Author name code: koza ADS astronomy entries on 2022-09-14 author:"Koza, Julius" ------------------------------------------------------------------------ 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. Bibcode: 2022A&A...665A...7B Altcode: 2022arXiv220210294B Context. On 2021 February 12, two subsequent eruptions occurred above the western limb of the Sun, as seen along the Sun-Earth line. The first event was a typical slow coronal mass ejection (CME), followed ∼7 h later by a smaller and collimated prominence eruption, originating south of the CME, followed by a plasma blob. These events were observed not only by the SOHO and STEREO-A missions, but also by the suite of remote-sensing instruments on board Solar Orbiter.
Aims: We show how data acquired by the Full Sun Imager (FSI), the Metis coronagraph, and the Heliospheric Imager (HI) from the Solar Orbiter perspective can be combined to study the eruptions and different source regions. Moreover, we show how Metis data can be analyzed to provide new information about solar eruptions.
Methods: Different 3D reconstruction methods were applied to the data acquired by different spacecraft, including remote-sensing instruments on board Solar Orbiter. Images acquired by the two Metis channels in the visible light (VL) and H I Ly-α line (UV) were combined to derive physical information about the expanding plasma. The polarization ratio technique was also applied for the first time to Metis images acquired in the VL channel.
Results: The two eruptions were followed in 3D from their source region to their expansion in the intermediate corona. By combining VL and UV Metis data, the formation of a post-CME current sheet (CS) was followed for the first time in the intermediate corona. The plasma temperature gradient across a post-CME blob propagating along the CS was also measured for the first time. Application of the polarization ratio technique to Metis data shows that by combining four different polarization measurements, the errors are reduced by ∼5 − 7%. This constrains the 3D plasma distribution better.

Movies associated to Figs. 4-7 are available at https://www.aanda.org Title: Dark off-limb gap: manifestation of temperature minimum and dynamic nature of the chromosphere Authors: Kuridze, D.; Heinzel, P.; Koza, J.; Oliver, R. Bibcode: 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. 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 Bibcode: 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. 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 Bibcode: 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. 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 Bibcode: 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. 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. Bibcode: 2021yCat..22550016G Altcode: Since its launch, the Interface Region Imaging Spectrograph (IRIS) commenced a quasi-regular acquisition of maps of the entire solar disk in both NUV and FUV spectral ranges. At the time of writing, the archive of the IRIS full-Sun mosaics contained 91 observations spanning the period from 2013 September 30 to 2020 October 19 which cover two spectral windows of +/-1.75Å centered at 2803.53Å (MgII h) and 2796.35Å (MgII k).

(4 data files). Title: 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 Bibcode: 2021ApJS..255...16G Altcode: We derived high-precision reference profiles of the Mg II h and k lines that represent the quiet Sun during a minimum of the solar activity. To do so, we used the broad catalog of full-Sun mosaics obtained by the Interface Region Imaging Spectrograph (IRIS). To minimize the influence of the local variations due to the on-disk solar features and to achieve low levels of uncertainties, we used 12 IRIS full-Sun mosaics without sunspots or other significant signs of solar activity. These mosaics were obtained between 2019 April and 2020 September in the near-ultraviolet spectral range. In this paper, we present the disk-averaged reference profiles of Mg II h and Mg II k lines, together with a series of reference profiles spanning the distance between the disk center and the solar limb. These series of profiles offer a detailed representation of the center-to-limb variation of both Mg II h and Mg II k lines. The reference Mg II h and k line profiles provided in this paper can be used as the incident radiation boundary condition for radiative-transfer modeling of prominences, spicules, and other coronal and chromospheric structures. Title: Semi-empirical Models of Spicule from Inversion of Ca II 8542 Å Line Authors: Kuridze, David; Socas-Navarro, Hector; Koza, Július; Oliver, Ramon Bibcode: 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. Title: Mapping the Magnetic Field of Flare Coronal Loops Authors: Kuridze, David; Morgan, Huw; Oliver, Ramon; Mathioudakis, Mihalis; Koza, Julius Bibcode: 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. Title: Quiet-Sun hydrogen Lyman-α line profile derived from SOHO/SUMER solar-disk observations Authors: Gunár, S.; Schwartz, P.; Koza, J.; Heinzel, P. Bibcode: 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 http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/644/A109 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. Bibcode: 2020A&A...642A..52A Altcode: 2020arXiv200802688A
Aims: Our aim is to investigate the role of acoustic and magneto-acoustic waves in heating the solar chromosphere. Observations in strong chromospheric lines are analyzed by comparing the deposited acoustic-energy flux with the total integrated radiative losses.
