and it is not possible
to disentangle between these two contributions. E.g. solar flare
brightening observed in SDO/AIA 160 nm channel can be visible both due
to the strong line emission in C IV 154.8 nm or due to the continuum
increase. Spectral lines and continua are formed in plasma of different
temperature and location. Therefore, in order to obtain the parameters
of plasma we should know quantitatively the contribution from lines and
continua.Such analysis would be possible using the UV spectrograph,
where we can see the intensity of lines and continua separately. For
example Interface Region Imaging Spectrograph (IRIS) provides such
spectra of flares, where the enhanced lines and continuum is visible
both in NUV (near UV) and FUV (far UV) channels.In our work we used
IRIS flare observations in FUV channel to determine the intensity of
spectral lines, including Si IV 139.4 nm line. Then, using CHIANTI
procedures and the observed intensities of some FUV lines we computed
the synthetic UV spectrum for given flare model. IRIS spectrum does not
include C IV line, which contaminates the SDO/AIA images, but this line
can be calculated in the theoretical CHIANTI spectrum. In this way, we
can subtract the C IV (and other lines) emission from SDO/AIA images and
obtain the pure UV continuum intensity. Finally, the obtained continuum
emission can used to study the physics of heated chromosphere of flares.

---------------------------------------------------------
Title: High-resolution fine-structure synthetic imaging of an entire
prominence using 3D whole-prominence fine structure modelling
Authors: Gunar, Stanislav; Mackay, Duncan; Heinzel, Petr; Anzer, Ulrich
2015IAUGA..2251323G Altcode:
The newly developed 3D whole-prominence fine structure (WPFS)
model (Gunár &amp; Mackay 2015) allows us for the first time to
simulate entire prominences/filaments including their numerous fine
structures. This model combines a 3D magnetic field configuration of an
entire prominence obtained from non-linear force-free field simulations,
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 within the 3D magnetic model. The
prominence plasma has realistic density and temperature distributions
including the prominence-corona transition region.To produce the
high-resolution synthetic H-alpha images of the WPFS model we use
a novel fast approximate radiative transfer visualization technique
(Heinzel et al. 2015). This allows us for the first time to produce
images of the prominences in emission on the solar limb and filaments in
absorption against the solar disk using a single model. The prominence
plasma and magnetic field are described in the WPFS model on scales
that allow us to produce synthetic images with resolution matching that
of the state-of-the-art observations, or indeed that of the upcoming
solar observatories, such as DKIST or Solar-C. Moreover, to complement
the prominence/filament synthetic images we have consistent information
about the magnetic field and plasma parameters everywhere in the modeled
prominences. This allows us to investigate the apparent puzzling nature
of the observed prominence and filament fine structures. We can also
study the connections between the local configuration of the magnetic
field and the observable structure of the finest prominence/filament
features. In addition, we are able to investigate the prominence
evolution. We can consistently study the influence of the varying
photospheric flux distribution on the prominence magnetic field
configuration and its effect on the observable prominence plasma.

---------------------------------------------------------
Title: On the Visibility of Prominence Fine Structures at Radio
Millimeter Wavelengths
Authors: Heinzel, P.; Berlicki, A.; Bárta, M.; Karlický, M.;
Rudawy, P.
2015SoPh..290.1981H Altcode: 2015SoPh..tmp...87H
Prominence temperatures have so far mainly been determined by analyzing
spectral line shapes, which is difficult when the spectral lines are
optically thick. The radio spectra in the millimeter range offer
a unique possibility to measure the kinetic temperature. However,
studies in the past used data with insufficient spatial resolution
to resolve the prominence fine structures. The aim of this article
is to predict the visibility of prominence fine structures in the
submillimeter/millimeter (SMM) domain, to estimate their brightness
temperatures at various wavelengths, and to demonstrate the feasibility
and usefulness of future high-resolution radio observations of
solar prominences with ALMA (Atacama Large Millimeter-submillimeter
Array). Our novel approach is the conversion of Hα coronagraphic images
into microwave spectral images. We show that the spatial variations
of the prominence brightness both in the Hα line and in the SMM
domain predominantly depend on the line-of-sight emission measure of
the cool plasma, which we derive from the integrated intensities of
the observed Hα line. This relation also offers a new possibility to
determine the SMM optical thickness from simultaneous Hα observations
with high resolution. We also describe how we determine the prominence
kinetic temperature from SMM spectral images. Finally, we apply the
ALMA image-processing software Common Astronomy Software Applications
(CASA) to our simulated images to assess what ALMA would detect at a
resolution level that is similar to the coronagraphic Hα images used
in this study. Our results can thus help in preparations of first
ALMA prominence observations in the frame of science and technical
verification tests.

---------------------------------------------------------
Title: Fast approximate radiative transfer method for visualizing
the fine structure of prominences in the hydrogen Hα line
Authors: Heinzel, P.; Gunár, S.; Anzer, U.
2015A&A...579A..16H Altcode:
 Aims: We present a novel approximate radiative transfer method
developed to visualize 3D whole-prominence models with multiple fine
structures using the hydrogen Hα spectral line. Methods: This
method employs a fast line-of-sight synthesis of the Hα line profiles
through the whole 3D prominence volume and realistically reflects the
basic properties of the Hα line formation in the cool and low-density
prominence medium. The method can be applied both to prominences seen
above the limb and filaments seen against the disk. Results:
We provide recipes for the use of this method for visualizing the
prominence or filament models that have multiple fine structures. We
also perform tests of the method that demonstrate its accuracy
under prominence conditions. Conclusions: We demonstrate that
this fast approximate radiative transfer method provides realistic
synthetic Hα intensities useful for a reliable visualization of
prominences and filaments. Such synthetic high-resolution images of
modeled prominences/filaments can be used for a direct comparison with
high-resolution observations.

---------------------------------------------------------
Title: Prominence Visibility in Hinode/XRT Images
Authors: Schwartz, P.; Jejčič, S.; Heinzel, P.; Anzer, U.; Jibben,
P. R.
2015ApJ...807...97S Altcode: 2015arXiv150606078S
In this paper we study the soft X-ray (SXR) signatures of one
particular prominence. The X-ray observations used here were made by the
Hinode/X-Ray Telescope instrument using two different filters. Both of
them have a pronounced peak of the response function around 10 Å. One
of them has a secondary smaller peak around 170 Å, which leads to a
contamination of SXR images. The observed darkening in both of these
filters has a very large vertical extension. The position and shape of
the darkening correspond nicely with the prominence structure seen in
SDO/AIA images. First, we have investigated the possibility that the
darkening is caused by X-ray absorption. However, detailed calculations
of the optical thickness in this spectral range show clearly that
this effect is completely negligible. Therefore, the alternative is
the presence of an extended region with a large emissivity deficit,
which can be caused by the presence of cool prominence plasmas within
an otherwise hot corona. To reproduce the observed darkening, one needs
a very large extension along the line of sight of the region amounting
to around 105 km. We interpret this region as the prominence
spine, which is also consistent with SDO/AIA observations in EUV.

---------------------------------------------------------
Title: Understanding the Mg II and Hα Spectra in a Highly Dynamical
Solar Prominence
Authors: Heinzel, P.; Schmieder, B.; Mein, N.; Gunár, S.
2015ApJ...800L..13H Altcode:
Mg ii h and k and Hα spectra in a dynamical prominence have been
obtained along the slit of the Interface Region Imaging Spectrograph
(IRIS) and with the Meudon Multi-channel Subtractive Double Pass
spectrograph on 2013 September 24, respectively. Single Mg ii line
profiles are not much reversed, while at some positions along
the IRIS slit the profiles show several discrete peaks that are
Doppler-shifted. The intensity of these peaks is generally decreasing
with their increasing Doppler shift. We interpret this unusual behavior
as being due to the Doppler dimming effect. We discuss the possibility
to interpret the unreversed single profiles by using a two-dimensional
(2D) model of the entire prominence body with specific radiative
boundary conditions. We have performed new 2D isothermal-isobaric
modeling of both Hα and Mg ii lines and show the ability of such models
to account for the line profile variations as observed. However, the Mg
ii line-center intensities require the model with a temperature increase
toward the prominence boundary. We show that even simple one-dimensional
(1D) models with a prominence-to-corona transition region (PCTR) fit the
observed Mg ii and Hα lines quite well, while the isothermal-isobaric
models (1D or 2D) are inconsistent with simultaneous observations in
the Mg ii h and k and Hα lines, meaning that the Hα line provides a
strong additional constraint on the modeling. IRIS far-UV detection of
the C ii lines in this prominence seems to provide a direct constraint
on the PCTR part of the model.

---------------------------------------------------------
Title: Total mass of six quiescent prominences estimated from their
multi-spectral observations
Authors: Schwartz, P.; Heinzel, P.; Kotrč, P.; Fárník, F.;
Kupryakov, Yu. A.; DeLuca, E. E.; Golub, L.
2015A&A...574A..62S Altcode:
Context. Total masses of six solar prominences were estimated using
prominence multi-spectral observations (in EUV, X-rays, Hα, and Ca
ii H). The observations were made during the observing campaign from
April through June 2011. Aims: The aim of the work was to apply
a complex method for the prominence mass estimations that can be used
later for other prominences observed during the observing campaign. Methods: Our method is based on the fact that intensity of the EUV
solar corona at wavelengths below 912 Å is reduced by the absorption
in resonance continua of hydrogen and helium (photoionisation) and at
the same time also by a deficit of the coronal emissivity in volume
occupied by the cool prominence plasma. Both mechanisms contribute to
intensity decrease simultaneously. The observations in X-rays allow us
to separate these mechanisms from each other. Coronal emission behind a
prominence is not estimated by any temporal or spatial interpolation,
but by using a new method based on comparing the ratio of the optical
thickness at 193 Å and 211 Å determined from the observations
with the theoretical ratio. Results: Values of the total mass
estimated for six prominences are between 2.9 × 1011 and
1.7 × 1012 kg. The column density of hydrogen is of the
order of 1018-1019 cm-2. Our results
agree with results of other authors. Conclusions: The method
is now ready to be used for all 30 prominences observed during the
campaign. Then in the near future it will be possible to obtain a
statistics of the total mass of quiescent solar prominences.

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Title: Radiative Transfer in Solar Prominences
Authors: Heinzel, Petr
2015ASSL..415..103H Altcode:
Critical information about prominence physical conditions can be
obtained only by analyzing prominence spectra or high-resolution
monochromatic images. Solar prominences are low-density structures
and, therefore, the non-equilibrium (NLTE) spectroscopy tools have
to be used. We describe the basics of the NLTE radiative-transfer
theory applied to typical prominence conditions and demonstrate why
the NLTE approach is necessary. Starting from the simplest 1D slab
models, we gradually move to more complex problems which include 2D
transfer, importance of partial redistribution in the formation of
resonance lines and details of multilevel problems including the most
up-to-date numerical methods for constructing NLTE models. We also
mention some recent achievements in prominence modeling (e.g. magnetic
dips, radiative equilibrium models, oscillations), although detailed
description of such results is the subject of other chapters.

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Title: On the Origin of Linear Polarization in Solar Flares
Authors: Štěpán, J.; Heinzel, P.
2014ASPC..489..133S Altcode:
A significant degree of linear polarization (up to few percent) of
some spectral lines is occasionally reported from the observations of
solar flares. This polarization is often found at the edges of the
flare ribbons and it is usually radial or tangential. The mechanism
usually considered as being responsible for this effect is the
impact polarization by electron and/or proton beams bombarding the
chromosphere. We point out that resonant scattering polarization in a
multi-dimensional geometry of the chromosphere has to be considered as
an important ingredient of the problem. The significant horizontal
inhomogeneities at the boundaries of the flare ribbons causes a
considerable change in the radiation field anisotropy which may lead
to emission of strongly linearly polarized spectral lines. For more
details see Štěpán, &amp; Heinzel (2013)

---------------------------------------------------------
Title: Hydrogen Balmer Continuum in Solar Flares Detected by the
Interface Region Imaging Spectrograph (IRIS)
Authors: Heinzel, P.; Kleint, L.
2014ApJ...794L..23H Altcode: 2014arXiv1409.5680H
We present a novel observation of the white light flare (WLF) continuum,
which was significantly enhanced during the X1 flare on 2014 March
29 (SOL2014-03-29T17:48). Data from the Interface Region Imaging
Spectrograph (IRIS) in its near-UV channel show that at the peak of
the continuum enhancement, the contrast at the quasi-continuum window
above 2813 Å reached 100%-200% and can be even larger closer to Mg
II lines. This is fully consistent with the hydrogen recombination
Balmer-continuum emission, which follows an impulsive thermal and
non-thermal ionization caused by the precipitation of electron beams
through the chromosphere. However, a less probable photospheric
continuum enhancement cannot be excluded. The light curves of the
Balmer continuum have an impulsive character with a gradual fading,
similar to those detected recently in the optical region on the
Solar Optical Telescope on board Hinode. This observation represents
a first Balmer-continuum detection from space far beyond the Balmer
limit (3646 Å), eliminating seeing effects known to complicate the
WLF detection. Moreover, we use a spectral window so far unexplored
for flare studies, which provides the potential to study the Balmer
continuum, as well as many metallic lines appearing in emission
during flares. Combined with future ground-based observations of the
continuum near the Balmer limit, we will be able to disentangle various
scenarios of the WLF origin. IRIS observations also provide a critical
quantitative measure of the energy radiated in the Balmer continuum,
which constrains various models of the energy transport and deposit
during flares.

---------------------------------------------------------
Title: Multi-Wavelength Eclipse Observations of a Quiescent Prominence
Authors: Jejčič, S.; Heinzel, P.; Zapiór, M.; Druckmüller, M.;
Gunár, S.; Kotrč, P.
2014SoPh..289.2487J Altcode: 2014SoPh..tmp...30J
We construct the maps of temperatures, geometrical thicknesses,
electron densities and gas pressures in a quiescent prominence. For
this we use the RGB signal of the prominence visible-light emission
detected during the total solar eclipse of 1 August 2008 in Mongolia
and quasi-simultaneous Hα spectra taken at Ondřejov Observatory. The
method of disentangling the electron density and geometrical (effective)
thickness was described by Jejčič and Heinzel (Solar Phys.254,
89 - 100, 2009) and is used here for the first time to analyse
the spatial variations of prominence parameters. For the studied
prominence we obtained the following range of parameters: temperature
6000 - 15 000 K, effective thickness 200 - 15000 km, electron density
5×109 - 1011 cm−3 and gas pressure
0.02 - 0.2 dyn cm−2 (assuming a fixed ionisation degree
np/nH=0.5). The electron density increases
towards the bottom of the prominence, which we explain by an enhanced
photoionisation due to the incident solar radiation. To confirm this,
we construct a two-dimensional radiative-transfer model with realistic
prominence illumination.

---------------------------------------------------------
Title: Observations and NLTE modeling of Ellerman bombs
Authors: Berlicki, A.; Heinzel, P.
2014A&A...567A.110B Altcode: 2014arXiv1406.5702B
Context. Ellerman bombs (EBs) are short-lived, compact, and spatially
well localized emission structures that are observed well in the wings
of the hydrogen Hα line. EBs are also observed in the chromospheric
CaII lines and in UV continua as bright points located within active
regions. Hα line profiles of EBs show a deep absorption at the line
center and enhanced emission in the line wings with maxima around
±1 Å from the line center. Similar shapes of the line profiles are
observed for the CaII IR line at 8542 Å. In CaII H and K lines the
emission peaks are much stronger, and EBs emission is also enhanced
in the line center. Aims: It is generally accepted that
EBs may be considered as compact microflares located in lower solar
atmosphere that contribute to the heating of these low-lying regions,
close to the temperature minimum of the atmosphere. However, it is
still not clear where exactly the emission of EBs is formed in the
solar atmosphere. High-resolution spectrophotometric observations
of EBs were used for determining of their physical parameters and
construction of semi-empirical models. Obtained models allow us to
determine the position of EBs in the solar atmosphere, as well as
the vertical structure of the activated EB atmosphere Methods:
In our analysis we used observations of EBs obtained in the Hα and
CaII H lines with the Dutch Open Telescope (DOT). These one-hour
long simultaneous sequences obtained with high temporal and spatial
resolution were used to determine the line emissions. To analyze them,
we used NLTE numerical codes for the construction of grids of 243
semi-empirical models simulating EBs structures. In this way, the
observed emission could be compared with the synthetic line spectra
calculated for all such models. Results: For a specific model
we found reasonable agreement between the observed and theoretical
emission and thus we consider such model as a good approximation to EBs
atmospheres. This model is characterized by an enhanced temperature in
the lower chromosphere and can be considered as a compact structure (hot
spot), which is responsible for the emission observed in the wings of
chromospheric lines, in particular in the Hα and CaII H lines. 
Conclusions: For the first time the set of two lines Hα and CaII H was
used to construct semi-empirical models of EBs. Our analysis shows that
EBs can be described by a "hot spot" model, with the temperature and/or
density increase through a few hundred km atmospheric structure. We
confirmed that EBs are located close to the temperature minimum or
in the lower chromosphere. Two spectral features (lines in our case),
observed simultaneously, significantly strengthen the constraints on
a realistic model.

---------------------------------------------------------
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: F-CHROMA.Flare Chromospheres: Observations, Models and Archives
Authors: Cauzzi, Gianna; Fletcher, Lyndsay; Mathioudakis, Mihalis;
Carlsson, Mats; Heinzel, Petr; Berlicki, Arek; Zuccarello, Francesca
2014AAS...22412339C Altcode:
F-CHROMA is a collaborative project newly funded under the EU-Framework
Programme 7 "FP7-SPACE-2013-1", involving seven different European
research Institutes and Universities. The goal of F-CHROMA is to
substantially advance our understanding of the physics of energy
dissipation and radiation in the flaring solar atmosphere, with a
particular focus on the flares' chromosphere. A major outcome of the
F-CHROMA project will be the creation of an archive of chromospheric
flare observations and models to be made available to the community
for further research.In this poster we describe the structure and
milestones of the project, the different activities planned, as well
as early results. Emphasis will be given to the dissemination efforts
of the project to make results of these activities available to and
usable by the community.

---------------------------------------------------------
Title: On the formation of Mg ii h and k lines in solar prominences
Authors: Heinzel, P.; Vial, J. -C.; Anzer, U.
2014A&A...564A.132H Altcode:
 Aims: With the recent launch of the IRIS mission, it has become
urgent to develop the spectral diagnostics using the Mg ii resonance
h and k lines. In this paper, we aim to demonstrate the behavior of
these lines under various prominence conditions. Our results serve
as a basis for analysis of new IRIS data and for more sophisticated
prominence modeling. Methods: For this exploratory work,
we use a canonical 1D prominence-slab model, which is isobaric
and may have three different temperature structures: isothermal,
PCTR-like (prominence-corona transition region), and consistent with
the radiative equilibrium. The slabs are illuminated by a realistic
incident solar radiation obtained from the UV observations. A five-level
plus continuum Mg ii model atom is used to solve the full NLTE problem
of the radiative transfer. We use the numerical code based on the ALI
techniques and apply the partial frequency redistribution for both
Mg ii resonance lines. We also use the velocity-dependent boundary
conditions to study the effect of Doppler dimming in the case of
moving prominences. Finally, the relaxation technique is used to
compute a grid of models in radiative equilibrium. Results:
We computed the Mg ii h and k line profiles that are emergent from
prominence-slab models and show their dependence on kinetic temperature,
gas pressure, geometrical extension, and microturbulent velocity. By
increasing the line opacity, significant departures from the complete
frequency redistribution take place in the line wings. Models with a
PCTR temperature structure show that Mg ii becomes ionized to Mg iii
in the temperature range between roughly 15 000 and 30 000 K. Doppler
dimming is significant for Mg ii resonance lines. At the velocity 300
km s-1, the line intensity decreases to about 20% of the
value for static prominences. Finally, we demonstrate the role of Mg
ii h and k radiation losses on the prominence energy balance. Their
dominant role is at lower pressures, while the losses due to hydrogen
and Ca ii dominate at higher pressures.

---------------------------------------------------------
Title: Synthetic hydrogen spectra of prominence oscillations
Authors: Heinzel, P.; Zapiór, M.; Oliver, R.; Ballester, J. L.
2014A&A...562A.103H Altcode: 2014arXiv1401.2131H
Context. Prominence oscillations have been mostly detected using
Doppler velocity, although there are also claimed detections by means
of periodic variations in half-width or line intensity. However,
scarce observational evidence exists about simultaneous detection of
oscillations in several spectral indicators. Aims: Our main aim
here is to explore the relationship between spectral indicators, such
as Doppler shift, line intensity, and line half-width, and the linear
perturbations excited in a simple prominence model. Methods:
Our equilibrium background model consists of a bounded, homogeneous
slab, which is permeated by a transverse magnetic field, having
prominence-like physical properties. Assuming linear perturbations,
the dispersion relation for fast and slow modes has been derived, as
well as the perturbations for the different physical quantities. These
perturbations have been used as the input variables in a one-dimensional
radiative transfer code, which calculates the full spectral profile
of the hydrogen Hα and Hβ lines. Results: We have found that
different oscillatory modes produce spectral indicator variations in
different magnitudes. Detectable variations in the Doppler velocity
were found for the fundamental slow mode only. Substantial variations
in the Hβ line intensity were found for specific modes. Other modes
lead to lower and even undetectable parameter variations. 
Conclusions: To perform prominence seismology, analysis of the Hα
and Hβ spectral line parameters could be a good tool to detect and
identify oscillatory modes.

---------------------------------------------------------
Title: A comparison between observed IRIS profiles of the h &amp;
k doublet of Mg II and profiles from quiescent prominence NLTE models
Authors: Vial, Jean-Claude; Anzer, Ulrich; Heinzel, Petr; Kleint, Lucia
2014cosp...40E3515V Altcode:
With the advent of IRIS, it is now possible to investigate the cool core
of prominences through the detailed profiles of the Mg II resonance
lines with an unprecedented spatial resolution of 0.33 arcsecond. The
slit-jaw camera also allows to record the temporal evolution of the
prominence fine structure. We present IRIS observations of quiescent
prominence profiles that we analyse in terms of reversal (if any),
width, k/h line ratio, prominence/ quiet Sun line ratio. Comparing these
parameters with the results of NLTE modelling (see Heinzel et al. 2014),
we can derive thermodynamic parameters of the cool prominence plasma,
along with the (line-of-sight) velocities and mass flows.

---------------------------------------------------------
Title: Possible measurements of the magnetic field in eruptive
prominences using the PROBA-3 coronagraph
Authors: Serge, Koutchmy; Zhukov, Andrei; Dolla, Laurent; Heinzel,
Petr; Lamy, Philippe; Bazin, Cyrille; Bommier, Veronique; Faurobert,
Marianne
2014cosp...40E2971S Altcode:
The PROBA-3 mission will fly a spacecraft put in the shadow of a
precisely occulting sister satellite orbiting “in formation” at a
distance of 150 m in front of it to make artificial total eclipses. The
region right above the solar limb will be studied for the first time
over a coronal background not polluted by any spurious light. Although
the priority will be the high-resolution fast imaging of the dynamic
white-light corona, the use of a narrow filter centered on a low
excitation D3 line of He I, is planned for imaging prominences. Adding
the linear polarization analysis would permit the measurements of the
magnetic field using the Hanle effect. We evaluate the possibility
offered during the eruptive phase of a CME with prominence material
inserted inside, for studying the associated magnetic field changes
related to both the heating process and the ejection of material. The
background highly polarized K-corona is taken into account. Sequences of
quasi- simultaneous white-light processed images at high resolution are
an additional feature of great interest for interpreting the overall
magnetic structure.

---------------------------------------------------------
Title: A study of H I Lyman-alpha emission from prominences erupting
in the intermediate corona and possible future applications for
Solar Orbiter/METIS data
Authors: Bemporad, Alessandro; Heinzel, Petr; Jejcic, Sonja; Susino,
Roberto
2014cosp...40E.273B Altcode:
Over almost the last 20 years hundreds of Coronal Mass Ejections
(CME) have been observed by the UV Coronagraph Spectrometer (UVCS)
onboard SOHO. For many of these events a significant emission in the HI
Lyman-alpha lambda 1216 Å line was sampled during the transit across
the slit of the erupting prominences embedded in the core of CMEs. The
origin of this emission is completely different from what is typically
observed by UVCS: because of the higher density and lower temperatures
of such plasmas, the number of neutral H atoms is much larger than
under typical coronal conditions, and the plasma is generally not
optically thin at these wavelengths, as it is usually true for other
coronal structures. Hence, the observed H I Lyman-alpha emission can be
explained only if a radiative transport treatment across a moving plasma
structure is considered. Once the proper boundary conditions are derived
from the UV data, in combination with white light (WL) coronagraphic
observations (from LASCO), we will show how the temperature and
density of the erupting prominence could be derived even at large
altitudes (typically larger than 0.6 solar radii above the limb),
thus providing information on heating/cooling and ionization of the
CME core during the eruption. These results are very important in the
light of coronagraphic observations that will be provided by the METIS
instrument onboard the Solar Orbiter: because METIS will contemporary
observe the solar corona in WL and in UV (HI Lyman-alpha), it will be
possible to derive, with a technique similar to what is shown here,
very important information on prominence plasmas embedded in the core
of CMEs and crossing the METIS instrument field of view.

---------------------------------------------------------
Title: Chromospheric heating during a flare
Authors: Heinzel, Petr
2014cosp...40E1183H Altcode:
Flares are now believed to be complex processes initiated in the corona
and largely influencing the lower atmospheric layers. The energy
is transported from the corona down to the chromosphere and even
photosphere in various modes and this leads to significant heating
of the chromospheric plasma. We will review individual processes
among which the most important is the particle-beam propagation and
dissipation, but others as conduction, XUV heating, wave heating
etc. are also to be considered. We will summarize recent results of
the radiation-hydrodynamical simulations of the chromospheric heating
during flares and the progress in our understanding of the basic
heating mechanisms and flows. We will also point to new space and
ground observations which provide the critical constraints to modeling.

---------------------------------------------------------
Title: Mapping prominence plasma parameters from eclipse observations
Authors: Jejčič, Sonja; Heinzel, Petr; Zapiór, Maciej; Druckmüller,
Miloslav; Gunár, Stanislav; Kotrč, Pavel
2014IAUS..300..420J Altcode:
Using the eclipse observations, we construct the maps of quiescent
prominence temperatures, electron densities, pressures and geometrical
thicknesses. For this we use the RGB signal of prominence visible-light
emission detected during the total solar eclipse on August 1, 2008
in Mongolia, and quasi-simultaneous Hα spectra taken at Ondřejov
observatory. The method of disentangling the electron density and
effective geometrical thickness was described by Jejčič &amp;
Heinzel (2009) and is used here for the first time to analyse the
spatial variations of various prominence parameters.

---------------------------------------------------------
Title: An Estimate of Chromospheric Heating by Acoustic Waves
Authors: Sobotka, M.; Švanda, M.; Jurčak, J.; Heinzel, P.; Del Moro,
D.; Berrilli, F.
2014CEAB...38...53S Altcode:
Several mechanisms may heat the solar chromosphere: acoustic waves,
magnetoacoustic waves (slow, fast, and Alfvén waves), and small-scale
magnetic reconnections. Based on observations in the Ca II 854.2 nm
line, the contribution of acoustic waves to the heating of quiet and
plage regions in the chromosphere is discussed. The energy released
by radiative losses is compared with the energy deposited by acoustic
waves. Radiative losses are computed using a grid of six semi-empirical
models VAL A--F. The deposited acoustic flux is calculated using power
spectra of Doppler oscillations measured in the Ca~II line core. The
comparison shows that the spatial correlation of maps of radiative
losses and acoustic flux is 70 %. The deposited acoustic flux provides
at least 25--30~% of the energy radiated in the quiet chromosphere
and 50~% in plage regions.

---------------------------------------------------------
Title: Non-LTE Modeling and Observations of Oscillating Prominences
Authors: Zapiór, M.; Heinzel, P.; Oliver, R.; Ballester, J. L.;
Kotrč, P.
2014IAUS..300...52Z Altcode:
Prominence oscillations have been mostly detected using Doppler
velocity, although there are also claimed detections by means of the
periodic variations of half-width or line intensity. Our main aim
here is to explore the relationship between spectral indicators such
as Doppler shift, line intensity and line half-width and the linear
perturbations excited in a simple prominence model.

---------------------------------------------------------
Title: Kappa-distributions and Temperature Structure of the
Prominence-Corona Transition Region
Authors: Dzifčáková, Elena; Mackovjak, Šimon; Heinzel, Petr
2014IAUS..300..408D Altcode:
The influence of the electron κ - distributions on the differential
emission measure (DEM) of the prominence-corona transition region
(PCTR) derived from observed line intensities has been investigated. An
important consequence of the κ - distribution is formation of the
emission lines in much wider temperature ranges. The implications
for the formation temperature of the observed SDO/AIA band emissions
are shown.

---------------------------------------------------------
Title: MgII lines in solar flares: IRIS observations and NLTE modeling
Authors: Heinzel, Petr; Kasparova, Jana; Kleint, Lucia; Dzifcakova,
Elena
2014cosp...40E1182H Altcode:
Chromospheric flares have been recently observed in MgII resonance
lines by the IRIS instrument. Apart from the resonance lines h and k,
also subordinate line emissions due to transitions between the MgII
levels 3P and 3D have been now detected by IRIS during flares. We apply
the NLTE radiative-transfer code to synthesize all these MgII lines
under typical flare conditions. In particular, we focus on the role
of the non-thermal excitations and ionizations, which are due to the
presence of the electron beams and corresponding return currents. The
results of this modeling are compared with new IRIS data.

---------------------------------------------------------
Title: Dynamics of the solar atmosphere above a pore with a light
bridge
Authors: Sobotka, M.; Švanda, M.; Jurčák, J.; Heinzel, P.; Del Moro,
D.; Berrilli, F.
2013A&A...560A..84S Altcode: 2013arXiv1309.7790S
Context. Solar pores are small sunspots lacking a penumbra that have
a prevailing vertical magnetic-field component. They can include light
bridges at places with locally reduced magnetic field. Like sunspots,
they exhibit a wide range of oscillatory phenomena. Aims:
A large isolated pore with a light bridge (NOAA 11005) is studied
to obtain characteristics of a chromospheric filamentary structure
around the pore, to analyse oscillations and waves in and around
the pore, and to understand the structure and brightness of the light
bridge. Methods: Spectral imaging observations in the line Ca II
854.2 nm and complementary spectropolarimetry in Fe I lines, obtained
with the DST/IBIS spectrometer and HINODE/SOT spectropolarimeter,
were used to measure photospheric and chromospheric velocity fields,
oscillations, waves, the magnetic field in the photosphere, and
acoustic energy flux and radiative losses in the chromosphere. 
Results: The chromospheric filamentary structure around the pore has
all important characteristics of a superpenumbra: it shows an inverse
Evershed effect and running waves, and has a similar morphology and
oscillation character. The granular structure of the light bridge in
the upper photosphere can be explained by radiative heating. Acoustic
waves leaking up from the photosphere along the inclined magnetic
field in the light bridge transfer enough energy flux to balance
the entire radiative losses of the light-bridge chromosphere. 
Conclusions: A penumbra is not a necessary condition for the formation
of a superpenumbra. The light bridge is heated by radiation in the
photosphere and by acoustic waves in the chromosphere.

---------------------------------------------------------
Title: Scattering Polarization in Solar Flares
Authors: Štěpán, Jiří; Heinzel, Petr
2013ApJ...778L...6S Altcode: 2013arXiv1310.3284S
There is ongoing debate about the origin and even the very existence
of a high degree of linear polarization of some chromospheric
spectral lines observed in solar flares. The standard explanation
of these measurements is in terms of the impact polarization caused
by non-thermal proton and/or electron beams. In this work, we study
the possible role of resonance line polarization due to radiation
anisotropy in the inhomogeneous medium of the flare ribbons. We
consider a simple two-dimensional model of the flaring chromosphere
and we self-consistently solve the non-LTE problem taking into
account the role of resonant scattering polarization and of the
Hanle effect. Our calculations show that the horizontal plasma
inhomogeneities at the boundary of the flare ribbons can lead to a
significant radiation anisotropy in the line formation region and,
consequently, to a fractional linear polarization of the emergent
radiation of the order of several percent. Neglecting the effects of
impact polarization, our model can provide a clue for resolving some
of the common observational findings, namely: (1) why a high degree
of polarization appears mainly at the edges of the flare ribbons;
(2) why polarization can also be observed during the gradual phase of
a flare; and (3) why polarization is mostly radial or tangential. We
conclude that radiation transfer in realistic multi-dimensional models
of solar flares needs to be considered as an essential ingredient for
understanding the observed spectral line polarization.

