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Author name code: koza
ADS astronomy entries on 2022-09-14
author:"Koza, Julius"
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Title: Coronal mass ejection followed by a prominence eruption and
a plasma blob as observed by Solar Orbiter
Authors: Bemporad, A.; Andretta, V.; Susino, R.; Mancuso, S.; Spadaro,
D.; Mierla, M.; Berghmans, D.; D'Huys, E.; Zhukov, A. N.; Talpeanu,
D. -C.; Colaninno, R.; Hess, P.; Koza, J.; Jejčič, S.; Heinzel,
P.; Antonucci, E.; Da Deppo, V.; Fineschi, S.; Frassati, F.; Jerse,
G.; Landini, F.; Naletto, G.; Nicolini, G.; Pancrazzi, M.; Romoli,
M.; Sasso, C.; Slemer, A.; Stangalini, M.; Teriaca, L.
2022A&A...665A...7B Altcode: 2022arXiv220210294B
Context. On 2021 February 12, two subsequent eruptions occurred above
the western limb of the Sun, as seen along the Sun-Earth line. The
first event was a typical slow coronal mass ejection (CME), followed
∼7 h later by a smaller and collimated prominence eruption,
originating south of the CME, followed by a plasma blob. These
events were observed not only by the SOHO and STEREO-A missions,
but also by the suite of remote-sensing instruments on board Solar
Orbiter. <BR /> Aims: We show how data acquired by the Full Sun
Imager (FSI), the Metis coronagraph, and the Heliospheric Imager
(HI) from the Solar Orbiter perspective can be combined to study
the eruptions and different source regions. Moreover, we show how
Metis data can be analyzed to provide new information about solar
eruptions. <BR /> Methods: Different 3D reconstruction methods were
applied to the data acquired by different spacecraft, including
remote-sensing instruments on board Solar Orbiter. Images acquired
by the two Metis channels in the visible light (VL) and H I Ly-α
line (UV) were combined to derive physical information about the
expanding plasma. The polarization ratio technique was also applied
for the first time to Metis images acquired in the VL channel. <BR
/> Results: The two eruptions were followed in 3D from their source
region to their expansion in the intermediate corona. By combining
VL and UV Metis data, the formation of a post-CME current sheet (CS)
was followed for the first time in the intermediate corona. The
plasma temperature gradient across a post-CME blob propagating
along the CS was also measured for the first time. Application
of the polarization ratio technique to Metis data shows that by
combining four different polarization measurements, the errors are
reduced by ∼5 − 7%. This constrains the 3D plasma distribution
better. <P />Movies associated to Figs. 4-7 are available at <A
href="https://www.aanda.org/10.1051/0004-6361/202243162/olm">https://www.aanda.org</A>
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Title: Dark off-limb gap: manifestation of temperature minimum and
dynamic nature of the chromosphere
Authors: Kuridze, D.; Heinzel, P.; Koza, J.; Oliver, R.
2022arXiv220814134K Altcode:
We study off-limb emission of the lower solar atmosphere using
high-resolution imaging spectroscopy in the H$\beta$ and Ca II 8542 Å
lines obtained with the CHROMospheric Imaging Spectrometer (CHROMIS)
and the CRisp Imaging SpectroPolarimeter (CRISP) on the Swedish 1-m
Solar Telescope. The H$\beta$ line wing images show the dark intensity
gap between the photospheric limb and chromosphere which is absent
in the Ca II images. We calculate synthetic spectra of the off-limb
emissions with the RH code in the one-dimension spherical geometry and
find good agreement with the observations. The analysis of synthetic
line profiles shows that the gap in the H$\beta$ line wing images maps
the temperature minimum region between the photosphere and chromosphere
due to the well known opacity and emissivity gap of Balmer lines in this
layer. However, observed gap is detected farther from the line core
in the outer line wing positions than in the synthetic profiles. We
found that an increased microturbulence in the model chromosphere is
needed to reproduce the dark gap in the outer line wing, suggesting that
observed H$\beta$ gap is the manifestation of the temperature minimum
and the dynamic nature of the solar chromosphere. The temperature
minimum produces a small enhancement in synthetic Ca II line-wing
intensities. Observed off-limb Ca II line-wing emissions show similar
enhancement below temperature minimum layer near the edge of the
photospheric limb.
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Title: Data-driven Model of Temporal Evolution of Solar Mg II h and
k Profiles over the Solar Cycle
Authors: Koza, Július; Gunár, Stanislav; Schwartz, Pavol; Heinzel,
Petr; Liu, Wenjuan
2022ApJS..261...17K Altcode:
The solar radiation in the cores of the Mg II h and k spectral lines
plays a significant role in the illumination of prominences, coronal
mass ejections (CMEs), spicules, flare loops, and surges. Moreover,
the radiation in these lines strongly correlates with solar magnetic
activity and the ultraviolet solar spectral irradiance affecting
the photochemistry, especially of oxygen and nitrogen, in the middle
atmosphere of the Earth. This work provides a data-driven model of
temporal evolution of the solar full-disk Mg II h and k profiles over
the solar cycle. The capability of the model to reproduce the Mg II h
and k profiles for an arbitrary date is statistically assessed. Based
on selected 76 IRIS near-UV full-Sun mosaics covering almost the full
solar cycle 24, we find the parameters of double-Gaussian fits of the
disk-averaged Mg II h and k profiles and a model of their temporal
evolution parameterized by the Bremen composite Mg II index. The
model yields intensities within the uncertainties of the observed
data in more than 90% of the reconstructed profiles assuming a
statistically representative set of Bremen Mg II index values in the
range of 0.150-0.165. The relevant full-disk Mg II h and k calibrated
profiles with uncertainties and spectral irradiances are provided as an
online machine-readable table. The model yields Mg II h and k profiles
representing the disk incident radiation for the radiative-transfer
modeling of prominences, CMEs, spicules, flare loops, and surges
observed at arbitrary time.
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Title: Large Impact of the Mg II h and k Incident Radiation Change
on Results of Radiative Transfer Models and the Importance of Dynamics
Authors: Gunár, Stanislav; Heinzel, Petr; Koza, Július; Schwartz,
Pavol
2022ApJ...934..133G Altcode:
We demonstrate that changes in the incident radiation in Mg II h
and k lines have a significant impact on the results of radiative
transfer modeling of prominence-like plasmas. To uncover the extent
of this impact and allow easy comparison, here we study two cases,
one representing the minimum of the solar activity and the other
corresponding to the typical conditions during solar maxima. To
represent well the properties of the prominence plasma, we use the 2D
non-LTE (i.e., departures from local thermodynamic equilibrium) model
of prominence fine structures in both the single-thread configuration
and the multithread configuration incorporating prominence dynamics. We
show that in the modeled environment of prominence fine structures,
the change in the central, integrated, and peak intensities of the
synthetic Mg II h and k profiles can be as large as the change in the
incident radiation itself. This means that the Mg II h and k spectra
of observed prominences can be affected by tens of percent because the
illumination from the solar disk can change by such a degree over the
solar cycle. That makes the knowledge and use of event-specific incident
radiation data very important for the diagnostics of prominences
and other chromospheric and coronal structures when using Mg II h
and k spectral observations. In addition, the observed Mg II h and k
spectra are strongly influenced by the line-of-sight dynamics, as the
multithread configuration of the 2D model allows us to reveal. The
effect of dynamics is, unsurprisingly, most pronounced in the line
widths and integrated intensities.