Methods: Quiet-Sun and weak-plage regions were observed in the Ca II 854.2 nm and Hα lines with the Fast Imaging Solar Spectrograph (FISS) at the 1.6-m Goode Solar Telescope on 2019 October 3 and in the Hα and Hβ lines with the echelle spectrograph attached to the Vacuum Tower Telescope on 2018 December 11 and 2019 June 6. The deposited acoustic energy flux at frequencies up to 20 mHz was derived from Doppler velocities observed in line centers and wings. Radiative losses were computed by means of a set of scaled non-local thermodynamic equilibrium 1D hydrostatic semi-empirical models obtained by fitting synthetic to observed line profiles.
Results: In the middle chromosphere (h = 1000-1400 km), the radiative losses can be fully balanced by the deposited acoustic energy flux in a quiet-Sun region. In the upper chromosphere (h > 1400 km), the deposited acoustic flux is small compared to the radiative losses in quiet as well as in plage regions. The crucial parameter determining the amount of deposited acoustic flux is the gas density at a given height.
Conclusions: The acoustic energy flux is efficiently deposited in the middle chromosphere, where the density of gas is sufficiently high. About 90% of the available acoustic energy flux in the quiet-Sun region is deposited in these layers, and thus it is a major contributor to the radiative losses of the middle chromosphere. In the upper chromosphere, the deposited acoustic flux is too low, so that other heating mechanisms have to act to balance the radiative cooling. Title: VizieR Online Data Catalog: Quiet-sun hydrogen Lyman-alpha line profile (Gunar+, 2020) Authors: Gunar, S.; Schwartz, P.; Koza, J.; Heinzel, P. Bibcode: 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&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). 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. Bibcode: 2020ApJ...896..120K Altcode: 2020arXiv200510924K Flare ribbons are bright manifestations of flare energy dissipation in the lower solar atmosphere. For the first time, we report on high-resolution imaging spectroscopy observations of flare ribbons situated off limb in the Hβ and Ca II 8542 Å lines and make a detailed comparison with radiative hydrodynamic simulations. Observations of the X8.2 class solar flare SOL 2017-09-10T16:06 UT obtained with the Swedish Solar Telescope reveal bright horizontal emission layers in Hβ line-wing images located near the footpoints of the flare loops. The apparent separation between the ribbon observed in the Hβ wing and the nominal photospheric limb is about 300-500 km. The Ca II 8542 Å line-wing images show much fainter ribbon emissions located right on the edge of the limb, without clear separation from the limb. RADYN models are used to investigate synthetic spectral line profiles for the flaring atmosphere, and good agreement is found with the observations. The simulations show that, toward the limb, where the line of sight is substantially oblique with respect to the vertical direction, the flaring atmosphere model reproduces the high contrast of the off-limb Hβ ribbons and their significant elevation above the photosphere. The ribbons in the Ca II 8542 Å line-wing images are located deeper in the lower solar atmosphere with a lower contrast. A comparison of the height deposition of electron beam energy and the intensity contribution function shows that the Hβ line-wing intensities can be a useful tracer of flare energy deposition in the lower solar atmosphere. Title: Signatures of Helium Continuum in Cool Flare Loops Observed by SDO/AIA Authors: Heinzel, Petr; Schwartz, Pavol; Lörinčík, Juraj; Koza, Július; Jejčič, Sonja; Kuridze, David Bibcode: 2020ApJ...896L..35H Altcode: 2020arXiv200600574H We present an analysis of off-limb cool flare loops observed by the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) during the gradual phase of SOL2017-09-10T16:06 X8.2-class flare. In the extreme-ultraviolet (EUV) channels starting from the 335 Å one, cool loops appear as dark structures against the bright loop arcade. These dark structures were precisely coaligned (spatially and temporally) with loops observed by Swedish Solar Telescope (SST) in emission lines of hydrogen and ionized calcium. A recently published semi-empirical model of cool loops based on SST observations serves to predict the