---------------------------------------------------------
Title: Atmosphere above a large solar pore
Authors: Sobotka, M.; Švanda, M.; Jurčák, J.; Heinzel, P.; Del
Moro, D.
2013JPhCS.440a2049S Altcode: 2013arXiv1302.4893S
A large solar pore with a granular light bridge was observed on October
15, 2008 with the IBIS spectrometer at the Dunn Solar Telescope and a
69-min long time series of spectral scans in the lines Ca II 854.2 nm
and Fe I 617.3 nm was obtained. The intensity and Doppler signals in the
Ca II line were separated. This line samples the middle chromosphere
in the core and the middle photosphere in the wings. Although no
indication of a penumbra is seen in the photosphere, an extended
filamentary structure, both in intensity and Doppler signals, is
observed in the Ca II line core. An analysis of morphological and
dynamical properties of the structure shows a close similarity to a
superpenumbra of a sunspot with developed penumbra. A special attention
is paid to the light bridge, which is the brightest feature in the
pore seen in the Ca II line centre and shows an enhanced power of
chromospheric oscillations at 3-5 mHz. Although the acoustic power
flux in the light bridge is five times higher than in the "quiet"
chromosphere, it cannot explain the observed brightness.

---------------------------------------------------------
Title: Puzzling nature of the fine structure of quiescent prominences
and filaments
Authors: Gunár, Stanislav; Heinzel, Petr; Anzer, Ulrich; Mackay,
Duncan H.
2013JPhCS.440a2035G Altcode:
Even after more than 160 years of observations and modelling of solar
prominences their true nature contains many open questions. In this
work we argue that current 2D prominence fine structure models can
help us to understand the puzzling connection between quasi-vertical
fine structures often seen in quiescent prominences observed on the
solar limb and horizontally aligned dark fibrils representing the fine
structures of prominences observed in absorption against the solar disk
(filaments).

---------------------------------------------------------
Title: Observations and Modeling of Stellar Flares
Authors: Heinzel, P.
2013POBeo..92...87H Altcode:
We briefly review the current status of observations of stellar flares
with meter-class telescopes and their relation to observations of flares
on the Sun-as-a-star. Both stellar photometry and spectroscopy will
be discussed. Solar and stellar flares are modeled using the methods
of radiation hydrodynamics and we will make a summary of recent results.

---------------------------------------------------------
Title: Non-linear force-free magnetic dip models of quiescent
prominence fine structures
Authors: Gunár, S.; Mackay, D. H.; Anzer, U.; Heinzel, P.
2013A&A...551A...3G Altcode:
 Aims: We use 3D non-linear force-free magnetic field modeling
of prominence/filament magnetic fields to develop the first 2D models
of individual prominence fine structures based on the 3D configuration
of the magnetic field of the whole prominence. Methods: We use
an iterative technique to fill the magnetic dips produced by the 3D
modeling with realistic prominence plasma in hydrostatic equilibrium
and with a temperature structure that contains the prominence-corona
transition region. With this well-defined plasma structure the radiative
transfer can be treated in detail in 2D and the resulting synthetic
emission can be compared with prominence/filament observations. Results: Newly developed non-linear force-free magnetic dip models
are able to produce synthetic hydrogen Lyman spectra in a qualitative
agreement with a range of quiescent prominence observations. Moreover,
the plasma structure of these models agrees with the gravity induced
prominence fine structure models which have already been shown to
produce synthetic spectra in good qualitative agreement with several
observed prominences. Conclusions: We describe in detail the
iterative technique which can be used to produce realistic plasma
models of prominence fine structures located in prominence magnetic
field configurations containing dips, obtained using any kind of
magnetic field modeling.

---------------------------------------------------------
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: 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: Magnetism of Solar Flares and Prominences
Authors: Heinzel, P.; Hudson, H. S.
2012ASPC..463..121H Altcode:
We give an overview of magnetic fields in solar flares and
prominences. Magnetic fields related to flares play a crucial role in
the process of energy release and transport to the lower atmosphere,
and thus magnetometry under the coronal and chromospheric conditions is
extremely challenging. Magnetic fields in prominences are supposed to
keep the prominence plasma at coronal heights against the gravity. Their
measurements have been numerous, but high-resolution mapping is still
missing. We discuss various flare and prominence models in connection
to current and future high-resolution observations.

---------------------------------------------------------
Title: Study of an Extended EUV Filament Using SoHO/SUMER Observations
of the Hydrogen Lyman Lines. II. Lyman α Line Observed During a
Multi-wavelength Campaign
Authors: Schwartz, P.; Schmieder, B.; Heinzel, P.; Kotrč, P.
2012SoPh..281..707S Altcode: 2012SoPh..tmp..201S
A filament and its channel close to the solar disk were observed in the
complete hydrogen Lyman spectrum, and in several EUV lines by the SUMER
(Solar Ultraviolet Measurement of Emitted Radiation) and CDS (Coronal
Diagnostic Spectrometer) spectrographs on the SoHO satellite, and in
Hα by ground-based telescopes during a multi-instrument campaign in
May 2005. It was a good opportunity to get an overview of the volume
and the density of the cold plasma in the filament channel; these are
essential parameters for coronal mass ejections. We found that the
width of the filament depends on the wavelength in which the filament
is observed (around 15 arcsec in Hα, 30 arcsec in Lα, and 60 arcsec
in EUV). In Lα the filament is wider than in Hα because cool plasma,
not visible in Hα, is optically thick at the Lα line center, and its
presence blocks the coronal emission. We have derived physical plasma
properties of this filament fitting the Lyman spectra and Hα profiles
by using a 1D isobaric NLTE model. The vertical temperature profile
of the filament slab is flat (T≈7000 K) with an increase to ≈ 20
000 K at the top and the bottom of the slab. From an analysis of the
Lα and Hα source functions we have concluded that these lines are
formed over the whole filament slab. We have estimated the geometrical
filling factor in the filament channel. Its low value indicates the
presence of multi-threads.

---------------------------------------------------------
Title: Formation of Balmer Lines in Impulsively Heated Flare
Atmosphere by Neutral Beams
Authors: Varady, M.; Kašparová, J.; Moravec, Z.; Karlický, M.;
Heinzel, P.
2012ASPC..454..341V Altcode:
In the context of interpreting non-thermal hard X-ray emission and γ
lines emanating from the footpoints of flare loops, most contemporary
flare models assign a fundamental role during the flare energy release,
transport and deposition to the high energy non-thermal particle
beams. In this contribution we concentrate on modelling of the
spectroscopic properties of chromospheric flare emission in optical
hydrogen lines generated due to the bombardment of the chromosphere
and photosphere by neutral beams with power-law spectra. In order
to obtain an estimate of the neutral beam flare heating in the solar
atmosphere we produced a simple model describing the propagation and
thermalisation of neutral beams. We compare the neutral beam flare
heating with the flare heating produced by corresponding pure electron
and proton beams. Further we compare the contribution functions for
Hα line obtained for neutral and electron beam heating.

---------------------------------------------------------
Title: Velocity Vector, Ionization Degree, and Temperature of
Prominence Fine Structures Observed by Hinode/SOT
Authors: Schmieder, B.; Mein, P.; Chandra, R.; Molodij, G.; Heinzel,
P.; Berlicki, A.; Schwartz, P.; Fárník, F.; Labrosse, N.; Anzer,
U.; Watanabe, T.
2012ASPC..454..107S Altcode:
Prominences have been successfully observed by Hinode in April 2007
exhibiting a strong dynamics of their fine structures. The dynamics
of a prominence is a challenge to understand the formation of cool
prominence plasma embedded in the hot corona. Combining simultaneous
observations obtained in Hα with Hinode/SOT and the MSDP spectrograph
operating at the Meudon solar tower, velocity vectors have been
derived. The Doppler-shifts of bright threads are of the same order
as the velocities measured perpendicular to the line of sight. This
suggests that the vertical structures of the prominence could be a pile
up of dips in magnetic field lines viewed in 3D. Using Hα, Hinode/XRT
and TRACE data, the hydrogen ionization degree has been determined to
be 0.5-0.8, and the optical thickness in Hα between 0.2 and 1.3. The
Extreme Ultraviolet Imaging Spectrometer (EIS) on Hinode produced images
of the prominence in 11 selected lines with formation temperatures
between log(T) = 4.7 and log(T) = 6.1. We comment on the absorption,
emissivity blocking and emission involved for interpreting the different
structures of the prominence in terms of the temperature and density.

---------------------------------------------------------
Title: Mass of Solar Prominences Estimated from Multi-Wavelength Data
Authors: Schwartz, P.; Fárník, F.; Heinzel, P.; Kotrč, P.; Anzer, U.
2012ASPC..454..117S Altcode:
The mass of selected prominences was estimated using their
multi-wavelength observations: in Hα by the HSFA2 spectrograph of
the Ondřejov observatory, in EUV by SoHO/EIT and in the soft X-rays
by Hinode XRT. The results are compared with values estimated by
other authors.

---------------------------------------------------------
Title: Prominences observations with SDO/AIA
Authors: Parenti, Susanna; Schmieder, Brigitte; Golub, Leon; Heinzel,
Petr
2012cosp...39.1447P Altcode: 2012cosp.meet.1447P
The Prominence-Corona-Transition-Region (PCTR) plays a key role in
the thermal and pressure equilibrium of prominences. However, several
open issues limit our knowledge of this important interface. Among
them we find the thermal structure and the maximum temperature of
its emitting plasma. This work is a new step toward resolving these
issues. By noting that prominences may be observed in emission in
the 171 and 131 SDO/AIA images, while they are seen in absorption in
others (e.g. 193) we investigate the temperature content of these
channels. Using the CHIANTI atomic database and previously derived
prominence DEMs, we built synthetic spectra in these AIA channels to
establish the main contributors. We find that the Fe IX line always
dominates the 171 band, even in absence of a coronal plasma, while
the 131 channel is dominated by Fe VIII. Our conclusion is that the
PCTR reaches, at least, 4x 10^5 K.

---------------------------------------------------------
Title: On the Nature of Prominence Emission Observed by SDO/AIA
Authors: Parenti, S.; Schmieder, B.; Heinzel, P.; Golub, L.
2012ApJ...754...66P Altcode: 2012arXiv1205.5460P
The prominence-corona transition region (PCTR) plays a key role in the
thermal and pressure equilibrium of solar prominences. Our knowledge
of this interface is limited and several major issues remain open,
including the thermal structure and, in particular, the maximum
temperature of the detectable plasma. The high signal-to-noise
ratio of images obtained by the Atmospheric Imaging Assembly (AIA)
on NASA's Solar Dynamics Observatory clearly shows that prominences
are often seen in emission in the 171 and 131 bands. We investigate the
temperature sensitivity of these AIA bands for prominence observations,
in order to infer the temperature content in an effort to explain the
emission. Using the CHIANTI atomic database and previously determined
prominence differential emission measure distributions, we build
synthetic spectra to establish the main emission-line contributors
in the AIA bands. We find that the Fe IX line always dominates
the 171 band, even in the absence of plasma at &gt;106 K
temperatures, while the 131 band is dominated by Fe VIII. We conclude
that the PCTR has sufficient plasma emitting at &gt;4 × 105
K to be detected by AIA.

---------------------------------------------------------
Title: Dynamics of quiescent prominences
Authors: Heinzel, Petr
2012cosp...39..742H Altcode: 2012cosp.meet..742H
We review the state-of-the-art of the observations and modeling of
prominence fine structures, with special emphasis on the dynamics. Fine
structures of quiescent prominences have been recently observed by
Hinode/SOT and these observations revealed a rather complex dynamics
of bright threads and blobs and of dark plumes originating from large
prominence bubbles. SOHO/SUMER spectra of hydrogen Lyman lines, together
with H-alpha observations from MSDP, provide us with constraints on
the dynamics of cool fine structures. 2D non-LTE modeling is used for
analysis of the line profiles and their asymmetries. On the contrary,
the SDO/AIA images, together with RHD modeling of dipped magnetic loops,
lead to a better understanding of the dynamics and energetics of hotter
prominence plasmas. Finally, some more global dynamics is revealed by
the spectroscopic detection of quiescent prominence oscillations. We
show recent results of such observations and new radiative-transfer
modeling.

---------------------------------------------------------
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: Prominence fine-structure dynamics as inferred from 2D
non-LTE models
Authors: Gunar, Stanislav; Schmieder, Brigitte; Mein, Pierre;
Heinzel, Petr
2012cosp...39..683G Altcode: 2012cosp.meet..683G
2D multi-thread prominence fine structure models are able to
produce synthetic Lyman spectra in very good agreement with spectral
observations by SOHO/SUMER including the spectral line asymmetries. The
synthetic differential emission measure curves derived from these
models are also in a good agreement with observations. Now we show that
these models are also able to produce synthetic H-alpha line profiles
in very good agreement with observations which allows us to analyze
not only the physical parameters of the prominence fine-structure
plasma but also some aspects of its dynamical behaviour. We compare
the synthetic H-alpha spectra with the observed spectra of the
April 26, 2007 prominence using three statistical parameters: the
line integrated intensity, the line full-width at the half-maximum
(FWHM), and the Doppler velocity derived from shifts of the line
profiles. This statistical analysis allows us to conclude that the
overall statistical distribution of the LOS velocities in the April 26,
2007 prominence at the time of the observations was below +/-15 km/s
and in the prominence core was close to +/-10 km/s. In combination
with the analysis of the Lyman spectra we determine several physical
parameters of the observed prominence fine structures which show that
the April 26, 2007 prominence was relatively less massive. We are also
able to put some constrains on the prominence core temperature that
might be relatively low, reaching values below 6000 K.

---------------------------------------------------------
Title: SDO/EVE spectra of solar flares
Authors: Heinzel, Petr; Avrett, Eugene; Dzifcakova, Elena; Hudson,
Hugh S.
2012cosp...39..743H Altcode: 2012cosp.meet..743H
For selected flare events we present the SDO/EVE spectra of hydrogen
and helium resonance continua and compare them with the results of
non-LTE transfer computations based on various flare models. We
discuss the formation of these continua and their diagnostic
potential for determination of the temperature structure of the
flaring atmosphere. Under the optically-thin conditions, we synthesize
these resonance continua using the CHIANTI database where we added
the relevant non-thermal atomic rates. This shows how the electron
or proton beams may affect the continua during an impulsive phase of
solar flares. As a benchmark we present our comparison of the quiet-Sun
EVE spectra with the flux synthesized from the model C6 of Avrett and
Loeser (2008). Our study has a more general relevance to the physics
of stellar flares.

---------------------------------------------------------
Title: Dynamics of quiescent prominence fine structures analyzed by
2D non-LTE modelling of the Hα line
Authors: Gunár, S.; Mein, P.; Schmieder, B.; Heinzel, P.; Mein, N.
2012A&A...543A..93G Altcode:
 Aims: We analyze the dynamics of the prominence fine
structures of a quiescent prominence observed on April 26, 2007
during a coordinated campaign of several spaceborne and ground-based
instruments. We use Lyman spectra observed by SOHO/SUMER and the
Hα line spectra obtained by MSDP spectrograph working at the
Meudon Solar Tower. Methods: We employ the 2D multi-thread
prominence fine-structure modelling that includes randomly distributed
line-of-sight (LOS) velocities of individual threads to derive models
producing synthetic Lyman lines in good agreement with the SOHO/SUMER
observations. We then use these models to produce synthetic Hα
line spectra that we compare with the observed spectra using three
statistical parameters: the line integrated intensity, the line
full-width at half-maximum (FWHM), and the Doppler velocity derived
from shifts of the line profiles. Results: We demonstrate that
the 2D multi-thread models that produce synthetic Lyman spectra in
agreement with observations also generate synthetic Hα spectra in
good agreement with the observed ones. The statistical analysis of the
FWHM and Doppler velocities of the synthetic Hα line profiles show
that the overall LOS velocities in the April 26, 2007 prominence at
the time of the observations were below 15 km s-1 and in
the prominence core were close to 10 km s-1. In combination
with the analysis of the Lyman spectra, we determine several physical
parameters of the observed prominence fine-structures that show
that the April 26, 2007 prominence had a relatively low-mass weakly
magnetized structure. We are also able to impose some constraints
on the prominence core temperature, which may be relatively low,
with values below 6000 K. Conclusions: The combination of
2D non-LTE prominence fine-structure modelling with the statistical
analysis of the observed and synthetic Lyman and Hα spectra allows us
to analyze the influence of the model input parameters and the velocity
fields on the synthetic Hα line profiles, thus determine the overall
dynamics of the observed prominence as well as the physical parameters
of its plasma. Appendix A is available in electronic form at <A
href="http://www.aanda.org">http://www.aanda.org</A>

---------------------------------------------------------
Title: On the Visibility of Solar Prominences in SDO/AIA Channels
Authors: Heinzel, P.; Schmieder, B.; Parenti, S.; Golub, L.
2012ASPC..456...75H Altcode:
Prominences in EUV lines are observed as dark structures over the
limb due absorption and emission blocking mechanisms. However, at 171
Å is observed emission in prominences with TRACE and SDO/AIA, and
it is believed to be due to the prominence-corona transition region
(PCTR) emitting in cool lines. To check this, we use the Differential
Emission Measure (DEM) recently obtained for quiescent prominences
using SOHO/SUMER spectra (Parenti and Vial 2007) and compute the
synthetic spectra in selected AIA channels. We then compare 171 Å and
195 Å channels and derive conclusions concerning the PCTR emissivity,
as well well as the absorption and blocking. The emission seen in the
171 Å channel can be used to better constrain prominence DEM curves.

---------------------------------------------------------
Title: On the Nature of Prominence Bubbles and Plumes
Authors: Schmieder, B.; Zapior, M.; Heinzel, P.; Aulanier, G.
2012ASPC..456...77S Altcode:
An example of bubble and related plume, using time series in
selected SDO/AIA channels and co-temporal MSDP observations in the
Hα line obtained at Wroclaw-Bialkow observatory on April 20, 2011 is
presented. The formation of bubbles may be due to emerging arcades in
the filament channel, below the prominence. After discussing on MHD
modeling, we conclude that bubbles and plumes are parts of the corona
observed through gaps/windows in the prominence.

---------------------------------------------------------
Title: Optical-to-Radio Continua in Solar Flares
Authors: Heinzel, P.; Avrett, E. H.
2012SoPh..277...31H Altcode:
Spectral continua observed during solar flares may contain information
about both thermal and non-thermal heating mechanisms. Using two
semi-empirical flare models F2 and FLA, we synthesize the thermal
continua from optical to mm-radio domains and compare their intensities
with quiet-Sun values computed from a recent model C7. In this
way, the far-infrared and sub-mm/mm continua are studied for the
first time, and we present our results as a benchmark for further
modeling and for planning new observations, especially with the ALMA
instrument. Finally, we demonstrate how these continua are formed and
show a close correspondence between their brightness temperature and
the kinetic-temperature structure of the flaring atmosphere.

---------------------------------------------------------
Title: Radiative equilibrium in solar prominences reconsidered
Authors: Heinzel, P.; Anzer, U.
2012A&A...539A..49H Altcode:
 Aims: We reconsider the question which kinetic temperatures
can lead to prominence configurations that are in radiative
equilibrium. We compare these temperatures to those from other
calculations. Methods: For this purpose we solved the full
non-LTE radiative-transfer problem for a gas consisting of hydrogen,
helium and calcium. We used simple isobaric 1D slabs and began with
isothermal models. Then we solved the radiative-relaxation problem
and determined the radiative-equilibrium conditions within the
whole slab. Results: By adding the calcium radiative losses,
we found that these equilibrium temperatures are considerably lower
than those obtained for a pure hydrogen gas. This is because the newly
calculated CaII line losses appear to play a significant role in the
energy balance, similar to chromospheric conditions. The equilibrium
temperatures obtained span the range between 4400-9500 K, depending
on the gas pressure and slab thickness.

---------------------------------------------------------
Title: The nature of hydrogen and helium continua in SDO/EVE spectra
of solar flares
Authors: Heinzel, P.; Avrett, E. H.
2012decs.confE.109H Altcode:
For selected flare events we present the SDO/EVE spectra of hydrogen
and helium resonance continua and compare them with the results
of the non-LTE transfer computations based on semi-empirical flare
models. We discuss the formation of these continua and their diagnostic
potential for determination of the temperature structure of the flaring
atmosphere. Non-thermal processes are also considered. As a benchmark
we present our comparison of the quiet-Sun EVE spectra with the flux
synthesized from the model C6 of Avrett and Loeser (2008).

---------------------------------------------------------
Title: Formation of MgII lines in solar prominences
Authors: Heinzel, Petr
2012decs.confE.108H Altcode:
Solar prominences have been observed in MgII h and k lines, both from
space (OSO-8) or from stratospheric balloons. Non-LTE modeling of these
resonance lines was then performed and the results have been compared
to available observations. We briefly review this past effort and
present new transfer computations which take into account all details
of the MgII line formation under realistic prominence conditions. We
estimate the role of MgII lines in radiation cooling of prominence
plasmas and show how they affect the radiative relaxation in these
structures. Finally, we also demonstrate the diagnostic capabilities
of these lines useful for thermodynamic and velocity measurements.

---------------------------------------------------------
Title: Splinter Session "Solar and Stellar Flares"
Authors: Fletcher, L.; Hudson, H.; Cauzzi, G.; Getman, K. V.; Giampapa,
M.; Hawley, S. L.; Heinzel, P.; Johnstone, C.; Kowalski, A. F.; Osten,
R. A.; Pye, J.
2011ASPC..448..441F Altcode: 2011csss...16..441F; 2012arXiv1206.3997F
This summary reports on papers presented at the Cool Stars-16 meeting in
the splinter session "Solar and Stellar flares." Although many topics
were discussed, the main themes were the commonality of interests,
and of physics, between the solar and stellar flare communities,
and the opportunities for important new observations in the near future.

---------------------------------------------------------
Title: Synthetic differential emission measure curves of prominence
fine structures. II. The SoHO/SUMER prominence of 8 June 2004
Authors: Gunár, S.; Parenti, S.; Anzer, U.; Heinzel, P.; Vial, J. -C.
2011A&A...535A.122G Altcode:
 Aims: This study is the first attempt to combine the prominence
observations in Lyman, UV, and EUV lines with the determination of the
prominence differential emission measure derived using two different
techniques, one based on the inversion of the observed UV and EUV lines
and the other employing 2D non-LTE prominence fine-structure modeling
of the Lyman spectra. Methods: We use a trial-and-error method
to derive the 2D multi-thread prominence fine-structure model producing
synthetic Lyman spectra in good agreement with the observations. We then
employ a numerical method to perform the forward determination of the
DEM from 2D multi-thread models and compare the synthetic DEM curves
with those derived from observations using inversion techniques. Results: A set of available observations of the June 8, 2004
prominence allows us to determine the range of input parameters, which
contains models producing synthetic Lyman spectra in good agreement
with the observations. We select three models, which represent this
parametric-space area well and compute the synthetic DEM curves for
multi-thread realizations of these models. The synthetic DEM curves
of selected models are in good agreement with the DEM curves derived
from the observations. Conclusions: We show that the evaluation
of the prominence fine-structure DEM complements the analysis of the
prominence hydrogen Lyman spectra and that its combination with the
detailed radiative-transfer modeling of prominence fine structures
provides a useful tool for investigating the prominence temperature
structure from the cool core to the prominence-corona transition region.

---------------------------------------------------------
Title: EUV lines observed with EIS/Hinode in a solar prominence
Authors: Labrosse, N.; Schmieder, B.; Heinzel, P.; Watanabe, T.
2011A&A...531A..69L Altcode: 2011arXiv1105.1400L
Context. During a multi-wavelength observation campaign with Hinode
and ground-based instruments, a solar prominence was observed for
three consecutive days as it crossed the western limb of the Sun
in April 2007. Aims: We report on observations obtained on
26 April 2007 using EIS (Extreme ultraviolet Imaging Spectrometer)
on Hinode. They are analysed to provide a qualitative diagnostic
of the plasma in different parts of the prominence. Methods:
After correcting for instrumental effects, the rasters at different
wavelengths are presented. Several regions within the same prominence
are identified for further analysis. Selected profiles for lines
with formation temperatures between log (T) = 4.7 and log (T) = 6.3,
as well as their integrated intensities, are given. The profiles of
coronal, transition region, and He ii lines are discussed. We pay
special attention to the He ii line, which is blended with coronal
lines. Results: Some quantitative results are obtained by
analysing the line profiles. They confirm that depression in EUV lines
can be interpreted in terms of two mechanisms: absorption of coronal
radiation by the hydrogen and neutral helium resonance continua, and
emissivity blocking. We present estimates of the He ii line integrated
intensity in different parts of the prominence according to different
scenarios for the relative contribution of absorption and emissivity
blocking to the coronal lines blended with the He ii line. We estimate
the contribution of the He ii 256.32 Å line to the He ii raster image
to vary between ~44% and 70% of the raster's total intensity in the
prominence according to the different models used to take into account
the blending coronal lines. The inferred integrated intensities of
the He ii 256 Å line are consistent with the theoretical intensities
obtained with previous 1D non-LTE radiative transfer calculations,
yielding a preliminary estimate of the central temperature of 8700 K,
a central pressure of 0.33 dyn cm-2, and a column mass of
2.5 × 10-4 g cm-2. The corresponding theoretical
hydrogen column density (1020 cm-2) is about
two orders of magnitude higher than those inferred from the opacity
estimates at 195 Å. The non-LTE calculations indicate that the He
ii 256.32 Å line is essentially formed in the prominence-to-corona
transition region by resonant scattering of the incident radiation. The movie associated to Fig. 2 is available in electronic form at
<A href="http://www.aanda.org">http://www.aanda.org</A>

---------------------------------------------------------
Title: 2D radiative-magnetohydrostatic model of a prominence observed
by Hinode, SoHO/SUMER and Meudon/MSDP
Authors: Berlicki, A.; Gunar, S.; Heinzel, P.; Schmieder, B.;
Schwartz, P.
2011A&A...530A.143B Altcode:
 Aims: Prominences observed by Hinode show very dynamical and
intriguing structures. To understand the mechanisms that are responsible
for these moving structures, it is important to know the physical
conditions that prevail in fine-structure threads. In the present work
we analyse a quiescent prominence with fine structures, which exhibits
dynamic behaviour, which was observed in the hydrogen Hα line with
Hinode/SOT, Meudon/MSDP and Ondřejov/HSFA2, and simultaneously in
hydrogen Lyman lines with SoHO/SUMER during a coordinated campaign. We
derive the fine-structure physical parameters of this prominence and
also address the questions of the role of the magnetic dips and of
the interpretation of the flows. Methods: We calibrate the
SoHO/SUMER and Meudon/MSDP data and obtain the line profiles of the
hydrogen Lyman series (Lβ to L6), the Ciii (977.03 Å) and Svi (933.40
Å), and Hα along the slit of SoHO/SUMER that crosses the Hinode/SOT
prominence. We employ a complex 2D radiation-magnetohydrostatic (RMHS)
modelling technique to properly interpret the observed spectral
lines and derive the physical parameters of interest. The model
was constrained not only with integrated intensities of the lines,
but also with the hydrogen line profiles. Results: The slit
of SoHO/SUMER is crossing different prominence structures: threads
and dark bubbles. Comparing the observed integrated intensities, the
depressions of Hα bubbles are clearly identified in the Lyman, Ciii,
and Svi lines. To fit the observations, we propose a new 2D model
with the following parameters: T = 8000 K, pcen = 0.035
dyn cm-2, B = 5 Gauss, ne = 1010
cm-3, 40 threads each 1000 km wide, plasma β is 3.5 ×
10-2. Conclusions: The analysis of Ciii and Svi
emission in dark Hα bubbles allows us to conclude that there is no
excess of a hotter plasma in these bubbles. The new 2D model allows us
to diagnose the orientation of the magnetic field versus the LOS. The
40 threads are integrated along the LOS. We demonstrate that integrated
intensities alone are not sufficient to derive the realistic physical
parameters of the prominence. The profiles of the Lyman lines and also
those of the Hα line are necessary to constrain 2D RMHS models. The
magnetic field in threads is horizontal, perpendicular to the LOS,
and in the form of shallow dips. With this geometry the dynamics of
fine structures in prominences could be interpreted by a shrinkage of
the quasi-horizontal magnetic field lines and apparently is not caused
by the quasi-vertical bulk flows of the plasma, as Hinode/SOT movies
seemingly suggest.

---------------------------------------------------------
Title: Synthetic differential emission measure curves of prominence
fine structures
Authors: Gunár, S.; Heinzel, P.; Anzer, U.
2011A&A...528A..47G Altcode:
 Aims: We use 2D single and multi-thread prominence fine-structure
models to obtain the synthetic DEM curves. These are then compared
with the DEM curves derived from observations. Methods: We use
the temperature and electron density structure resulting from the
2D models and numerically compute the average synthetic DEM curves
for different orientations of the threads with respect to the line of
sight. Results: We show that the synthetic DEM curves obtained
by 2D modelling are similar to the DEM curves derived from observations
of quiescent prominences. Conclusions: The DEM curves derived
from observations, which are most reliable above temperatures of 20
000 K, can be extended towards cool prominence-core temperatures by
supplementing them with synthetic DEM values obtained by modelling
hydrogen Lyman spectra originating mainly at temperatures below 20 000
K. On the other hand, the observed DEM can constrain the temperature
structure of the prominence fine structures above the formation
temperatures of the Lyman spectrum.

---------------------------------------------------------
Title: Solar Research with ALMA
Authors: Karlický, M.; Bárta, M.; DaÌ§browski, B. P.; Heinzel, P.
2011SoPh..268..165K Altcode: 2010SoPh..tmp..231K; 2010SoPh..tmp..207K
The Atacama Large Millimeter/sub-millimeter Array (ALMA) is a large
interferometer that will consist up to 64 high-precision antennas
operating in the 31.3 - 950 GHz frequency range. In this frequency
range, which is largely unexplored, unique observations with a broad
range of scientific objectives (cosmology, cold universe, galaxies,
stars and their formation, planets and so on) are expected. Among
these tasks there is a unique possibility to observe the Sun and to
address several outstanding issues of solar physics. First, the ALMA
is briefly described and then the new ESO-ALMA European node (ARC),
built at Ondřejov Observatory, is presented. In Europe, this ARC is
the only one oriented to solar physics. Consequently, the requirements
and limitations for ALMA solar observations, as well as some examples
of possible solar-oriented ALMA projects, are shown. A procedure of
the preparation and submission of proposals for ALMA observations
is mentioned.

---------------------------------------------------------
Title: Solar Flares and the Chromosphere
Authors: Fletcher, L.; Turkmani, R.; Hudson, H. S.; Hawley, S. L.;
Kowalski, A.; Berlicki, A.; Heinzel, P.
2010arXiv1011.4650F Altcode:
A white paper prepared for the Space Studies Board, National Academy
of Sciences (USA), for its Decadal Survey of Solar and Space Physics
(Heliophysics), reviewing and encouraging studies of flare physics in
the chromosphere.

---------------------------------------------------------
Title: Solar Flares and the Chromosphere: A white paper for the
Decadal Survey
Authors: Hudson, H. S.; Fletcher, L.; Turkmani, R.; Hawley, S. L.;
Kowalski, A. F.; Berlicki, A.; Heinzel, P.
2010helio2010....1H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Modeling of Solar Flare Plasma and Its Radiation
Authors: Varady, Michal; Kasparova, Jana; Moravec, Zdeněk; Heinzel,
Petr; Karlicky, Marian
2010ITPS...38.2249V Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Towards a New Formation Flying Solar Coronagraph
Authors: Lamy, P.; Vives, S.; Curdt, W.; Dame, L.; Davila, J.; Defise,
J. M.; Fineschi, S.; Heinzel, P.; Kuzin, S.; Schmutz, W.; Tsinganos,
K.; Turck-Chieze, S.; Zhukov, A.
2010ASPC..424...15L Altcode:
We briefly describe an investigation aiming at the development of a
giant solar coronagraph instrument onboard of two satellites, separated
by about 150 m in formation flight for the detailed observation of the
solar coronal plasma. The European Space Agency (ESA) has selected this
instrument as the only payload onboard the Proba 3 satellites which
will be launched in 2013. The Greek team is developing the command
control board of the coronagraph.