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Title: Variability of solar Lyman-alpha and Mg II h&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&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&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&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&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&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: VizieR Online Data Catalog: Quiet-Sun MgII h & 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). <P />(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: Semi-empirical Models of Spicule from Inversion of Ca II 8542
Å Line
Authors: Kuridze, David; Socas-Navarro, Hector; Koza, Július;
Oliver, Ramon
2021ApJ...908..168K Altcode: 2020arXiv201203702K
We study a solar spicule observed off-limb using high-resolution imaging
spectroscopy in the Ca II 8542 Å line obtained with the CRisp Imaging
SpectroPolarimeter (CRISP) on the Swedish 1 m Solar Telescope. Using
a new version of the non-LTE code NICOLE specifically developed
for this problem we invert the spicule single- and double-peak line
profiles. This new version considers off-limb geometry and computes
atomic populations by solving the 1D radiative transfer assuming
a vertical stratification. The inversion proceeds by fitting the
observed spectral profiles at 14 different heights with synthetic
profiles computed in the model by solving the radiative transfer
problem along its length. Motivated by the appearance of double-peak
Ca II 8542 Å spicule profiles, which exhibit two distinct emission
features well separated in wavelength, we adopt a double-component
scenario. We start from the ansatz that the spicule parameters are
practically constant along the spicule axis for each component,
except for a density drop. Our results support this ansatz by
attaining very good fits to the entire set of 14 × 4 profiles (14
heights and 4 times). We show that the double-component model with
uniform temperature of 9560 K, exponential decrease of density with a
height scale of 1000-2000 km, and the counter-oriented line-of-sight
velocities of components reproduce the double-peak line profiles at
all spicule segments well. Analyses of the numerical response function
reveals the necessity of the inversions of spectra at multiple height
positions to obtain height-dependent, degeneracy-free reliable models
with a limited number of free parameters.
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Title: Mapping the Magnetic Field of Flare Coronal Loops
Authors: Kuridze, David; Morgan, Huw; Oliver, Ramon; Mathioudakis,
Mihalis; Koza, Julius
2021cosp...43E1791K Altcode:
The magnetic field is key to the dynamics, evolution, and heating
of the solar atmosphere, yet direct measurements are rare and highly
uncertain. We report on the unique observation of flaring coronal loops
at the solar limb using high-resolution imaging spectropolarimetry from
the Swedish 1-m Solar Telescope. The vantage position, orientation,
and nature of the chromospheric material that filled the flare loops
allowed us to determine their magnetic field with unprecedented accuracy
using the weak-field approximation method. Our analysis reveals coronal
magnetic field strengths as high as 350 G at heights up to 25 Mm above
the solar limb. These measurements are substantially higher than a
number of previous estimates and may have considerable implications
for our current understanding of the extended solar atmosphere.
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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. <BR />
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. <BR /> 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. <BR /> 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. <P />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: Observational study of chromospheric heating by acoustic waves
Authors: Abbasvand, V.; Sobotka, M.; Švanda, M.; Heinzel, P.;
García-Rivas, M.; Denker, C.; Balthasar, H.; Verma, M.; Kontogiannis,
I.; Koza, J.; Korda, D.; Kuckein, C.
2020A&A...642A..52A Altcode: 2020arXiv200802688A
<BR /> Aims: Our aim is to investigate the role of acoustic and
magneto-acoustic waves in heating the solar chromosphere. Observations
in strong chromospheric lines are analyzed by comparing the deposited
acoustic-energy flux with the total integrated radiative losses. <BR
/> Methods: Quiet-Sun and weak-plage regions were observed in the Ca
II 854.2 nm and Hα lines with the Fast Imaging Solar Spectrograph
(FISS) at the 1.6-m Goode Solar Telescope on 2019 October 3 and
in the Hα and Hβ lines with the echelle spectrograph attached
to the Vacuum Tower Telescope on 2018 December 11 and 2019 June
6. The deposited acoustic energy flux at frequencies up to 20 mHz
was derived from Doppler velocities observed in line centers and
wings. Radiative losses were computed by means of a set of scaled
non-local thermodynamic equilibrium 1D hydrostatic semi-empirical
models obtained by fitting synthetic to observed line profiles. <BR />
Results: In the middle chromosphere (h = 1000-1400 km), the radiative
losses can be fully balanced by the deposited acoustic energy flux in
a quiet-Sun region. In the upper chromosphere (h > 1400 km), the
deposited acoustic flux is small compared to the radiative losses in
quiet as well as in plage regions. The crucial parameter determining
the amount of deposited acoustic flux is the gas density at a given
height. <BR /> Conclusions: The acoustic energy flux is efficiently
deposited in the middle chromosphere, where the density of gas is
sufficiently high. About 90% of the available acoustic energy flux in
the quiet-Sun region is deposited in these layers, and thus it is a
major contributor to the radiative losses of the middle chromosphere. In
the upper chromosphere, the deposited acoustic flux is too low, so that
other heating mechanisms have to act to balance the radiative cooling.
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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 lambda<SUB>0</SUB> of the
Lyman-alpha line is 1215.67Å (121.567nm). <P />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 lambda<SUB>0</SUB> of the
Lyman-alpha line is 1215.67Å (121.567nm). <P />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&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). <P />(3 data files).
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Title: Spectral Characteristics and Formation Height of Off-limb
Flare Ribbons
Authors: Kuridze, David; Mathioudakis, Mihalis; Heinzel, Petr; Koza,
Július; Morgan, Huw; Oliver, Ramon; Kowalski, Adam F.; Allred, Joel C.
2020ApJ...896..120K Altcode: 2020arXiv200510924K
Flare ribbons are bright manifestations of flare energy dissipation
in the lower solar atmosphere. For the first time, we report on
high-resolution imaging spectroscopy observations of flare ribbons
situated off limb in the Hβ and Ca II 8542 Å lines and make a detailed
comparison with radiative hydrodynamic simulations. Observations of
the X8.2 class solar flare SOL 2017-09-10T16:06 UT obtained with the
Swedish Solar Telescope reveal bright horizontal emission layers
in Hβ line-wing images located near the footpoints of the flare
loops. The apparent separation between the ribbon observed in the Hβ
wing and the nominal photospheric limb is about 300-500 km. The Ca II
8542 Å line-wing images show much fainter ribbon emissions located
right on the edge of the limb, without clear separation from the
limb. RADYN models are used to investigate synthetic spectral line
profiles for the flaring atmosphere, and good agreement is found
with the observations. The simulations show that, toward the limb,
where the line of sight is substantially oblique with respect to the
vertical direction, the flaring atmosphere model reproduces the high
contrast of the off-limb Hβ ribbons and their significant elevation
above the photosphere. The ribbons in the Ca II 8542 Å line-wing
images are located deeper in the lower solar atmosphere with a lower
contrast. A comparison of the height deposition of electron beam energy
and the intensity contribution function shows that the Hβ line-wing
intensities can be a useful tracer of flare energy deposition in the
lower solar atmosphere.
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Title: Signatures of Helium Continuum in Cool Flare Loops Observed
by SDO/AIA
Authors: Heinzel, Petr; Schwartz, Pavol; Lörinčík, Juraj; Koza,
Július; Jejčič, Sonja; Kuridze, David
2020ApJ...896L..35H Altcode: 2020arXiv200600574H
We present an analysis of off-limb cool flare loops observed by the
Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA)
during the gradual phase of SOL2017-09-10T16:06 X8.2-class flare. In the
extreme-ultraviolet (EUV) channels starting from the 335 Å one, cool
loops appear as dark structures against the bright loop arcade. These
dark structures were precisely coaligned (spatially and temporally)
with loops observed by Swedish Solar Telescope (SST) in emission lines
of hydrogen and ionized calcium. A recently published semi-empirical
model of cool loops based on SST observations serves to predict the
level of hydrogen and helium recombination continua. The continua were
synthesized using an approximate non-LTE (I.e., departures from local
thermodynamic equilibrium) approach and theoretical spectra were then
transformed to AIA signals. Comparison with signals detected inside
the dark loops shows that only in AIA 211 Å channel the computed
level of recombination continua is consistent with observations for
some models, while in all other channels that are more distant from
the continua edges the synthetic continuum is far too low. In analogy
with on-disk observations of flares we interpret the surplus emission
as due to numerous EUV lines emitted from hot but faint loops in front
of the cool ones. Finally we briefly comment on failure of the standard
absorption model when used for analysis of the dark-loop brightness.