level of hydrogen and helium recombination continua. The continua were synthesized using an approximate non-LTE (I.e., departures from local thermodynamic equilibrium) approach and theoretical spectra were then transformed to AIA signals. Comparison with signals detected inside the dark loops shows that only in AIA 211 Å channel the computed level of recombination continua is consistent with observations for some models, while in all other channels that are more distant from the continua edges the synthetic continuum is far too low. In analogy with on-disk observations of flares we interpret the surplus emission as due to numerous EUV lines emitted from hot but faint loops in front of the cool ones. Finally we briefly comment on failure of the standard absorption model when used for analysis of the dark-loop brightness. Title: 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 Bibcode: 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. 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 Bibcode: 2019ApJ...885..154K Altcode: 2019arXiv190907356K Flare loops form an integral part of eruptive events, being detected in the range of temperatures from X-rays down to cool chromospheric-like plasmas. While hot loops are routinely observed by the Solar Dynamics Observatory’s Atmospheric Imaging Assembly, cool loops seen off-limb are rare. In this paper we employ unique observations of the SOL2017-09-10T16:06 X8.2-class flare which produced an extended arcade of loops. The Swedish 1 m Solar Telescope made a series of spectral images of the cool off-limb loops in the Ca II 8542 Å and the hydrogen Hβ lines. Our focus is on the loop apices. Non-local thermal equilibrium (non-LTE; i.e., departures from LTE) spectral inversion is achieved through the construction of extended grids of models covering a realistic range of plasma parameters. The Multilevel Accelerated Lambda Iterations code solves the non-LTE radiative-transfer problem in a 1D externally illuminated slab, approximating the studied loop segment. Inversion of the Ca II 8542 Å and Hβ lines yields two similar solutions, both indicating high electron densities around 2 × 1012 cm-3 and relatively large microturbulence around 25 km s-1. These are in reasonable agreement with other independent studies of the same or similar events. In particular, the high electron densities in the range 1012-1013 cm-3 are consistent with those derived from the Solar Dynamics Observatory’s Helioseismic and Magnetic Imager white-light observations. The presence of such high densities in solar eruptive flares supports the loop interpretation of the optical continuum emission of stars which manifest superflares. Title: 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. Bibcode: 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. 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. Bibcode: 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. Bibcode: 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 }500 ≈ -2.5 {and} -3.5, where τ 500 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 }500≈ -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 D3 Line in a Quiescent Prominence Observed by THEMIS Authors: Koza, Július; Rybák, Ján; Gömöry, Peter; Kozák, Matúš; López Ariste, Arturo Bibcode: 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 D3) multiplet aiming to measure the spectral characteristics of the He I D3 profiles and to find for them an adequate fitting model. The component characteristics of the He I D3 Stokes I profiles are measured by the fitting system by approximating them with a double Gaussian. This model yields an He I D3 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−1, with a standard deviation of ± 1.7 km s−1 around the peak value of 0.4 km s−1. 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 D3 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 D3 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 D3 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 D3 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. Bibcode: 2017A&A...602A..60G Altcode: 2017arXiv170406089G
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.
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).
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.
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.