---------------------------------------------------------
Title: Statistical comparison of the observed and synthetic hydrogen
Lyman line profiles in solar prominences
Authors: Gunár, S.; Schwartz, P.; Schmieder, B.; Heinzel, P.;
Anzer, U.
2010A&A...514A..43G Altcode:
 Aims: We analyse a unique set of prominence SOHO/SUMER
Lyman spectra by comparing it with synthetic spectra obtained by 2D
multi-thread prominence fine-structure models. Methods: We
employed a novel statistical approach to the analysis of the observed
and synthetic Lyman spectra. We compared the statistical distributions
of the line properties of the observed and synthetic Lyman spectra using
a set of four statistical criteria. Results: We demonstrate
the very good agreement between the observed Lyman spectra and
synthetic spectra obtained by modelling. Conclusions: Our set
of statistical criteria is well-suited to analyses of the prominence
Lyman spectra because of its sensitivity to a number of different
parameters governing the conditions in the prominence fine structures.

---------------------------------------------------------
Title: Physics of Solar Prominences: I—Spectral Diagnostics and
Non-LTE Modelling
Authors: Labrosse, N.; Heinzel, P.; Vial, J. -C.; Kucera, T.; Parenti,
S.; Gunár, S.; Schmieder, B.; Kilper, G.
2010SSRv..151..243L Altcode: 2010SSRv..tmp...34L; 2010arXiv1001.1620L
This review paper outlines background information and covers recent
advances made via the analysis of spectra and images of prominence
plasma and the increased sophistication of non-LTE ( i.e. when there is
a departure from Local Thermodynamic Equilibrium) radiative transfer
models. We first describe the spectral inversion techniques that have
been used to infer the plasma parameters important for the general
properties of the prominence plasma in both its cool core and the
hotter prominence-corona transition region. We also review studies
devoted to the observation of bulk motions of the prominence plasma and
to the determination of prominence mass. However, a simple inversion
of spectroscopic data usually fails when the lines become optically
thick at certain wavelengths. Therefore, complex non-LTE models become
necessary. We thus present the basics of non-LTE radiative transfer
theory and the associated multi-level radiative transfer problems. The
main results of one- and two-dimensional models of the prominences and
their fine-structures are presented. We then discuss the energy balance
in various prominence models. Finally, we outline the outstanding
observational and theoretical questions, and the directions for future
progress in our understanding of solar prominences.

---------------------------------------------------------
Title: How do unresolved motions affect the prominence hydrogen
Lyman spectrum.
Authors: Gunar, Stanislav; Schwartz, Pavol; Schmieder, Brigitte;
Heinzel, Petr; Anzer, Ulrich
2010cosp...38.2830G Altcode: 2010cosp.meet.2830G
Space-born observations of quiescent prominences in the hydrogen
Lyman line series provide a considerable amount of information
about their structure and physical properties. Lyman line series
thus represents a focus of several detailed studies. However, the
substantial asymmetries exhibited by considerable number of observed
Lyman line profiles present a strong indication for the existence of
hidden fine-structure dynamics. If attributed merely to the Doppler
shift effect, these asymmetries would correspond to radial velocities
of the order of 100 km/s. Such high velocities, however, were never
observed in quiescent prominences. Typical fine-structure velocities are
of the order of 10 km/s. To tackle this problem, we have modified our
2D multi-thread prominence models and randomly assigned line-of-sight
(LOS) velocities of the order of 10 km/s to each thread. The obtained
synthetic Lyman spectrum exhibits substantial asymme-tries of the line
profiles comparable with SOHO/SUMER observations. Moreover, our results
do indicate that the synthetic Lyman-α profiles may exhibit an opposite
asymmetry to that of the higher Lyman lines. This is consistent with
observations which often show opposite asym-metries of these lines at
the same prominence location. We have demonstrated the agreement of
synthetic and observed spectra not only by comparing asymmetries of
individual profiles but also by exploiting statistically significant
sets of the observed and synthetic data. These results represent an
important step in our understanding of hidden fine-structure dynamics
of quiescent prominences.

---------------------------------------------------------
Title: ASPIICS / PROBA-3: a formation flying externally-occulted
giant coronagraph mission
Authors: Lamy, Philippe; Damé, Luc; Curdt, W.; Davila, J.; Defise,
J. M.; Fineschi, S.; Heinzel, P.; Howard, R.; Kuzin, S.; Schmutz,
W.; Tsinganos, K.; Turck-Chièze, S.; Zhukov, A.
2010cosp...38.2858L Altcode: 2010cosp.meet.2858L
Classical externally-occulted coronagraphs are presently limited in
their performances by the distance between the external occulter and
the front objective. The diffraction fringe from the occulter and
the vignetted pupil which degrades the spatial resolution prevent
useful observa-tions of the white light corona inside typically 2-2.5
Rsun. Formation flying offers an elegant solution to these limitations
and allows conceiving giant, externally-occulted coronagraphs
us-ing a two-component space system with the external occulter on
one spacecraft and the optical instrument on the other spacecraft
at distances of hundred meters. Such an instrument has just been
selected by ESA to fly (by the end of 2013) on its PROBA-3 mission,
presently in phase B, to demonstrate formation flying. It will perform
both high spatial resolution imaging of the solar corona as well as
2-dimensional spectroscopy of several emission lines (in partic-ular
the forbidden line of FeXIV at 530.285 nm) from the coronal base out
to 3 Rsun using a Fabry-Perot interferometer. The classical design of
an externally-occulted coronagraph is adapted to the formation flying
configuration allowing the detection of the very inner corona as close
as 0.05 Rsun from the solar limb. By tuning the position of the occulter
spacecraft, it may even be possible to try reaching the chromosphere
and the upper part of the spicules. ASPIICS/PROBA-3 mission, payload
and scientific objectives are detailed.

---------------------------------------------------------
Title:

---------------------------------------------------------
Title: Can purely emissive Ly_beta prominence spectra be
caused by the line of sight oriented parallelly to the magnetic field?
Authors: Schwartz, Pavol; Gunar, Stanislav; Heinzel, Petr; Schmieder,
Brigitte
2010cosp...38.2852S Altcode: 2010cosp.meet.2852S
Small bright prominence was observed on the SW limb on April 26,
2007 between 13:01 and 23:50 UT by SUMER spectrograph on-board SoHO
in hydrogen Lyman line series except the Lyα line. Profiles of the
Lyβ line are peculiar for a prominence because they do not exhibit any
central reversals (dips in cores of the lines). This could be explained
by the fact that the line of sight is parallel with the direction of
the magnetic field in the prominence. We can investigate this fact
by a statistical comparison of observed profiles with the synthetic
ones computed using the 2D multi-thread model of the prominence. We
use synthetic profiles obtained for various orientations of the
line of sight with respect to the magnetic field, ranging from
perpendicular to parallel. Profiles are compared statistically using
their characteristics such as integral intensities, so-called Lyman
decrement (ratio of integral intensity of the line to integral intensity
of the Lyβ line, etc.).

---------------------------------------------------------
Title: Relations between theoretical and observational plasma
parameters and the radiation of the prominence
Authors: Berlicki, Arkadiusz; Schwartz, Pavol; Schmieder, Brigitte;
Heinzel, Petr; Gunar, Stanislav
2010cosp...38.2945B Altcode: 2010cosp.meet.2945B
On April 26, 2007 the quiescent prominence was observed during the
coordinated campaign of prominence studies icluding SOT, XRT, and
EIS on Hinode, MDI, EIT, SUMER, and CDS on SOHO, TRACE, and several
ground-based observatories. This was the first Hinode-SUMER ob-serving
campaign. In this analysis we use the data obtained with Hinode/SOT,
SOHO/SUMER and Multichannel Spectrograph MSDP (Meudon, France). The
SUMER instrument provide us the UV spectra of the prominence in several
spectral lines along the 120 arcsec slit crossing the prominence. We
used the following lines: Lβ, Lγ, Lδ, L , C III and S VI. Using
these spectra we calculated the integrated intensities along the slit
for all these lines. We also calculated the integrated intensity of
the Hα line from the spectroscopic ground-based MSDP observations
for the same parts of the prominence observed at the same time. These
intensities were used to calibrate the Hinode/SOT data. Next, we
analyzed the relations between different observed intensities in these
lines and compared them with the values obtained from the theoretical
simulations. We analyzed the correlations between observations and
theoretical modeling and as a results we estimated the different
physical parameters of the prominence plasma.

---------------------------------------------------------
Title: Multi-spacecraft observation of a magnetic cloud
Authors: de Lucas, Aline; Dal Lago, Alisson; Schwenn, Rainer; Clúa de
Gonzalez, Alicia L.; Marsch, Eckart; Lamy, Philippe; Damé, Luc; Curdt,
W.; Davila, J.; Defise, J. M.; Fineschi, S.; Heinzel, P.; Howard, R.;
Kuzin, S.; Schmutz, W.; Tsinganos, K.; Turck-Chièze, S.; Zhukov, A.
2010cosp...38.1921D Altcode: 2010cosp.meet.1921D
Classical externally-occulted coronagraphs are presently limited in
their performances by the distance between the external occulter and
the front objective. The diffraction fringe from the occulter and
the vignetted pupil which degrades the spatial resolution prevent
useful observa-tions of the white light corona inside typically 2-2.5
Rsun. Formation flying offers an elegant solution to these limitations
and allows conceiving giant, externally-occulted coronagraphs
us-ing a two-component space system with the external occulter on
one spacecraft and the optical instrument on the other spacecraft
at distances of hundred meters. Such an instrument has just been
selected by ESA to fly (by the end of 2013) on its PROBA-3 mission,
presently in phase B, to demonstrate formation flying. It will perform
both high spatial resolution imaging of the solar corona as well as
2-dimensional spectroscopy of several emission lines (in partic-ular
the forbidden line of FeXIV at 530.285 nm) from the coronal base out
to 3 Rsun using a Fabry-Perot interferometer. The classical design of
an externally-occulted coronagraph is adapted to the formation flying
configuration allowing the detection of the very inner corona as close
as 0.05 Rsun from the solar limb. By tuning the position of the occulter
spacecraft, it may even be possible to try reaching the chromosphere
and the upper part of the spicules. ASPIICS/PROBA-3 mission, payload
and scientific objectives are presented.

---------------------------------------------------------
Title: Prominence fine structures and corresponding differential
emission measures
Authors: Gunar, Stanislav; Heinzel, Petr; Anzer, Ulrich
2010cosp...38.2845G Altcode: 2010cosp.meet.2845G
We use the temperature and density structure resulting from multi-thread
prominence fine-structure models (consisting of individual 2D
vertical threads) to compute the differential emission measures
(DEM). We derive the DEM at various positions along the length of
the foremost thread of the multi-thread model and also for various
angles between the line-of-sight and the magnetic field. We compare
the calculated DEM values with those obtained by in-versions from
the observed intensities of the transition-region UV lines. We show
that the unresolved fine-structuring of quiescent prominences along a
particular line-of-sight has consid-erable effect on shape of the DEM
curve due to fracturing of the prominence-corona transition region into
many thin layers corresponding to individual prominence fine structures.

---------------------------------------------------------
Title: Photometric analysis of Ellerman bombs .
Authors: Berlicki, A.; Heinzel, P.; Avrett, E. H.
2010MmSAI..81..646B Altcode:
Observations of Ellerman bombs (EBs) show them as short-lived,
compact, and spatially localized emissions that are well observable
in the wings of the Halpha hydrogen line. The Halpha line profiles
of EBs are characterized by deep absorption at the line center and
enhanced emission in the wings with maximum around ± 1 Å from the
line center, fading beyond ± 5 Å. EBs may also be observed in the
chromospheric Ca II lines and in the UV as bright points often located
within active regions. Previous work suggests that EBs may be considered
as micro-flares and may contribute significantly to the heating of the
lower chromosphere in newly emerging magnetic flux regions. However,
it is still not clear at what height in the solar atmosphere the
emission of EBs originates. In our analysis we used observations of
EBs obtained in the Halpha line with the Dutch Open Telescope (DOT)
and in the UV range with the TRACE 1600 Å channel. These one-hour
long simultaneous sequences obtained with high temporal and spatial
resolution were used to analyze the relation between the emission in
the Halpha line and at 1600 Å. The observations show fast variations of
EB emission in both channels. Comparison between the observed emission
in Halpha and at 1600 Å and theoretical calculations allowed us to
draw conclusions about the vertical structure of EBs.

---------------------------------------------------------
Title: Solar quiescent prominences. Filamentary structure and
energetics
Authors: Heinzel, P.; Anzer, U.; Gunár, S.
2010MmSAI..81..654H Altcode:
We present a first attempt to solve the non-LTE radiative-transfer
problem within a 2D numerical domain consisting of several randomly
distributed vertical threads. This represents a starting point
to simulate mutual radiative interaction between such prominence
threads. The second part of the paper presents our new results which
concern the radiative equilibrium in prominences and in their fine
structure. We show that adding the non-hydrogenic radiative losses
significantly lowers the central equilibrium temperatures. To match the
observed temperatures, an additional heating seems to be unavoidable.

---------------------------------------------------------
Title: RMHS Modeling of Solar Prominences
Authors: Heinzel, P.
2009AIPC.1171..331H Altcode:
In 1976 J. Heasley and D. Mihalas published a seminal paper devoted
to the modeling of solar prominences. They applied their stellar
atmospheric code based on the novel complete linearization method to
model the radiation-magnetohydrostatic (RMHS) coupling in prominences,
to solve the multilevel transfer problem for a mixture of hydrogen
and helium and to investigate the prominence energy balance. Their
results served as a benchmark for future developments in this
field and today, 33 years after that, we would like to show how
significantly they influenced the current research. With the link
to this pioneering work, we will discuss recent progress in the RMHS
modeling of solar prominences, focused on multidimensional/multithread
radiative transfer, coupling of non-LTE transfer to MHS, the importance
of partial redistribution for interpreting strong UV lines etc. New
light was shed recently on the issues of energy balance, again having
a direct link to the 1976 paper.

---------------------------------------------------------
Title: Response of optical hydrogen lines to beam heating. I. Electron
beams
Authors: Kašparová, J.; Varady, M.; Heinzel, P.; Karlický, M.;
Moravec, Z.
2009A&A...499..923K Altcode: 2009arXiv0904.2084K
Context: Observations of hydrogen Balmer lines in solar flares remain an
important source of information on flare processes in the chromosphere
during the impulsive phase of flares. The intensity profiles of
optically thick hydrogen lines are determined by the temperature,
density, and ionisation structure of the flaring atmosphere, by the
plasma velocities and by the velocity distribution of particles in
the line formation regions. Aims: We investigate the role of
non-thermal electrons in the formation regions of Hα, Hβ, and Hγ
lines in order to unfold their influence on the formation of these
lines. We concentrate on pulse-beam heating varying on a subsecond
timescale. Furthermore, we theoretically explore possibility that a new
diagnostic tool exists indicating the presence of non-thermal electrons
in the flaring chromosphere based on observations of optical hydrogen
lines. Methods: To model the evolution of the flaring atmosphere
and the time-dependent hydrogen excitation and ionisation, we used a
1-D radiative hydrodynamic code combined with a test-particle code that
simulates the propagation, scattering, and thermalisation of a power-law
electron beam in order to obtain the flare heating and the non-thermal
collisional rates due to the interaction of the beam with the hydrogen
atoms. To not bias the results by other effects, we calculate only
short time evolutions of the flaring atmosphere and neglect the plasma
velocities in the radiative transfer. Results: All calculated
models have shown a time-correlated response of the modelled Balmer line
intensities on a subsecond timescale, with a subsecond timelag behind
the beam flux. Depending on the beam parameters, both line centres
and wings can show pronounced intensity variations. The non-thermal
collisional rates generally result in an increased emission from a
secondary region formed in the chromosphere. Conclusions: Despite
the clear influence of the non-thermal electron beams on the Balmer line
intensity profiles, we were not able on the basis of our simulations
to produce any unambiguous diagnostic of non-thermal electrons in the
line-emitting region, which would be based on comparison of individual
Balmer line intensity profiles. However, fast line intensity variations,
well-correlated with the beam flux variations, represent an indirect
indication of pulsating beams.

---------------------------------------------------------
Title: Examples of Science Cases and Requirements for EST
Authors: Sobotka, M.; Heinzel, P.; Kašparová, J.
2009ASPC..405..455S Altcode:
We present various suggestions for the study of flares (fast emission
variations, heating mechanisms), prominences (fine structure, magnetic
field, energy balance), and sunspots (umbral structure, heating
mechanisms, depth and structure of the penumbra, Evershed flow). From
these cases we derive the requirements for the future European Solar
Telescope: spectropolarimetric capabilities, high signal-to-noise ratio,
multi-line spectroscopy, high spatial and temporal resolution.

---------------------------------------------------------
Title: Oscillatory phenomena in a solar network region
Authors: Tsiropoula, Georgia; Tziotziou, Kostas; Schwartz, Pavol;
Heinzel, Petr
2009IAUS..257..181T Altcode:
We examine oscillatory phenomena in a solar network region from
multi-wavelength, observations obtained by the ground-based Dutch
Open Telescope (DOT), and by instruments on the spacecraft Solar and
Heliospheric Observatory (SoHO). The observations were obtained during
a coordinated observing campaign on October 14, 2005. The temporal
variations of the intensities and velocities in two distinct regions of
the quiet Sun were investigated: one containing several dark mottles
and the other several bright points defining the network boundaries
(NB). The aim is to find similarities and/or differences in the
oscillatory phenomena observed in these two regions and in different
spectral lines formed from the chromosphere to the transition region,
as well as propagation characteristics of waves.

---------------------------------------------------------
Title: Multiwavelength analysis of a solar quiet region
Authors: Tsiropoula, G.; Tziotziou, K.; Schwartz, P.; Heinzel, P.
2009A&A...493..217T Altcode:
Context: We examine oscillatory phenomena in a solar network region
from multi-wavelength observations obtained by the ground-based Dutch
Open Telescope (DOT) and by the Coronal Diagnostic Spectrometer (CDS)
on the spacecraft Solar and Heliospheric Observatory (SoHO). The
observations were obtained during a coordinated observing campaign in
October 2005. Aims: We investigate the temporal variations of the
intensities and the velocities in two distinct regions of the quiet Sun,
one containing several dark mottles and the other several bright points
defining the network boundaries (NB). The aim is to find similarities
and/or differences in the oscillatory phenomena observed in these two
regions and in different spectral lines formed from the chromosphere
to the transition region, as well as the propagation characteristics
of waves. Methods: Intensity and velocity variations are
studied with wavelet and phase difference analyses. Results:
Both regions (i.e. mottles and NB) show a periodicity of ~5 min in all
considered lines. The V-V phase differences in the NB region point to
an upward propagation of waves; in the region of mottles, for periods
of 250-400 s, the phase difference is mainly negative, which suggests
a downward propagation, in turn indicating a refraction of waves from
the inclined magnetic field of mottles along the line-of-sight. Conclusions: The phase differences at the NB arise from a predominance
of upward propagating waves. In the mottles' region, the negative phase
differences we found suggest that propagating waves encounter a boundary
and are refracted and reflected. Of course, several limitations exist
in the exact interpretation of the phase differences, e.g. the complex
topology of the magnetic field, the formation conditions and heights
of the examined spectral lines, and the low spatial resolution.

---------------------------------------------------------
Title: Far-IR and Radio Thermal Continua in Solar Flares
Authors: Kašparová, J.; Heinzel, P.; Karlický, M.; Moravec, Z.;
Varady, M.
2009CEAB...33..309K Altcode: 2009arXiv0901.3465K
With the invention of new far-infrared (FIR) and radio mm and sub-mm
instruments (DESIR on SMESE satellite, ESO-ALMA), there is a growing
interest in observations and analysis of solar flares in this so far
unexplored wavelength region. Two principal radiation mechanisms play a
role: the synchrotron emission due to accelerated particle beams moving
in the magnetic field and the thermal emission due to the energy deposit
in the lower atmospheric layers. In this contribution we explore the
time-dependent effects of beams on thermal FIR and radio continua. We
show how and where these continua are formed in the presence of time
dependent beam heating and non-thermal excitation/ionisation of the
chromospheric hydrogen plasma.

---------------------------------------------------------
Title: Electron Densities in Quiescent Prominences Derived from
Eclipse Observations
Authors: Jejčič, S.; Heinzel, P.
2009SoPh..254...89J Altcode:
We develop a diagnostic tool for determination of the electron
densities in solar prominences using eclipse data. The method is based
on analysis of the hydrogen Balmer-line intensities (namely Hα and
Hβ) and the white-light emission due to Thomson scattering on the
prominence electrons. Our approach represents a generalization of
the ratio method already used by Koutchmy, Lebecq, and Stellmacher
(Astron. Astrophys.119, 261, 1983). In this paper we use an extended
grid of non-LTE prominence models of Gouttebroze, Heinzel, and Vial
(Astron. Astrophys. Suppl. Ser.99, 513, 1993) and derive various
useful relations between prominence radiation properties and electron
densities. Simultaneously, an effective geometrical thickness of the
prominence can also be obtained. As an example we apply our general
technique to original eclipse data of Koutchmy, Lebecq, and Stellmacher
(Astron. Astrophys.119, 261, 1983). Finally, we use our results to
determine the color of prominences as it should be seen during total
eclipses.

---------------------------------------------------------
Title: On Lyman-line asymmetries in quiescent prominences
Authors: Gunár, S.; Heinzel, P.; Anzer, U.; Schmieder, B.
2008A&A...490..307G Altcode:
Aims: We study the asymmetries of the synthetic hydrogen Lyman
lines and the process responsible for their formation. Methods: To obtain the synthetic Lyman line profiles, we use a
multi-thread prominence fine-structure model consisting of identical
2D threads. The 2D thread models are in MHS equilibrium, include an
empirical prominence-corona transition region, and solve consistently
2D non-LTE radiative transfer. Each thread of the multi-thread model
has a randomly assigned line-of-sight (LOS) velocity. Results:
The synthetic Lyman spectrum obtained by multi-thread modelling
exhibits substantial asymmetries of the line profiles, even though
the LOS velocities of individual threads are only of the order of 10
km s-1. Moreover, our results indicate that the synthetic
Lyman-α profiles may exhibit an opposite asymmetry to that of the
higher Lyman lines. Conclusions: The presence and behaviour
of the asymmetrical profiles of the synthetic Lyman lines agree with
observed profiles acquired by SUMER. Appendix A is only available
in electronic form at http://www.aanda.org

---------------------------------------------------------
Title: NLTE modelling of the flaring atmosphere above sunspot
Authors: Berlicki, A.; Heinzel, P.; Schmieder, B.; Li, H.
2008A&A...490..315B Altcode:
Aims: We performed an analysis of the solar flaring atmosphere above
sunspots. During the flare on October 20, 2003 many flaring structures
were observed projected onto the sunspots. We analysed the Hα and
Ca II line profiles emitted by the ribbons partially overlapping the
sunspots. In the penumbra, the line intensity in the far wings is lower
than in a typical quiet Sun profile but the core emission of Hα and
Ca II lines is typical for flares. We tried to find the structure of
the flare observed above the sunspot penumbra using the observations
of these chromospheric line profiles. Methods: NLTE radiative
transfer techniques allowed us to model the atmosphere of flaring
structures and fit both the synthetic Hα and Ca II line profiles to
the observed ones. We have derived semiempirical models of the flaring
structure observed above sunspots. Results: Our analysis shows
that the flare emission observed within the sunspot penumbra comes from
geometrically thin loop-like structures (cool flare loops) located
above the fibrils of the penumbra. The structure of the penumbra
located below the flare is almost not affected by the flare i.e. the
flare emission in Hα and Ca II comes not from the upper chromosphere
but from the structures that are higher in the corona. Therefore, a
two-component modelling is necessary to reproduce the flare emission
above the sunspot penumbra detected in our observations.

---------------------------------------------------------
Title: Hinode, TRACE, SOHO, and Ground-based Observations of a
Quiescent Prominence
Authors: Heinzel, P.; Schmieder, B.; Fárník, F.; Schwartz, P.;
Labrosse, N.; Kotrč, P.; Anzer, U.; Molodij, G.; Berlicki, A.;
DeLuca, E. E.; Golub, L.; Watanabe, T.; Berger, T.
2008ApJ...686.1383H Altcode:
A quiescent prominence was observed by several instruments on
2007 April 25. The temporal evolution was recorded in Hα by the
Hinode SOT, in X-rays by the Hinode XRT, and in the 195 Å channel by
TRACE. Moreover, ground-based observatories (GBOs) provided calibrated
Hα intensities. Simultaneous extreme-UV (EUV) data were also taken by
the Hinode EIS and SOHO SUMER and CDS instruments. Here we have selected
the SOT Hα image taken at 13:19 UT, which nicely shows the prominence
fine structure. We compare this image with cotemporaneous ones taken
by the XRT and TRACE and show the intensity variations along several
cuts parallel to the solar limb. EIS spectra were obtained about half
an hour later. Dark prominence structure clearly seen in the TRACE and
EIS 195 Å images is due to the prominence absorption in H I, He I,
and He II resonance continua plus the coronal emissivity blocking due
to the prominence void (cavity). The void clearly visible in the XRT
images is entirely due to X-ray emissivity blocking. We use TRACE, EIS,
and XRT data to estimate the amount of absorption and blocking. The
Hα integrated intensities independently provide us with an estimate of
the Hα opacity, which is related to the opacity of resonance continua
as follows from the non-LTE radiative-transfer modeling. However,
spatial averaging of the Hα and EUV data have quite different natures,
which must be taken into account when evaluating the true opacities. We
demonstrate this important effect here for the first time. Finally,
based on this multiwavelength analysis, we discuss the determination
of the column densities and the ionization degree of hydrogen in
the prominence.

---------------------------------------------------------
Title: Modelling of the Flare Observed Above Sunspot Penumbra
Authors: Berlicki, A.; Heinzel, P.; Schmieder, B.; Li, H.
2008ESPM...12.3.19B Altcode:
The solar flaring atmosphere above sunspot observed during the event
on October 20, 2003 was analysed. Many flaring structures were visible
in projection onto the sunspot penumbra. We analysed the H? and Ca
II line profiles emitted by the ribbons partially overlapping the
sunspots. These observations were performed with the Multi-channel
Infrared Solar Spectrograph (MISS) at Purple Mountain Observatory (PMO,
China). In the sunspot penumbra, the line intensity in far wings
is lower than in a typical quiet-Sun profile but in the line centre
the intensity of H? and Ca II lines is typical for flares. Using 1D
approximation we tried to find the vertical structure of the flare
observed above sunspot penumbra using the observations of these
chromospheric line profiles. NLTE radiative transfer techniques
allowed us to model the atmosphere of flaring structures and fit both
the synthetic H? and Ca II line profiles to the observed ones. We
have determined semiempirical models of the flaring structure observed
above sunspots. In our analysis we showed that the flare emission
observed within sunspot penumbra comes from geometrically thin loop-like
structures located above the fibrils of the penumbra. The structure
of the penumbra located below the flare is almost not affected by
the flare. The flare emission in chromospheric lines comes not from
the upper chromosphere but from the structures located higher in the
corona. Therefore, we performed two-component modelling which well
reproduce the flare emission above sunspot penumbra. In our model of
the flaring layer we included the transition region which is necessary
to obtain agreement between the observed and calculated line profiles.

---------------------------------------------------------
Title: Hydrogen Balmer Lines in the Solar Atmosphere Heated by
Electron Beams
Authors: Kasparova, J.; Varady, M.; Moravec, Z.; Heinzel, P.;
Karlicky, M.
2008ESPM...12.3.16K Altcode:
Accelerated particle beam are one of the mechanisms of the flare
energy transport from the corona to the transition region and the
chromosphere. Such beams heat ambient plasma and may affect atomic
population via collisions. Using 1D NLTE radiative hydrodynamics
we model influence of electron beams on hydrogen Balmer lines. In
the contribution we focus on the effect of so-called non-thermal
collisional rates on Halpha and Hbeta lines. Based on our results we
discuss diagnostic methods for determination of beam presence in the
formation regions of Halpha and Hbeta lines.

---------------------------------------------------------
Title: Understanding the Solar Chromosphere
Authors: Heinzel, P.
2008AIPC.1043..238H Altcode:
We discuss the latest high-resolution ground and space-based
observations of the solar chromosphere and their relevance to problems
of chromospheric modeling. In particular, we briefly review recent as
well as previous attempts to understand the solar chromosphere as the
atmospheric layer with an apparently increasing temperature. Various
heating mechanisms are also mentioned.

---------------------------------------------------------
Title: Prominence and its Coronal Cavity Observed by Hinode, TRACE
and SOHO
Authors: Schmieder, B.; Heinzel, P.; Schwartz, P.; Gunar, S.
2008ESPM...12.2.95S Altcode:
We will first give a definition of what is a prominence according to
the glossary of Solar Physicists. A prominence is a filament observed
at the limb. A filament lies over the inversion line of photospheric
longitudinal magnetic field and is supported in dips of horizontal
magnetic field lines. Recent models of flux tubes prove that fine
structures of prominences could be represented by vertical structures
embedded in dips of horizontal field lines. Observations of a
prominence observed in H? by Hinode/SOT and the solar tower of Meudon
show a very high dynamic nature. SUMER spectra in Lyman series show
no reverse profiles indicating a large prominence corona transition
region. This prominence is surrounded by a large coronal cavity
as show spatial telescopes (TRACE, XRT). These results will be
discussed in term of different formation models.

---------------------------------------------------------
Title: Far-IR and Radio Continua in Solar Flares
Authors: Heinzel, P.; Kasparova, J.; Varady, M.; Karlicky, M.;
Moravec, Z.
2008ESPM...12.3.20H Altcode:
With the invention of new far-infrared (FIR) and radio mm and sub-mm
instruments (DESIR on SMESE satellite, ESO ALMA), there is a growing
interest in observations and analysis of solar flares in this so far
unexplored wavelength region. Two principal radition mechanisms play a
role: the synchrotron emission due to accelerated particle beams moving
in the magnetic field and the thermal emission due to energy deposit
in the lower atmospheric layers. The latter one was recently explored
for the case of semiempirical flare models, without considering the
temporal evolution. However, as the radiation-hydrodynamical simulations
do show, the lower atmosphere heated by beams exhibits fast temporal
changes which are typically reflected in variations of spectral-line
intensities. In this contribution we explore the time-dependent effects
of beams on FIR and radio continua. We show how and where these
continua are formed in the presence of time dependent beam heating
and non-thermal excitation/ionization of the chromospheric hydrogen
plasma. Our results should contribute to planning of new observations
in FIR and radio domain.

---------------------------------------------------------
Title: Influence of Seeing on Cloud Model Parameters Obtained from
Hα Observations
Authors: Tziotziou, K.; Tsiropoula, G.; Heinzel, P.
2008ASPC..397...63T Altcode:
We study the influence of atmospheric seeing due to terrestrial
atmospheric turbulence on cloud model parameters obtained from Hα
observations with Beckers' cloud model. The analysis indicates that
atmospheric seeing does not affect the velocity determination, but
does influence significantly the determination of the Doppler width
when velocity gradients are present, and hence, the determination of
the temperature, while the optical thickness and source function are
also quantitatively affected, especially for high values of atmospheric
seeing.

---------------------------------------------------------
Title: On Lyman-line Asymmetries in Quiescent Prominences
Authors: Gunár, S.; Heinzel, P.; Anzer, U.; Schmieder, B.
2008ESPM...12.3.18G Altcode:
We present a new study of the asymmetries of synthetic hydrogen Lyman
line profiles and suggest the mechanism of their formation. In
order to obtain the synthetic Lyman line profiles, we use multi-thread
prominence fine-structure model consisting of identical vertical
2D threads. The 2D thread models are in magnetohydrostatic (MHS)
equilibrium, include an empirical prominence-corona transition
region (PCTR) and consistently solve the 2D non-LTE radiative
transfer. Individual threads of the multi-thread fine-structure model
have a randomly assigned LOS velocities. The synthetic Lyman
spectrum obtained by our multi-thread modelling exhibits substantial
asymmetries of the line profiles even thought the LOS velocities
of individual threads are only of the order of 10 km s-1. Moreover,
our results show that the synthetic Lyman-? profiles may exhibit an
opposite asymmetry as compared to higher Lyman lines. These results are
in agreement with the observed Lyman line profiles from SOHO/SUMER. The presence and the behaviour of the asymmetrical profiles of the
synthetic Lyman spectrum is in agreement with observed profiles taken
by SUMER.