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Title: Magnetic Flux Emergence in a Coronal Hole
Authors: Palacios, Judith; Utz, Dominik; Hofmeister, Stefan; Krikova,
Kilian; Gömöry, Peter; Kuckein, Christoph; Denker, Carsten; Verma,
Meetu; González Manrique, Sergio Javier; Campos Rozo, Jose Iván;
Koza, Július; Temmer, Manuela; Veronig, Astrid; Diercke, Andrea;
Kontogiannis, Ioannis; Cid, Consuelo
2020SoPh..295...64P Altcode: 2020arXiv200611779P
A joint campaign of various space-borne and ground-based observatories,
comprising the Japanese Hinode mission (Hinode Observing Plan 338,
20 - 30 September 2017), the GREGOR solar telescope, and the Vacuum
Tower Telescope (VTT), investigated numerous targets such as pores,
sunspots, and coronal holes. In this study, we focus on the coronal
hole region target. On 24 September 2017, a very extended non-polar
coronal hole developed patches of flux emergence, which contributed
to the decrease of the overall area of the coronal hole. These flux
emergence patches erode the coronal hole and transform the area into a
more quiet-Sun-like area, whereby bipolar magnetic structures play an
important role. Conversely, flux cancellation leads to the reduction
of opposite-polarity magnetic fields and to an increase in the area
of the coronal hole.
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Title: Spectral Diagnostics of Cool Flare Loops Observed by the
SST. I. Inversion of the Ca II 8542 Å and Hβ Lines
Authors: Koza, Július; Kuridze, David; Heinzel, Petr; Jejčič,
Sonja; Morgan, Huw; Zapiór, Maciej
2019ApJ...885..154K Altcode: 2019arXiv190907356K
Flare loops form an integral part of eruptive events, being detected in
the range of temperatures from X-rays down to cool chromospheric-like
plasmas. While hot loops are routinely observed by the Solar Dynamics
Observatory’s Atmospheric Imaging Assembly, cool loops seen
off-limb are rare. In this paper we employ unique observations of
the SOL2017-09-10T16:06 X8.2-class flare which produced an extended
arcade of loops. The Swedish 1 m Solar Telescope made a series of
spectral images of the cool off-limb loops in the Ca II 8542 Å and
the hydrogen Hβ lines. Our focus is on the loop apices. Non-local
thermal equilibrium (non-LTE; i.e., departures from LTE) spectral
inversion is achieved through the construction of extended grids of
models covering a realistic range of plasma parameters. The Multilevel
Accelerated Lambda Iterations code solves the non-LTE radiative-transfer
problem in a 1D externally illuminated slab, approximating the studied
loop segment. Inversion of the Ca II 8542 Å and Hβ lines yields two
similar solutions, both indicating high electron densities around 2 ×
10<SUP>12</SUP> cm<SUP>-3</SUP> and relatively large microturbulence
around 25 km s<SUP>-1</SUP>. These are in reasonable agreement with
other independent studies of the same or similar events. In particular,
the high electron densities in the range 10<SUP>12</SUP>-10<SUP>13</SUP>
cm<SUP>-3</SUP> are consistent with those derived from the Solar
Dynamics Observatory’s Helioseismic and Magnetic Imager white-light
observations. The presence of such high densities in solar eruptive
flares supports the loop interpretation of the optical continuum
emission of stars which manifest superflares.
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Title: Mapping the Magnetic Field of Flare Coronal Loops
Authors: Kuridze, D.; Mathioudakis, M.; Morgan, H.; Oliver, R.; Kleint,
L.; Zaqarashvili, T. V.; Reid, A.; Koza, J.; Löfdahl, M. G.; Hillberg,
T.; Kukhianidze, V.; Hanslmeier, A.
2019ApJ...874..126K Altcode: 2019arXiv190207514K
Here, we report on the unique observation of flaring coronal loops at
the solar limb using high-resolution imaging spectropolarimetry from
the Swedish 1 m Solar Telescope. The vantage position, orientation,
and nature of the chromospheric material that filled the flare loops
allowed us to determine their magnetic field with unprecedented accuracy
using the weak-field approximation method. Our analysis reveals coronal
magnetic field strengths as high as 350 G at heights up to 25 Mm above
the solar limb. These measurements are substantially higher than a
number of previous estimates and may have considerable implications
for our current understanding of the extended solar atmosphere.
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Title: The Distributed Cloud Based Engine for Knowledge Discovery
in Massive Archives of Astronomical Spectra
Authors: Škoda, P.; Koza, J.; Palička, A.; Lopatovský, L.;
Peterka, T.
2017ASPC..512..689S Altcode: 2017adass..25..689S; 2018ASPC..512..689S
The current archives of large-scale spectroscopic surveys, such as SDSS
or LAMOST, contain millions of spectra. As some interesting objects
(e.g. emission line stars or quasars) can be identified only by checking
the shapes of certain spectral lines, machine learning techniques have
to be applied, complemented by flexible visualisation of results. We
present VO-CLOUD, the distributed cloud-based engine, providing the user
with a comfortable web-based environment for conducting machine learning
experiments with different algorithms running on multiple nodes. It
allows visual backtracking of the individual input spectra at different
stages of preprocessing, which is important for checking the nature
of outliers or precision of classification. The engine consists of a
single master server, representing the user portal, and several workers,
running various types of machine learning tasks. The master holds
the database of users and their experiments, predefined configuration
parameters for individual machine learning models and a repository for
data to be preprocessed. The workers have different capabilities based
on the installed libraries and the hardware configuration of their host
(e.g. number of CPU cores or GPU card type) and more may be dynamically
added to provide new machine learning methods.
---------------------------------------------------------
Title: Spectroscopic Inversions of the Ca II 8542 Å Line in a
C-class Solar Flare
Authors: Kuridze, D.; Henriques, V.; Mathioudakis, M.; Koza, J.;
Zaqarashvili, T. V.; Rybák, J.; Hanslmeier, A.; Keenan, F. P.
2017ApJ...846....9K Altcode: 2017arXiv170800472K
We study the C8.4-class solar flare SOL2016-05-14T11:34 UT using
high-resolution spectral imaging in the Ca II 8542 Å line obtained
with the CRISP imaging spectropolarimeter on the Swedish 1 m Solar
Telescope. Spectroscopic inversions of the Ca II 8542 Å line using
the non-LTE code NICOLE are used to investigate the evolution of
the temperature and velocity structure in the flaring chromosphere. A
comparison of the temperature stratification in flaring and non-flaring
areas reveals strong footpoint heating during the flare peak in the
lower atmosphere. The temperature of the flaring footpoints between
{log} {τ }<SUB>500</SUB> ≈ -2.5 {and} -3.5, where τ <SUB>500</SUB>
is the continuum optical depth at 500 nm, is ∼ 5{--}6.5 {kK} close
to the flare peak, reducing gradually to ∼ 5 {kK}. The temperature in
the middle and upper chromosphere, between {log} {τ }<SUB>500</SUB>≈
-3.5 and -5.5, is estimated to be ∼6.5-20 kK, decreasing to preflare
temperatures, ∼5-10 kK, after approximately 15 minutes. However, the
temperature stratification of the non-flaring areas is unchanged. The
inverted velocity fields show that the flaring chromosphere is dominated
by weak downflowing condensations at the formation height of Ca II
8542 Å.
