gunar

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Author name code: gunar
ADS astronomy entries on 2022-09-14
author:"Gunar, Stanislav"

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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: Science with the ASPIICS coronagraph onboard PROBA-3
Authors: Gunár, Stanislav; Fineschi, Silvano; Inhester, Bernd;
Zhukov, Andrei; Mierla, Marilena; Tsinganos, Kanaris; Lamy, Philippe;
Rudawy, Pawel
2022cosp...44.1326G Altcode:
The giant distributed coronagraph ASPIICS onboard the formation-flying
mission PROBA-3 of ESA will investigate hitherto practically
unexplored inner depths of the solar corona. This region lies above
the reach of disk imagers such as SDO and below the inner limit of
other coronagraphs. Although difficult to observe, the inner corona
is a place of great interest. This is where the fast solar wind gets
accelerated to supersonic velocities and where CMEs also reach their
maximum accelerations. It is also the place where the transition between
the regions of the closed and open magnetic field often happens and
the slow solar wind originates. Thanks to its field of view (2048 x
2048 pixels) reaching from 1.098 to 3 Rsun, good spatial resolution
(2.8 arcsec per pixel) and minimized straylight, ASPIICS will be able
to follow the connectivity of magnetic structures in corona down to the
solar surface. When coupled with regular (every week) long duration
(up to 6 hours) observations, it will allow us to comprehensively
compare and validate the MHD models of the large-scale coronal magnetic
field configuration and its evolution. The inner field-of-view limit
reaching very close to the solar surface will also enable us to study
the onset and early evolution of CMEs or to follow erupting prominences
beyond the reaches of the disk imagers. Thanks to the high cadence
(up to 2 seconds) we can start to investigate the manifestation of
small-scale solar dynamic processes within the inner corona. Moreover,
together with the DARA instrument measuring the total solar irradiance
onboard the occulting spacecraft of PROBA-3, ASPIICS will help us to
understand the partition of the magnetic free energy into the radiative
energy and the kinetic energy during solar eruptions. The pursuit of
these science goals will happen in coordination with Solar Orbiter,
Parker Solar Probe, Aditya-L1, and ASO-S. The synergies stemming from
these collaborations are promising to lead us into a golden age of
space coronagraphy.

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Title: Co-located Data Relay and Storage Spacecraft as a data-downlink
solution for small satellites and their constellations
Authors: Gunár, Stanislav
2022cosp...44.1993G Altcode:
We explore the potential of the use of co-located Data Relay and
Storage Spacecraft (DRS S/C) as data-handling hubs providing enhanced
downlink and data storage capabilities for research satellites and
their constellations. Why should we search for such a solution? Because
the volumes of data produced by research satellites continue to rise
and will do so in future. However, the data-transfer bottlenecks,
and the trade-offs that they pose, impact both large and small
scientific missions already today. Indeed, the constraints imposed
by the current data-downlink technologies affect the small satellites
the hardest, making the entry of smaller players into space research
difficult. On the other hand, at the time when the research satellites
grapple with limited throughput, vast volumes of data are routinely
relayed via telecommunication satellites every day. These advanced
spacecraft produced by commercial companies are being built in
series which continually drives down their cost and increases their
capabilities. This contrast between the scientific and commercial
worlds highlights the need for the exploration of new, innovative
data-downlink technologies. One of such enabler technologies could be
the co-located DRS S/C. These infrastructure-building platforms would
open new possibilities for small research and technology demonstration
satellites and might lead to a change of paradigm of space research
from the use of single, all-purpose satellites to constellations of
large and small spacecraft anchored by DRS S/C hubs.

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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: The European Solar Telescope
Authors: Quintero Noda, C.; Schlichenmaier, R.; Bellot Rubio, L. R.;
Löfdahl, M. G.; Khomenko, E.; Jurcak, J.; Leenaarts, J.; Kuckein,
C.; González Manrique, S. J.; Gunar, S.; Nelson, C. J.; de la Cruz
Rodríguez, J.; Tziotziou, K.; Tsiropoula, G.; Aulanier, G.; Collados,
M.; the EST team
2022arXiv220710905Q Altcode:
The European Solar Telescope (EST) is a project aimed at studying
the magnetic connectivity of the solar atmosphere, from the deep
photosphere to the upper chromosphere. Its design combines the knowledge
and expertise gathered by the European solar physics community during
the construction and operation of state-of-the-art solar telescopes
operating in visible and near-infrared wavelengths: the Swedish 1m Solar
Telescope (SST), the German Vacuum Tower Telescope (VTT) and GREGOR,
the French Télescope Héliographique pour l'Étude du Magnétisme
et des Instabilités Solaires (THÉMIS), and the Dutch Open Telescope
(DOT). With its 4.2 m primary mirror and an open configuration, EST will
become the most powerful European ground-based facility to study the Sun
in the coming decades in the visible and near-infrared bands. EST uses
the most innovative technological advances: the first adaptive secondary
mirror ever used in a solar telescope, a complex multi-conjugate
adaptive optics with deformable mirrors that form part of the optical
design in a natural way, a polarimetrically compensated telescope design
that eliminates the complex temporal variation and wavelength dependence
of the telescope Mueller matrix, and an instrument suite containing
several (etalon-based) tunable imaging spectropolarimeters and several
integral field unit spectropolarimeters. This publication summarises
some fundamental science questions that can be addressed with the
telescope, together with a complete description of its major subsystems.