---------------------------------------------------------
Title: Eclipse Observations of Quiescent Prominences
Authors: Jejcic, S.; Heinzel, P.; Kotrc, P.; Druckmuller, M.
2008ESPM...12.2.66J Altcode:
In this study we demonstrate how to analyze the solar eclipse data
taken by a digital camera. We use the observations of a quiescent
prominence obtained during the total solar eclipse on March 29, 2006
(Side, Turkey). Using the RGB signal of the white light emission
and co-temporal H? spectra taken at Ondrejov Observatory, we derive
the electron density, temperature and geometrical thickness of the
studied prominence.

---------------------------------------------------------
Title: Solar Prominence Diagnostic with Hinode/EIS
Authors: Labrosse, N.; Schmieder, B.; Heinzel, P.; Gunar, S.
2008ESPM...12.2.21L Altcode:
We report here on observations of a solar prominence obtained on 26
April 2007 using the Extreme Ultraviolet Imaging Spectrometer (EIS)
on Hinode. Selected profiles for lines with formation temperatures
between log(T)=4.7 and log(T)=6.3 are given and are used to explain
the existence of dark features in the raster images. We estimate
the contribution of the He II 256.32 Å line in the raster image at
256 Å in the prominence region. We compare the observed prominence
profiles with theoretical profiles from non-LTE radiative transfer
models and deduce the contribution of resonant scattering in the He
II 256 Å emission.

---------------------------------------------------------
Title: Contrast of Fine-scale Structures in a Quiet Sun Network Region
Authors: Schwartz, P.; Tziotziou, K.; Heinzel, P.; Tsiropoula, G.
2008ESPM...12.2.35S Altcode:
We study the contrast of fine structures (mottles), found in a quiet-Sun
network region and close to a filament, observed by the SOHO/SUMER
spectrograph. The observations were made during August 29 -- 30, 1996,
in several chromospheric, transition-region and coronal EUV lines. The
contrasts of the fine-scale structures were obtained in the different
spectral lines and compared to find whether they have any dependence
on the inclination of the magnetic field lines and the line formation
height. Also contributions of the absorption and emissivity blocking
to the depression of brightness in these fine-scale structures are
studied by comparing the observations in transition-region lines
with wavelengths above and below 912 A (the head of the hydrogen
Lyman continuum).

---------------------------------------------------------
Title: Oscillatory Phenomena in a Solar Network Region
Authors: Tziotziou, K.; Tsiropoula, G.; Schwartz, P.; Heinzel, P.
2008ESPM...12.2.41T Altcode:
Multi-wavelength, multi-instrument observations, obtained during a
coordinated observing campaign on October 2005 by the ground-based
Dutch Open Telescope (DOT), and by instruments on the spacecraft Solar
and Heliospheric Observatory (SoHO) and Transition Region and Coronal
Explorer (TRACE), are used to study oscillatory phenomena in a solar
network region. Temporal variations of the intensities and velocities
in a region of the quiet Sun containing several dark mottles and in a
region with several bright points defining the network boundaries (NB)
are investigated with the aim of finding similarities and/or differences
in the oscillatory phenomena observed in these two regions and in
different spectral lines formed from the chromosphere to the transition
region, as well as propagation characteristics of waves. A wavelet,
phase difference and coherence analyses were performed indicating a
periodicity around 5 min in all considered lines for both regions. V-V
phase differences in the NB region point to an upward propagation of,
most probably, acoustic waves, while in the region of mottles they
indicate a non vertical propagation of waves, due to the presence
of several inclined mottles along the line-of-sight. In mottles, for
periods of 250-400 s the phase difference is mainly negative suggesting
that propagating waves encounter a boundary and are refracted and
reflected. However, limitations arising from the complex topology
of the magnetic field, the formation conditions and heights of the
examined spectral lines and the low spatial resolution of the space
instruments influence the exact interpretation of the phase differences.

---------------------------------------------------------
Title: Prominence modelling: from observed emission measures to
temperature profiles
Authors: Anzer, U.; Heinzel, P.
2008A&A...480..537A Altcode:
Aims:We outline the construction of prominence - corona transition
region models based upon the observations of one particular
prominence. Methods: The differential emission measure curves from
observations were approximated by simple analytical functions. On this
basis we constructed the temperature curve and calculated the radiative
losses, the gains by thermal conduction, and some estimates for the
wave heating. Results: The temperature curve was calculated in
the range between 23 000 K and 450 000 K. The resulting transition
region can be divided into an inner region where the temperature is
low and the radiative losses are very large, a part with a very steep
temperature rise from 40 000 K to around 250 000 K over a width of only
500 km, and an extended high temperature region. Both the conductive
heating and our estimates for a possible wave cooling/heating peak very
sharply in the region with the very large temperature gradient. The
consequences for the energy balance are discussed.

---------------------------------------------------------
Title: Modelling of Optical Emission in Solar Flares
Authors: Varady, M.; Kašparová, J.; Heinzel, P.; Karlický, M.;
Moravec, Z.
2008CEAB...32..101V Altcode:
We present recent progress achieved by our group in the field of flare
optical emission modelling. We concentrate on two problems. Firstly,
on the possibility of modelling of the time evolution of several Balmer
line profiles calculated for real electron fluxes obtained from the hard
X--ray observations of a particular flare with the prospect to compare
the theoretical results with the observed data for the corresponding
flare. Secondly, we discuss the influence of the non--thermal electrons
in the line emitting region on the formation and time evolution of
Balmer hydrogen line profiles.

---------------------------------------------------------
Title: Multi-wavelength Analysis of a Solar Network Region
Authors: Tsiropoula, G.; Tziotziou, K.; Schwartz, P.; Heinzel, P.
2008CEAB...32..109T Altcode:
We analyse co-temporal observations of a network region found near
the solar disc centre, obtained by the Dutch Open Telescope (DOT)
and the Coronal Diagnostic Spectrometer (CDS) on-board SOHO during a
coordinated observing campaign in October 2005. DOT obtained images in
5 wavelengths along the ha\ profile, while CDS obtained sit-and-stare
observations in several EUV spectral lines that span the upper solar
atmosphere. After fitting the CDS spectral line profiles we obtained
2-D space-time maps of intensities, Doppler velocities and Doppler
widths. We study the appearance of the network region in the different
spectral lines and the temporal variations of the obtained physical
parameters. We employ a wavelet analysis to examine the existence of
oscillations at the network in the different solar layers.

---------------------------------------------------------
Title: Limb Prominences Seen in UV, EUV and SXR
Authors: Heinzel, P.; Fárník, F.; Anzer, U.; Dammasch, I.
2007ASPC..369..279H Altcode:
We use SOHO/SUMER, EIT and Yohkoh/SXT prominence observations to study
the absorption and/or volume blocking of UV, EUV and SXR coronal
radiation by cool prominence plasma. An example of such a complex
behaviour is the limb prominence observed on 5 September 1996. The
SUMER spectrograph has detected two coronal lines, MgX at 625 Å,
which is absorbed by the hydrogen Lyman continuum and blocked within
a volume occupied by cool prominence plasma, and FeXII at 1242 Å,
where the prominence appears dark due to blocking (no absorption at
this wavelength). A similar behaviour show also the EUV images taken by
EIT. We find that a darkening similar to that detected in the FeXII line
is quite well visible also in the SXR images obtained by Yohkoh/SXT. To
explain this feature, we exclude the absorption by the HeI and HeII
resonance continua (hydrogen absorption is quite negligible) and suggest
that it is entirely due to the volume blocking. Based on a quantitative
analysis of these data, we discuss the physical conditions in cool
prominences and their coronal environment. Finally, we propose new
high-resolution EUV and SXR observations of prominences by Solar-B,
using the EUV imaging spectrometer (EIS) and the X-ray telescope
(XRT), respectively.

---------------------------------------------------------
Title: Hydrogen Balmer line formation in solar flares affected by
return currents
Authors: Štepán, J. Å.; Kašparová, J.; Karlický, M.; Heinzel, P.
2007A&A...472L..55S Altcode: 2007arXiv0708.0265S
Aims:We investigate the effect of the electric return currents in
solar flares on the profiles of hydrogen Balmer lines. We consider the
monoenergetic approximation for the primary beam and runaway model of
the neutralizing return current. Methods: Propagation of the
10 keV electron beam from a coronal reconnection site is considered
for the semiempirical chromosphere model F1. We estimate the local
number density of return current using two approximations for beam
energy fluxes between 4 × 1011 and 1 × 1012
erg cm-2 s-1. Inelastic collisions of beam and
return-current electrons with hydrogen are included according to their
energy distributions, and the hydrogen Balmer line intensities are
computed using an NLTE radiative transfer approach. Results:
In comparison to traditional NLTE models of solar flares that neglect
the return-current effects, we found a significant increase emission
in the Balmer line cores due to nonthermal excitation by return
current. Contrary to the model without return current, the line
shapes are sensitive to a beam flux. It is the result of variation
in the return-current energy that is close to the hydrogen excitation
thresholds and the density of return-current electrons.

---------------------------------------------------------
Title: Influence of seeing effects on cloud model inversions
Authors: Tziotziou, K.; Heinzel, P.; Tsiropoula, G.
2007A&A...472..287T Altcode:
Context: Atmospheric seeing due to terrestrial atmospheric turbulence
is a process that distorts solar ground-based observations. Aims: We study the influence of atmospheric seeing on Hα cloud
model inversions. Methods: We use Beckers' cloud model which
assumes a constant source function to obtain physical parameters from
observed quiet-Sun Hα profiles, and profiles convolved with a Gaussian
point spread function that simulates the effect of atmospheric seeing
on solar observations. Results: Our analysis indicates that
atmospheric seeing does not affect the velocity determination, but
does influence significantly the determination of the Doppler width
when velocity gradients are present, and hence, the determination of
the temperature, while the optical thickness and source function are
also quantitatively affected, especially for high values of atmospheric
seeing. Conclusions: The effects of atmospheric seeing on cloud
model inversions also depend on the actual size of the structures
under study. For the presented observations, the derived cloud model
parameter distributions do not change significantly for atmospheric
seeing up to ∼0.5”.

---------------------------------------------------------
Title: Properties of prominence fine-structure threads derived from
SOHO/SUMER hydrogen Lyman lines
Authors: Gunár, S.; Heinzel, P.; Schmieder, B.; Schwartz, P.;
Anzer, U.
2007A&A...472..929G Altcode:
Context: The SOHO/SUMER observations provide us for the first time with
the prominence spectra in the Lyman-α line outside the attenuator
together with the higher members of the hydrogen Lyman series. Aims: We derive the prominence fine-structure thread properties
by comparing the SOHO/SUMER hydrogen Lyman series observations with
the synthetic Lyman lines. Methods: To obtain the synthetic
profiles of the Lyman lines, we used 2D prominence fine-structure
thread models with a PCTR and consistently solved the 2D non-LTE
multilevel radiative transfer. The trial-and-error method was applied
to find the model with the best agreement between the synthetic Lyman
line profiles and the observed ones. Results: The properties of
the resulting model with the best match of the synthetic and observed
line profiles are central (minimum) temperature T0 = 7000
K, maximum column mass in the centre of the thread M0 =
1.1×10-4 g cm-2, horizontal field strength in
the middle of the thread Bx(0) = 6 Gauss and the boundary
pressure p0 = 0.015 dyn cm-2. Conclusions:
The Lyman line profiles observed by SOHO/SUMER can be better reproduced
by using multi-thread models consisting of a set of the 2D prominence
fine-structure threads placed perpendicularly to the line-of-sight,
rather than with the single-thread model.

---------------------------------------------------------
Title: Is the magnetic field in quiescent prominences force-free?
Authors: Anzer, U.; Heinzel, P.
2007A&A...467.1285A Altcode:
Aims:We describe under which conditions the magnetic fields of quiescent
prominences are force-free and under which gravity plays the dominant
role. Methods: The existing observational determinations of the
magnetic field are summarised and the calculation of the plasma β
is outlined. We derive the dependence of β on the prominence weight
and the field strength. Results: We show that in many cases of
well-developed quiescent prominences the field can deviate substantially
from the force-free situation and gravity fully determines the structure
of the magnetic dips.

---------------------------------------------------------
Title: Hα with Heating by Particle Beams
Authors: Kašparová, J.; Varady, M.; Karlický, M.; Heinzel, P.;
Moravec, Z.
2007ASPC..368..441K Altcode: 2007astro.ph..3800K
Using 1D NLTE radiative hydrodynamics we model the influence of the
particle beams on the Hα line profile treating the beam propagation and
the atmosphere evolution self-consistently. We focus on the influence
of the non-thermal collisional rates and the return current. Based on
our results, we propose a diagnostic method for determination of the
particle beam presence in the formation regions of the Hα line.

---------------------------------------------------------
Title: Prominence Parameters from 2D Modeling of Lyman Lines Measured
with SUMER
Authors: Gunár, S.; Heinzel, P.; Schmieder, B.; Anzer, U.
2007ASPC..368..317G Altcode:
We present SOHO/SUMER observations of a solar prominence in the hydrogen
Lyman series lines and compare the line profiles with the synthetic
ones obtained using our 2D prominence modeling. The observations
contain the Ly-β, Ly-γ, and Ly-δ lines on 25 May 2005. In
order to derive the prominence parameters we used our 2D fine structure
models of vertical threads in magnetohydrostatic (MHS) equilibrium. By
varying the input model parameters (central temperature, boundary
pressure, magnetic field, central column mass and turbulent velocity)
we obtained a model having the synthetic Lyman line profiles in good
agreement with the observed ones. In this way we are able to determine
the structure of the magnetic dip and the thermodynamical parameters
in the observed prominence.

---------------------------------------------------------
Title: Multiwavelength Observations of Solar Prominences
Authors: Heinzel, P.
2007ASPC..370...46H Altcode:
We briefly review the multiwavelength observations of solar prominences
and filaments ranging from the infrared up to soft X-rays. We give
several examples of current observations and mention those specific to
the total solar eclipses. Our particular focus is on the ultraviolet
(UV) and extreme-UV images taken in various lines of different species.

---------------------------------------------------------
Title: The Physics of Chromospheric Plasmas
Authors: Heinzel, P.; Dorotovič, I.; Rutten, R. J.
2007ASPC..368.....H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Prominences on the Limb: Diagnostics with UV EUV Lines and
the Soft X-Ray Continuum
Authors: Anzer, U.; Heinzel, P.; Fárnik, F.
2007SoPh..242...43A Altcode:
In this paper we discuss the two mechanisms by which solar prominences
on the limb can manifest themselves when observed in coronal UV -
EUV lines and in the soft X-ray continuum. These mechanisms are the
absorption in the resonance continua of hydrogen and helium on one hand
and the reduction of the emissivity in a part of the coronal volume
occupied by a prominence on the other one. We briefly describe earlier
observations made with SOHO/SUMER, EIT and Yohkoh/SXT. We then discuss
how the instruments on the new Japanese satellite Hinode can be used
for more detailed studies of prominences. We also propose some combined
observations between the Hinode satellite and the SOHO/SUMER instrument.

---------------------------------------------------------
Title: Non-LTE Analysis of Lyman-Line Observations of a Filament
with SUMER
Authors: Schwartz, P.; Schmieder, B.; Heinzel, P.
2007ASPC..368..359S Altcode: 2007arXiv0704.3539S
We present non-LTE diagnostics of the filament observed by SOHO/SUMER
on May 27, 2005 in the whole Lyman series. The filament was situated
close to the disk center. The Lα observations were carried out with
normal voltage of detector A. The slit was placed at the central part
of the detector -- outside the Lα attenuator. Therefore, the observed
profiles of this line could be calibrated reliably.

---------------------------------------------------------
Title: Multi-wavelength Analysis of a Quiet Solar Region
Authors: Tsiropoula, G.; Tziotziou, K.; Giannikakis, J.; Young, P.;
Schühle, U.; Heinzel, P.
2007ASPC..368..171T Altcode: 2007arXiv0704.1592T
We present observations of a solar quiet region obtained by the
ground-based Dutch Open Telescope (DOT), and by instruments on the
spacecraft SOHO and TRACE. The observations were obtained during a
coordinated observing campaign on October 2005. The aim of this work
is to present the rich diversity of fine-scale structures that are
found at the network boundaries and their appearance in different
instruments and different spectral lines that span the photosphere
to the corona. Detailed studies of these structures are crucial to
understanding their dynamics in different solar layers, as well as
the role such structures play in the mass balance and heating of the
solar atmosphere.

---------------------------------------------------------
Title: Optical and UV Emission of Solar Flares: Multiwavelength
Observations and Modelling
Authors: Kasparova, J.; Heinzel, P.
2007AGUSMSH22A..07K Altcode:
Solar flares reveal themselves in various ranges of electromagnetic
emission and exhibit temporal variations down to sub-second scale,
namely during the so-called impulsive phase. This contribution will
focus on spatial and temporal variations of the optical and UV emissions
which are thought to be driven by flare energy transport in the form
of accelerated particles. We will review our current understanding
of the formation of optical and UV emissions during the impulsive
phase. Namely, we will discuss recent radiative-hydrodynamic models
and various physical processes playing an important role in radiation
transfer and formation of optical and UV spectra. We will also report on
recent interpretations of observations in various lines and continua and
discuss their importance for the diagnostics of the flare atmosphere
structure and the presence of accelerated particles in the emission
formation regions.

---------------------------------------------------------
Title: White-Light Emission of Solar Prominences
Authors: Jejčič, S.; Heinzel, P.
2007ASPC..368..325J Altcode:
Using an extended grid of prominence models we compute the prominence
white-light (WL) emission due to Thomson scattering and compare it
with that in Hα. The ratio of the WL emission and the total emission
can explain the color of prominences as observed during the total
eclipses and can tell us whether the pink color of prominences is due
to their intrinsic white-light emission or due to coronal contribution
at the prominence location. We also show how this ratio depends on
the prominence electron density, temperature and thickness.

---------------------------------------------------------
Title: The Fine Structure of Solar Prominences
Authors: Heinzel, P.
2007ASPC..368..271H Altcode: 2007arXiv0705.1464H
Solar prominences and filaments (prominences projected against the solar
disk) exhibit a large variety of fine structures which are well observed
down to the resolution limit of ground-based telescopes. We describe
the morphological aspects of these fine structures which basically
depend on the type of a prominence (quiescent or active-region). Then
we review current theoretical scenarios which are aimed at explaining
the nature of these structures. In particular we discuss in detail
the relative roles of magnetic pressure and gas pressure (i.e.,
the value of the plasma-β), as well as the dynamical aspects of
the fine structures. Special attention is paid to recent numerical
simulations which include a complex magnetic topology, energy balance
(heating and cooling processes), as well as the multidimensional
radiative transfer. Finally, we also show how new ground-based and
space observations can reveal various physical aspects of the fine
structures including their prominence-corona transition regions in
relation to the orientation of the magnetic field.

---------------------------------------------------------
Title: Hydrogen Hα line polarization in solar flares. Theoretical
investigation of atomic polarization by proton beams considering
self-consistent NLTE polarized radiative transfer
Authors: Štěpán, J.; Heinzel, P.; Sahal-Bréchot, S.
2007A&A...465..621S Altcode: 2007astro.ph..1617S
Context: We present a theoretical review of the effect of impact
polarization of a hydrogen Hα line due to an expected proton beam
bombardment in solar flares. Aims: Several observations indicate
the presence of the linear polarization of the hydrogen Hα line
observed near the solar limb above 5% and preferentially in the radial
direction. We theoretically review the problem of deceleration of the
beam originating in the coronal reconnection site due to its interaction
with the chromospheric plasma, and describe the formalism of the density
matrix used in our description of the atomic processes and the treatment
of collisional rates. Methods: We solve the self-consistent NLTE
radiation transfer problem for the particular semiempirical chromosphere
models for both intensity and linear polarization components of the
radiation field. Results: In contrast to recent calculations,
our results show that the energy distribution of the proton beam at Hα
formation levels and depolarizing collisions by background electrons
and protons cause a significant reduction of the effect below 0.1%. The
radiation transfer solution shows that tangential resonance-scattering
polarization dominates over the impact polarization effect in all
considered models. Conclusions: . In the models studied, proton
beams are unlikely to be a satisfying explanation for the observed
linear polarization of the Hα line.

---------------------------------------------------------
Title: Spectral Diagnostics of the Magnetic Field Orientation in a
Prominence Observed with SOHO/SUMER
Authors: Schmieder, B.; Gunár, S.; Heinzel, P.; Anzer, U.
2007SoPh..241...53S Altcode:
During several campaigns focused on prominences we have obtained
coordinated spectral observations from the ground and from space. The
SOHO/SUMER spectrometer allows us to observe, among others, the
whole Lyman series of hydrogen, while the Hα line was observed
by the MSDP spectrograph at the VTT. For the Lyman lines, non-LTE
radiative-transfer computations have shown the importance of the optical
thickness of the prominence - corona transition region (PCTR) and its
relation to the magnetic field orientation for the explanation of the
observed line profiles. Moreover, Heinzel, Anzer, and Gunár (2005,
Astron. Astrophys.442, 331) developed a 2D magnetostatic model of
prominence fine structures that demonstrates how the shapes of Lyman
lines vary, depending on the orientation of the magnetic field with
respect to the line of sight. To support this result observationally,
we focus here on a round-shaped filament observed during three days as
it was crossing the limb. The Lyman profiles observed on the limb are
different from day to day. We interpret these differences as being due
to the change of orientation of the prominence axis (and therefore the
magnetic field direction) with respect to the line of sight. The Lyman
lines are more reversed if the line of sight is across the prominence
axis as compared to the case when it is aligned along its axis.

---------------------------------------------------------
Title: Prominence fine structures in a magnetic
equilibrium. III. Lyman continuum in 2D configurations
Authors: Gunár, S.; Heinzel, P.; Anzer, U.
2007A&A...463..737G Altcode:
Aims:We discuss the behavior of the Lyman continuum profiles
studied on the grid of 2D vertical-thread models for prominence fine
structures. Methods: Multilevel non-LTE transfer calculations for
a 12-level plus continuum hydrogen model atom are used. Results:
Since the Lyman continuum is formed in regions with different
temperatures for different orientations between the magnetic field
direction and the line-of-sight, our Lyman continuum modeling, together
with additional information from Lyman lines, represents a very useful
tool for the determination of the thread structure. Conclusions:
.A comparison between our theoretical Lyman continuum models between
800 Å and 911 Å with the observed values shows that such a modeling
can give interesting new constraints on the temperature structure in
prominence threads.

---------------------------------------------------------
Title: Study of an extended EUV filament using SoHO/SUMER observations
of the hydrogen Lyman lines
Authors: Schwartz, P.; Heinzel, P.; Schmieder, B.; Anzer, U.
2006A&A...459..651S Altcode:
Context: .In previous work we determined the 3D structure of an
EUV extension of the filament observed by SoHO/CDS on 15 October
1999. The determination of the 3D structure depends on the optical
thickness τ912 at the hydrogen Lyman-continuum edge at
912 Å. The τ912 value was unknown, therefore it was taken
as a free parameter for the 3D-structure determinations. Aims:
.The plasma properties (including τ912) of this EUV filament
are estimated using non-LTE modelling of profiles of the hydrogen Lyman
lines. Methods: .The lines Lβ, Lδ, L ɛ, L6 and L7 were observed
by SoHO/SUMER with the slit positioned across the EUV filament. In our
modelling the EUV filament was approximated by a horizontal 1D slab with
constant pressure and the temperature decreasing vertically from the
edges to interior of the slab. The values of the geometrical thickness
of the slab in the EUV extension were taken from its 3D structure
determined for the τ912 values estimated iteratively. The
synthetic profiles were fitted to observed ones using the χ2
minimization. Results: .For the Hα-filament part we obtained
the expected results: a small geometrical thickness between several
thousand and 15 000 km, temperatures around 5000 K in the interior and
around 20 000 K in PCTRs, and pressure ~0.1~dyn~cm-2. That
leads to an optical thickness in the Hα line center larger than 1. In
the EUV extension, temperatures of 10 000-40 000 K in the interior
and 35 000-50 000 K in the vertically extended PCTRs and a pressure
of ~0.01~dyn~cm-2 were determined. Such large variations
of the temperature lead to large variations of τ912. 
Conclusions: .The EUV extension is inhomogeneous - areas both optically
thick and thin at 912 Å are present close to each other. Parts
optically thick at 912 Å are visible also in Hα as faint and tiny dark
structures around the very dark and well pronounced Hα filament. The
volume blocking mechanism is an important mechanism throughout the
whole EUV extension even in its optically thick parts. The absorption
dominates only in the Hα-filament part of the EUV filament.

---------------------------------------------------------
Title: Polarization Diagnostics of Proton Beams in Solar Flares
Authors: Stepan, J.; Heinzel, P.; Kasparova, J.; Sahal-Brechot, S.
2006IAUJD...1E..55S Altcode:
We review the problem of proton beam bombardment of solar chromosphere
considering the self-consistent NLTE polarized radiation transfer in
hydrogen lines. Several observations indicate a linear polarization
of H-alpha line of the order of 5% or higher and preferentially in
radial direction. This polarization is often explained as anisotropic
collisional excitation of the n= 3 level by vertical proton beams. Our
calculations indicate that deceleration of the proton beam with initial
power-law energy distribution together with increased electron and
proton densities in H-alpha forming layers lead to negligible line
polarization. Thus the proton beams seem not to be a good candidate
for explanation of the observed polarization degree.

---------------------------------------------------------
Title: Study of a Small-Scale Eruptive Event Observed by SOHO/SUMER
Authors: Tomasz, F.; Régnier, S.; Schwarz, P.; Rybák, J.; Kucera,
A.; Heinzel, P.; Curdt, W.; Wöhl
2006ESASP.617E..79T Altcode: 2006soho...17E..79T
No abstract at ADS

---------------------------------------------------------
Title: What We Have Learned about Prominences and Filaments from
SOHO/SUMER and CDS Spectral Observations
Authors: Heinzel, P.; Schmieder, B.; Vial, J. -C.
2006ESASP.617E..65H Altcode: 2006soho...17E..65H
No abstract at ADS

---------------------------------------------------------
Title: Hα Chromospheric Mottles and their UV/EUV Counterparts Seen
by SOHO/Sumer
Authors: Tziotziou, K.; Heinzel, P.; Tsiropoula, G.; Schühle, U.
2006ESASP.617E.112T Altcode: 2006soho...17E.112T
No abstract at ADS

---------------------------------------------------------
Title: Darkening of Coronal Lines by Limb Prominences Observed
by SOHO/SUMER
Authors: Dammasch, I. E.; Heinzel, P.; Anzer, U.
2006ESASP.617E..66D Altcode: 2006soho...17E..66D
No abstract at ADS

---------------------------------------------------------
Title: Importance of Absorption and Volume Blocking for Line Intensity
Depression in EUV Filaments
Authors: Schwartz, P.; Schmieder, B.; Heinzel, P.
2006ESASP.617E..75S Altcode: 2006soho...17E..75S
No abstract at ADS

---------------------------------------------------------
Title: Prominence Parameters Derived from Hydrogen Lyman-α Spectral
Profiles Measured by SOHO/SUMER
Authors: Gunár, S.; Teriaca, L.; Heinzel, P.; Schühle, U.
2006ESASP.617E..63G Altcode: 2006soho...17E..63G
No abstract at ADS

---------------------------------------------------------
Title: The Dynamics and Structure of the Solar Atmosphere As Obtained
from Combined SUMER/SOHO and TIP2/VTT Observations
Authors: Tomasz, F.; Régnier, S.; Schwartz, P.; Rybák, J.; Kucera,
A.; Heinzel, P.; Curdt, W.; Wöhl
2006ESASP.617E..78T Altcode: 2006soho...17E..78T
No abstract at ADS

---------------------------------------------------------
Title: New perspectives on prominences as observed by SOHO/SUMER
Authors: Schmieder, B.; Vial, J. -C.; Heinzel, P.
2006sf2a.conf..563S Altcode:
We summarize the results of our prominence and filament studies
based on extensive spectral observations with SOHO/SUMER and CDS
instruments. During the past decade we have gathered several sets
of UV and EUV spectral data, containing various emission lines of
different species. Our main objective was to better understand the
formation of hydrogen Lyman lines and continuum (using the results
of complex non-LTE transfer simulations). However we have also
analysed also UV and EUV lines formed under transition-region and
coronal conditions. Some highlights of our studies are: reproduction
of Lyman-line profiles with partial redistribution, understanding the
role of prominence-corona interface in the formation of Lyman-line
cores, establishing the effect of the magnetic-field orientation
on the shape of Lyman lines, discovery of EUV filament extensions
(invisible in the Hα line) and their explanation, reconstruction of
a 3D topology of the filament using EUV coronal lines, temperature
diagnostics based on measurements of the hydrogen Lyman continuum,
proper explanation of a prominence darkening detected in coronal lines.

---------------------------------------------------------
Title: On the Fine Structure of Solar Filaments
Authors: Heinzel, P.; Anzer, U.
2006ApJ...643L..65H Altcode:
High-resolution Hα images of solar filaments show a variety of
dark fine-structure fibrils, most of them aligned with the magnetic
field that is sheared with respect to the filament long axis. Here we
demonstrate how such fibrils can be explained in terms of the magnetic
field dips produced by realistic mass loading due to plasma condensation
along the top of a magnetic prominence arcade. Our interpretation is
supported by (2+1)-dimensional radiation-magnetohydrostatic simulations
that predict quantitatively the properties of such condensations that
are suspended in the dipped magnetic field.

---------------------------------------------------------
Title: A periodic arcade model for extended EUV filaments
Authors: Anzer, U.; Heinzel, P.
2006A&A...446..301A Altcode:
The extensions of Hα filaments that are observed in EUV spectral lines
require the presence of cool material in a large volume surrounding
these filaments. This material can only be supported by magnetic fields
with dips. Such dips can be generated by a sufficiently strong twisting
of magnetic flux tubes. In the present paper we have extended earlier
work to more realistic magnetic field configurations that are periodic
in the x-direction. We derived approximate equilibria for twisted
slender flux tubes and determined the region that contains dips. In
addition we investigated the effects on our models of the mass loading
due to a heavy prominence. Finally we compared our theoretical models
with the EUV - observations. We conclude that these types of models
are capable of explaining the basic features of the observations.

---------------------------------------------------------
Title: Prominence Fine Structures in Amagnetic Equilibrium: a Grid
Oftwo-Dimensional Models
Authors: Gunár, S.; Heinzel, P.; Anzer, U.
2005ESASP.600E..85G Altcode: 2005dysu.confE..85G; 2005ESPM...11...85G
No abstract at ADS

---------------------------------------------------------
Title: Multi-Wavelength Analysis of Plasma Flows during Solar Flares
Authors: Berlicki, A.; Schmieder, B.; Heinzel, P.; Li, H.; Del Zanna,
G.; Rudawy, P.
2005ESASP.600E..58B Altcode: 2005dysu.confE..58B; 2005ESPM...11...58B
No abstract at ADS

---------------------------------------------------------
Title: Physical Parameters of Dark Mottles Derived from High
Resolution Optical Spectra
Authors: Tsiropoula, G.; Tziotziou, K.; Schwartz, P.; Kotrč, P.;
Heinzel, P.
2005ESASP.600E..72T Altcode: 2005ESPM...11...72T; 2005dysu.confE..72T
No abstract at ADS

---------------------------------------------------------
Title: Non-Lte Modelling of the EUV Filament Based on Soho/sumer
Observations of the Hydrogen Lyman Lines
Authors: Schwartz, P.; Heinzel, P.; Schmieder, B.
2005ESASP.600E..97S Altcode: 2005dysu.confE..97S; 2005ESPM...11...97S
No abstract at ADS

---------------------------------------------------------
Title: Hα Line in Solar Atmosphere Heated by Particle Beams
Authors: Kašparová, J.; Varady, M.; Karlický, M.; Moravec, Z.;
Heinzel, P.
2005ESASP.600E.127K Altcode: 2005dysu.confE.127K; 2005ESPM...11..127K
No abstract at ADS

---------------------------------------------------------
Title: Prominence fine structures in a magnetic equilibrium. II. A
grid of two-dimensional models
Authors: Heinzel, P.; Anzer, U.; Gunár, S.
2005A&A...442..331H Altcode:
We construct a grid of 2D vertical-thread models for prominence fine
structures which are in magnetohydrostatic (MHS) equilibrium. Such
thread models have been described in a previous paper by Heinzel
&amp; Anzer (2001), but here we use a modified 2D transfer code with
an adaptive MHS grid. Multilevel non-LTE transfer calculations are
now performed for a 12-level plus continuum hydrogen model atom,
in order to study the behaviour of the Lyman-series lines observed
by SOHO/SUMER. Our grid consists of 18 models which cover a range of
central column masses, magnetic-field intensities and two parameters
characterising the 2D temperature structure of the thread. Since
different Lyman lines and their parts (line center, peak, wings) are
formed at different places within the thread, the Lyman series may
serve as a good diagnostic tool for thermodynamic conditions varying
from central cool parts to a prominence-corona transition region. We
demonstrate this behaviour for various lines, showing their synthetic
profiles as seen from two perpendicular directions along and across
the magnetic field lines, respectively, and displaying the respective
contribution functions. This study confirms our earlier conclusion
that the Lyman line profiles are much more reversed when seen across
the field lines, compared to those seen along the lines. The latter
can be even unreversed. We also show the geometrical cross-section
(shape) of all 18 models. Their thread-like shape with a considerable
aspect ratio resembles recent high-resolution Hα images. Finally,
we discuss the relation of our thread models to the vertical threads
studied by Fontenla et al. (1996, ApJ, 466, 496).