---------------------------------------------------------
Title: Spectral Characteristics of the He I D<SUB>3</SUB> Line in
a Quiescent Prominence Observed by THEMIS
Authors: Koza, Július; Rybák, Ján; Gömöry, Peter; Kozák, Matúš;
López Ariste, Arturo
2017SoPh..292...98K Altcode: 2017arXiv171209255K
We analyze the observations of a quiescent prominence acquired by
the Téléscope Heliographique pour l'Étude du Magnetisme et des
Instabilités Solaires (THEMIS) in the He I 5876 Å (He I D<SUB>3</SUB>)
multiplet aiming to measure the spectral characteristics of the He
I D<SUB>3</SUB> profiles and to find for them an adequate fitting
model. The component characteristics of the He I D<SUB>3</SUB> Stokes I
profiles are measured by the fitting system by approximating them with
a double Gaussian. This model yields an He I D<SUB>3</SUB> component
peak intensity ratio of 5.5 ±0.4 , which differs from the value of
8 expected in the optically thin limit. Most of the measured Doppler
velocities lie in the interval ± 5 km s<SUP>−1</SUP>, with a standard
deviation of ± 1.7 km s<SUP>−1</SUP> around the peak value of 0.4
km s<SUP>−1</SUP>. The wide distribution of the full-width at half
maximum has two maxima at 0.25 Å and 0.30 Å for the He I D<SUB>3</SUB>
blue component and two maxima at 0.22 Å and 0.31 Å for the red
component. The width ratio of the components is 1.04 ±0.18 . We show
that the double-Gaussian model systematically underestimates the blue
wing intensities. To solve this problem, we invoke a two-temperature
multi-Gaussian model, consisting of two double-Gaussians, which
provides a better representation of He I D<SUB>3</SUB> that is free
of the wing intensity deficit. This model suggests temperatures of
11.5 kK and 91 kK, respectively, for the cool and the hot component
of the target prominence. The cool and hot components of a typical He
I D<SUB>3</SUB> profile have component peak intensity ratios of 6.6
and 8, implying a prominence geometrical width of 17 Mm and an optical
thickness of 0.3 for the cool component, while the optical thickness of
the hot component is negligible. These prominence parameters seem to
be realistic, suggesting the physical adequacy of the multi-Gaussian
model with important implications for interpreting He I D<SUB>3</SUB>
spectropolarimetry by current inversion codes.
---------------------------------------------------------
Title: Flare-induced changes of the photospheric magnetic field in
a δ-spot deduced from ground-based observations
Authors: Gömöry, P.; Balthasar, H.; Kuckein, C.; Koza, J.;
Veronig, A. M.; González Manrique, S. J.; Kučera, A.; Schwartz,
P.; Hanslmeier, A.
2017A&A...602A..60G Altcode: 2017arXiv170406089G
<BR /> Aims: Changes of the magnetic field and the line-of-sight
velocities in the photosphere are being reported for an M-class
flare that originated at a δ-spot belonging to active region NOAA
11865. <BR /> Methods: High-resolution ground-based near-infrared
spectropolarimetric observations were acquired simultaneously in
two photospheric spectral lines, Fe I 10783 Å and Si I 10786 Å,
with the Tenerife Infrared Polarimeter at the Vacuum Tower Telescope
(VTT) in Tenerife on 2013 October 15. The observations covered several
stages of the M-class flare. Inversions of the full-Stokes vector of
both lines were carried out and the results were put into context using
(extreme)-ultraviolet filtergrams from the Solar Dynamics Observatory
(SDO). <BR /> Results: The active region showed high flaring activity
during the whole observing period. After the M-class flare, the
longitudinal magnetic field did not show significant changes along
the polarity inversion line (PIL). However, an enhancement of the
transverse magnetic field of approximately 550 G was found that
bridges the PIL and connects umbrae of opposite polarities in the
δ-spot. At the same time, a newly formed system of loops appeared
co-spatially in the corona as seen in 171 Å filtergrams of the
Atmospheric Imaging Assembly (AIA) on board SDO. However, we cannot
exclude that the magnetic connection between the umbrae already existed
in the upper atmosphere before the M-class flare and became visible
only later when it was filled with hot plasma. The photospheric
Doppler velocities show a persistent upflow pattern along the PIL
without significant changes due to the flare. <BR /> Conclusions:
The increase of the transverse component of the magnetic field after
the flare together with the newly formed loop system in the corona
support recent predictions of flare models and flare observations. <P
/>The movie associated to Figs. 4 and 5 is available at <A
href="http://www.aanda.org/10.1051/0004-6361/201730644/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: Probing the lower solar atmosphere with CRSIP-SST Data
Authors: Hanslmeier, Arnold; Zaqarashvili, Teimuraz; Koza, Julius;
Rybak, Jan
2017psio.confE.113H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Flare induced changes of the photospheric magnetic field in
a delta-spot deduced from ground-based observations
Authors: Gömöry, P.; Balthasar, H.; Kuckein, C.; Koza, J.;
Kuĉera, A.; González Manrique, S. J.; Schwartz, P.; Veronig, A. M.;
Hanslmeier, A.
2017psio.confE.107G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: NLTE modeling of a small active region filament observed with
the VTT
Authors: Schwartz, P.; Balthasar, H.; Kuckein, C.; Koza, J.; Gömöry,
P.; Rybák, J.; Heinzel, P.; Kučera, A.
2016AN....337.1045S Altcode:
An active region mini-discretionary-filament was observed with the
Vacuum Tower Telescope (VTT) in Tenerife simultaneously in the He
I infrared triplet using the Tenerife Infrared Polarimeter 1 (TIP
1), in Hα with the TESOS Fabry-Pérot interferometer, and in Ca II
8542 Å with the VTT spectrograph. The spectropolarimetric data were
inverted using the HAZEL code and Hα profiles were modelled by solving
a NLTE radiative transfer in a simple isobaric and isothermal 2D slab
irradiated both from its bottom and sides from the solar surface. It was
found that the mini-discretionary-filament is composed of horizontal
fluxtubes, along which the cool plasma of T∼10 000 K can flow with
very large, even supersonic, velocities.
---------------------------------------------------------
Title: Non-LTE Inversion of Spectropolarimetric and Spectroscopic
Observations of a Small Active-region Filament Observed at the VTT
Authors: Schwartz, P.; Balthasar, H.; Kuckein, C.; Koza, J.; Gömöry,
P.; Rybák, J.; Kučera, A.; Heinzel, P.
2016ASPC..504..205S Altcode:
An active region mini-filament was observed by VTT simultaneously
in the He<small>I</small> 10 830 Å triplet by the TIP 1
spectropolarimeter, in Hα by the TESOS Fabry-Pérot interferometer, and
in Ca <small>II</small> 8542 Å by the VTT spectrograph. The
spectropolarimetric data were inverted using the HAZEL code and Hα
profiles were modelled solving a NLTE radiative transfer in a simple
isobaric and isothermal 2D slab irradiated both from bottom and
sides. It was found that the mini-filament is composed of horizontal
fluxtubes, along which the cool plasma of T∼10 000 K can flow by
very large - even supersonic - velocities.
---------------------------------------------------------
Title: Photoelectric photometry era at the Astronomical Institute
of the Slovak Academy of Sciences III. Fast photometry
Authors: Vaňko, M.; Kollár, V.; Komžík, R.; Koza, J.; Pribulla, T.
2015CoSka..45...99V Altcode:
We present a continuation of the article series describing the
photoelectric photometry era at the Astronomical Institute of the Slovak
Academy of Sciences. The paper aims to provide a comprehensive technical
description of implementation of the fast photometry at the Stará
Lesná Observatory and estimates its photometric precision. Using
integration times of 0.1 s and 0.01 s, an estimated photometric
precision of the fast photometry is about 0.02 mag and 0.06 mag,
respectively. Here, we also show the observation principles of the fast
photometry and its use in positive observation of stellar occultation
lasting 18.44 s by the asteroid (85) Io.