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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: 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.

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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.

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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: 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).

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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.

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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.

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

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

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Title: 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>

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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.

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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: 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.

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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.

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Title: The influence of Hinode/SOT NFI instrumental effects on the
visibility of simulated prominence fine structures in Hα
Authors: Gunár, S.; Jurčák, J.; Ichimoto, K.
2019A&A...629A.118G Altcode:
Context. Models of entire prominences with their numerous fine
structures distributed within the prominence magnetic field use
approximate radiative transfer techniques to visualize the simulated
prominences. However, to accurately compare synthetic images of
prominences obtained in this way with observations and to precisely
analyze the visibility of even the faintest prominence features,
it is important to take into account the influence of instrumental
properties on the synthetic spectra and images. Aims: In the
present work, we investigate how synthetic Hα images of simulated
prominences are impacted by the instrumental effects induced by the
Narrowband Filter Imager (NFI) of the Solar Optical Telescope (SOT)
onboard the Hinode satellite. Methods: To process the synthetic
Hα images provided by 3D Whole-Prominence Fine Structure (WPFS) models
into SOT-like synthetic Hα images, we take into account the effects of
the integration over the theoretical narrow-band transmission profile
of NFI Lyot filter, the influence of the stray-light and point spread
function (PSF) of Hinode/SOT, and the observed noise level. This allows
us to compare the visibility of the prominence fine structures in the
SOT-like synthetic Hα images with the synthetic Hα line-center images
used by the 3D models and with a pair of Hinode/SOT NFI observations
of quiescent prominences. Results: The comparison between
the SOT-like synthetic Hα images and the synthetic Hα line-center
images shows that all large and small-scale features are very similar
in both visualizations and that the same very faint prominence fine
structures can be discerned in both. This demonstrates that the
computationally efficient Hα line-center visualization technique
can be reliably used for the purpose of visualization of complex 3D
prominence models. In addition, the qualitative comparison between the
SOT-like synthetic images and prominence observations shows that the
3D WPFS models can reproduce large-scale prominence features rather
well. However, the distribution of the prominence fine structures
is significantly more diffuse in the observations than in the models
and the diffuse intensity areas surrounding the observed prominences
are also not present in the synthetic images. We also found that the
maximum intensities reached in the models are about twice as high as
those present in the observations-an indication that the mass-loading
assumed in the present 3D WPFS models might be too large.

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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: 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: 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: On the Dynamic Nature of a Quiescent Prominence Observed by
IRIS and MSDP Spectrographs
Authors: Ruan, Guiping; Schmieder, Brigitte; Mein, Pierre; Mein,
Nicole; Labrosse, Nicolas; Gunár, Stanislav; Chen, Yao
2018ApJ...865..123R Altcode:
Quiescent solar prominences are generally considered to have a stable
large-scale structure. However, they consist of multiple small-scale
structures that are often significantly dynamic. To understand
the nature of prominence plasma dynamics we use the high spatial,
temporal, and spectral resolution observations obtained by Interface
Region Imaging Spectrograph (IRIS) during a coordinated campaign
with the Multichannel Subtractive Double Pass spectrograph at the
Meudon Solar Tower. Detailed analysis of the IRIS observations of
Mg II lines, including the analysis of Dopplershift and line width
obtained with two different methods (quantile method and Gaussian-fit
method) are discussed in the frame of the dynamic nature of the
structures. Large-scale coherent blueshift and redshift features are
observed in Mg II lines and Hα exhibiting a slow evolution during 1:40
hr of observations. We explain the presence of several significantly
asymmetric peaks in the observed Mg II line profiles by the presence
of several prominence fine structures moving with different velocities
located along the line of sight (LOS). 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. We show that C II line profiles may be used
to confirm the existence of multi-components along the LOS.