---------------------------------------------------------
Title: On the Nature of Dark Extreme Ultraviolet Structures Seen by
SOHO/EIT and TRACE
Authors: Anzer, U.; Heinzel, P.
2005ApJ...622..714A Altcode:
Spectral lines in the extreme ultraviolet (EUV) observed on the Sun
can originate either from the hot corona or the cooler chromosphere
to corona transition region. In the present paper we concentrate on
coronal lines and in particular on iron lines at 171, 195, and 284
Å, which have been frequently observed by the Solar and Heliospheric
Observatory (SOHO)/Extreme Ultraviolet Imaging Telescope (EIT) and the
Transition Region and Coronal Explorer (TRACE). The intensity of these
lines emitted by the corona can be reduced by the presence of a cool
gas, e.g., by prominence-like material, located in the corona. There
are two mechanisms that can lead to a reduction of the line intensity:
absorption and volume blocking. That part of the coronal radiation
that comes from behind the cool gas can be partially absorbed. The
main absorbers for the iron lines studied here are neutral hydrogen
and neutral plus singly ionized helium. In this paper we calculate
the optical thickness of their resonance continua at the wavelength
positions of iron lines and compare it with that in the Hα line
center. The comparison of the derived values shows that they are quite
similar. The second effect is due to the fact that cool structures in
the corona do not emit any radiation in the EUV lines, which gives rise
to an additional reduction of the observed intensity as compared with
the surrounding corona-we have termed this “volume blocking.” We
further describe in this paper how these two effects can be used in
a new way of performing prominence diagnostics. Our results are also
applicable to other coronal lines detected by, e.g., the SOHO CDS or
SUMER instruments.

---------------------------------------------------------
Title: Non-LTE diagnostics of velocity fields during the gradual
phase of a solar flare
Authors: Berlicki, A.; Heinzel, P.; Schmieder, B.; Mein, P.; Mein, N.
2005A&A...430..679B Altcode:
We perform an analysis of the velocity field within the Hα ribbons
during the gradual phase of an M 1.0 solar flare observed on October 22,
2002. We use spectroscopic observations performed with the German VTT
(Vacuum Tower Telescope) working in the MSDP (Multichannel Subtractive
Double Pass spectrograph) observing mode. From these observations
the Hα line profiles in chosen areas of the flare ribbons were
reconstructed and these observational profiles were compared with
a grid of synthetic Hα line profiles calculated by the non-LTE
radiative-transfer code. This code allows us to calculate different
models of the chromosphere with a prescribed velocity field. By
optimising the best fit between the observed and synthetic profiles
we find the most appropriate models of the chromosphere and vertical
structure of the velocity field in the analysed areas of the flare
ribbons. By means of the non-LTE radiative-transfer calculations
we show that in most analysed areas of the Hα flare ribbons the
chromospheric plasma exhibited upward motion with a mean velocity of
a few km;s-1. These results are consistent with previous
estimates and support the scenario of a gentle evaporation during the
gradual phase.

---------------------------------------------------------
Title: Physics of Solar Prominences
Authors: Heinzel, P.; Anzed, U.
2005ASSL..320..115H Altcode: 2005smp..conf..115H
No abstract at ADS

---------------------------------------------------------
Title: Diagnostics of Dark Chromospheric Mottles Based on High
Resolution Spectra I - Observational Data
Authors: Kotrč, P.; Schwartz, P.; Heinzel, P.; Tsiropoula, G.;
Tziotziou, K.
2005HvaOB..29..289K Altcode:
High resolution optical spectra of dark mottles in H and Ca lines
were observed with the Echelle spectrograph of the VTT at Sacramento
Peak Observatory. Until now, only Hα spectra and slit-jaw images
were processed. Used methods of identification of the dark mottles in
the slit-jaw images and in the spectra, as well as a calibration and
correction on the scattered light are described. Individual steps of
the procedure, as well as crucial problems are discussed. The finally
processed line profiles are comparable to the profiles of dark
mottles obtained by other instruments including MSDP.

---------------------------------------------------------
Title: Influence of Electron Beam Pulses on Hα Line Formation
Authors: Varady, M.; Kašparova, J.; Karlický, M.; Heinzel, P.;
Moravec, Z.
2005HvaOB..29..167V Altcode:
In this contribution we present results of our simulations focused on
determination of spectroscopic signs of the presence of non--thermal
electrons in the formation region of Hα using three mutually
communicating codes. The originally autonomous and highly specialised
codes model three simultaneously acting processes in flares: the
precipitation and energy dissipation of the non-thermal power--law
electron beams in the solar atmosphere, the hydrodynamic response of
the atmosphere to the energy deposited by the beams, and the radiative
transfer in chromosphere and photosphere which determines the hydrogen
line profiles and their time evolution. The results show possible
existence of a new diagnostic method on presence of electron beams in
the formation region of the Hα line.

---------------------------------------------------------
Title: Determination of the 3D structure of an EUV-filament observed
by SoHO/CDS, SoHO/SUMER and VTT/MSDP
Authors: Schwartz, P.; Heinzel, P.; Anzer, U.; Schmieder, B.
2004A&A...421..323S Altcode:
Heinzel et al. (\cite{hein1}) found that filaments seem to be much
more extended in EUV spectral lines than in Hα. In this paper we
reconstruct the 3D structure of the extensions of the EUV-filament
observed on 15 October 1999 by SoHO/CDS and SoHO/SUMER. Small Hα
structures were observed by VTT/MSDP. We computed the bottom and top
heights of the EUV-filament extensions for several values of the
hydrogen Lyman-continuum optical thickness τ912 using
the spectroscopic model of Heinzel et al. (\cite{hein2}). For this
we used CDS observations of the two coronal lines Mg X 624.94 Å and
Si XII 520.60 Å. Further, we develop a new method for estimating
τ912 using the O V line measured by CDS and the O VI
measured by SUMER onboard SoHO. The latter line is used as a proxy to
deduce the intensity variations of O V underneath the filament. This
method also takes into account the presence of prominence-corona
transition regions. Resulting heights of the EUV-filament
extensions are around 15 000 km for the bottom and around 40 000 km
for the top boundaries. However, there are significant variations
around these representative values and we show that in about half
of observed pixels the Lyman-continuum absorption dominates in
the coronal-line depression, while in the other half it is the
volume blocking effect. The latter situation corresponds to a large
(larger than 30 000 km) geometrical thickness of the EUV-filament
extension. From the heights of the boundaries of the EUV-filament the
geometrical thickness can be computed and used to estimate the total
mass loading which was found to be comparable to that of typical CMEs.

---------------------------------------------------------
Title: Soft X-ray heating of the solar chromosphere during the
gradual phase of two solar flares
Authors: Berlicki, A.; Heinzel, P.
2004A&A...420..319B Altcode:
In this paper we perform an analysis of the energetics of the solar
flaring chromosphere irradiated by soft X-rays (SXR) emitted from
overlying hot flare loops. To study an expected SXR heating we used
the observations of two solar flares obtained with the Multichannel
Subtractive Double Pass (MSDP) spectrograph attached to the Large
Coronagraph of the Wrocław University. SXR observations of these flares
come from the Yohkoh SXR telescope (SXT). From MSDP spectral images
we derived mean Hα line profiles which were then used to construct
semi-empirical non-LTE models of the chromosphere in the analyzed areas
of flares. On the basis of SXR observations we calculated the mean
emission measure EM and the temperature in flaring coronal structures
located above the Hα kernels under study and these two quantities were
used to compute the SXR irradiation of the chromosphere between 1-300
Å. For each flare model we then evaluated the energy deposit due to
such irradiation and compared it with the net radiative cooling rates
at all depths in the chromosphere. By means of such modelling we were
able to demonstrate that the enhanced emission of selected Hα kernels
observed during the gradual phase of these two solar flares cannot be
explained in terms of the SXR heating of the chromosphere. We found
that radiative losses in all layers of the chromosphere exceeded
the amount of the energy deposited by the SXR radiation. However,
for stronger flares with much enhanced EM a certain contribution of
SXR to the heating cannot be ruled out.

---------------------------------------------------------
Title: Multi-wavelength study of a high-latitude EUV filament
Authors: Schmieder, Brigitte; Lin, Yong; Heinzel, Petr; Schwartz, Pavol
2004SoPh..221..297S Altcode:
A large filament was observed during a multi-wavelength coordinated
campaign on June 19, 1998 in the Hα line with the Swedish Vacuum Solar
Telescope (SVST) at La Palma, in the coronal lines Fe ix/x 171 Å and
Fe xi 195 Å with the Transition Region and Coronal Explorer (TRACE)
and in EUV lines with the SOHO/CDS spectrometer and the hydrogen Lyman
series with the SOHO/SUMER spectrometer. Because of its high-latitude
location, it is possible to disentangle the physical properties of the
Hα filament and the filament channel seen in EUV lines. TRACE images
point out a dark region fitting the Hα fine-structure threads and a
dark corridor (filament channel), well extended south of the magnetic
inversion line. A similar pattern is observed in the CDS EUV-line
images. The opacity of the hydrogen and helium resonance continua at
171 Å is almost two orders of magnitude lower than that at the Hi head
(912 Å) and thus similar to the opacity of the Hα line. Since we do
not see the filament channel in Hα, this would imply that it should
also be invisible in TRACE lines. Thus, the diffuse dark corridor is
interpreted as due to the coronal `volume blocking' by a cool plasma
which extends to large altitudes. Such extensions were also confirmed by
computing the heights from the projection geometry and by simulations
of the CDS and TRACE line intensities using the spectroscopic model
of EUV filaments (Heinzel, Anzer, and Schmieder, 2003). Finally,
our NLTE analysis of selected hydrogen Lyman lines observed by SUMER
also leads to a conclusion that the dark filament channel is due to
a presence of relatively cool plasma having low densities and being
distributed at altitudes reaching the Hα filament.

---------------------------------------------------------
Title: Collisional excitation and ionization of hydrogen by return
current in solar flares
Authors: Karlický, M.; Kašparová, J.; Heinzel, P.
2004A&A...416L..13K Altcode:
First a problem of the transport of electron beams with high energy
fluxes into the cold chromosphere during the flare is presented. Then
it is shown that the problem might be solved by the return current
formed by superthermal (runaway) electrons. In such a case the
return current electrons could influence hydrogen excitations and
ionizations. Therefore, we computed collisional rates of such a
return current and compared them with those of the thermal plasma
and of a monoenergetic (10 keV) electron beam with the energy flux
FE = 1012 erg cm-2 s-1
penetrating into the flare atmosphere described by the F1 model (Machado
et al. \cite{Machado1980}). We show that in this situation the return
current collisional rates can be dominant for some transitions.

---------------------------------------------------------
Title: Collisional Excitation and Ionization of Hydrogen by Return
Current in Solar Flares
Authors: Kašparová, J.; Heinzel, P.; Karlický, M.
2004IAUS..219..760K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Parameters of dark mottles based on high resolution optical
spectra
Authors: Kotrc, P.; Heinzel, P.; Tziotziou, K.; Tsiropoula, G.
2004IAUS..223..275K Altcode: 2005IAUS..223..275K
High resolution optical spectra of hydrogen and calcium lines
observed with the Echelle spectrograph of the VTT at Sacramento Peak
Observatory were analyzed. The observed line profiles in some parts
of dark chromospheric mottles are to be matched with theoretical ones
using the cloud model and several parameters (e.g. the temperature,
gas pressure, flow velocity) are to be derived. Individual steps of
the procedure, as well as crucial problems are discussed.

---------------------------------------------------------
Title: Multi-Wavelength Observations of an M1.0 Flare on 22 October
2002
Authors: Berlicki, A.; Schmieder, B.; Vilmer, N.; Mein, P.; Mein,
N.; Heinzel, P.; Staiger, J.; Deluca, E. E.
2004IAUS..219..669B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Multiwavelength determination of the density and total mass
of the EUV filament observed by SoHO/CDS, SoHO/SUMER and MSDP/VTT
Authors: Schwartz, P.; Schmieder, B.; Heinzel, P.; Anzer, U.
2004IAUS..223..219S Altcode: 2005IAUS..223..219S
It was found that filaments observed in EUV could be much more extended
than in Halpha. These extended dark structures visible in EUV are named
EUV filaments. Their parts seen only in EUV (not observable in Halpha
because of low opacity at the Halpha wavelength) are called EUV-filament
extensions (or simply EUV extensions). For the EUV filament observed
by SoHO on 15 October 1999 as northern polar crown filament, only
a few small dark structures were seen in Halpha. This suggests that
the mass of the EUV extension is larger than, or at least comparable
with, the mass of the parts of the filament observed in Halpha. In
our previous work we determined the 3D structure of the EUV extension
of this EUV filament. In this paper we present the determinations of
mass and average density of this EUV extension. For better density
estimates we interpret the hydrogen Lyman lines observed by SUMER
using non-LTE radiative transfer code. From the best fitting of Lyman
lines we obtained a reasonable model of the EUV extension with low gas
pressure, temperatures from 2times10^4 K to 10^5 K and with extended
prominence-corona transition regions.

---------------------------------------------------------
Title: A Spectroscopic Model of euv Filaments
Authors: Heinzel, P.; Anzer, U.; Schmieder, B.
2003SoPh..216..159H Altcode:
We propose a new spectroscopic model for extended dark structures
around Hα filaments observed in EUV lines. As in previous papers,
we call these structures EUV filaments. Our model uses at least three
observed EUV lines (located shortward the hydrogen Lyman-continuum
limit) to compute iteratively the altitudes at which the EUV filament
extensions are located. A transition-region line (O v in the present
case) can be used to derive the opacity of the Lyman continuum and the
other two coronal lines (e.g., Mg x and Si xii) then give two heights:
the bottom and top of the EUV filament. The method takes into account
self-consistently the absorption of EUV-line radiation by the Lyman
continuum, as well as the volume-blocking effect potentially important
for coronal lines. As an example we compute the heights of the EUV
filament at one particular position, using CDS data for the 5 May 2000
filament. At this position, the EUV filament extension lies between
altitudes 28 700 and 39 000 km, so that the geometrical thickness of the
structure is 10300 km (we discuss also the sensitivity of our models
to variations of the line intensities). These heights are consistent
with the concept of twisted magnetic flux tubes, but there could be
also some influence on our results due to additional low lying cool
structures from parasitic polarities.

---------------------------------------------------------
Title: Determination of the 3D-topology of an EUV-filament observed
by SoHO/CDS SoHO/SUMER and VTT/MSDP
Authors: Schwartz, P.; Heinzel, P.; Schmieder, B.; Anzer, U.
2003ESASP.535..495S Altcode: 2003iscs.symp..495S
We have constructed a spatial model of an extended EUV-filament
observed on 15 October 1999 (polar crown N 38 deg) by SoHO/CDS. The
narrow Hα counterparts were observed by VTT/MSDP. As found in 2001,
EUV-filaments are much more extended than those parts visible in Hα. We
have computed the bottom and top heights of this EUV-filament for the
whole CDS raster for different values of the Lyman-continuum optical
thickness using CDS measurements of two coronal lines (Mg X 624.94
Å and Si XII 520.60 Å) and the model of Heinzel et al., 2003. For
the scale height of the MgX line we used the value from Fludra et
al. 1999, assuming that this line is not solar cycle and activity
dependent. We created a new method for τ912 determination
from O VI and O V line intensities. Because of the inhomogeneity in
the O V 629.37 Å line intensity distribution in the vicinitiy of
the EUV-filament it was not possible to estimate this intensity under
the filament. So we used observations made by SoHO/SUMER of the O VI
1031.91 Å line not absorbed by EUV-filament cold plasma. The knowledge
of the heights of the bottom and top boundaries of an EUV-filament
gives us the EUV-filament geometrical thickness. From this the mass
of the EUV-filament was computed.

---------------------------------------------------------
Title: EUV-filaments and their mass loading
Authors: Heinzel, P.; Anzer, U.; Schmieder, B.; Schwartz, P.
2003ESASP.535..447H Altcode: 2003iscs.symp..447H
It was found recently (Heinzel et al., 2001; Schmieder et al., 2003)
that solar filaments observed in EUV lines by SOHO/CDS are much more
extended than their Hα counterparts. This was explained by a large
difference between the hydrogen Lyman-continuum and Hα opacities. Two
different MHD models were suggested to explain the EUV-filament
extensions: the model based on parasitic polarities (Aulanier &amp;
Schmieder, 2002) and the model with twisted flux tubes (Anzer &amp;
Heinzel, 2003). The latter model can explain our recent findings
that at least some parts of the EUV-filament extensions are located
relatively high in the corona. These heights can be computed using a
new spectroscopic model of EUV-filaments. The mass which is loaded into
the EUV-filament extensions is then estimated on the basis of non-LTE
transfer calculation. The total filament mass is larger than that
derived for the Hα filament itself and this may have consequences
for the structure and mass loading of CMEs whenever they form from
such filaments - this may answer the question how the extended CME
structures can form from rather narrow Hα filaments. We summarize
the basic properties of EUV-filaments, present their spectroscopic
analysis and give some estimates for mass loading. We then discuss
possible relations between EUV-filaments and CMEs, in particular the
problems of their masses.

---------------------------------------------------------
Title: On the nature of extended EUV filaments
Authors: Anzer, U.; Heinzel, P.
2003A&A...404.1139A Altcode:
This paper describes the properties of extended EUV filaments and the
theoretical modelling of them. We summarise the general aspects of the
depression of EUV-line emission and give an interpretation of recent
filament observations in transition-region and coronal lines. The
EUV filament was found to be located relatively high in the corona
(at least 20 000 km above the solar surface) and this requires an
MHD scenario alternative to the parasitic-polarity model of Aulanier
&amp; Schmieder (\cite{Aulanier02}). Here we present a new idea
for the support of cool gas in the magnetic arcade of a prominence
which is capable of explaining both wide and vertically extended EUV
filaments. Our mechanism is based upon the twisting of individual
flux tubes, similar to the one which was suggested by Priest et
al. (\cite{Priest89}). Finally, the consequences of this new model
are discussed.

---------------------------------------------------------
Title: Spectroscopic diagnostics of an Hα and EUV filament observed
with THEMIS and SOHO
Authors: Schmieder, B.; Tziotziou, K.; Heinzel, P.
2003A&A...401..361S Altcode:
A long filament has been observed with THEMIS/MSDP and SOHO/CDS -
SUMER, during a coordinated campaign (JOPs 131/95) on May 5, 2000. The
data were (a) 2-D Hα spectra, observed using THEMIS, (b) Lyman series
spectra and Lyman continuum, observed using SOHO/SUMER, and (c) EUV
spectra (in O V 629 Å, Mg X 624 Å, Si Xii 520 Å, Ca X 557 Å and
He I 584 Å) observed using SOHO/CDS. A large depression of the line
emissions in CDS images represents the EUV filament. A computed model
shows that the EUV filament consists of an extended in height cloud of
low gas pressure at an altitude lower than the top of the Hα filament,
volume-blocking and absorbing coronal emission and absorbing transition
region line emission. The optical thickness of the Lyman continuum is
estimated by using the ratio of O V intensity inside and outside the
EUV filament, while the optical thickness of Hα is computed from the
Hα line profile by using an inversion technique. Using simultaneous
Hα , Lyman lines and Lyman continuum spectroscopic data, we performed
detailed, non-LTE radiative transfer diagnostics of the filament plasma
conditions. The optical thickness of the Lyman continuum is larger than
that of the Hα line by one to two orders of magnitude. This could be
of a great importance for filament formation modeling, if we consider
that more cool material exists in filament channels but is optically
too thin to be visible in Hα images.

---------------------------------------------------------
Title: 2D Radiative Transfer in Magnetically Confined Structures
Authors: Heinzel, P.; Anzer, U.
2003ASPC..288..441H Altcode: 2003sam..conf..441H
Magnetically confined structures in the solar atmosphere exhibit
a large complexity in their shapes and physical conditions. As an
example, we show the case of so-called magnetic dips in prominences
which are in magnetohydrostatic equilibria. For such models we solve
2D non-LTE multilevel problem for hydrogen with PRD in Lyman resonance
lines. The iterative technique used is based on the MALI approach with
simple diagonal ALO and SC formal solver. To compute the hydrogen
ionization balance, the preconditioned MALI equations are linearized
with respect to atomic level populations and electron density and
solved iteratively using the Newton-Raphson scheme. Two additional
problems are addressed: (i) an adequate iteration method for cases when
the column-mass scale is used in one of the two dimensions but varies
along the other dimension (which has a geometrical scaling); and (ii)
a possibility of using AMR (Adaptive Mesh Refinement) algorithms to
account for steep 2D gradients of selected variables (temperature,
density, etc.).

---------------------------------------------------------
Title: Transport of Energy from the Corona to the Chromosphere
During Flares
Authors: Heinzel, P.; Karlický, M.
2003LNP...612..161H Altcode: 2003ecpa.conf..161H
Hard X-ray (HXR) observations frequently exhibit fast temporal
variations during the impulsive phase of solar flares and this
is usually ascribed to the propagation of beams of accelerated
particles and to the dissipation of their energy in lower layers of
the solar atmosphere. As a result of fast heating and non-thermal
processes, several chromospheric lines show significant impulsive
brightenings. We first review observational attempts of detecting
such fast (sub-second) variations of the line intensities, namely
in the Halpha line, and discuss the problems associated with such
observations. Second, we describe new radiation-hydrodynamical (RHD)
simulations of the pulse-beam heating and show how they predict both
HXR and optical-line intensity variations on very short time scales. We
also discuss the effect of the return current on the energy deposit in
the atmosphere. Using new spatially-resolved HXR observations (RHESSI)
made simultaneously with a high-cadence detection of selected optical
lines, one should be able to diagnose the properties of particle beams,
provided that the response of the lower atmospheric layers to beam
pulses is strong enough.

---------------------------------------------------------
Title: Understanding solar flares from optical observations: How do
particle beams affect the lower atmosphere?
Authors: Heinzel, P.
2003AdSpR..32.2393H Altcode:
During the impulsive phase of solar flares, both hard X-ray (HXR) and
optical emissions exhibit fast temporal fluctuations detectable down
to sub-second scales. This is usually ascribed to the propagation
of beams of accelerated particles and to the dissipation of their
energy in lower layers of the solar atmosphere. Although it is rather
difficult to prove a temporal correlation between HXR and optical
intensity variations, we discuss here some previous results and
recent attempts. Namely in coordination with RHESSI observations,
several ground-based observatories started to detect fast optical
variations in the H α line. In addition to this, we also mention a
possibility of using some other diagnostically important lines. The
proper interpretation of coordinated HXR and optical observations
further requires robust tools for radiation-hydrodynamical (RHD) forward
modeling. We briefly describe a new 'hybrid' code which consists of RHD
part and particle-simulation part. Short-duration heating due to beam
pulses is modeled which allows us to predict temporal fluctuations of
HXR and selected optical and UV lines formed in chromospheric layers and
in the transition region. Particularly the line asymmetries originating
in a highly dynamical lower atmosphere of the flare can be used to
diagnose the response of these layers to particle beams.

---------------------------------------------------------
Title: Soft X-ray Heating of Stellar Chromospheres
Authors: Heinzel, P.; Berlicki, A.
2003IAUS..210P.B15H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Time-dependent Flare Models with MALI
Authors: Kašparová, J.; Heinzel, P.; Varady, M.; Karlický, M.
2003ASPC..288..544K Altcode: 2003sam..conf..544K
Temporal variations of Hα line profile intensities related to electron
beams are presented. We show first results of time dependent simulations
of a chromospheric response to a 1 sec monoenergetic electron beam. 1-D
hydrodynamic code together with particle representation of the beam have
been used to calculate atmospheric evolution. Time dependent radiative
transfer problem has been solved for the resulting atmosphere in the
MALI approach, using the Crank-Nicholson implicit scheme. Non-thermal
collisional rates were included in linearised equations of statistical
equilibrium.

---------------------------------------------------------
Title: Time dependent flare model with non-LTE radiative transfer
Authors: Varady, M.; Karlický, M.; Kašparová, J.; Heinzel, P.
2002ESASP.506..521V Altcode: 2002svco.conf..521V; 2002ESPM...10..521V
The first results of a time dependent simulation of chromospheric
response to a high energy electron beam are presented. The hybrid code,
i.e. a combination of a 1-D hydrodynamic code and a test particle code,
has been used to calculate the energy losses of a high energy electron
beam propagating through the solar atmosphere and the consequent
response of the ambient solar plasma to the energy deposition. The
resulting time evolution of the solar plasma temperature, density,
velocity and energy deposit on hydrogen has then been used as an input
for a time dependent radiative transfer code in the MALI approach
to determine the time variation of the Hα line profile. Non-thermal
collisional rates have been included in the linearised ESE.

---------------------------------------------------------
Title: A prominence with transition region: horizontal two-dimensional
filament model
Authors: Gorshkov, A. B.; Anzer, U.; Heinzel, P.
2002ESASP.506..405G Altcode: 2002ESPM...10..405G; 2002svco.conf..405G
SOHO/SUMER observations of solar filaments in Lyman lines of hydrogen
have revealed, in general, a two-peak form of the emission line
profiles with peak to center ratio less than an order of magnitude. This
fact strongly contradicts the results of numerical radiative transfer
simulations, where profiles with strong dips and large (1.5-2 orders of
magnitude) peak to center ratio are usually obtained due to the absence
of incident radiation from above the filament and, as a consequence,
very low atomic populations on the upper energy levels at the top of
the filament. Recently it was shown (Schmieder et al. 1998) that this
discrepancy can be removed by introducing a prominence-corona transition
region (PCTR) to the radiative transfer models. This paper continues
a set of publications (Anzer &amp; Heinzel, 1999 and Heinzel &amp;
Anzer, 2001) devoted to the modelling of prominences as structures in
MHS equilibrium. Here the prominence is represented by a horizontal
2D slab supported by a magnetic field. In our model we use a constant
gas pressure and assume that the kinetic temperature profile and the
PCTR extension are different in the vertical and horizontal directions
due to magnetic field. In the PCTR the temperature sharply increases
outwards from 8000K to 50000K on the scale of 100-600 km. To solve
the radiative transfer problem we apply a 2D code based on the MALI
iteration scheme and the modified long characteristics method.

---------------------------------------------------------
Title: Soft X-ray heating of the solar chromosphere: gradual phase
of a solar flare
Authors: Berlicki, A.; Heinzel, P.; Jakimiec, J.
2002ESASP.506..549B Altcode: 2002svco.conf..549B; 2002ESPM...10..549B
In this paper we present the analysis of energetics of solar flaring
chromosphere heated by soft X-ray radiation coming from overlying
hot flare loops. During the solar flare, a large amount of its energy
is emitted from hot coronal part in soft X-ray spectral range. This
radiation can penetrate into the chromosphere and transmit the
energy. This additional heating modifies vertical structure of the
chromosphere and it can cause the enhanced emission from some parts of
the flare. Therefore, such a mechanism can be responsible for emission
of chromospheric flaring structures commonly observed in Hα and other
spectral lines during the gradual phases when non-thermal processes
are unimportant. To analyze the effect of X-ray heating we used the
observations of the solar flare of 25 September 1997. This flare
was observed with the Wroclaw Multichannel Subtractive Double Pass
spectrograph (MSDP) coupled with the Large Coronagraph. We also use
X-ray observations of the flare taken with the SXT telescope. Within
the approximation of the quasi steady-state we have calculated the
deposit of X-ray energy in the chromosphere. By means of the non-LTE
radiative transfer calculations we show that enhanced emission of some
H-alpha structures observed during the gradual phase of this solar
flare can be partially explained in terms of the soft X-ray heating of
the chromosphere by hot 'post-flare' loops seen on the SXT images. We
also analyzed the energy budget of X-ray heated flaring chromosphere
and found that radiative losses from the chromosphere can be balanced
by soft X-ray heating only in some layers of the solar chromosphere.

---------------------------------------------------------
Title: Line profiles and intensity ratios in prominence models with
a prominence to corona interface
Authors: Labrosse, N.; Gouttebroze, P.; Heinzel, P.; Vial, J. -C.
2002ESASP.506..451L Altcode: 2002svco.conf..451L; 2002ESPM...10..451L
In this work we study the hydrogen, helium and calcium spectra
emitted by a one-dimensional prominence model in magneto-hydrostatic
equilibrium. The prominence slab consists of two parts: a cool
core where the plasma is optically thick for some lines, and a
prominence-to-corona transition region (PCTR) with a strong temperature
gradient. The models are defined by 5 parameters: temperature, pressure,
slab thickness, microturbulent velocity and altitude. We solve the NLTE
radiative transfer equations for all optically thick transitions. We
present line ratios between infrared, optical and EUV lines, as well
as line profiles. We show that the presence of a PCTR, where both
collisional and radiative excitations are important, affects H, He,
and Ca populations and emergent lines in different manners.

---------------------------------------------------------
Title: Spectral diagnostics of the magnetic field orientation in a
round-shaped filament
Authors: Schmieder, B.; Mein, N.; Heinzel, P.; Anzer, U.
2002ESASP.506..469S Altcode: 2002ESPM...10..469S; 2002svco.conf..469S
During several campaigns focused on prominences we have obtained
coordinated spectral observations from the ground and from space. The
SOHO/SUMER spectrometer allows us to observe, among others, the whole
Lyman series of hydrogen, while the Hα line was observed by the MSDP
spectrograph at the VTT. For Lyman lines, the non-LTE radiative-transfer
computations have shown the importance of the prominence-corona
transition region (PCTR) and its relation to the magnetic field
orientation for the explanation of the observed line profiles (Schmieder
et al. 1998, Heinzel et al. 2001). Moreover, Heinzel and Anzer (2001)
developed new 2D models which demonstrate how the shapes of Lyman
lines vary depending on the orientation of the magnetic field with
respect to the line of sight. To confirm this result observationally,
we focus here on a round-shaped filament observed during three days
as it was crossing the limb. The Lyman profiles observed on the limb
are different from day to day and we interpret these differences by
the change of orientation of the prominence axis (and therefore the
magnetic field direction) with respect to the line-of-sight.

---------------------------------------------------------
Title: Prediction of line intensity ratios in solar prominences
Authors: Gouttebroze, P.; Labrosse, N.; Heinzel, P.; Vial, J. -C.
2002ESASP.505..421G Altcode: 2002solm.conf..421G; 2002IAUCo.188..421G
Solar prominences are made of relatively cool and dense plasma
embedded in the solar corona, supported and structured by the magnetic
field. Since this plasma is definitely out of LTE, the diagnosis
of physical conditions in prominences needs the use of specific
radiative transfer (RT) codes to predict the spectrum emitted by
models and compare it to observations. For optically thin lines, the
solution of RT equations in the transition itself is not required,
but the emitted intensities depend, via the statistical equilibrium
equations, on RT in other transitions which are optically thick. We
use two different sets of models. The first one contains monolithic
models defined by 5 parameters: temperature, pressure, thickness,
microturbulent velocity and altitude above the solar surface. For
each parameter, we assume a range of variation. For each model, the
values of the 5 parameters are randomly chosen within the corresponding
range of variation. The second set contains composite models made of
multiple layers, in order to simulate the penetration of radiation into
inhomogeneous prominences. We use NLTE radiative transfer codes to
compute the intensities of the lines of hydrogen, helium and calcium
emitted by each model. So, for any couple of lines, we may obtained
their intensity ratio as a function of the 5 parameters. We discuss
the behaviour of some of these intensity ratios as a function of the
principal parameters and construct distribution diagrams, which are
compared to different published observations.