---------------------------------------------------------
Title: The Košice meteorite fall: Recovery and strewn field
Authors: Tóth, Juraj; Svoreň, Ján; BorovičKa, Jiří Spurný,
Pavel; Igaz, Antal; Kornoš, Leonard; Vereš, Peter; Husárik,
Marek; Koza, Július; Kučera, Aleš Zigo, Pavel; Gajdoš, Štefan;
Világi, Jozef; Čapek, David; Krišandová, Zuzana; Tomko, Šdušan;
Ilha, Jiří Schunová, Eva; Bodnárová, Marcela; Búzová, Diana;
Krejčová, Tereza
2015M&PS...50..853T Altcode: 2015M&PS..tmp..174T
We provide the circumstances and details of the fireball observation,
search expeditions, recovery, strewn field, and physical characteristics
of the Košice meteorite that fell in Slovakia on February 28,
2010. The meteorite was only the 15th case of an observed bolide with
a recovered mass and subsequent orbit determination. Despite multiple
eyewitness reports of the bolide, only three videos from security
cameras in Hungary were used for the strewn field determination and
orbit computation. Multiple expeditions of professionals and individual
searchers found 218 fragments with total weight of 11.3 kg. The strewn
field with the size of 5 × 3 km is characterized with respect to the
space distribution of the fragments, their mass and size-frequency
distribution. This work describes a catalog of 78 fragments, mass,
size, volume, fusion crust, names of discoverers, geographic location,
and time of discovery, which represents the most complex study of a
fresh meteorite fall. From the analytical results, we classified the
Košice meteorite as an ordinary H5 chondrite.
---------------------------------------------------------
Title: Density, porosity and magnetic susceptibility of the Košice
meteorite shower and homogeneity of its parent meteoroid
Authors: Kohout, Tomáš; Havrila, Karol; Tóth, Juraj; Husárik,
Marek; Gritsevich, Maria; Britt, Daniel; Borovička, Jiří; Spurný,
Pavel; Igaz, Antal; Svoreň, Ján; Kornoš, Leonard; Vereš, Peter;
Koza, Július; Zigo, Pavol; Gajdoš, Štefan; Világi, Jozef; Čapek,
David; Krišandová, Zuzana; Tomko, Dušan; Šilha, Jiří; Schunová,
Eva; Bodnárová, Marcela; Búzová, Diana; Krejčová, Tereza
2014P&SS...93...96K Altcode: 2014arXiv1404.1245K
Bulk and grain densities, porosities, and magnetic susceptibilities
of 67 individuals of Košice H chondrite fall were measured. The mean
bulk and grain densities were determined to be 3.43 g/cm<SUP>3</SUP>
with standard deviation (s.d.) of 0.11 g/cm<SUP>3</SUP> and 3.79
g/cm<SUP>3</SUP> with s.d. 0.07 g/cm<SUP>3</SUP>, respectively. Porosity
is in the range from 4.2% to 16.1%. The logarithm of the apparent
magnetic susceptibility (in 10<SUP>-9</SUP> m<SUP>3</SUP>/kg) shows
narrow distribution from 5.17 to 5.49 with mean value at 5.35 with
s.d. 0.08. These results indicate that all studied Košice meteorites
are of the same composition down to ~g scale without the presence of
foreign (non-H) clasts and are similar to other H chondrites. Košice is
thus a homogeneous meteorite fall derived from a homogeneous meteoroid.
---------------------------------------------------------
Title: Inferring spectral characteristics of the Hα spectral line
observed by the DOT Lyot filter
Authors: Koza, J.; Rybák, J.; Gömöry, P.; Kučera, A.
2014CoSka..44...43K Altcode:
A tunable Lyot filter can serve as a spectroscopic device rendering
wide-field 2-D pseudospectroscopy of solar structures and follow-up
crude reconstruction of a spectral line profile at each pixel within the
field of view. We developed a method of inferring of the Doppler shift,
the core intensity, the core width, and the core asymmetry of the Hα
spectral line observed by the Lyot filter installed on the Dutch Open
Telescope (DOT). The spectral characteristics are inferred through the
fitting of five intensity samples, separated from each other by 0.35 Å,
by a 4<SUP>th</SUP>-order polynomial, a Gaussian, and a parabola. We
use the atlas Hα profile as a reference in estimating deviations
of the derived spectral characteristics. The Gaussian is the most
preferable means for measurements of the Doppler shift with deviations
smaller than 1 km s<SUP>-1</SUP>. When using the 4<SUP>th</SUP>-order
polynomial, deviations are within the interval ±2.5 km s<SUP>-1</SUP>,
but it renders comparable deviations of the core intensity and the
width as the Gaussian. The deviations are largely insensitive to the
shape of the filter transmission, but depend mostly non-linearly on
the Doppler shift. Therefore, they do not cancel out if the spectral
characteristics are represented by their relative variations. Results
can be used as corrections of spectral characteristics extracted from
area-averaged Hα profiles acquired by the DOT Lyot filter.
---------------------------------------------------------
Title: Chromospheric fine structure didactically
Authors: Koza, J.
2014CEAB...38...39K Altcode:
The solar chromosphere is occupied with a wealth of fine structures
referred to by diverse nomenclature. Recent identification of slow-mode
magnetoacoustic shocks, excited by p-modes of photospheric oscillations,
as plausible drivers of dynamic fibrils and spicules was followed by
a surge of observational studies and numerical simulations attempting
to reveal the role of chromospheric fine structure in energizing of
the upper solar atmosphere. The paper summarizes didactically this
breakthrough and provides ample references on the pertinent literature.
---------------------------------------------------------
Title: Transmission profile of the Dutch Open Telescope Hα Lyot
filter
Authors: Koza, J.; Hammerschlag, R. H.; Rybák, J.; Gömöry, P.;
Kučera, A.; Schwartz, P.
2014AN....335..409K Altcode: 2017arXiv171209253K
Context Accurate knowledge of the spectral transmission profile of
a Lyot filter is important, in particular in comparing observations
with simulated data. The paper summarizes available facts about the
transmission profile of the Dutch Open Telescope (DOT) Hα Lyot filter
pointing to a discrepancy between sidelobe-free Gaussian-like profile
measured spectroscopically and signatures of possible leakage of
parasitic continuum light in DOT Hα images. We compute wing-to-center
intensity ratios resulting from convolutions of Gaussian and square
of the sinc function with the Hα atlas profile and compare them with
the ratios derived from observations of the quiet Sun chromosphere at
disk center. We interpret discrepancies between the anticipated and
observed ratios and the sharp limb visible in the DOT Hα image as an
indication of possible leakage of parasitic continuum light. A method
suggested here can be applied also to indirect testing of transmission
profiles of other Lyot filters. We suggest two theoretical transmission
profiles of the DOT Hα Lyot filter which should be considered as the
best available approximations. Conclusive answer can only be given by
spectroscopic re-measurement of the filter.
---------------------------------------------------------
Title: Search for Alfvén waves in a bright network element observed
in Hα
Authors: Koza, J.; Sütterlin, P.; Gömöry, P.; Rybák, J.;
Kučera, A.
2013CoSka..43....5K Altcode: 2013arXiv1304.4027K
Alfvén waves are considered as potential transporters of energy
heating the solar corona. We seek spectroscopic signatures of the
Alfvén waves in the chromosphere occupied by a bright network element,
investigating temporal variations of the spectral width, intensity,
Dopplershift, and the asymmetry of the core of the Hα spectral
line observed by the tunable Lyot filter installed on the Dutch Open
Telescope. The spectral characteristics are derived through the fitting
of five intensity samples, separated from each other by 0.35 Å, by a
4<SUP>th</SUP>-order polynomial. The bright network element displays
the most pronounced variations of the Dopplershift varying from 0 to 4
km s<SUP>-1</SUP> about the average of 1.5 km s<SUP>-1</SUP>. This fact
implies a persistent redshift of the Hα core with a redward asymmetry
of about 0.5 km s<SUP>-1</SUP>, suggesting an inverse-C bisector. The
variations of the core intensity up to ±10 % and the core width up to
±5 % about the respective averages are much less pronounced, but still
detectable. The core intensity variations lag behind the Dopplershift
variations about 2.1 min. The Hα core width tends to correlate with
the Dopplershift and anticorrelate with the asymmetry, suggesting that
more redshifted Hα profiles are wider and the broadening of the Hα
core is accompanied with a change of the core asymmetry from redward
to blueward. We also found a striking anticorrelation between the
core asymmetry and the Dopplershift, suggesting a change of the core
asymmetry from redward to blueward with an increasing redshift of the
Hα core. The data and the applied analysis do not show meaningful
tracks of Alfvén waves in the selected network element.