The movie associated to Figs. 4 and 5 is available at http://www.aanda.org Title: Probing the lower solar atmosphere with CRSIP-SST Data Authors: Hanslmeier, Arnold; Zaqarashvili, Teimuraz; Koza, Julius; Rybak, Jan Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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/cm3 with standard deviation (s.d.) of 0.11 g/cm3 and 3.79 g/cm3 with s.d. 0.07 g/cm3, respectively. Porosity is in the range from 4.2% to 16.1%. The logarithm of the apparent magnetic susceptibility (in 10-9 m3/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. Bibcode: 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 4th-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-1. When using the 4th-order polynomial, deviations are within the interval ±2.5 km s-1, 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 4th-order polynomial. The bright network element displays the most pronounced variations of the Dopplershift varying from 0 to 4 km s-1 about the average of 1.5 km s-1. This fact implies a persistent redshift of the Hα core with a redward asymmetry of about 0.5 km s-1, 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. Bibcode: 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 Bibcode: 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 Porb of the exoplanet. Planets orbiting stars with Teff < 5 500 K and with Porb < 20 days generally have much stronger emission than planets at similar temperatures but at longer orbital periods. Porb = 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. Bibcode: 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. Bibcode: 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. Bibcode: 2010A&A...511A..14G Altcode: 2009arXiv0910.4449G
Aims: We investigate the temporal evolution of magnetic flux emerging within a granule in the quiet-Sun internetwork at disk center.
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.
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 × 1017 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.
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. Bibcode: 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.
Aims: We seek to find whether such dynamic fibrils are also observed in Lyα.
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.
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.
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. Bibcode: 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. Bibcode: 2008ESPM...12.2.52K Altcode: Spatial and temporal evolution of dynamic fibrils (DF) as well as coupling with photospheric features was investigated.

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.

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. Title: Temporal Variations in Fibril Orientation Authors: Koza, J.; Sütterlin, P.; Kučera, A.; Rybák, J. Bibcode: 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-1 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. Title: The height dependence of temperature velocity correlation in the solar photosphere Authors: Koza, J.; Kučera, A.; Rybák, J.; Wöhl, H. Bibcode: 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. Title: The Height Dependence of Quiet-Sun Photospheric Temperature Fluctuations in Observations and Simulations Authors: Koza, J.; Kučera, A.; Rybák, J.; Wöhl, H. Bibcode: 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. Title: Photospheric modeling through spectral line inversion. Temperature and radial velocity stratifications and fluctuations Authors: Koza, J.; Kučera, A.; Rybák, J.; Wöhl, H. Bibcode: 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.
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.
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.
Title: Response Functions of Spectral Lines Suitable for Diagnostics of Solar Rotation Authors: Koza, J.; Kučera, A. Bibcode: 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

rotation profile. Title: Velocity field in the intergranular atmosphere Authors: Kučera, A.; Koza, J.; Bellot Rubio, L. R.; Hanslmeier, A.; Rybák, J.; Wöhl, H. Bibcode: 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(logτ5,t) and (t) on the continuum optical depth τ5 at 500 nm and time t. A ľof several hundreds of meters per second was found in the upper photosphere (logτ5≤-1.5), where the plasma flows away from the observer. On the contrary, upflows directed toward the observer were found in deeper layers (logτ5>-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. Title: The range of reliability of the line-of-sight velocity in a semiempirical model of a granule Authors: Koza, J.; Kučera, A. Bibcode: 2003CoSka..33..224K Altcode: Stokes I response functions to the line-of-sight velocity vLOS 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 vLOS is examined and the range of reliability of vLOS 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 vLOS. In the case of the Fe I 522.5 nm line the impact of a vLOS 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. Title: Evolution of temperature in granule and intergranular space Authors: Koza, J.; Bellot Rubio, L. R.; Kučera, A.; Hanslmeier, A.; Rybák, J.; Wöhl, H. Bibcode: 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. 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. Bibcode: 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 vLOS is presented in the form of the functional dependence of vLOS(logτ5, t) on the optical depth τ5 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 logτ5 = -0.3 to logτ5 = -2.5 reaching a maximum of ~1.2 km s-1. 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 logτ5 ~ -2 to logτ5 ~ -3.5. Title: Temporal evolution of physical parameters in granule Authors: Koza, J.; Kucera, A.; Hanslmeier, A.; Rybák, J.; Wöhl, H. Bibcode: 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 vLOS(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 τ5 > 0) and upper layers (log τ5 < -2.5). In contrary, the layers from log τ5 ~= -0.5 to log τ5 ~= -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-1 in upper layers. 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. Bibcode: 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 τ5, 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.