---------------------------------------------------------
Title: Calcium to hydrogen line ratios in solar prominences
Authors: Gouttebroze, P.; Heinzel, P.
2002A&A...385..273G Altcode:
The ratio of Ca II 8542 Å to Hβ line intensities has been used for a
long time to diagnose the gas pressure in solar prominences. In this
paper we reconsider the theoretical dependence of E(8542)/E(Hβ ) on
the gas pressure, as originally computed by Heasley &amp; Milkey (1978),
and extend this theoretical correlation to higher pressures. Firstly, we
revise the formation of calcium lines in prominences, using in parallel
two independently developed NLTE radiative transfer codes. Computations
consist of two subsequent steps: (i) the formation of hydrogen spectrum
(treated in a similar way as in Gouttebroze et al. 1993), and (ii)
the formation of calcium lines, using the electron-density structure
obtained in step (i). The influence of hydrogen Lyman lines on Ca II to
Ca III ionization is found to be very important for the determination
of calcium-to-hydrogen line ratios. In particular, the intensities
obtained for calcium lines at low pressures are significantly lower than
those obtained by Heasley &amp; Milkey (1978), which is the result
of a greater Ca III/Ca II ratio. Our numerical results have been
further checked against an approximate analytical model. Secondly,
we have performed an extended computation using a large grid of
models covering different temperatures, gas pressures, geometrical
thicknesses, microturbulent velocities and prominence altitudes. For
temperatures lower than 10 000 K and pressures lower than 0.1 dyn
cm-2, the line ratio E(8542)/E(Hβ ) undergoes only small
variations, remaining between 0.2 and 0.3. At higher pressures (0.1
to 1 dyn cm-2), the behaviour of this ratio appears to be
strongly dependent on temperature: rapidly increasing below 6000 K,
moderately increasing between 6000 and 8000 K, and generally decreasing
at higher temperatures. A comparison of the present models with recent
observations of Stellmacher &amp; Wiehr (2000) suggests the existence
of cool prominence structures with temperatures around 6000 K and gas
pressures higher than 0.1 dyn cm-2.

---------------------------------------------------------
Title: Theoretical hydrogen population relations for horizontal
cloud-like solar structures
Authors: Tziotziou, K.; Mein, N.; Mein, P.; Heinzel, P.
2002ESASP.477..183T Altcode: 2002scsw.conf..183T
A large set of parameterized NLTE models has been computed for a 1D
horizontal cloud-like structure standing above the solar surface. The
used input model parameters are temperature, velocity, microturbulence,
electronic density and geometrical thickness of the structure. From
the output of our computations which is the hydrogen level populations
as a function of the line center optical depth, we calculate several
relations between the hydrogen population levels and the considered
electron density. These relations are important for the study of
prominence-like structures from observations.

---------------------------------------------------------
Title: Diagnostics of electron bombardment in solar flares from
hydrogen Balmer lines
Authors: Kašparová, J.; Heinzel, P.
2002A&A...382..688K Altcode:
Influence of non-thermal collisional rates, related to an electron
beam, on hydrogen Balmer line profiles is investigated. Semi-empirical
temperature structure of the flare model F1 has been used for computing
non-LTE profiles of Hα , Hβ , and Hγ . Contribution functions
and their change due to different values of beam parameters are
shown. Unlike the line core intensity, the intensity of line wings
considerably depends on beam parameters and it is significantly
enhanced for typical values of the beam energy flux. The ratio of
line intensities at a selected wavelength is proposed to be used for
diagnostics of electron beams during solar flares, particularly at
impulsive phases. Obtained Hα line profiles are compared to those of
Fang et al. (\cite{fhg93}).

---------------------------------------------------------
Title: Understanding solar flares from optical observations
Authors: Heinzel, P.
2002cosp...34E1097H Altcode: 2002cosp.meetE1097H
During the impulsive phase of solar flares, both hard X-ray (HXR) and
optical emissions exhibit fast temporal fluctuations detectable down to
sub-second scales. This is usually ascribed to the propagation of beams
of accelerated particles and to the dissipation of their energy in lower
layers of the solar atmosphere. Although it is rather difficult to prove
a temporal correlation between HXR and optical intensity variations,
we discuss here some previous results and recent attempts. Namely
in coordination with RHESSI observations, several GBO's started to
detect fast optical variations in the H-alpha line. In addition to
this, we also explore a possibility of using some other diagnostically
relevant lines. The proper interpretation of coordinated HXR and optical
observations further requires robust tools for radiation-hydrodynamical
(RHD) forward modeling. We briefly describe a new 'hybrid' code which
consists of RHD part and particle-simulation part. Short-duration beam
heating (pulses) is modeled and we predict temporal fluctuations of HXR
and selected optical and UV lines formed in chromospheric layers and in
the transition region. Particularly the line asymmetries originating
in a highly dynamical lower atmosphere of the flare can be used to
diagnose the response of these layers to particle beams.

---------------------------------------------------------
Title: Why Are Solar Filaments More Extended in Extreme-Ultraviolet
Lines than in Hα?
Authors: Heinzel, P.; Schmieder, B.; Tziotziou, K.
2001ApJ...561L.223H Altcode:
A long solar filament was observed simultaneously in the Hα line
by THEMIS/MSDP and in selected EUV lines by the Coronal Diagnostic
Spectrometer on SOHO. Co-alignment of optical and EUV images reveals
that the dark EUV filament is much more extended than the Hα
filament. Assuming that the EUV filament represents Lyman continuum
absorption of the background EUV-line radiation, a straightforward
explanation of this effect is suggested. Based on non-LTE filament
models, we demonstrate that the ratio of the Lyman continuum to Hα
opacity can reach a factor of 50-100, and thus the EUV filament is
still well visible while the Hα line contrast diminishes below the
detection limit. This kind of interpretation leads to an important
conclusion that the cool filament material in which the Lyman continuum
absorption takes place is more abundant than one would expect from
Hα disk observations. This then may have significant consequences
on the filament structure and on formation models, as well as on mass
considerations related to coronal mass ejections.

---------------------------------------------------------
Title: Prominence fine structures in a magnetic equilibrium:
Two-dimensional models with multilevel radiative transfer
Authors: Heinzel, P.; Anzer, U.
2001A&A...375.1082H Altcode:
In this paper we construct theoretical models for vertical prominence
threads which are in magnetohydrostatic (MHS) equilibrium. These
models are fully two-dimensional (2D) and take the form of vertically
infinite threads hanging in a horizontal magnetic field. A typical
example of such a 2D magnetic-dip structure is shown for the case
when the central cool parts are surrounded by the prominence-corona
transition region (PCTR). We display 2D variations of the pressure,
density and temperature. While the pressure variations follow from the
MHS equilibrium, the kinetic temperature was specified empirically. As a
next step, we have solved the 2D multilevel non-LTE transfer problem in
such thread-like structures, in order to predict the spatial variations
of the emergent hydrogen spectrum. It is demonstrated that the hydrogen
Lyman lines (treated with partial redistribution) show significant
spatial variations of the intensity and that an important difference
exists between the line profiles emergent along and across the magnetic
field lines. We also discuss how these intensity variations compare to
recent SOHO/SUMER prominence observations, namely we show the effects
of line-profile averaging over the fine-structure threads which are
below the instrumental resolution. Finally we make some suggestions
for future modelling and observations.

---------------------------------------------------------
Title: A Study of Hydrogen Density in Emerging Flux Loops from
a Coordinated Transition Region and Coronal Explorer and Canary
Islands Observation Campaign
Authors: Mein, N.; Schmieder, B.; DeLuca, E. E.; Heinzel, P.; Mein,
P.; Malherbe, J. M.; Staiger, J.
2001ApJ...556..438M Altcode:
During an international ground-based campaign in the Canary Islands
coordinated with space instruments (i.e., Transition Region and Coronal
Explorer [TRACE]), we observed an active region on 1998 September
10 with high spatial and temporal resolution. New emerging flux in
the central part of the active region was observed in magnetograms
of the Swedish Vacuum Solar Telescope, La Palma. Emerging loops
(arch-filament systems [AFSs]) are well developed in Hα and Ca II
according to the observations made at the Vacuum Tower Telescope (VTT)
and THEMIS telescope in Tenerife with the Multichannel Subtractive
Double Pass (MSDP) spectrographs. The TRACE images obtained at 171
and 195 Å show low-emission regions that are easily identified as
the individual AFS. They are due to absorption by hydrogen and helium
continua in the cool filament plasma. We compare two techniques of
measuring the hydrogen density in the cool dense fibrils of AFSs. The
first method based on TRACE observations derived the neutral hydrogen
column density of the plasma absorbing coronal lines. The second one
using Hα line profiles provided by the MSDP spectrographs is based on
the cloud model. The results are consistent. We derive also electron
density values using Hα lines that are in good agreement with those
derived from the 8542 Å Ca II line observed with THEMIS (Mein et
al.). The three types of observations (TRACE, VTT, THEMIS) are well
complementary: absorption of coronal lines giving a good approximation
for the maximum value of the neutral hydrogen column density, the Hα
line giving a good determination of ne, and the 8542 Å Ca
II line a good determination of the electronic temperature.

---------------------------------------------------------
Title: SOHO/SUMER observations and analysis of the hydrogen Lyman
spectrum in solar prominences
Authors: Heinzel, P.; Schmieder, B.; Vial, J. -C.; Kotrč, P.
2001A&A...370..281H Altcode:
The complete hydrogen Lyman spectrum in several prominences has been
observed with the UV spectrometer SUMER on-board the SOHO, during
the Joint Observing Programme 107, together with other space and
ground-based observatories. Based on these observations, we are able to
demonstrate, for the first time, that there exists a large variety of
intensities and shapes of Lyman lines in different prominences and in
various parts thereof. Therefore, no “canonical” Lyman spectrum can
be considered for modelling purposes. However, we have identified at
least two representative properties of the observed spectra: in one case
(May 28, 1999 prominence) we detected high integrated intensities and
no reversals in lines higher than Lalpha . Another prominence (June 2,
1999) exhibited quite similar integrated intensities, but all lines have
rather strongly reversed profiles. This behaviour cannot be explained in
terms of standard isothermal-isobaric models and we thus consider more
general models which are in pressure equilibrium with the magnetic field
and which have significant prominence-corona transition region (PCTR)
temperature gradients. This type of model, recently suggested by Anzer
&amp; Heinzel (\cite{anhe99}), is capable of explaining strong emission
profiles without reversal. Based on extended non-LTE computations,
we suggest that quite different Lyman spectra mentioned above may
correspond to two types of PCTRs, one seen along the magnetic-field
lines (unreversed profiles) and the other one seen across the field
lines (reversed profiles). Finally, we again confirm the importance
of partial-redistribution (PRD) scattering processes for Lyman lines
in prominences. However, our analysis of new SUMER data also points
to a critical role of the PCTR in radiative transport in these lines.

---------------------------------------------------------
Title: Non-LTE inversion of chromospheric {\Ca Ii} cloud-like features
Authors: Tziotziou, K.; Heinzel, P.; Mein, P.; Mein, N.
2001A&A...366..686T Altcode:
A chromospheric cloud-like feature observed in the 8542 Å {{Ca Ii}
line is studied by a two step inversion procedure which provides
estimates of its temperature, electronic density, microturbulence,
geometrical thickness and bulk velocity. The first step involves the
computation of a large grid of models by a multi-level non-LTE transfer
code which gives the {{Ca Ii} line depth-dependent mean intensity
inside an isolated, isothermal cloud lying above the chromosphere. The
second step involves the inversion of the observed profiles with the
grid of computed synthetic {{Ca Ii} profiles. A searching and matching
chi 2 algorithm is implemented followed by an interpolation
algorithm which permits a more accurate determination of the parameters
on which the profiles depend. The five grid parameters are reduced to
four by defining the emission measure from the geometrical thickness
and electronic density. We show that this inversion procedure gives
accurate results for some of our inversion parameters when dealing
with solar filaments and is complementary to a previous study of the
same object in the {{Hα }} line. The main advantages, problems and
future extension of the inversion approach are also discussed.

---------------------------------------------------------
Title: Simultaneous SOHO and Ground-Based Observations of a Large
Eruptive Prominence and Coronal Mass Ejection
Authors: Plunkett, S. P.; Vourlidas, A.; Šimberová, S.; Karlický,
M.; Kotrč, P.; Heinzel, P.; Kupryakov, Yu. A.; Guo, W. P.; Wu, S. T.
2000SoPh..194..371P Altcode:
Coronal mass ejections (CMEs) are frequently associated with
erupting prominences near the solar surface. A spectacular eruption
of the southern polar crown prominence was observed on 2 June 1998,
accompanied by a CME that was well-observed by the LASCO coronagraphs
on SOHO. The prominence was observed in its quiescent state and was
followed throughout its eruption by the SOHO EIT and later by LASCO
as the bright, twisted core of the CME. Ground-based Hα observations
of the prominence were obtained at the Ondřejov Observatory in the
Czech Republic. A great deal of fine structure was observed within
the prominence as it erupted. The prominence motion was found to
rotate about its axis as it moved outward. The CME contained a helical
structure that is consistent with the ejection of a magnetic flux rope
from the Sun. Similar structures have been observed by LASCO in many
other CMEs. The relationship of the flux rope to other structures in
the CME is often not clear. In this event, the prominence clearly lies
near the trailing edge of the structure identified as a flux rope. This
structure can be observed from the onset of the CME in the low corona
all the way out to the edge of the LASCO field of view. The initiation
and evolution of the CME are modeled using a fully self-consistent,
3D axisymmetric, MHD code.

---------------------------------------------------------
Title: Energy considerations for solar prominences with mass inflow
Authors: Anzer, U.; Heinzel, P.
2000A&A...358L..75A Altcode:
In this Letter we study the inflow of enthalpy and ionisation
energy into solar prominences. We use 1D stationary slab models for
the prominence to calculate this inflow. We compare the resulting
energy gain with the integrated radiative losses obtained for such
slab models. We find that for reasonable inflow velocities many of our
models can be in energy equilibrium; only the very massive prominences
will either require some additional heating or they have to cool down
to low central temperatures. We also discuss the possibility or heating
the prominence by vertical downflows.

---------------------------------------------------------
Title: Decaying post-flare loops system observed by SOHO/CDS and
Yohkoh/SXT
Authors: Varady, M.; Fludra, A.; Heinzel, P.
2000A&A...355..769V Altcode:
The results of an analysis of joint SOHO/CDS and Yohkoh/SXT observations
of a decaying post-flare loops system with a rapid time evolution are
presented. The loop system was a remnant of a small single loop flare
(GOES class C2.9). Using the CDS raster taken in several EUV lines with
different formation temperatures and a temperature sensitive line pair
Fe XVI 360.8/Si XII 520.7 we confirmed the existence of the vertical
stratification in the loop system according to the line formation
temperature. The analysis of the SXT data showed a strong decay of the
system with time. While the temperature of the hot part of the system
(T =~ 2.5 MK) decreased only slightly, the total emission measure
dropped by more than a factor of four in approximately 103
s. This could be explained by a plasma outflow from the loops with
velocity approximately 10 km/s. On the other hand, signs of rapid,
probably radiative cooling can be identified in the images obtained
from the CDS raster taken in cool lines of O V and O III. Using the
density sensitive line pair of Fe XIV 334.2/353.8 and the integrated
intensity of Fe XIV 334.2 line we determined the electron densities
and emission measures across the top of the loop system. From the
results of these measurements, taking all known uncertainties into
account, we obtained that the geometrical filling factor at the top of
the system in the regions with maximum electron density in the Fe XIV
line lies in the interval from =~ 0.01 to =~ 0.2. A simple theoretical
approximation of the energy balance in the post-flare plasma gives a
total cooling time =~ 750 s.

---------------------------------------------------------
Title: Solar arch filaments observed with THEMIS
Authors: Mein, P.; Briand, C.; Heinzel, P.; Mein, N.
2000A&A...355.1146M Altcode:
Arch Filaments (AF) have been observed in the Ca Ii 8542 Å line with
the THEMIS telescope in September 1998. We present a preliminary
analysis of MSDP spectro-imaging data. A cloud-model fit provides
line-of-sight velocities and a set of plausible values for the model
parameters. The high sensitivity of the filament opacity to temperature,
coupled with the rough linearity versus electronic density, shows that
this Ca Ii line should be very efficient to complement usual Hα data
for a more rigorous diagnostics. Based on observations made with the
THEMIS telescope operated on the island of Tenerife by CNRS-CNR in
the spanish Observatorio del Teide of the Instituto de Astrofisica
de Canarias

---------------------------------------------------------
Title: Study of Chromospheric Ca II Cloud-like Structures
Authors: Tziotziou, K.; Heinzel, P.; Mein, P.; Mein, N.
2000ESASP.463..443T Altcode: 2000sctc.proc..443T
No abstract at ADS

---------------------------------------------------------
Title: Commission 12: Solar Radiation and Structure (Radiation et
Structure Solaires)
Authors: Foukal, Peter; Solanki, Sami; Mariska, J.; Baliunas, S.;
Dravins, D.; Duvall, T.; Fang, C.; Gaizauskas, V.; Heinzel, P.;
Kononovich, E.; Koutchmy, S.; Melrose, D.; Stix, M.; Suematsu, Y.;
Deubner, F.
2000IAUTA..24...73F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Models of the solar atmosphere
Authors: Heinzel, P.
2000ASIC..558..201H Altcode: 2000asre.conf..201H
Contents: Basic equations of radiation hydrodynamics. Solution of
NLTE problems. Semiempirical models of the solar atmosphere. Dynamical
models.

---------------------------------------------------------
Title: Phase Relations between Chromospheric and Transition Region
Oscillations
Authors: Krijger, J. M.; Curdt, W.; Heinzel, P.; Schmidt, W.
2000ESASP.463..353K Altcode: 2000sctc.proc..353K
No abstract at ADS

---------------------------------------------------------
Title: Solar Prominences Observed by Soho (SUMER, CDS, EIT) and
Ground-Based Observatories (GBO)
Authors: Heinzel, P.; Schmieder, B.; Vial, J. C.; Rudawy, P.
2000AdSpR..25.1777H Altcode:
We present two sets of prominence observations in higher lines
of the hydrogen Lyman series (from Lδ to L-9), together with
some other UV lines. These data have been obtained by the Solar
Ultraviolet Measurements of Emitted Radiation (SUMER) onboard the
SOHO satellite in June 1997. Coordinated observations were also taken
by other SOHO instruments: Coronal Diagnostic Spectrometer (CDS) and
Extreme-Ultraviolet Imaging Telescope(EIT) and with the coronagraph
of the Wroclaw University Observatory at Bialkóv, the spectrograph
of the Ondřejov Observatory. We demonstrate the basic characteristics
of the calibrated line profiles and compare them with the theoretical
profiles computed from isothermal-isobaric models

---------------------------------------------------------
Title: Chromospheric Response to a Short-Duration Beam Heating:
Observing Programme and Numerical Simulations
Authors: Heinzel, P.; Karlický, M.; Kotrč, P.; Kupryakov, Yu. A.
2000ASPC..206..289H Altcode: 2000hesp.conf..289H
No abstract at ADS

---------------------------------------------------------
Title: Diagnostics Constraints on Prominence Parameters from SOHO
and Ground-based Observations
Authors: Schmieder, B.; Kotrč, P.; Heinzel, P.; Kucera, T.;
Andretta, V.
1999ESASP.448..439S Altcode: 1999ESPM....9..439S; 1999mfsp.conf..439S
No abstract at ADS

---------------------------------------------------------
Title: Simultaneous Observations of Chromospheric and Transition
Region Oscillations in HI Lyman Transitions and in Optical Lines
Authors: Curdt, W.; Heinzel, P.; Schmidt, W.; Tarbell, T.; von
Uexküll, M.; Wilken, V.
1999ESASP.448..177C Altcode: 1999mfsp.conf..177C; 1999ESPM....9..177C
No abstract at ADS

---------------------------------------------------------
Title: Decaying Post-Flare Loops System Observed By SOHO/CDS And
Yohkoh/SXT
Authors: Varady, M.; Fludra, A.; Heinzel, P.
1999ESASP.446..669V Altcode: 1999soho....8..669V
The results of an analysis of joint CDS of SOHO and SXT of Yohkoh
observations of a decaying post-flare loop system are presented. The SXT
images were used to explain some peculiar structural features visible
in the examined CDS raster, resulting from the rapid evolution of the
observed system and from the way the CDS rasters are built. The SXT
data was also used to determine the time evolution of the temperature
and the emission measure of the hot part of the system during its
decay. The CDS data, with a very good temperature coverage, contains
a density sensitive line pair of Fe XIV which was used for electron
density analysis and a temperature sensitive line pair of Fe XVI and
Si XII which was used to study the temperature structure of the loop
system. From the integrated intensities of selected lines the emission
measures were calculated. From these measurements we estimated the
filling factor of the loop system in Fe XIV line.

---------------------------------------------------------
Title: Hydrogen Lyman Lines and Continuum Emission in a Polar-Crown
Prominence Observed with SUMER/SOHO
Authors: Schmieder, B.; Kucera, T.; Heinzel, P.; Vial, J. -C.
1999ESASP.446..605S Altcode: 1999soho....8..605S
We present, for the first time, a quasi-simultaneous spectroscopic
observation of the whole Lyman series of HI and continuum in a
quiescent prominence. Namely we have extended our previous study of
higher Lyman lines to lower members of the series, particularly
L-alpha and L-beta. For the latter two lines, we compare our
calibrated profiles (free of geocoronal absorption) with previous
data from OSO-8 LPSP spectrometer and (for L-alpha) from UVSP/SMM. We
demonstrate the importance of Lyman lines for studies of the base of
the prominence-corona transition region.

---------------------------------------------------------
Title: SOHO/SUMER observations and analysis of hydrogen Lyman lines
in a quiescent prominence
Authors: Schmieder, B.; Heinzel, P.; Vial, J. C.; Rudawy, P.
1999SoPh..189..109S Altcode:
A quiescent prominence was observed in June 1997 by instruments
onboard the SOHO spacecraft: the Solar Ultraviolet Measurements of
Emitted Radiation (SUMER), Coronal Diagnostic Spectrometer (CDS)
and Extreme-Ultraviolet Imaging Telescope (EIT), along with the
coronagraph of the Wrocław University Observatory at Bialków and
the spectrograph of the Ondřejov Observatory. We present prominence
observations in higher lines of the hydrogen Lyman series (from Lδ
to L-9), together with some other UV lines obtained by SUMER. We
extract the basic characteristics of the calibrated line profiles
of these Lyman lines and compare them with the theoretical profiles
computed from three kinds of NLTE models which also include prominence
filamentation. Our principal result is that the current NLTE models are
in principle capable of explaining the SUMER calibrated intensities
in the observed Lyman lines. We also find that in order to fit all
these lines, one has to consider a prominence-corona transition region
(PCTR) with a temperature gradient. At low pressures, higher Lyman
lines are still rather sensitive to the incident radiation which must
be carefully taken into account in the modeling. From PCTR models,
which also take into account the effect of ambipolar diffusion on the
heating, we have derived the formation depths for the Lyman series
lines. High Lyman lines seem to be formed just at the base of the PCTR.

---------------------------------------------------------
Title: Coordinated Prominence Observations by SOHO and Ground-Based
Observatories
Authors: Schmieder, B.; Heinzel, P.; Vial, J. -C.; Malherbe, J. M.;
Mein, P.; Rudawy, P.; Ceppatelli, G.
1999ASPC..184..296S Altcode:
Coordinated observations obtained during the JOP12 (Joint Observing
Programme between SOHO and ground-based instruments) allow us to
analyse the physical conditions in a prominence of 5 June 1997 and
its environment in the solar corona. The arch-shaped prominence shows
either vertical or horizontal structures according to the observed
lines (Hα with the coronagraph of the Wroclaw University Observatory
at Bialków and lines in a broad temperature range by the Coronal
Diagnostic Spectrometer CDS). The less dynamic behaviour of this
prominence was shown by the persistence of bubbles in the prominence
and confirmed by the Dopplershifts measured in CDS lines and in Hα
by the Italian Panoramic Monochromator (IPM) filter on the THEMIS
telescope in Tenerife. We explain the complex morphology of this
prominence by recent 3D MHD models. Finally, we present prominence
spectra in higher lines of the hydrogen Lyman series (from Lδ to L-9),
together with some other UV lines. These data have been obtained by
the Solar Ultraviolet Measurements of Emitted Radiation (SUMER). We
demonstrate the basic characteristics of the calibrated line profiles
of Lyman lines and compare them with the theoretical profiles computed
from isothermal-isobaric models. This leads to some constraints on
the environment of the prominence.

---------------------------------------------------------
Title: Chromospheric Oscillations Observed by SUMER/SOHO
Authors: Heinzel, P.; Curdt, W.
1999ASPC..184..201H Altcode:
We discuss first observations of the temporal behaviour of the hydrogen
Lyman lines made by the SUMER/SOHO spectrometer. Using the Ly 5 line,
we show here the global oscillatory pattern of the whole line profile
for three representative quiet-Sun structures: cell interior, network
boundary, and bright network. Mean power spectra for these structures
show several maxima, some of which are quite well correlated with the
maxima derived from Ca II K_2V observations. In the cell interior, the
power peak is centred between 4.5-5 mHz. No clear evidence of a 3 minute
chromospheric mode was found. In the network, we observe a broad range
of frequencies, with a maximum between 2-3 mHz. Lyman lines exhibit
certain Doppler shifts and asymmetries, but the oscillatory behaviour is
mainly due to the intensity variations which are small compared to the
line intensity itself (they reach 10-20 % of the mean line intensity).

---------------------------------------------------------
Title: The energy balance in solar prominences
Authors: Anzer, U.; Heinzel, P.
1999A&A...349..974A Altcode:
In this paper we study the energy balance in quiescent solar
prominences. For this investigation we use a simple 1D slab model in
magneto-hydrostatic equilibrium. We divide the studied region into two
parts: The inner region consisting of the prominence itself and the
cool part of the transition region (up to 30000 K). In this region the
plasma is optically thick in several atomic transitions and therefore we
have to solve the non-LTE radiative transfer problem in this part. This
allows us to derive self-consistently the gas density, the ionization
degree of hydrogen and the hydrogenic radiation losses. The energy
transport by thermal conduction can be neglected in this region. In the
outer part of the transition region, the thermal conduction becomes very
important but the treatment of radiation is simplified by the fact that
the plasma is optically thin. We find that energy balance in prominences
can only be obtained for special forms of the heating function. This
requirement is very stringent for the inner parts, while in the outer
region thermal conduction can transport large amounts of the heat
energy and therefore a wider class of heating functions will be allowed.

---------------------------------------------------------
Title: Proton and hydrogen temperatures at the base of the solar
polar corona
Authors: Marsch, E.; Tu, C. -Y.; Heinzel, P.; Wilhelm, K.; Curdt, W.
1999A&A...347..676M Altcode:
The SUMER (Solar Ultraviolet Measurements of Emitted Radiation)
Spectrometer on SOHO (Solar and Heliospheric Observatory) has been
used to observe the lines of the Lyman series (up to quantum numbers
larger than 20) of hydrogen emitted in the solar atmosphere. The
line shapes and intensities versus height are obtained near the limb
from about -10\arcsec to 70\arcsec. The lines are broad and show the
typical self-absorption reversal near the limb, where the emission
comes from optically thick material, and change systematically with
increasing height. The H i Ly6, Ly7 and Ly9 lines attain a Gaussian
shape at heights above the visible limb between about 19\arcsec and
22\arcsec, where the emission comes from an optically thin plasma. The
line shapes and intensities can be fitted well by model profiles
obtained from multilevel NLTE (Non Local-Thermodynamic-Equilibrium)
radiative transfer calculations which allow us, assuming excitation
and ionization equilibrium, to derive consistently the temperatures and
densities of the hydrogen atoms and, with additional assumptions, of the
protons. Temperature values range between 1 10(5) K to 2 10(5) K. We
present the systematics of the line shapes as observed in different
emission regions and discuss briefly the relevance of these results
for the solar wind acceleration and coronal heating.

---------------------------------------------------------
Title: Cloud model with variable source function for solar Hα
structures. II. Dynamical models
Authors: Heinzel, P.; Mein, N.; Mein, P.
1999A&A...346..322H Altcode:
It was demonstrated in the previous paper (Paper I)that the cloud
model technique can be largely improved if one considers realistic
boundary conditions in evaluating the true form of the line source
function. For structures seen against the solar disk, the Hα line
source function is decreasing from bottom towards the top. In the
present paper we investigate the effect of Doppler brightening on Hα
source function. In frame of 1D non-LTE models it is demonstrated how
the Hα line source function is increased depending on the velocity
of the moving cloud and direction of the motion. For the same set of
cloud models as used in Paper I, we have reevaluated the variations of
the source function with optical depth including the effect of cloud
motion. The resulting curves have been approximated by a second-degree
polynomial and the respective coefficients have been subsequently
used in a modified iterative method in order to derive the cloud
model parameters. As expected, dynamical models lead to more precise
specification of these parameters, namely the optical thickness, as
compared to the static case investigated in Paper I. We have applied
this new method to MSDP observations of a dark chromospheric feature
(loop) with considerable flows.

---------------------------------------------------------
Title: A non-LTE inversion procedure for chromospheric cloud-like
features
Authors: Molowny-Horas, R.; Heinzel, P.; Mein, P.; Mein, N.
1999A&A...345..618M Altcode:
A fast inversion procedure which provides estimates of the temperature,
electronic density, microturbulence, geometrical thickness and bulk
velocity of chromospheric features, so-called “clouds”, has been
implemented. The procedure has been divided into two steps: 1) the
construction of a large grid of models by means of a multi-level non-LTE
transfer code, which solves in a fast and reliable way the radiative
transfer problem of the formation of the Hα line inside an isolated,
isothermal cloud laying above the photosphere, and 2) the implementation
of searching, matching and interpolating algorithms which yield an
inversion of the observed line profile in terms of the grid's computed
profiles. The aforementioned 5 parameters, on which the profiles depend,
can be reduced to 4 if one defines the so-called emission measure from
the geometrical thickness and electronic density parameters. We show
that this strategy yields excellent results when dealing with solar
filaments. The main advantages of this approach are also discussed.

---------------------------------------------------------
Title: Magnetic Dips in Prominences
Authors: Heinzel, P.; Anzer, U.
1999SoPh..184..103H Altcode:
Magnetic dips are generally assumed to be basic equilibrium
configurations in quiescent solar prominences. Here we discuss two types
of the magnetic dips which were considered in the literature: (1) dips
resulting from a force-free magnetic equilibrium in the corona, and (2)
magnetic dips which are formed in situations where the Lorentz force
balances the weight of the prominence plasma. An important parameter
which decides between these two cases is the plasma β. For β⋘1,
the effect of the prominence material on the equilibrium structure is
quite negligible and the case (1) holds. If, however, β is larger,
say between 0.1 and 1 or even higher, magnetic dips of the second kind
are formed and they can be characterized by the angle ψ1 between the
vertical and the direction of the field lines at the surface of the
prominence structure. A simple and illustratory formula is derived
to relate this angle to the plasma β at the prominence center,
namely βc≃cot2ψ1. βc=1 thus corresponds to ψ1=45°. Finally,
we discuss the range of values of both βc and ψ1 as deduced from
various observations and conclude that the dips of the second kind are
important for the prominence equilibria. We also suggest a new method
for determination of the field-line inclination.

---------------------------------------------------------
Title: Eruptive filament of May 31, 1997, observed by SOHO.
Authors: Schmieder, B.; Heinzel, P.; Vial, J. -C.; Delaboudinière,
J. -P.; Delannée, C.
1999joso.proc..147S Altcode:
In the frame of the SUMER/CDS Joint Programme (JOP 17) the authors
have detected the four Lyman lines in an erupting filament. The
strong self-absorption in these lines, already reported for quiescent
filaments, is still present in this highly dynamical event, but the
authors observe a significant red asymmetry in the intensities of the
two peaks. They ascribe it to an upward bulk motion of the filament,
which they can actually see on a series of EIT images taken in the
Fe XII line. Both sets of observations can lead to a determination
of the velocity vector. The Doppler velocities are also derived from
other lines detected by SUMER/CDS and can be correlated with the
observations of the Pic-du-Midi MSDP obtained for this event. The
filament eruption was also well observed by other GBO instruments in
the Hα line (Meudon and Ondřejov).