---------------------------------------------------------
Title: Košice meteorite - recovery and the strew field
Authors: Toth, J.; Porubčan, V.; Borovička, J.; Igaz, A.; Spurný,
P.; Svoreň, J.; Husárik, M.; Kornoš, L.; Vereš, P.; Zigo, P.;
Koza, J.; Kučera, A.; Gajdoš, S.; Világi, J.; Čapek, D.; Šilha,
J.; Schunová, E.; Krišandová, Z.; Tomko, D.; Bodnárová, M.;
Búzová, D.; Krejčová, T.
2012epsc.conf..708T Altcode: 2012espc.conf..708T
The glare of the bolide on the night of February 28, 2010,
illuminated streets and interior of apartments, at some places in
Eastern Slovakia and Northern Hungary and cannon-like burst or series
of low frequency blasts were heard. Due to bad weather, cloudy skies
and scatter showers the Central European Fireball Network (operated
by Pavel Spurný of the Czech Academy of Sciences) did not take direct
optical records of the bolide and also the Slovak Video Meteor Network
(operated by Juraj Tóth of Comenius University in Bratislava) did
not operate that night so that at first moment it seemed that there
were no scientific records available of this event. Fortunately, fast
photoelectric sensors on 7 automated fireball stations in the Czech
Republic (6) and Austria (1) worked also under cloudy sky and recorded
the light curve of the bolide. It enabled to determine the exact time
and duration of the event and to estimate its brightness as well. The
bolide reached the maximum brightness of at least -18 magnitudes in one
huge flare. This light curve was used also for modeling of meteoroid
atmospheric fragmentation. Later, several surveillance cameras data
were published showing the moment when the night became a day. Three
videos from Hungary (Örkény village, Fazzi Daniella and Vass Gábor;
Telki village, contact persons Sárneczky Krisztián, Kiss László and
Budapest) actually captured the fireball itself. Thanks to calibration
of videos by several members of the Hungarian Astronomical Association
(MCSE - www.mcse.hu, namely by Igaz Antal) and the trajectory analysis
done by Jiří Borovička gave the hope that significant number
of meteorite fragments reached the surface. He also calculated the
impact area western of the city of Košice in Eastern Slovakia. The
data from the Local Seismic Network of Eastern Slovakia (Peter Moczo
of the Comenius University) analyzed by Pavel Kalenda confirmed the
atmospheric trajectory as well [1].
---------------------------------------------------------
Title: Search for the Star-Planet Interaction
Authors: Krejčová, Tereza; Budaj, Ján; Koza, Július
2012IAUS..282..125K Altcode: 2011arXiv1107.5940K
We analyse the chromospherical activity of stars with extrasolar
planets and search for a possible correlation between the equivalent
width of the core of the Ca II K line and orbital parameters of the
planet. We found statistically significant evidence that the equivalent
width of the Ca II K line reversal, which originates in the stellar
chromosphere, depends on the orbital period P<SUB>orb</SUB> of the
exoplanet. Planets orbiting stars with T<SUB>eff</SUB> < 5 500 K
and with P<SUB>orb</SUB> < 20 days generally have much stronger
emission than planets at similar temperatures but at longer orbital
periods. P<SUB>orb</SUB> = 20 days marks a sudden change in behaviour,
which might be associated with a qualitative change in the star-planet
interaction.
---------------------------------------------------------
Title: The spectral line Ba II 6497 Å as a sensitive Doppler
diagnostics
Authors: Koza, J.
2011CoSka..41..167K Altcode:
We present a quantitative and comparative analysis of sensitivity to the
line-of-sight velocity of the spectral line Ba II 6497 Å identified
as a very promising Doppler mapper of the solar photosphere and low
chromosphere. We examine its sensitivity to changes of the line-of-sight
velocity by sharpness of its line profile and the response function
to the line-of-sight velocity evaluated by the 1-D model of the
quiet solar atmosphere in the LTE approximation. We compare its
sensitivity with selected barium, iron, and chromium lines widely
used in the diagnostics of the solar photosphere. The set of selected
lines includes the Ba II 4554 Å line, generally considered to be an
excellent Doppler mapper. The comparison clearly shows that the line
Ba II 6497 Å is one of the most sensitive from the lines included
in our set. This is due to a favorable combination of a relatively
sharp line profile and a long wavelength implying a large Doppler
sensitivity. The line Ba II 6497 Å offers many advantages, making it
a highly recommendable choice for dedicated studies of line-of-sight
velocities in the photosphere and low chromosphere.
---------------------------------------------------------
Title: Sensitivity of Selected Ba II, Fe I, Fe II, and Cr I Spectral
Lines to Velocity in Quiet Solar Atmosphere
Authors: Koza, J.
2010SoPh..266..261K Altcode: 2010SoPh..tmp..161K
We examine the sensitivity of selected Ba II, Fe I, Fe II, and Cr I
spectral lines to changes of the line-of-sight velocity by sharpness of
their line profiles and response functions to line-of-sight velocity
evaluated by the 1-D model of the quiet solar atmosphere in the LTE
approximation. The set of selected lines includes the Ba II 4554
Å line, generally considered to be an excellent Doppler mapper. Our
findings confirm earlier results showing that the sensitivity increases
not only with wavelength, as anticipated from the Doppler relation,
but mainly with the sharpness of line profiles given by the ratio of
their depths and widths. The line Fe I 5247 Å is the most sensitive
in our set, whereas the Fe I and Fe II infrared lines show very low
sensitivity because of their large thermal widths. The line Ba II 4554
Å shows only moderate sensitivity due to its large width, given by a
broad hyperfine structure and isotopic split. For the first time we
identify a very promising and so far unknown Doppler mapper of the
solar photosphere and low chromosphere, which is the line Ba II 6497
Å. Its sensitivity is comparable with the sensitivity of Fe I 5247 Å
and clearly surpasses the sensitivity of Ba II 4554 Å. The line Ba II
6497 Å offers many advantages, making it a highly recommendable choice
for future studies of line-of-sight velocities in the photosphere and
low chromosphere.
---------------------------------------------------------
Title: Magnetic loop emergence within a granule
Authors: Gömöry, P.; Beck, C.; Balthasar, H.; Rybák, J.; Kučera,
A.; Koza, J.; Wöhl, H.
2010A&A...511A..14G Altcode: 2009arXiv0910.4449G
<BR /> Aims: We investigate the temporal evolution of magnetic
flux emerging within a granule in the quiet-Sun internetwork at
disk center. <BR /> Methods: We combined IR spectropolarimetry of
high angular resolution performed in two Fe i lines at 1565 nm with
speckle-reconstructed G-band imaging. We determined the magnetic
field parameters by a LTE inversion of the full Stokes vector using
the SIR code, and followed their evolution in time. To interpret
the observations, we created a geometrical model of a rising loop in
3D. The relevant parameters of the loop were matched to the observations
where possible. We then synthesized spectra from the 3D model for a
comparison to the observations. <BR /> Results: We found signatures of
magnetic flux emergence within a growing granule. In the early phases,
a horizontal magnetic field with a distinct linear polarization signal
dominated the emerging flux. Later on, two patches of opposite circular
polarization signal appeared symmetrically on either side of the linear
polarization patch, indicating a small loop-like structure. The mean
magnetic flux density of this loop was roughly 450 G, with a total
magnetic flux of around 3 × 10<SUP>17</SUP> Mx. During the ~12 min
episode of loop occurrence, the spatial extent of the loop increased
from about 1 to 2 arcsec. The middle part of the appearing feature
was blueshifted during its occurrence, supporting the scenario of an
emerging loop. There is also clear evidence for the interaction of
one loop footpoint with a preexisting magnetic structure of opposite
polarity. The temporal evolution of the observed spectra is reproduced
to first order by the spectra derived from the geometrical model. During
the phase of clearest visibility of the loop in the observations,
the observed and synthetic spectra match quantitatively. <BR />
Conclusions: The observed event can be explained as a case of flux
emergence in the shape of a small-scale loop. The fast disappearance
of the loop at the end could possibly be due to magnetic reconnection.