---------------------------------------------------------
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: 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: 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: 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.

---------------------------------------------------------
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: Properties of the prominence magnetic field and plasma
distributions as obtained from 3D whole-prominence fine structure
modeling
Authors: Gunár, S.; Mackay, D. H.
2016A&A...592A..60G Altcode:
 Aims: We analyze distributions of the magnetic field strength
and prominence plasma (temperature, pressure, plasma β, and mass) using
the 3D whole-prominence fine structure model. Methods: The model
combines a 3D magnetic field configuration of an entire prominence,
obtained from non-linear force-free field simulations, with a detailed
semi-empirically derived description of the prominence plasma. The
plasma is located in magnetic dips in hydrostatic equilibrium and is
distributed along multiple fine structures within the 3D magnetic
model. Results: We show that in the modeled prominence, the
variations of the magnetic field strength and its orientation are
insignificant on scales comparable to the smallest dimensions of the
observed prominence fine structures. We also show the ability of the
3D whole-prominence fine structure model to reveal the distribution
of the prominence plasma with respect to its temperature within the
prominence volume. This provides new insights into the composition
of the prominence-corona transition region. We further demonstrate
that the values of the plasma β are small throughout the majority
of the modeled prominences when realistic photospheric magnetic flux
distributions and prominence plasma parameters are assumed. While this
is generally true, we also find that in the region with the deepest
magnetic dips, the plasma β may increase towards unity. Finally,
we show that the mass of the modeled prominence plasma is in good
agreement with the mass of observed non-eruptive prominences.

---------------------------------------------------------
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: ALMA Observations of the Sun in Cycle 4 and Beyond
Authors: Wedemeyer, S.; Fleck, B.; Battaglia, M.; Labrosse, N.;
Fleishman, G.; Hudson, H.; Antolin, P.; Alissandrakis, C.; Ayres, T.;
Ballester, J.; Bastian, T.; Black, J.; Benz, A.; Brajsa, R.; Carlsson,
M.; Costa, J.; DePontieu, B.; Doyle, G.; Gimenez de Castro, G.;
Gunár, S.; Harper, G.; Jafarzadeh, S.; Loukitcheva, M.; Nakariakov,
V.; Oliver, R.; Schmieder, B.; Selhorst, C.; Shimojo, M.; Simões,
P.; Soler, R.; Temmer, M.; Tiwari, S.; Van Doorsselaere, T.; Veronig,
A.; White, S.; Yagoubov, P.; Zaqarashvili, T.
2016arXiv160100587W Altcode:
This document was created by the Solar Simulations for the Atacama
Large Millimeter Observatory Network (SSALMON) in preparation of
the first regular observations of the Sun with the Atacama Large
Millimeter/submillimeter Array (ALMA), which are anticipated to start
in ALMA Cycle 4 in October 2016. The science cases presented here
demonstrate that a large number of scientifically highly interesting
observations could be made already with the still limited solar
observing modes foreseen for Cycle 4 and that ALMA has the potential
to make important contributions to answering long-standing scientific
questions in solar physics. With the proposal deadline for ALMA Cycle
4 in April 2016 and the Commissioning and Science Verification campaign
in December 2015 in sight, several of the SSALMON Expert Teams composed
strategic documents in which they outlined potential solar observations
that could be feasible given the anticipated technical capabilities
in Cycle 4. These documents have been combined and supplemented
with an analysis, resulting in recommendations for solar observing
with ALMA in Cycle 4. In addition, the detailed science cases also
demonstrate the scientific priorities of the solar physics community
and which capabilities are wanted for the next observing cycles. The
work on this White Paper effort was coordinated in close cooperation
with the two international solar ALMA development studies led by
T. Bastian (NRAO, USA) and R. Brajsa, (ESO). This document will be
further updated until the beginning of Cycle 4 in October 2016. In
particular, we plan to adjust the technical capabilities of the solar
observing modes once finally decided and to further demonstrate the
feasibility and scientific potential of the included science cases by
means of numerical simulations of the solar atmosphere and corresponding
simulated ALMA observations.