---------------------------------------------------------
Title: Chromospheric Oscillations Observed by SOHO/SUMER and VTT/GCT
on Tenerife
Authors: Curdt, W.; Heinzel, P.; Schmidt, W.; von Uexküll, M.;
Wilken, V.
1999AGAb...15R..11C Altcode: 1999AGM....15..A12C
Previous studies have revealed various oscillations in higher Lyman
lines of hydrogen, as observed with SUMER on SOHO (Curdt &amp; Heinzel
1998). The assumption that these periodic phenomena might be related
to similar effects observed in optical lines like Ca II K led to the
idea of simultaneous observations with the SOHO/SUMER instrument and
the VTT/GCT telescopes on Tenerife. First results are presented here
for the Lyman series and Lyman continuum. Power spectra in network and
internetwork regions have been derived and a preliminary interpretation
based on the wave propagation concept is given. In SUMER spectra
we found a well-pronounced asymmetry of all Lyman lines, which is
related to atmospheric dynamics. The time variation of co-spatial UV
and optical data is presented and basic characteristics are discussed.

---------------------------------------------------------
Title: Non-LTE inversions of solar filament in Hα profiles.
Authors: Molowny-Horas, R.; Mein, P.; Mein, N.; Heinzel, P.
1999joso.proc..209M Altcode:
Results are shown of a new grid-based, non-LTE inversion procedure
which can carry out fast and accurate spectral inversions of Hα line
profiles. The code has been applied to a set of observed MSDP Hα line
profiles of a solar filament. The results of this inversion are shown
as 2-D maps of temperature, microturbulence and emission measure.

---------------------------------------------------------
Title: Dynamic Behavior of the Upper Solar Atmosphere: Sumer/ Solar
and Heliospheric Observatory Observations of Hydrogen Lyman Lines
Authors: Curdt, Werner; Heinzel, Petr
1998ApJ...503L..95C Altcode:
We present first observations of the temporal evolution of hydrogen
Lyman lines, made by the Solar Ultraviolet Measurements of Emitted
Radiation (SUMER) spectrometer on the Solar and Heliospheric
Observatory. A time series of about 33 minutes was obtained on 1997
June 5. The entrance slit has crossed a quiet-Sun region of 115.3" with
two internetwork structures (cells) and the bright network regions. A
data set of 59 spectra with30 s exposure time was obtained, using
the SUMER tracking system to compensate for the solar rotation. For
our analysis, we have selected a Lyman continuum window around 907
Å and the three Lyman lines Ly5, Ly9, and Ly15, which are formed at
different depths in the upper chromosphere. In the cell interiors,
we have detected significant periodic intensity variations with a
Fourier transform power peak at 3.3-3.5 minutes, which is consistent
with 3 minute internetwork oscillations. They seem to be associated
with spatially unresolved “clusters” of grains. In the bright network
regions, we detect slower oscillations of 6.9-7.6 minutes. These waves
seem to propagate upward as we deduce from a phase shift between the
three Lyman lines studied. The phase velocity was estimated to be
roughly 3 km s-1 in the network. Finally, we discuss the
potential usefulness of the hydrogen Lyman lines for diagnostics of the
temperature structure of the upper solar atmosphere. Our observations,
in particular the fact that we see all Lyman lines in emission all of
the time, put certain constraints on the temperature gradients above
the region in which numerical simulations do predict a decrease of
the mean kinetic temperature.

---------------------------------------------------------
Title: Filament Observations with SOHO Sumer/cds: The Behaviour of
Hydrogen Lyman Lines
Authors: Schmieder, B.; Heinzel, P.; Kucera, T.; Vial, J. -C.
1998SoPh..181..309S Altcode:
On 21 September 1996, a filament close to an area of enhanced network
was observed with the Solar Ultraviolet Measurements of Emitted
Radiation (SUMER) spectrometer and Coronal Diagnostic Spectrometer
(CDS). CDS provided intensity, Doppler shift and linewidth maps of the
region in six lines whose temperature range covers 104 to
106 K. SUMER observations consisted of maps of the region
in four hydrogen Lyman lines (Lδ, L∈, L-6, L-7) and a Svi line
(944 Å). In all the Lyman lines we detect a central absorption
and an asymmetry in the intensity of the two peaks. First NLTE
computations indicate that such reversed Lyman profiles and their
absolute intensities can be reproduced with the existing filament models
provided that we take into account a prominence-corona transition region
(PCTR). We discuss the Lyman lines' asymmetry in terms of macroscopic
flows by comparison with the Hei line Doppler shifts observed with CDS.

---------------------------------------------------------
Title: Prominence Parameters Derived from Magnetic-Field Measurements
and NLTE Diagnostics
Authors: Anzer, U.; Heinzel, P.
1998SoPh..179...75A Altcode:
In this paper we present a detailed analysis of a number of quiescent
prominences for which the components of the magnetic field as well as
the electron density and emission measure were previously obtained from
quasi-simultaneous measurements in hydrogen Hα and helium D3
lines. From magnetic equilibrium models of the Kippenhahn-Schlüter
type one can calculate the gas pressure, density, column mass and
geometrical width. The same set of physical parameters can also
be derived from a NLTE hydrogen-line analysis. We have studied the
mutual correlations between these two sets of parameters. Very large
differences, reaching an order of magnitude, were found between these
two sets, both for individual prominences and for the mean values over
all prominences used in this investigation. Finally, we discuss some
implications of our results.

---------------------------------------------------------
Title: Lyman Lines in Prominences and Filaments: NLTE
ModellingStrategies
Authors: Heinzel, P.
1998ASPC..150..188H Altcode: 1998IAUCo.167..188H; 1998npsp.conf..188H
No abstract at ADS

---------------------------------------------------------
Title: SUMER/SOHO Filament Observations in Selected Lyman Lines
Authors: Schmieder, B.; Kucera, T.; Heinzel, P.; Vial, J. -C.
1998ASPC..150..205S Altcode: 1998IAUCo.167..205S; 1998npsp.conf..205S
No abstract at ADS

---------------------------------------------------------
Title: 2-D Radiative Transfer Simulations with Angle-Dependent
Partial Frequency Redistribution
Authors: Gorshkov, A. B.; Heinzel, P.
1998ASPC..150..209G Altcode: 1998IAUCo.167..209G; 1998npsp.conf..209G
No abstract at ADS

---------------------------------------------------------
Title: XIVth consultation on solar physics : conference proceedings
Authors: Rompolt, B.; Jakimiec, J.; Heinzel, P.
1998PAICz..88.....R Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Modelling of Non-Uniform Prominence Slabs
Authors: Heinzel, P.; Anzer, U.
1998ASPC..150..213H Altcode: 1998IAUCo.167..213H; 1998npsp.conf..213H
No abstract at ADS

---------------------------------------------------------
Title: New Evidence of Chromospheric Evaporation
Authors: Kasparova, J.; Kotrc, P.; Heinzel, P.; Nikulin, I. F.;
Rudawy, P.
1998ASPC..150..397K Altcode: 1998IAUCo.167..397K; 1998npsp.conf..397K
No abstract at ADS

---------------------------------------------------------
Title: Height variations of prominence plasma parameters
Authors: Kotrč , P.; Heinzel, P.; Vial, J. -C.; Rompolt, B.
1998PAICz..88..208K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Problems in prominence NLTE modeling
Authors: Heinzel, P.
1998PAICz..88..195H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Filament observations with SOHO SUMER/CDS.
Authors: Schmieder, B.; Kučera, T.; Heinzel, P.; Vial, J. -C.
1998joso.proc..136S Altcode:
During a coordinated campaign between SOHO and ground-based instruments
a filament located close to the central meridian has been the target
of SUMER and CDS spectrometers on September 21, 1996.

---------------------------------------------------------
Title: A chromospheric response to pulse beam heating (abstract)
Authors: Heinzel, P.
1998PAICz..88..137H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Flare Multi-Line 2D-SPECTROSCOPY
Authors: Mein, P.; Mein, N.; Malherbe, J. -M.; Heinzel, P.; Kneer,
F.; von Uexkull, M.; Staiger, J.
1997SoPh..172..161M Altcode: 1997ESPM....8..161M
A small flare was observed at the Teide Observatory on October 5,
1994. Simultaneous data were obtained at the German Vacuum Tower
Telescope (VTT) with the MSDP spectrograph providing high-resolution
imaging spectroscopy in two chromospheric lines, and the Gregory Coudé
Telescope (GCT) providing information about the magnetic field. Basic
flare characteristics are:

---------------------------------------------------------
Title: Formation of CA II Lines in Solar Prominences
Authors: Gouttebroze, P.; Vial, J. -C.; Heinzel, P.
1997SoPh..172..125G Altcode: 1997ESPM....8..125G
We compute the profiles of the resonance lines and infrared
triplet of ionized calcium emitted by some representative models of
prominences. These models consist of plane-parallel slabs of different
temperatures, pressures and thicknesses, standing vertically above
the solar surface. These slabs are assumed to be observed at the limb,
and to be perpendicular to the line of sight. They are irradiated by
the Sun on both sides, and the incoming intensities, at every relevant
wavelength, are taken from observations. The model atom includes 3
stages of ionization (Cai, Caii and Caiii) with 5 discrete levels for
Caii. We study the relations between emitted intensities and physical
properties of the slabs, and compare the intensities emitted in Caii and
hydrogen lines for the same set of models. As a result of ionization,
the intensity decreases more rapidly with temperature in Caii lines than
in Hi lines, so that the ratio of Caii to Hi line intensities may be
used as a temperature indicator. The intensity ratio between resonance
and infrared lines of Caii depends principally on the optical thickness
of the structure. At high pressure and low temperature, the ratio
Caii 8542Å/Hβ is found to increase with pressure. This behaviour,
which is due to the saturation of Hβ, is opposite to that found by
Heasley and Milkey (1978) for low pressures (optically thin structures).

---------------------------------------------------------
Title: Optical and Radio Spectral Analysis of a Recurrent Surge
Authors: Kotrč, Pavel; Schmieder, Brigitte; Karlický, Marian;
Heinzel, Petr
1997SoPh..172..199K Altcode: 1997ESPM....8..199K
Coordinated observations obtained at Meudon (MSDP) and at Ondřejov
provide surge spectra in optical range (Hα, Hβ, Hγ, Hµ, Ca H and
K lines) and in radio range. The MSDP data allowed us to follow the
time evolution of the surge. The spectra of Balmer lines were used to
derive the electron density of the expelled cool material. The radio
bursts indicate that the acceleration of electrons took place in the
low and dense atmosphere, giving a good argument for a reconnection
near the transition region.

---------------------------------------------------------
Title: Solar and heliospheric plasma physics. Proceedings. 8th
European Solar Physics Meeting, Halkidiki (Greece), 13 - 18 May 1996.
Authors: Heinzel, P.; Simnett, G.
1997SoPh..172....1H Altcode: 1997ESPM....8....1H
The main topic was the interaction of the Sun with the heliosphere,
focused on first results from SOHO and new results from Ulysses. The
following topics were dealt with: solar dynamos, solar shape, convection
zone, solar pulsations, solar activity, solar atmosphere, solar corona,
solar spectra, solar prominences, solar flares, UV spectra, solar wind,
radiowave emissions, solar instruments.

---------------------------------------------------------
Title: NLTE Analysis of SUMER Filament Observations on SOHO
Authors: Heinzel, P.; Schmieder, B.; Vial, J. -C.
1997ESASP.404..427H Altcode: 1997cswn.conf..427H
No abstract at ADS

---------------------------------------------------------
Title: A Comparison of Two Approximations for the Cooling of Hot
Post-Flare Loops
Authors: Varady, M.; Heinzel, P.
1997ESASP.404..705V Altcode: 1997cswn.conf..705V
No abstract at ADS

---------------------------------------------------------
Title: Dynamics and evolution of the post-flare loops of June 1992
Authors: Wiik, J. E.; van Driel-Gesztely, L.; Schmieder, B.;
Heinzel, P.
1997AdSpR..20.2345W Altcode:
Observations in X-rays (Yohkoh/SXT) and in Hα of a system of post-flare
loops which developed after a flare on 25 June 1992 provide a unique
set of data for a study of the relationship between the hot and cool
post-flare loops as they evolve. Through a study of the magnetic
configuration in which the flare occurred, we are able to reconstruct
the true, 3D geometry of the loops. We derive the bulk-flow velocities
along the loop as a function of height using Doppler velocities and
the results from the loop reconstruction. We also provide a set of
relative altitude data. These results are used to check the validity
of the reconnection model in the frame of the cooling time needed to
cool X-ray loops to Hα temperature.

---------------------------------------------------------
Title: Structure and Dynamics of Post-Flare Loops
Authors: Varady, M.; Heinzel, P.
1997HvaOB..21...33V Altcode:
We briefly review basic properties of the post-flare loops and their
structural and dynamical characteristics. Several new results have been
recently published using the Yohkoh SXT images, simultaneously obtained
with high-resolution H-alpha data. We pay a particular attention to
the problem of cooling times of hot loops.

---------------------------------------------------------
Title: Post-Flare Loops of 26 June 1992, III
Authors: Wiik, J. E.; Schmieder, B.; Heinzel, P.; Roudier, T.
1996SoPh..166...89W Altcode:
Post-flare loops were observed on June 26, 1992 in the Hα line
with the Multichannel Subtractive Double-Pass spectrograph (MSDP)
on Pic-du-Midi and with the Swedish telescope on La Palma. The highly
dynamic loops are inhomogeneous (blobs). The cool loops were observed
10-12 hours after the X 3.9 class flare which had a maximum on June
25 at 20∶11 UT. From 2D images obtained with the MSDP on June 26 we
derive Hα intensities and Doppler velocities of the loop plasma. Using
a geometrical reconstruction technique we show that these loops are
mainly perpendicular to the solar surface and have the shape of a
dipole magnetic configuration. We derive the bulk-flow velocities along
the loop as a function of height using the Doppler velocities and the
results from the loop reconstruction. Where the Doppler velocities are
too small, we derive the bulk-flow velocities from the displacements
of the falling blobs. We discuss existing deviations from free-fall
velocity in the lower parts of the loops.

---------------------------------------------------------
Title: Post-Flare Loops of 26 June 1992, II
Authors: Schmieder, B.; Heinzel, P.; Van Driel-Gesztelyi, L.; Lemen,
J. R.
1996SoPh..165..303S Altcode:
We observed the large post-flare loop system, which developed after the
X 3.9 flare of 25 June 1992 at 20∶11 UT, in Hα with the Multichannel
Subtractive Double Pass Spectrograph at Pic-du-Midi and in X-rays with
the it Yohkoh/SXT instrument. Following the long-term development of
cool and hot plasmas, we have determined the emission measure of the
cool plasma and, for the first time, the temporal evolution of the
hot-loop emission measure and temperature during the entire gradual
phase. Thus, it was possible to infer the temporal variation of electron
densities, leading to estimates of cooling times. A gradual decrease of
the hot-loop emission measure was observed, from 4 × 1030
cm−5 at 23∶00 UT on 25 June 1992 to 3 × 1028
cm−5 at 13∶10 UT on 26 June 1992. During the same period,
the temperature decreased only slowly from 7.2 to 6.0 × 106
K. Using recent results of NLTE modeling of prominence-like plasmas,
we also derive the emission measure of cool Hα loops and discuss
their temperature and ionisation degree. During two hours of Hα
observations (11-13 hours after the flare) the averaged emission
measure does not show any significant change, though the amount
of visible cool material decreases and the volume of the loops
increases. The emission measure in Hα, after correction for the
Doppler-brightening effect, is slightly lower than in soft X-rays. Since
the hot plasma seems to be more spatially extended, we arrive at
electron densities in the range ninfesupho≤
ninfesupcool∼ 2 × 1010
cm−3 at the time of the Hα observations.

---------------------------------------------------------
Title: Cloud model with variable source function for solar Hα
structures.
Authors: Mein, N.; Mein, P.; Heinzel, P.; Vial, J. -C.; Malherbe,
J. M.; Staiger, J.
1996A&A...309..275M Altcode:
The "cloud model" used to derive the physical parameters of solar
chromospheric features is extended to the cases of non-constant
source function and of velocity gradients. This model assumes a given
relationship between the source function and the opacity of the cloud
which is derived from non-LTE modelling. An algorithm using 4 points
of the Halpha_ profile is proposed to derive the optical
thickness, the line-of-sight velocity and the dopplerwidth. The
results are compared with a 5-points inversion which does not use the
given relationship between source function and opacity. Effects of the
uncertainty about the radiation coming from the underlying chromosphere,
as well as effects of data noise, are discussed. The inversion method
is illustrated by some examples of observed profiles obtained with
the MSDP spectrograph of the VTT telescope (Teide Observatory).

---------------------------------------------------------
Title: A Complex Diagnostic of Solar Prominences
Authors: Heinzel, P.; Bommier, V.; Vial, J. C.
1996SoPh..164..211H Altcode:
We use the polarimetric and intensity measurements of Hα and HeI
D3 lines in solar prominences to derive the true geometrical
thickness for several quiescent prominences. The electron densities,
derived from the collisional depolarization in Hα by Bommier et
al. (1994), are used to evaluate the thickness from the emission
measure. The emission measure was obtained from the theoretical
correlation with the Hα integrated intensity, according to Gouttebroze,
Heinzel, and Vial (1993). Theoretical electron densities obtained by
latter authors are also compared with those of Bommier et al. (1994) and
we find a very good agreement between them. The prominence geometrical
thickness exhibits a relatively large range of values from about 100 km
up to a few 104 km. The plasma densities vary by almost two
orders of magnitude in the observed structures, but the total column
mass in the direction perpendicular to the prominence sheet seems to
be fairly constant for the set of prominences studied.

---------------------------------------------------------
Title: Structure and evolution of post-flare loops: analysis of
YOHKOH and MSDP observations
Authors: Schmieder, B.; Heinzel, P.; Wiik, J. E.; Lemen, J.; Hiei, E.
1996AdSpR..17d.111S Altcode: 1996AdSpR..17..111S
Using coordinated observations of the June 26 1992 post-flare loops
(Yohkoh-SXT and MSDP at Pic-du-Midi), we have analyzed the physical
conditions in both hot and cool loops and studied their spatial
structure and temporal evolution. Coalignment of high-resolution images
from SXT and MSDP indicates that the cool Hα loops are located just
below the hot ones and that the whole loop system grows in time with
a velocity 1.4 km s^-1. The temperature of hot loops as derived from
SXT data amounts to 5 x 10^6 K, while the cool loops have temperatures
around 10^4 K. The electron density of hot loops was estimated from
SXT emission-measure analysis to 7 x 10^9 cm^-3, while Hα integrated
intensity gives an electron density in cool loops of 2.2 x 10^10
cm^-3. With these plasma parameters we have solved the energy equation
in order to estimate the cooling time. The basic result of this work
is that the cooling time is comparable to the characteristic growing
time of the loop system (~ 1500 - 2000 sec), which is in agreement
with the scenario of the post-flare loop system development.

---------------------------------------------------------
Title: NLTE modelling based on SOHO/SUMER and GBO coordinated
observations.
Authors: Heinzel, P.
1996joso.proc...92H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Observations and Analysis of Surges in Chromosphere and
Lower Corona
Authors: Kotrc, P.; Schmieder, B.; Karlický, M.; Heinzel, P.
1996RoAJ....6...69K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Hot and Cool Post-Flare Loops: Formation and Dynamics
Authors: Schmieder, B.; Heinzel, P.; van Driel-Gesztelyi, L.; Wiik,
J. E.; Lemen, J.
1996mpsa.conf..211S Altcode: 1996IAUCo.153..211S
No abstract at ADS

---------------------------------------------------------
Title: Dynamics of solar magnetic arches in the photosphere and
the chromosphere.
Authors: Mein, P.; Demoulin, P.; Mein, N.; Engvold, O.; Molowny-Horas,
R.; Heinzel, P.; Gontikakis, C.
1996A&A...305..343M Altcode:
Mass motions in chromospheric arch filaments have been observed
with imaging spectroscopy (MSDP) at the VTT telescope of the Teide
Observatory. Coordinated observations of time sequences of continuum
images were carried out at the SVST telescope of the Observatorio
del Roque de los Muchachos, which provided transverse velocities of
photospheric tracers, by "local correlation tracking." Hα profiles
along 3 arch filaments are analysed in terms of "differential
cloud MODel", to discuss the Doppler velocities of chromospheric
material. Models of ascending arches with downflows in both legs
are investigated. The gas pressure is neglected, but the free-fall
equations are integrated versus time (non-stationary case). We first
assume circular lines of force with constant radius. We can account
for chromospheric velocities, but we cannot fit the slow motion of
footpoints derived from photospheric tracers. A better agreement is
obtained by assuming lines of force with fixed footpoints and variable
radius. Typical values are: half distance between footpoints of 10 to
15Mm, upward velocity at the top of loops of 4km/s after an integration
time of 800s. The obtained values are consistent with the sizes and
the lifetime of arch filaments.

---------------------------------------------------------
Title: Relative Altitude of Hot and Cool Post-Flare Loops
Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Wiik, J. E.; Tarbell,
T.; Heinzel, P.; Kitai, R.; Funakoshi, Y.; Anwar, B.
1996ASPC..111..359V Altcode: 1997ASPC..111..359V
The authors collected a unique set of data obtained simultaneously at
4 different ground based observatories and with the Yohkoh satellite
to study the relationship between hot X-ray and cool Hα post-flare
loops as they evolved during the long gradual phase of the X3.9 flare
which occurred on 25 June 1992. They found reasonably good agreement
between the computed 'theoretical' cooling times and the 'observed'
cooling times derived from the relative altitudes of hot and cool
loops. Taking into account evolutionary effects, the authors also found
similar shape and configuration of hot and cool loops during the entire
observing period and confirmed that at any time hot loops are at higher
altitude than cool loops, suggesting that cool loops indeed descend
from hot loops. The results provide support for the reconnection model.

---------------------------------------------------------
Title: High resolution flare observations with multi-line imaging
spectroscopy.
Authors: Mein, P.; Heinzel, P.; Malherbe, J. -M.; Staiger, J.
1996joso.proc...68M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: On the nature of bright rims of filaments
Authors: Heinzel, Petr; Kotrč, Pavel; Mouradian, Zadig; Buyukliev,
Georgi T.
1995SoPh..160...19H Altcode:
A filament with a very bright rim was observed in the Hα line on May
11, 1989, using the Meudon spectroheliograph. Absolute calibration of
the spectroheliogram allows us to express the intensities in particular
sites of the filament, in its bright rim and inside the surrounding
chromosphere. From a large number of photometric scans, we obtained a
histogram of the intensity excess of the bright rim relative to the
quiet chromosphere. The mean value of this excess amounts to about
4%. We present a theoretical explanation of bright rims, based on
the nature of Hα radiative diffusion in the filaments. Computed NLTE
model of the filament leads to a rim intensity excess which is in good
agreement with our observations.

---------------------------------------------------------
Title: Multilevel NLTE radiative transfer in isolated atmospheric
structures: implementation of the MALI-technique.
Authors: Heinzel, P.
1995A&A...299..563H Altcode:
We have developed and extensively tested a new multilevel NLTE transfer
code for isolated solar atmospheric structures (loops, prominences,
spicules etc.). The code is based on the MALI approach of Rybicki &amp;
Hummer (1991, 1992) to multilevel accelerated lambda iterations. It is
demonstrated that this method is fully capable of treating a difficult
problem of NLTE hydrogen excitation and ionization equilibrium, provided
that we linearize the preconditioned statistical equilibrium equations
with respect to atomic level populations and the electron density. With
this generalization of the original MALI approach, the numerical code
is robust and stable. As compared to the standard linearization method
of Auer &amp; Mihalas (1969), the new MALI code designed for 1D slabs
is more than one order of magnitude faster and its accuracy is quite
satisfactory. We discuss several details of our implementation of the
MALI technique to isolated, externally irradiated, 1D structures and
finally draw some future prospects.

---------------------------------------------------------
Title: Relation between Cool and Hot Post-Flare Loops of 26 June
1992 Derived from Optical and X-Ray (SXT-YOHKOH) Observations
Authors: Schmieder, B.; Heinzel, P.; Wiik, J. E.; Lemen, J.; Anwar,
B.; Kotrc, P.; Hiei, E.
1995SoPh..156..337S Altcode:
We have analyzed the physical conditions of the plasma in post-flare
loops with special emphasis on dynamics and energy transport using
SXT-data (hot plasma) and optical ground-based data from Pic du Midi,
Wrocław, and Ondřejov (cool plasma). By combining the Hα observations
with the SXT images we can understand the relationship between cool and
hot plasmas, the process of cooling post-flare loops and the mechanism
which maintains the long duration of these loops. Using recent results
of NLTE modeling of prominence-like plasmas, we derive the emission
measure of cool Hα loops and this gives us a realistic estimate of
the electron density (2.2 × 1010 cm−3). Then,
by comparing this emission measure with that of hot loops derived from
SXT data, we are able to estimate the ratio between electron densities
in hot and cool loops taking into account the effect of geometrical
filling factors. This leads to the electron density in hot loops 7 ×
109 cm−3. We also derive the temperature of
hot X-ray loops (≃ 5.5 × 106 K), which, together with
the electron density, provides the initial values for solving the
time-dependent energy balance equation. We obtain the cooling times
which are compared to a typical growth-time of the whole loop system
(∼ 2000 s). In the legs of cool Hα loops, we observe an excess
of the emission measure which we attribute to the effect of Doppler
brightening (due to large downflow velocities).

---------------------------------------------------------
Title: Dynamic loops in the corona
Authors: Heinzel, P.
1994ESASP.373..133H Altcode: 1994soho....3..133H
No abstract at ADS

---------------------------------------------------------
Title: Theoretical correlations between prominence plasma parameters
and the emitted radiation.
Authors: Heinzel, P.; Gouttebroze, P.; Vial, J. -C.
1994A&A...292..656H Altcode:
Recently a set of 140 prominence NLTE models has been computed using
the best available numerical techniques (Gouttebroze et al. 1993,
hereafter GHV). Models are represented by one-dimensional (1D) slabs
vertically standing on the solar surface and irradiated by photospheric
and chromospheric radiation. They are parametrized by the gas pressure
and temperature (uniform), the geometrical thickness of the 1D slab,
the microturbulent velocity and the height above the solar surface. As
outputs we obtained several physical quantities and optical parameters
like the electron density, the total hydrogen density, the optical
thickness in hydrogen lines and continua, spectral line intensities
etc. (see GHV). In order to establish mutual correlations between
various plasma parameters and the basic characteristics of the
synthesized hydrogen spectrum, we construct some basic correlation
curves. A very important relation already mentioned in GHV concerns the
plasma emission measure found to be closely related to the integrated
intensity of the Balmer Hα line. We present several other correlations
which can be divided into four categories: (i) relations between
radiation properties themselves; (ii) radiation properties versus
plasma parameters; (iii) the Hα source function behaviour; and (iv)
correlations between plasma parameters. Together with the 24 presented
figures, we discuss the physical interpretation of these correlations
and we give some hints for their application to the observed data. When
appropriate, we also compare our results with existing observations.

---------------------------------------------------------
Title: Dynamics of post-flare loops observed on June 26, 1992
Authors: Wiik, J. E.; Schmieder, B.; Heinzel, P.; Roudier, T.
1994ESASP.373..207W Altcode: 1994soho....3..207W
No abstract at ADS

---------------------------------------------------------
Title: Chromospheric and transition-region heating phenomena:
coordinated GBO and SOHO observations
Authors: Heinzel, P.; Kotrc, P.; Karlicky, M.; Nejezchleba, T.;
Knizek, M.
1994ESASP.373..369H Altcode: 1994soho....3..369H
No abstract at ADS

---------------------------------------------------------
Title: Coordinated optical and YOHKOH observations of 26 June 1992
flare loops
Authors: Heinzel, P.; Kotrč, P.; Schmieder, B.; Hiei, E.; Anwar, B.
1994SSRv...70..181H Altcode:
Optical spectra of large flare loops were detected by the Ondřejov
Multichannel Flare Spectrograph (MFS) during coordinated observations
with MSDP at Pic du Midi (Hα) and the soft X-ray telescope (SXT)
on Yohkoh. The CCD video images taken by the MFS slit-jaw camera
document the time-development of the flare loops as seen through the
Hα filter. Preliminary analysis of the MSDP images shows the intensity
structure of the cool flare loops and their velocity fields. From the
spectra we can clearly see the intensity variations along the cool
loops. SXT images show the structure of hot X-ray loops similar to
that of cool loops. Special attention is devoted to the bright tops,
simultaneously observed in X-rays, Hα and other optical lines. Based
on a preliminary analysis of the optical spectra, we speculate about
possible mechanisms leading to an observed bright emission at the tops
of cool loops. We suggest that direct soft X-ray irradiation of cool
loops at their tops could be, at least partly, responsible for such
a strong brightening.

---------------------------------------------------------
Title: Energy Transport and Dynamics
Authors: Schmieder, B.; Peres, G.; Enome, S.; Falciani, R.; Heinzel,
P.; Hénoux, J. C.; Mariska, J.; Reale, F.; Rilee, M. L.; Rompolt, B.;
Shibasaki, K.; Stepanov, A. V.; Wülser, J. P.; Zarro, D.; Zharkova, V.
1994SoPh..153...55S Altcode:
We report findings concerning energy transport and dynamics in flares
during the impulsive and gradual phases based on new ground-based and
space observations (notably fromYohkoh). A preheating sometimes occurs
during the impulsive phase. CaXIX line shifts are confirmed to be
good tracers of bulk plasma motions, although strong blue shifts are
not as frequent as previously claimed. They often appear correlated
with hard X-rays but, forsome events, the concept that electron beams
provide the whole energy input to the thermal component seems not
to apply. Theory now yields: new diagnostics of low-energy proton
and electron beams; accurate hydrodynamical modeling of pulse beam
heating of the atmosphere; possible diagnostics of microflares (based
on X-ray line ratio or on loop variability); and simulated images of
chromospheric evaporation fronts. For the gradual phase, the continual
reorganization of magnetic field lines over active regions determines
where and when magnetic reconnection, the mechanism favoured for energy
release, will occur. Spatial and temporal fragmentation of the energy
release, observed at different wavelengths, is considered to be a
factor as well in energy transport and plasma dynamics.

---------------------------------------------------------
Title: On the Occurrence of Blue Asymmetry in Chromospheric Flare
Spectra
Authors: Heinzel, Petr; Karlicky, Marian; Kotrc, Pavel; Svestka, Zdenek
1994SoPh..152..393H Altcode:
We present observations of optical spectra of a flare in which blue line
asymmetry was seen for more than 4 min close to the flare onset. The
maximum blue asymmetry coincided with the maximum of a hard X-ray
and microwave burst. We discuss possible interpretations of the blue
asymmetry and conclude that the most plausible one is electron-beam
heating with return current. Although this process predicts downflows
in the lower transition region and upper chromosphere, its ultimate
effect on the line profiles can be blue asymmetry: the upper layers
moving away from us absorb the radiation of the red peak thus lowering
its intensity in comparison to the blue one.

---------------------------------------------------------
Title: Chromospheric fine structure: Black &amp; white mottles
Authors: Heinzel, P.; Schmieder, B.
1994A&A...282..939H Altcode:
H-alpha observations of the chromosphere have been obtained
on June 17, 1986 with a high spatial resolution using the MSDP
(Multichannel Subtractive Double Pass) spectrograph operating
at Pic du Midi observatory. Various fine structures are observed
in the chromosphere: bushes of fibrils around supergranules and
fibrils (mottles) in the rosettes. They are relatively stable, but
line-of-sight velocities +/- 5-10 km/s are observed at the boundaries
of supergranules (rosettes). Velocity images exhibit finer structures
than intensity ones, with no cospatial relationship between both of
them. Typical H-alpha line profiles of dark and bright (black &amp;
white) mottles, constructed from 11 MSDP channels, are used to derive
the physical conditions in these structures. Non-local thermodynamic
equilibrium (NLTE) models of dark and bright mottles are represented
by a grid of prominence-like models of Goutebroze et al. (1993). It is
demonstrated that higher-pressure models(pg approximately =
0.5-1 dyn/sq cm) with temperature around 104 K naturally
explain the profiles of both dark and bright structures. By introducing
a generalized two-cloud model with non-uniform source function, we
account schematically for a shear-type velocity field. However, the
velocities are found to be of a secondary importance when the broad
U-shaped profiles formation is considered. We conclude that dark
and bright mottles have a similar nature and that their brightness
difference is predominantly due to pressure variations of the plasma
injected into the rosette flux tubes. Finally, we discuss the ambiguity
of H-alpha contrast profiles and comment on applicability of the
classical cloud model.