---------------------------------------------------------
Title: Dynamic Lyα jets
Authors: Koza, J.; Rutten, R. J.; Vourlidas, A.
2009A&A...499..917K Altcode: 2008arXiv0807.4889K
Context: The solar chromosphere and transition region are highly
structured and complex regimes. A recent breakthrough has been
the identification of dynamic fibrils observed in Hα as caused
by field-aligned magnetoacoustic shocks. <BR />Aims: We seek to
find whether such dynamic fibrils are also observed in Lyα. <BR
/>Methods: We used a brief sequence of four high-resolution Lyα
images of the solar limb taken by the Very high Angular resolution
ULtraviolet Telescope (VAULT), which displays many extending and
retracting Lyα jets. We measured their top trajectories and fitted
parabolas to the 30 best-defined ones. <BR />Results: Most jet tops move
supersonically. Half of them decelerate, sometimes superballistically,
the others accelerate. This bifurcation may arise from incomplete
sampling of recurrent jets. <BR />Conclusions: The similarities between
dynamic Lyα jets and Hα fibrils suggest that the magnetoacoustic
shocks causing dynamic Hα fibrils also affect dynamic Lyα jets.
---------------------------------------------------------
Title: Dynamic Fibrils in Ly-alpha
Authors: Koza, J.; Rutten, R. J.; Vourlidas, A.; Suetterlin, P.
2008ESPM...12.2.16K Altcode:
We have detected dynamic fibrils (DFs) in Ly-alpha filtergrams taken
with the rocket-borne Very high Angular resolution ULtraviolet Telescope
(VAULT). Although the data consist of only a 1-min sequence of 4
images taken near the solar limb during the second VAULT flight, they
enable us to identify and study the time evolution of over 50 DFs. Most
show parabolic trajectories in their angular extent, with supersonic
maximum velocities. The measured decelerations vary from sub-ballistic
to super-ballistic. The similarities with DFs seen in Halpha suggest a
common cause, possibly the presence of hot transition-region interfaces
around cool oscillation-fed jets.
---------------------------------------------------------
Title: Multi-wavelength Observations of Dynamic Fibrils in the Upper
Photosphere and Chromosphere
Authors: Kucera, A.; Beck, Ch.; Gomory, P.; Koza, J.; Woehl, H.;
Rybak, J.
2008ESPM...12.2.52K Altcode:
Spatial and temporal evolution of dynamic fibrils (DF) as well as
coupling with photospheric features was investigated. <P />The
main target were remnants in the active region 10997 on May 28,
2008. We used about 1 hour series of multi wavelength simultaneous
observations of the DFs and corresponding photospheric features. The
observations were performed with the german Vacuum Tower Telescope
equipped with several post-focus instruments. Namely: TESOS (Triple
Etalon SOlar Spectrometer) instrument was used in polarimetric mode
(VIP=Visual Imaging Polarimeter) to register 2D spectra of the DFs in
H-alpha line and in magnetically sensitive Fe I 630.2 nm line. TIP
(Tenerife Infrared Polarimeter) mounted on the Echelle spectrograph
was used for spectropolarimetric observations of two neutral iron
lines at 1.56 micrometers. We scanned 2D area 80" x 5", producing
thus 2D maps of intensity, velocity and magnetic field of the low
photosphere under the chromospheric fibril field. <P />Additionally
G-band and H-alpha images were registered with high cadence and
the supporting data from the TRACE satellite (17.1 nm, WL, Lyman
alpha line and 160 nm continuum) are also available. After careful
spatial coalignment of 2D maps we first selected numerous DFs in the
H-alpha images. Then we investigated temporal evolution of those DFs
concerning changes of their dimensions, positions and fluctuations
and correlated these characteristics with temporal evolution of the
intensities, velocities and magnetic field characteristics observed in
the spatially corresponding photosphere. The poster demonstrates the
complex observations, data reduction and coalignment and preliminary
results on coupling between DFs and underlying photospheric features.
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Title: Temporal Variations in Fibril Orientation
Authors: Koza, J.; Sütterlin, P.; Kučera, A.; Rybák, J.
2007ASPC..368..115K Altcode: 2007astro.ph..3733K
We measure variations in orientation of fourteen dynamic fibrils as
a function of time in a small isolated plage and nearby network using
a 10-min time sequence of Hα filtergrams obtained by the Dutch Open
Telescope. We found motions with average angular velocities of the
order of 1 deg min<SUP>-1</SUP> suggesting systematic turning from
one limit position to another, particularly apparent in the case of
fibrils with lifetimes of a few minutes. Shorter fibrils tend to turn
faster than longer ones, which we interpret as due to vortex flows in
the underlying granulation that twist magnetic fields.
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Title: The height dependence of temperature velocity correlation in
the solar photosphere
Authors: Koza, J.; Kučera, A.; Rybák, J.; Wöhl, H.
2007msfa.conf..139K Altcode: 2007arXiv0704.0603K
We derive correlation coefficients between temperature and line-of-sight
velocity as a function of optical depth throughout the solar photosphere
for the non-magnetic photosphere and a small area of enhanced magnetic
activity. The maximum anticorrelation of about -0.6 between temperature
and line-of-sight velocity in the non-magnetic photosphere occurs at
log [tau] 5 = -0.4. The magnetic field is another decorrelating factor
along with 5-min oscillations and seeing.
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Title: The Height Dependence of Quiet-Sun Photospheric Temperature
Fluctuations in Observations and Simulations
Authors: Koza, J.; Kučera, A.; Rybák, J.; Wöhl, H.
2006ASPC..354...43K Altcode:
We derive rms temperature fluctuations as a function of height
throughout the solar photosphere for the non-magnetic photosphere and
a small area of enhanced magnetic activity, through semi-empirical
inversion based on response functions of a 15-minute time sequence
of 118 arcsec-long slit spectrograms taken at disk center. While the
observed low photosphere shows small temperature fluctuations (about
≈ 50 K), the sub-photospheric layers and the upper photosphere
show larger fluctuations, with similar gradients as in 3-D radiation
discretionary-hydrodynamics simulations. However, the observed rms
temperature fluctuations are lower than in the simulations at all
depths, which we attribute to smearing by atmospheric seeing.
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Title: Photospheric modeling through spectral line
inversion. Temperature and radial velocity stratifications and
fluctuations
Authors: Koza, J.; Kučera, A.; Rybák, J.; Wöhl, H.
2006A&A...458..941K Altcode:
Aims.We aim to determine average radial stratifications of various
physical parameters throughout the solar photosphere at high angular
resolution for non-magnetic and magnetic areas and to compare these
with standard semiempirical 1D modeling and with 3D hydrodynamics (HD)
and magnetohydrodynamics (MHD) simulations.<BR /> Methods: .We analyse
a 15-min sequence of adaptive-optics spectrograms of very high angular
resolution taken at solar disk centre. We split the data between a
quiet area and a magnetic one and derive mean temperature and velocity
stratifications and fluctuations for these separately by applying
LTE inversion based on response functions.<BR /> Results: .The mean
temperature stratifications in the non-magnetic region agree well with
the classical 1D models and the 3D simulations at all heights. However,
the observed rms temperature is much lower than in the simulations,
the observed mean velocities indicate more upflows, and the observed
velocity fluctuations are smaller except in upper layers. Some of
the discrepancies are likely to result from remaining smearing by
atmospheric seeing and instrumental limitations. The magnetic area
shows conspicuous behaviour at large height. We also find evidence of
fast low-photosphere downflows in the magnetic area and of enhanced
temperature above a small pore.<BR />
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Title: Response Functions of Spectral Lines Suitable for Diagnostics
of Solar Rotation
Authors: Koza, J.; Kučera, A.