---------------------------------------------------------
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: 3D Whole-prominence Fine Structure Modeling. II. Prominence
Evolution
Authors: Gunár, Stanislav; Mackay, Duncan H.
2015ApJ...812...93G Altcode:
We use the new three-dimensional (3D) whole-prominence fine structure
model to study the evolution of prominences and their fine structures
in response to changes in the underlying photospheric magnetic flux
distribution. The applied model combines a detailed 3D prominence
magnetic field configuration with a realistic description of the
prominence plasma distributed along multiple fine structures. In
addition, we utilize an approximate Hα visualization technique to
study the evolution of the visible cool prominence plasma both in
emission (prominence) and absorption (filament). We show that the
initial magnetic field configuration of the modeled prominence is
significantly disturbed by the changing position of a single polarity
of a magnetic bipole as the bipole is advected toward the main body
of the filament. This leads to the creation of a barb, which becomes
the dominant feature visible in the synthetic Hα images of both
the prominence and filament views. The evolution of the bipole also
creates conditions that lead to the disappearance and reappearance
of large portions of the main body. We also show that an arch-like
region containing a dark void (a bubble) can be naturally produced
in the synthetic prominence Hα images. While not visible in terms
of the magnetic field lines, it is due to a lack of Hα emission from
low-pressure, low-density plasma located in shallow magnetic dips lying
along the lines of sight intersecting the dark void. In addition, a
quasi-vertical small-scale feature consisting of short and deep dips,
piled one above the other, is produced.

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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.

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Title: Multi-wavelength synthetic flare loops from 2D simulations
with FLASH
Authors: none Heinzel, Petr; Gunar, Stanislav; Falewicz, Robert;
Rudawy, Pawel
2015IAUGA..2258400N Altcode:
MHD code FLASH has been used to simulate the temporal evolution of
the flare-loop system. Our 2D approach assumes a long arcade of
flare loops anchored in the chromospheric ribbons. As the result
of a gradual reconnection, the loop system is growing and the flare
ribbons are being more and more separated in agreement with typical
observations. Simultaneously, hot flare loops cool down and new hot
loops appear next to them. We simulate the temporal evolution of the
whole arcade of loops and synthesize the visibility of loops at various
stages of cooling. The coolest loops finally appear in the hydrogen
H-alpha line and are visualized using our new approximate method. The
resulting evolution demonstrates well both the spatial and temporal
behavior of multi-temperature loops, including their dynamics.

---------------------------------------------------------
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: Non-LTE modelling of prominence fine structures using hydrogen
Lyman-line profiles
Authors: Schwartz, P.; Gunár, S.; Curdt, W.
2015A&A...577A..92S Altcode:
 Aims: We perform a detailed statistical analysis of the spectral
Lyman-line observations of the quiescent prominence observed on May
18, 2005. Methods: We used a profile-to-profile comparison of
the synthetic Lyman spectra obtained by 2D single-thread prominence
fine-structure model as a starting point for a full statistical
analysis of the observed Lyman spectra. We employed 2D multi-thread
fine-structure models with random positions and line-of-sight velocities
of each thread to obtain a statistically significant set of synthetic
Lyman-line profiles. We used for the first time multi-thread models
composed of non-identical threads and viewed at line-of-sight angles
different from perpendicular to the magnetic field. Results:
We investigated the plasma properties of the prominence observed with
the SoHO/SUMER spectrograph on May 18, 2005 by comparing the histograms
of three statistical parameters characterizing the properties of the
synthetic and observed line profiles. In this way, the integrated
intensity, Lyman decrement ratio, and the ratio of intensity at the
central reversal to the average intensity of peaks provided insight
into the column mass and the central temperature of the prominence
fine structures.

---------------------------------------------------------
Title: 3D Whole-Prominence Fine Structure Modeling
Authors: Gunár, Stanislav; Mackay, Duncan H.
2015ApJ...803...64G Altcode:
We present the first 3D whole-prominence fine structure model. The
model combines a 3D magnetic field configuration of an entire prominence
obtained from nonlinear 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 multiple
fine structures within the 3D magnetic model. Through the use of a
novel radiative transfer visualization technique for the Hα line such
plasma-loaded magnetic field model produces synthetic images of the
modeled prominence comparable with high-resolution observations. This
allows us for the first time to use a single technique to consistently
study, in both emission on the limb and absorption against the solar
disk, the fine structures of prominences/filaments produced by a
magnetic field model.

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

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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: 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>

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Title: Modelling of quiescent prominence fine structures
Authors: Gunár, S.
2014IAUS..300...59G Altcode:
We review here the current status and the latest results of the
modelling of quiescent prominence fine structures. We begin with the
simulations of the prominence magnetic field configurations, through
an overview of the modelling of the fine structure formation and
dynamics, and with the emphasis on the radiative transfer modelling
of the realistic prominence fine structures. We also illuminate the
future directions of the field that lie in the combining of the existing
approaches into more complex multi-disciplinary models.

---------------------------------------------------------
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: 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: 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.

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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: 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: 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: 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: 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.

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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.

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Title:

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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.).

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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.

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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.

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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.

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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

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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

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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

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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).