---------------------------------------------------------
Title: Fine structures of the solar chromosphere
Authors: Schmieder, B.; Heinzel, P.; Tsiropoula, G.; Alessandrakis,
C. E.
1994ASIC..433..151S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Spectral Analysis of a Quiescent Filament
Authors: Kotrc, P.; Heinzel, P.; Gorshkov, A. V.; Kononovich, E. V.;
Kupryakov, Yu. A.; Smirnova, O. B.
1994scs..conf..361K Altcode: 1994IAUCo.144..361K
The authors have determined principal plasma parameters in a filament
by applying the appropriate cloud model to several observed spectral
lines. Then they compared them to prominence models from the recent
numerical NLTE modelling of Gouttebroze et al. (1993). Some preliminary
results of such an attempt are described and related problems are
briefly discussed.

---------------------------------------------------------
Title: Theoretical Correlations Between Various Prominence Parameters
Authors: Heinzel, P.; Gouttebroze, P.; Vial, J. -C.
1994scs..conf..439H Altcode: 1994IAUCo.144..439H
The authors present some examples of important correlations between the
prominence plasma parameters and radiation properties. For example,
the plasma emission measure was found to be closely related to the
integrated Hα line intensity which provides a new diagnostic tool
for determination of plasma densities.

---------------------------------------------------------
Title: Evolution of an Eruptive Prominence and its Magnetic System
on 2 September 1991
Authors: Rudawy, P.; Rompolt, B.; Kotrič, P.; Heinzel, P.; Knižek,
M.; Garczyńska, I.; Cader-Sroka, B.
1994emsp.conf...95R Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Contrast of Filament Bright Rims
Authors: Kononovich, E. V.; Smirnova, O. B.; Heinzel, P.; Kotrc, P.
1994scs..conf..365K Altcode: 1994IAUCo.144..365K
Hα filtergrams were measured in order to specify the bright rims
contrast at different points along the line profile. The mean
contrast value in the line center is about 25 percent. The bright
rims interpretation as the bases of magnetic structures supporting
the filaments is suggested.

---------------------------------------------------------
Title: Dragging out of the near-surface magnetic fields during the
prominence eruptions
Authors: Rudawy, P.; Rompolt, B.; Kotrč, P.; Heinzel, P.; Knižek, M.
1994smf..conf..372R Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Solar coronal structures
Authors: Rusin, Vojtech; Heinzel, Petr; Vial, Jean-Claude
1994scs..conf.....R Altcode: 1994IAUCo.144.....R
No abstract at ADS

---------------------------------------------------------
Title: Electron Densities in Solar Prominences
Authors: Wiik, J. E.; Heinzel, P.; Schmieder, B.
1994scs..conf..381W Altcode: 1994IAUCo.144..381W
The authors concentrate on the determination of electron densities,
using the MSDP spectrograph at Pic du Midi. They discuss a new approach
for diagnosing the electron densities by comparing the observed Hα
intensities with theoretically predicted variations of the line-center
intensity versus Ne.

---------------------------------------------------------
Title: Black and White Mottles
Authors: Heinzel, P.; Schmieder, B.
1994emsp.conf...81H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The hydrogen spectrum of model prominences.
Authors: Gouttebroze, P.; Heinzel, P.; Vial, J. C.
1993A&AS...99..513G Altcode:
The emission of hydrogen lines and continua from solar prominences is
investigated using a set of 140 simple models, covering the range of
physical conditions usually assumed for these objects. These models
are plane-parallel, isobaric and isothermal. The computations have been
carried out using a 20 level plus continuum hydrogen atom, and taking
into account the effects of partial frequency redistribution in the
Lyman-alpha and beta lines. The aim of these computations is twofold:
firstly, to describe the variations of hydrogen lines and continua
emitted by prominences when physical conditions vary. Secondly, to
provide observers with some diagnostic tool to interpret data such as
intensity ratios, line widths, etc... The results of computations are
given as mixed table-figure panels, each of them corresponding to a
given model and summarizing the associated physical parameters and
the principal features of the emitted hydrogen spectrum. Finally,
for some specific parameters (or couple of parameters), we present
figures illustrating the variations of these quantities across the
whole set of models.

---------------------------------------------------------
Title: Book Review: Solar interior and atmosphere / U Arizona
Press, 1991
Authors: Heinzel, P.; Priest, E. R.; Heinzel, P.
1993SoPh..144..203H Altcode: 1993SoPh..144..203C
No abstract at ADS

---------------------------------------------------------
Title: Book Review: Applying Fractals in Astronomy
Authors: Martens, P. C.; Kleczek, Josip; Heinzel, P.
1993SoPh..143..401M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book Review: Eruptive solar flares / Springer-Verlag, 1992
Authors: Heinzel, P.
1993SoPh..143..402H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Pulse-beam heating in flare loops.
Authors: Heinzel, Petr; Karlicky, M.
1992ESASP.348..237H Altcode: 1992cscl.work..237H
Using a 1D hydbrid code, the authors evaluate a response of the flare
loop atmosphere to a series of very short electron beam pulses with
subsecond duration. Loop dynamics and energy balance are treated by
solving the standard set of hydrodynamic equations, while the beam
deceleration in denser atmospheric layers is evaluated by using a
particle simulation technique. Ionization of hydrogen below T ≍
104K is obtained by solving simultaneously the time-dependent
non-LTE problem for a three-level hydrogen atom with continuum. The
resulting electron densities are then used to compute radiation losses
at each time step. The authors discuss the behaviour of time-dependent
heating, the ionization structure of the chromosphere, and the role of
relaxation processes. A series of short-duration electron beam pulses
represents schematically the non-stationary heating in the flare
loops. However, the time-dependent radiation-hydrodynamical approach
used in this paper can also be applied to study other processes taking
place in coronal loops.

---------------------------------------------------------
Title: Book Review: Exploring the sun; solar science since Galileo /
Johns Hopkins, 1991
Authors: Heinzel, P.
1992SoPh..141..411H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book reviews
Authors: Trams, N. R.; Heinzel, P.
1992SoPh..141..411T Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Determination of plasma parameters in a quiescent prominence
Authors: Wiik, J. E.; Heinzel, P.; Schmieder, B.
1992A&A...260..419W Altcode:
We present H-alpha observations and analysis of a quiescent, polar crown
prominence observed on June 11, 1988 with the MSDP spectrograph at the
Pic du Midi Observatory. Two-dimensional maps of H-alpha intensities and
line-of-sight velocities have been obtained. The large-scale velocity
pattern consisting of cells and elongated structures is stable on
a time scale of about 1 min, but evolves continuously and undergoes
large changes in shape and amplitude during one hour. This behavior
of the velocity field suggests the presence of twists in flux ropes
or shear motions. Further, comparing the absolute observed intensities
with values from non-LTE radiative computations we estimate the range
of electron densities, source functions and optical thicknesses in
different parts of the prominence. For upper parts of the prominence
we obtain electron densities in the range 1 - 5 x l0 exp 10/cu cm.

---------------------------------------------------------
Title: The fine structure of prominences.
Authors: Heinzel, P.; Vial, J. -C.
1992ESASP.344...57H Altcode: 1992spai.rept...57H
Ground-based observations evidence in prominences a fine structure both
in density and velocity fields at a subarcsec scale. The modeling of
such structures is necessary in order to account for heating and cooling
processes which depend critically on the geometry and the structure of
the magnetic field. For a rigorous treatment of the radiative losses,
one needs to solve the full NLTE problem especially in UV lines,
which are critical for the energy balance. Although some attempts
have already been made to model individual fine-structure elements,
quiescent prominences are still mostly considered as one-dimensional
structures. We discuss current improvements such as two-dimensional
geometry and bundle of threads.

---------------------------------------------------------
Title: Structure and Dynamics of Cool Flare Loops
Authors: Heinzel, P.; Schmieder, B.; Mein, P.
1992SoPh..139...81H Altcode:
MSDP observations of the 16 May, 1981 two-ribbon flare are used to
study the physical structure and the dynamical behaviour of cool flare
loops. The loops have been detected in the Hα line just after the
flare maximum and they appeared in absorption against the disk. Using
the first-order differential cloud model (DCM1) technique, we derive
empirically some basic plasma parameters at 15 points along one loop
leg. The flow velocities and the true heights have been reconstructed
with respect to a geometrical projection. Subsequently, detailed
non-LTE models of cool loops have been constructed in order to fit Hα
source function values previously derived from DCM1 analysis. It is
demonstrated that this source function is rather sensitive to the radial
component of the flow velocity (the so-called Doppler brightening)
and to enhanced irradiation of the loops from the underlying flare
ribbons. In this way, we have been able to estimate quantitatively
all plasma parameters which determine the physical structure of cool
loops (i.e., the temperature, pressure, density), as well as the
momentum-balance condition within the loops. For these dark loops we
have arrived at relatively low gas pressures of the order of 0.1-0.5
dyne cm-2 with corresponding electron densities around
1011 cm-3. Pressure-gradient forces have been
found to be of small importance in the momentum-balance equation, and
thus they cannot explain departures from a free-fall motion found in our
MSDP data analysis. We propose three possible solutions to this problem.

---------------------------------------------------------
Title: Hydrogen Photoionization Rates for Chromospheric and Prominence
Plasmas
Authors: Rudawy, P.; Heinzel, P.
1992SoPh..138..123R Altcode:
New values of hydrogen photoionization rates for subordinate continua
arising from bound levels with the principal quantum number i = 2-5
have been evaluated numerically, using an extensive compilation of the
observed photospheric radiation fields. These rates can be directly
incorporated into the equations of statistical equilibrium as so-called
fixed rates. We tabulate the photoionization rates and equivalent
radiation temperatures for various heights above the photosphere,
which is particularly useful for chromospheric and prominence non-LTE
modeling. Finally, we compare our results with those previously obtained
by other authors.

---------------------------------------------------------
Title: Subsecond Variations of HXR and Hα Flare Emission
Authors: Heinzel, P.; Karlicky, M.
1992LNP...399..359H Altcode: 1992esf..coll..359H; 1992IAUCo.133..359H
For a series of electron beam pulses, we have computed the
time-dependent chromospheric heating and the corresponding hard X-ray
(HXR) flux. Moreover, by solving the time-dependent NLTE problem for
hydrogen, we theoretically predict the Ha-line intensity variations
on sub-second time scales. Both HXR-fluxes and Ha wing intensities
do exhibit a spiky behaviour, consistent with short pulse-beam
heating. However, the spikes in Ha are unexpectedly inverse, i.e. the
line intensity decreases during the beam heating. They correlate rather
well with HXR emission peaks computed for 24 keV channel. We compare our
theoretical results with recent observations of Kiplinger et al. (1991).

---------------------------------------------------------
Title: Fine structure analysis of a prominence in H-alpha and
coronal lines
Authors: Wiik, J. E.; Schmieder, B.; Noens, J. C.; Heinzel, P.
1992sws..coll..131W Altcode:
Prominence observations made simultaneously with the MSDP spectrograph
and with the coronagraph at Pic du Midi are presented. The existence
of a coronal cavity is discussed. 2D maps of H-alpha intensities
and the line-of-sight velocities have been obtained. The behavior
of the velocity field suggests the presence of twists along flux
ropes or shear motions. Further, using a probabilistic approach to
the H-alpha-line formation, we estimate the range of temperatures,
electron densities and optical thicknesses in different parts of the
prominence by fitting the observed H-alpha intensity profiles.

---------------------------------------------------------
Title: Plasma Parameters Derived from MSDP Observations of Cool
Flare Loops
Authors: Heinzel, P.; Schmieder, B.; Mein, P.
1992LNP...399..134H Altcode: 1992IAUCo.133..134H; 1992esf..coll..134H
MSDP observations of 16 May 1981 two-ribbon flare are used to study the
physical structure and dynamical behaviour of cool flare loops. The
loops have been detected in the H line just after the flare maximum
and they appeared in absorption against the disk. Using the first-order
differential cloud model (DCM1) technique, we derive empirically some
basic plasma parameters at 15 points along one loop leg. The flow
velocities and true heights have been reconstructed with respect to
a geometrical projection. Subsequently, detailed non-LTE models of
cool loops have been constructed in order to fit H source-function
values previously derived from DCM1 analysis. It is demonstrated that
this source function is rather sensitive to the radial component
of the flow velocity (the so-called Doppler brightening) and to
the enhanced irradiation of the loops from the underlying flare
ribbons. In this way, we have been able to estimate quantitatively
all plasma parameters which determine the physical structure of
cool loops (i. e. the temperature, pressure, density, etc.), as well
as the momentum-balance condition within the loops. For these dark
loops we have arrived at relatively low gas pressures of the order
of 0.1 - 0.5 dyn cm-2 , with corresponding electron densities around
1011 cm-3. Pressure-gradient forces have been found to be of small
importance in the momentum-balance equation. However, the classical
momentum equation is not capable of explaining significant departures
from a free-fall motion under the gravity force, found from our MSDP
data. We propose three possible explanations to this problem.

---------------------------------------------------------
Title: A Chromospheric Response to Pulse Beam Heating
Authors: Heinzel, Petr
1991SoPh..135...65H Altcode:
Starting from the new flare models of Karlický (1990) and Karlický
and Hénoux (1991), we present here the first time-dependent numerical
simulations of hydrogen plasma excitation and ionization on time scales
of less than one second. These time scales are consistent with the spiky
behaviour of the kinetic temperature produced by non-thermal collisional
processes. Such temperature spikes represent a chromospheric response
to a series of short-duration electron beam pulses which are supposed
to heat the flare atmosphere. Self-consistent numerical solution
of a simplified, time-dependent, non-LTE problem for a three-level
hydrogen atom model with continuum allows us to predict theoretically
a qualitative behaviour of the Hα line intensity variations on very
short time intervals. Our Hα temporal profiles, evaluated at the line
center and for Δλ = 1 Å, can be qualitatively compared with some
recent flare observations obtained with high temporal resolution.

---------------------------------------------------------
Title: Chromospheric Inhomogeneities in Cool Stars - Possible Effect
on Hydrogen Line Profiles
Authors: Heinzel, P.
1991ASIC..341..297H Altcode: 1991sabc.conf..297H
No abstract at ADS

---------------------------------------------------------
Title: Formation of hydrogen lines under the influence of turbulent
electric fields in solar flares.
Authors: Heinzel, Petr
1990JQSRT..44..185H Altcode:
A new method of detecting low-frequency ion-sound turbulence in solar
chromospheric flares is proposed. The method is based on analysis of the
hydrogen Paschen γ line profiles, which exhibit - under the appropriate
conditions - diagnostically important humps in the line wings around
Δλ ≅ 1 Å. The author discusses the problem of Paschen γ line
formation under the influence of low-frequency turbulent electric
fields and compares his theoretical results with recent spectral
observations. From comparison with the observed profile, the author
derives a turbulent electric field mean intensity of F0
≅ 3 CGS.

---------------------------------------------------------
Title: Spectral line formation in plasmas under extreme or unusual
conditions. Proceedings. Workshop on Spectral Line Formation in
Plasmas Under Extreme or Unusual Conditions, Nice (France), 31 Aug -
4 Sep 1987.
Authors: Peyraud, N.; Heinzel, P.; Hooper, C. F., Jr.
1990JQSRT..44.....P Altcode:
Contents: 1. Plasma electric fields. 2. Diagnostics of laboratory
plasmas. 3. Spectral line formation and broadening. 4. Astrophysical
plasmas.

---------------------------------------------------------
Title: On the Presence of High-frequency Turbulent Electric Fields
in the August 7, 1960 Flare
Authors: Firstova, N. M.; Heinzel, P.; Kotrc, P.
1990BAICz..41...88F Altcode:
According to Oks (1978), the wings of some hydrogen Balmer lines
observed in the spectrum of the moustache-like flare of August 7,
1960 do exhibit theoretically predicted dips, which should indicate
the presence of Langmuir turbulence. However, these features are rather
subtle and thus several difficulties arise if one tries to identify them
in the noisy spectra with typically many blends. Moreover, the Balmer
profiles used for Oks' analysis were already 'filtered' in a special
manner, which strongly affects the results. In view of these problems,
consideration is given to whether these dips in this particular flare
were real, starting with newly obtained microphotometric records. Using
the same lines as Oks (i.e., H7, H8, H11-13), together with H14,
none of the expected dips in the line wings were identified. All
observational aspects of this analysis are discussed in detail, and
new special observations are proposed. The role of electron density
variations within the flare volume is also briefly discussed.

---------------------------------------------------------
Title: Hα diagnostics of 16 May 1981 flare loops.
Authors: Heinzel, P.; Mein, P.; Schmieder, B.
1990PDHO....7..272H Altcode:
MSDP observations (Meudon) of 16 May 1981 post-flare loops are used
to derive the hydrogen plasma parameters in flare loops. The authors
compare two recently developed methods: a differential cloud model
and a probabilistic transfer technique.

---------------------------------------------------------
Title: Hydrogen Line Formation in Filamentary Prominences
Authors: Heinzel, Petr
1990LNP...363..279H Altcode: 1990doqp.coll..279H; 1990IAUCo.117..279H
No abstract at ADS

---------------------------------------------------------
Title: Chromospheric Structure under an H-alpha Filament
Authors: Heinzel, P.; Kononovich, E. V.; Smirnova, O. B.
1990PDHO....7..172H Altcode: 1990dysu.conf..172H; 1990ESPM....6..172H
The authors discuss the morphology and intensity structure of the
chromosphere underlying the Hα filament located close to the solar
limb.

---------------------------------------------------------
Title: Analysis of HeI 10830 a line in a quiescent prominence
Authors: Kotrč, P.; Heinzel, P.
1990LNP...363..285K Altcode: 1990doqp.coll..285K; 1990IAUCo.117..285K
No abstract at ADS

---------------------------------------------------------
Title: Hydrogen Lines Formation in Filamentary Prominences
Authors: Heinzel, P.
1989HvaOB..13..317H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Analysis of HeI 10830 Line in a Quiescent Prominence
Authors: Kotrc, P.; Heinzel, P.
1989HvaOB..13..371K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Non LTE modelling of prominences.
Authors: Heinzel, P.; Gouttebroze, P.; Vial, J. -C.
1988dssp.conf...71H Altcode:
The authors present the results on non-LTE computations performed in
the major lines and continua of the hydrogen atom. The prominence is
represented by a slab illuminated by the neighbouring chromosphere and
corona. Classical models are recomputed and it appears that the low
pressure model represent well the observed Lα profiles. However the
Lβ-computed value is much lower than the observed one. Preliminary
computations where a transition region to the corona is included that
the Lβ line may be improved.

---------------------------------------------------------
Title: Hα diagnostics of (post)-flare loops based on narrow-band
filtergram observations
Authors: Heinzel, P.; Karlicky, M.
1987SoPh..110..343H Altcode:
Using narrow-band Hα filtergrams, we develop a quantitative
non-LTE approach to determine the physical conditions prevailing
at the tops of (post)-flare loops observed against the solar
disc. At temperatures 10000-15000 K, the tops of flare loops turn
to emission at Hα line center when the gas pressure Pg
reaches 1 dyn cm−2 and should be clearly visible for
Pg≳ 3 dyn cm−2, independently of the
loop diameter. This situation corresponds to the electron density
of the order 1012 cm−3. The contrast of
flare-loops (in projection on the disc) at Hα line center is mainly
the function of Pg, while in the line wings (Hα ± 1 Å)
the loop can be visible in absorption or emission only when rather
strong microturbulence is present or for unrealistically high gas
pressures. Finally, we briefly discuss our diagnostical results in
frame of the latest (post)-flare loop model.

---------------------------------------------------------
Title: Formation of the hydrogen spectrum in quiescent prominences -
One-dimensional models with standard partial redistribution
Authors: Heinzel, P.; Gouttebroze, P.; Vial, J. -C.
1987A&A...183..351H Altcode:
One-dimensional isothermal-isobaric static slab models are used to study
departures from complete frequency redistribution (CRD) in hydrogen
lines for quiescent solar prominences. Partial redistribution (PRD)
effects on the hydrogen L-alpha line are shown to be significant
in the near wings in addition to the far wings of L-alpha. It is
suggested that strong symmetrical peaks found in the theoretical
PRD L-alpha profiles are due to partially coherent penetration of
the incidence double-peaked solar L-alpha. The present results are
found to be consistent with OSO-8/LPSP observations and with UVSP/SMM
data. The possible interplay between the effects of lateral transport
or radiation, level-interlocking, and PRD is considered.

---------------------------------------------------------
Title: Book review
Authors: Heinzel, Petr
1987SoPh..110..411H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Hydrogen Emission from Moving Solar Prominences
Authors: Heinzel, P.; Rompolt, B.
1987SoPh..110..171H Altcode:
Brightness variations of the lines arising from a five-level hydrogen
model atom, depending upon prominence velocities, have been investigated
using a combination of two non-LTE techniques. The importance of the
Doppler brightening and/or Doppler dimming effects is demonstrated
for the lines of the Lyman and Balmer series.

---------------------------------------------------------
Title: Optical and infrared spectrophotometry of quiescent
prominences.
Authors: Novocky, D.; Heinzel, P.
1987PAICz..66..257N Altcode: 1987eram....1..257N
High-dispersion Ca II H and K, Ca II IR λ8542 Å, Hα, Hβ, and
D3 emission line profiles of quiescent prominences have
been recorded in Stará Lesná Observatory. After data reduction,
a full set of calibrated profiles is used to discuss semiempirical
non-LTE prominence models.

---------------------------------------------------------
Title: Non-Lte Modelling of Prominences
Authors: Heinzel, P.; Gouttebroze, P.; Vial, J. C.
1987dssp.work...71H Altcode: 1987ASSL..150...71H
No abstract at ADS

---------------------------------------------------------
Title: Physical conditions in cool flare loops.
Authors: Heinzel, P.
1987PAICz..66..199H Altcode: 1987eram....1..199H
Large two-ribbon flares are frequently accompanied by a system of
(post)-flare loops, cooler structures being visible in several optical
and UV lines. The author investigates the non-LTE formation of hydrogen
lines in stationary loop structures, taking into account the influence
of macroscopic velocity flows along the loop.

---------------------------------------------------------
Title: Non-LTE hydrogen-line formation in moving prominences.
Authors: Heinzel, P.; Rompolt, B.
1986NASCP2442..163H Altcode: 1986copp.nasa..163H
The behavior of hydrogen-line brightness variations, depending on the
prominence-velocity changes were investigated. By solving the NON-Local
thermodynamic equilibrium (LTE) problem for hydrogen researchers
determine quantitatively the effect of Doppler brightening and/or
Doppler dimming (DBE, DDE) in the lines of Lyman and Balmer series. It
is demonstrated that in low-density prominence plasmas, DBE in H alpha
and H beta lines can reach a factor of three for velocities around 160
km/sec, while the L alpha line exhibits typical DDE. L beta brightness
variations follow from a combined DBE in the H alpha and DDE in L alpha
and L beta itself, providing that all relevant multilevel interlocking
processes are taken into account.

---------------------------------------------------------
Title: Partial redistribution effects in the formation of hydrogen
lines in quiescent prominences.
Authors: Heinzel, P.; Gouttebroze, P.; Vial, J. C.
1986NASCP2442..155H Altcode: 1986copp.nasa..155H
Departures from complete frequency redistribution (CRD) in hydrogen
lines are investigated for solar prominences. Partial redistribution
effects (PRD) are found both in the wings (their already known lowering)
and in the central part of the L alpha line; a new feature is evidenced
here: the partially coherent scattering in the near wings of the
line leads to a double-peaked profile mirroring the incident solar
radiation. With a low density model, we obtain a good agreement with
OSO 8 observed profiles. On the contrary, the PRD computed L beta
profile (lower density, no reversal) departs from the observed one,
a result which calls for more progress in terms of non-LTE transfer
and modelling.

---------------------------------------------------------
Title: Comments on "The angle-dependent redistribution functions
RIII and RIV" by S. J. McKenna.
Authors: Hubeny, I.; Heinzel, P.
1986Ap&SS.119..409H Altcode:
It is shown that the complicated form of the line absorption probability
function for scattering in subordinate lines, derived by McKenna (1984),
is an artifact of adopting a mathematically inconvenient expression
for the corresponding redistribution function. It is demonstrated that
the absorption probability must be given by the Voigt function.

---------------------------------------------------------
Title: Non-LTE models of solar prominences
Authors: Heinzel, P.; Vial, J. C.; Gouttebroze, P.; Rompolt, B.
1986CoSka..15..183H Altcode:
The authors briefly review some representative non-LTE models of solar
prominences, developed during the past decade. Particular attention is
devoted to recent interpretation of hydrogen Lyman α line profiles
in quiescent prominences and to the solution of the non-LTE problem
for moving active prominences. Finally, the authors outline some of
the most important prospects of prominence plasma diagnostics.

---------------------------------------------------------
Title: Infrared observations of quiescent prominences
Authors: Heinzel, P.; Kotrč, P.; Sobotka, M.; Zloch, F.; Scherbakova,
Z. A.
1986CoSka..15..171H Altcode:
The authors have developed a sophisticated numerical technique to
reduce infrared photographic spectra of quiescent prominences, taking
into account the influence of instrumental profiles, scattered light
and the noise. The reduced profiles were subsequently compared with
theoretical ones.

---------------------------------------------------------
Title: Partial redistribution interlocking in the solar chromosphere.
Authors: Heinzel, P.; Hubeny, I.
1985ASIC..152..137H Altcode: 1985pssl.proc..137H
Starting with the model of a quiet solar chromosphere, the authors
have calculated the relative probabilities of radiative and natural
population of the second and third hydrogen levels, pertinent to
various population processes. The analysis indicates that, while the Lα
line is formed by resonance scattering between the first two levels,
the third hydrogen level, from which Lβ and Hα are generated,
is populated partly by direct photoexcitation 1→3 (about 55%),
and partly by two-photon absorption 1→2→3 (about 45%).

---------------------------------------------------------
Title: Redistribution functions: a review of computational methods.
Authors: Heinzel, P.
1985ASIC..152..115H Altcode: 1985pssl.proc..115H
This paper reviews and compares the existing computational methods
developed to evaluate various types of redistribution functions
applicable in astrophysics. It discusses in detail several numerical
aspects (codes) of calculating both the angle-dependent and
angle-averaged laboratory-frame functions.

---------------------------------------------------------
Title: Non-coherent scattering in subordinate lines - V. Solutions
of the transfer problem.
Authors: Hubeny, I.; Heinzel, P.
1984JQSRT..32..159H Altcode:
Redistribution functions are defined for resonance scattering and shown
to be of use in astrophysics problems. An isotropic approximation is
included in a definition of a two-level atom line source function and
the redistribution function is angle-averaged for scattered photons,
which are treated as negative absorption. Various redistribution
functions, either partial or complete, are then applied to slab,
isothermal, finite, and semi-infinite atmospheres for a given absorption
profile and the line source function to examine the resulting transfer
functions. The ratios of the upper/lower level damping are found to
have a significant impact on the type of redistribution expected. An
approximate form of the redistribution function is determined as
adequate for calculating line profiles, especially in the wings.

---------------------------------------------------------
Title: Non-coherent scattering in subordinate lines:
IV. Angle-averaged redistribution functions.
Authors: Heinzel, P.; Hubený, I.
1983JQSRT..30...77H Altcode:
It is demonstrated that a simple Gaussian quadrature over the
scattering angles provides a sufficiently accurate and stable method
for evaluating all the angle-averaged redistribution functions
Ri(xarcmin,x) (i = I-V). The authors display graphically
the functions RII,III,V and discuss in detail the behaviour
of the newly calculated redistribution RV(xarcmin,x).

---------------------------------------------------------
Title: OSO-8 observations of a quiescent prominence - A comparison
of Lyman-alpha with theoretical intensities
Authors: Heinzel, P.; Vial, J. -C.
1983A&A...121..155H Altcode:
Using simultaneous observations of hydrogen Lyman-α and Ca II K lines
obtained with the OSO 8 LPSP instrument, the authors compare Lα
emission from a quiescent prominence with those predicted from the
existing theoretical models. They use the observed relation between
Hα and Ca II K integrated intensities to obtain an estimate of
E(Hα)/E(Lα) vs. E(Hα). This ratio differs significantly from those
predicted theoretically under the assumption of complete frequency
redistribution during the scattering of Lα photons. On the other
hand, using the partial-redistribution treatment in the Lα wings,
as suggested by Milkey et al., the authors arrived at a reasonable
agreement with the corresponding theoretical curve. The possible
influence of macroscopic velocities on line ratios is briefly discussed.

---------------------------------------------------------
Title: Resonance Scattering of Radiation in Solar
Prominences. I. Partial Redistribution in Optically Thin Subordinate
Lines
Authors: Heinzel, P.
1983BAICz..34....1H Altcode:
In the present paper the author studies the resonance scattering of
photospheric and chromospheric radiation by a prominence located at
any given height above the solar surface. Applying the newly developed
partial redistribution treatment (PRD), he evaluates numerically
the scattering integral in order to assess possible PRD effects on
subordinate-line emission profiles and/or integrated intensities
emerging from an optically thin prominence plasma.

---------------------------------------------------------
Title: Book-Review - Laser Spectroscopy - Basic Concepts and
Instrumentation
Authors: Demtroder, W.; Heinzel, P.
1982BAICz..33..192D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Nekoherentní rozptyl záření v subordinátních čarách

---------------------------------------------------------
Title: Nekoherentní rozptyl záření v subordinátních čarách
Authors: Heinzel, Petr
1982PhDT.......141H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Erratum: "Non-coherent scattering in subordinate
lines: a unified approach to redistributions"
[J. Quant. Spectrosc. Radiat. Transfer, Vol. 25, p. 483 - 499 (1981)].
Authors: Heinzel, P.
1982JQSRT..27..109H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Non-coherent scattering in subordinate lines: II. Collisional
redistribution.
Authors: Heinzel, P.; Hubený, I.
1982JQSRT..27....1H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Partial frequency redistribution in subordinate lines.
Authors: Heinzel, P.
1981PAICz..57....5H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Non-coherent scattering in subordinate lines: a unified
approach to redistribution functions.
Authors: Heinzel, P.
1981JQSRT..25..483H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book-Review - Nonradial and Nonlinear Stellar Pulsation -
Workshop - Tucson - 1979MAR12-16
Authors: Hill, H. A.; Dziembowski, W. A.; Heinzel, P.
1981BAICz..32..254H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Conference on stellar atmospheres, June 1981, Brno.
Authors: Heinzel, P.
1981Rise...62..203H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Partial frequency redistribution in subordinate lines
Authors: Heinzel, P.
1981sspi.book....5H Altcode:
An appropriate laboratory-frame redistribution function (LFR)
subordinate lines formed in stellar atmospheres and solar prominences
is presented under the assumption of a Maxwellian velocity distribution
for the lower state atoms. Starting from quantum mechanical results. A
LFR is obtained for the case of radiative broadening of both levels. One
general routine that can be used to evaluate all is R sub IS.

---------------------------------------------------------
Title: Derivatives of the Voigt Functions
Authors: Heinzel, P.
1978BAICz..29..159H Altcode:
A procedure for computing the partial derivatives of the Voigt functions
H(a, u) and K(a, u) is set forth, based on introducing the complex
function D(w) = H(a, u) + iK(a, u). Recurrence relations for the partial
derivatives up to the n-th order with respect to the variables a and
u are derived. The direct formulas for these derivatives up to third
order are also given. As an example of an astrophysical application,
the expression for a hydrogen line profile as a linear combination of
the partial derivatives of a Voigt function is given.

---------------------------------------------------------
Title: Astronomy at the Jagellonian University.
Authors: Heinzel, P.
1976Rise...57...81H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Precise Measurements of Radial Velocity Using a Lirepho
Microphotometer
Authors: Heinzel, P.; Hadrava, P.
1975BAICz..26...90H Altcode:
No abstract at ADS

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Title: European seminary of the students of astronomy in Poland, 1973.
Authors: Heinzel, P.; Solc, M.
1974Rise...55...29H Altcode:
No abstract at ADS