2005HvaOB..29...21K Altcode:
The response functions for temperature and line-of-sight velocity
of the medium-strong Fe II, strong Fe I and weak N II spectral lines
are examined. The lines were previously used for determination of the
depth dependence of the solar rotation velocity. The positions of local
maxima of the response functions to temperature and the calculated
optical depths of formation of line cores are confronted. The close
coincidence of these quantities is demonstrated and thus verifying
the correctness of the optical depth scale of the investigated solar
<P />rotation profile.
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Title: Velocity field in the intergranular atmosphere
Authors: Kučera, A.; Koza, J.; Bellot Rubio, L. R.; Hanslmeier, A.;
Rybák, J.; Wöhl, H.
2004HvaOB..28...19K Altcode:
The line-of-sight velocity ľand macroturbulent velocity are studied
in the centre of the intergranular space in the solar photosphere. An
inversion method is applied to a 4-min time sequence of Stokes
I spectra of the 5, 6 and 7 lines observed with high spatial and
temporal resolutions at solar disk centre. The results are presented
in the form of the functional dependence of ľ(logτ<SUB>5</SUB>,t)
and (t) on the continuum optical depth τ<SUB>5</SUB> at 500 nm and
time t. A ľof several hundreds of meters per second was found in the
upper photosphere (logτ<SUB>5</SUB>≤-1.5), where the plasma flows
away from the observer. On the contrary, upflows directed toward the
observer were found in deeper layers (logτ<SUB>5</SUB>>-1.5). The
typical value of in the centre of the intergranular space is found to be
∼1.7 kms, which is about 0.5 kms greater than in the adjacent granule.
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Title: The range of reliability of the line-of-sight velocity in a
semiempirical model of a granule
Authors: Koza, J.; Kučera, A.
2003CoSka..33..224K Altcode:
Stokes I response functions to the line-of-sight velocity
v<SUB>LOS</SUB> of two medium-strong Fe I 522.5 nm and Fe I 557.6 nm
lines and the weak line Fe I 557.7 nm have been calculated using a
semiempirical 1D model of the granular photosphere affected by 5-min
oscillations. A new method is presented allowing to estimate the range
of optical depths within which the inferred values of an atmospheric
parameter can be considered as reliable. The sensitivity of the
individual lines to the variations of v<SUB>LOS</SUB> is examined and
the range of reliability of v<SUB>LOS</SUB> is estimated applying the
new method. It is shown that for the given line set the Fe I 522.5 nm
line is the most sensitive one and, in turn, the Fe I 557.7 nm line
has very low sensitivity to the variations of v<SUB>LOS</SUB>. In
the case of the Fe I 522.5 nm line the impact of a v<SUB>LOS</SUB>
perturbation on the intensity of a profile point is about 50% greater
than that on the Fe I 557.6 nm line. As a consequence of evolution of
the physical conditions in a granule the range of reliability of the
model varies and it consists of two separate regions occupying the
lower and upper photosphere.
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Title: Evolution of temperature in granule and intergranular space
Authors: Koza, J.; Bellot Rubio, L. R.; Kučera, A.; Hanslmeier, A.;
Rybák, J.; Wöhl, H.
2003AN....324..349K Altcode:
The temporal evolution of temperature in a dissolving granule and
in an adjacent intergranular space is presented. The semi-empirical
evolutionary models have been calculated using an inversion method
applied to 4-min time series of Stokes I spectral line profiles. The
models are presented in the form of the functional dependence of
temperature T(log tau_5 ,t) on optical depth tau_5 at 500 nm and time
t. The observed disappearance of the granule is accompanied with overall
cooling of the granular photosphere. Temperature changes greater than
100 K have been found in deeper (log tau_5 >=0) and upper layers
(log tau_5 <=-2) whereas the intermediate layers are thermally
stable. The intergranular space, which is 2 arcsec off the granule,
keeps the temperature structure of the layers from log tau_5 =0.5 to
log tau_5 =-2 without global evolutionary changes except short-term
and spatially confined heating. Finally, the significant temperature
changes in the upper layers (log tau_5 <=-2.5) observed during the
time interval of 4 min are found to be typical for the granular and
intergranular photosphere.
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Title: Line-of-sight velocity in a semiempirical model of a
disappearing granule
Authors: Koza, J.; Bellot Rubio, L. R.; Kučera, A.; Hanslmeier, A.;
Rybák, J.; Wöhl, H.
2002ESASP.506..443K Altcode: 2002svco.conf..443K; 2002ESPM...10..443K
The behaviour of the line-of-sight velocity in the centre of a
disappearing granule is analyzed using an inversion method applied
to a time-series of spectra containing the Fe I 522.5 nm, 557.6
nm and 557.7 nm lines. The temporal evolution of the line-of-sight
velocity v<SUB>LOS</SUB> is presented in the form of the functional
dependence of v<SUB>LOS</SUB>(logτ<SUB>5</SUB>, t) on the optical
depth τ<SUB>5</SUB> at 500 nm and time t. An oscillatory behaviour
is found in the velocity stratification with nearly constant phase
through the photosphere. The amplitude of variations increases from
logτ<SUB>5</SUB> = -0.3 to logτ<SUB>5</SUB> = -2.5 reaching a maximum
of ~1.2 km s<SUP>-1</SUP>. A zero velocity layer is detected in every
instantaneous model of the velocity stratification. The results suggest,
that the zero velocity may occur in a considerable range of the optical
depths from logτ<SUB>5</SUB> ~ -2 to logτ<SUB>5</SUB> ~ -3.5.
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Title: Temporal evolution of physical parameters in granule
Authors: Koza, J.; Kucera, A.; Hanslmeier, A.; Rybák, J.; Wöhl, H.
2002ESASP.505..457K Altcode: 2002solm.conf..457K; 2002IAUCo.188..457K
The temporal evolution of the physical parameters inside a granule
is presented. This is a step towards a more realistic 1D modeling
of the solar granulation, avoiding the temporal averaging used up
to now. The granulation is treated as a dynamical phenomenon and our
model has been calculated using an inversion method applied to time
series of spectra. The granular evolutionary model is presented in
the form of the functional dependence of temperature T(log τ, t) and
line-of-sight velocity v<SUB>LOS</SUB>(log τ, t) on optical depth τ
and time t. The observed disappearance of the granule is accompanied
with significant temperature changes greater than ~300K in deeper layers
(log τ<SUB>5</SUB> > 0) and upper layers (log τ<SUB>5</SUB> <
-2.5). In contrary, the layers from log τ<SUB>5</SUB> ~= -0.5 to log
τ<SUB>5</SUB> ~= -1.5 are more stable in the sense of temperature
variations, which are less than ~150K. An oscillatory behavior is
found in the line-of-sight velocity stratification from log τ5 ~= 0
upwards with increasing amplitude reaching up to ~= 2 km s<SUP>-1</SUP>
in upper layers.
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Title: Spectral line response to temperature perturbation in solar
and stellar photospheric models. I. Neutral Fe I line 522.5nm case
Authors: Koza, J.; Kučera, A.
2002CoSka..32..190K Altcode:
The sensitivity of the line profile of the neutral Fe I 522.5nm line to
Gaussian perturbations of temperature distribution in the photospheric
models is examined. Stokes I response functions to temperature of
the Fe I 522.5nm line have been calculated using different classes
of the solar photospheric models. In the LTE approximation three
one-component models HOLMU, HSRA, VAL3C and a new two-component
photospheric model are tested. In the (log τ<SUB>5</SUB>, λ) plane
the response functions have been calculated for all four models. It
is shown that in the case of one-component models, the temperature
perturbation in the upper photospheric layers only affects the core
of the line profile and in contrast, the temperature perturbation
of the deep photosphere affects only the line-wings. This is not the
case in the two-component model, where the heating or cooling of the
upper photosphere significantly modifies not only the line-core but
also the wings. A detailed examination of this effect is presented and
discussed to point out the incompatibility of simplified one-component
models with the real physical conditions of the stellar photosphere.
