Author name code: bodnarova ADS astronomy entries on 2022-09-14 author:"Bodnarova, Marcela" ------------------------------------------------------------------------ Title: The Effect of Area Averaging on the Approximated Profile of the H α Spectral Line Authors: Bodnárová, M.; Utz, D.; Rybák, J. Bibcode: 2016ASPC..504...23B Altcode: The Hα line is massively used as a diagnostics of the chromosphere. Often one needs to average the line profile over some area to increase the signal to noise ratio. Thus it is important to understand how derived parameters vary with changing approximations. In this study we investigate the effect of spatial averaging of a selected area on the temporal variations of the width, the intensity and the Dopplershift of the Hα spectral line profile. The approximated profile was deduced from co-temporal observations in five points throughout the Hα line profile obtained by the tunable Lyot filter installed on the Dutch Open Telescope. We found variations of the intensity and the Doppler velocities, which were independent of the size of the area used for the computation of the area averaged Hα spectral line profile. Title: Long-term trends of magnetic bright points. I. Number of magnetic bright points at disc centre Authors: Utz, D.; Muller, R.; Thonhofer, S.; Veronig, A.; Hanslmeier, A.; Bodnárová, M.; Bárta, M.; del Toro Iniesta, J. C. Bibcode: 2016A&A...585A..39U Altcode: 2015arXiv151107767U Context. The Sun shows an activity cycle that is caused by its varying global magnetic field. During a solar cycle, sunspots, I.e. extended regions of strong magnetic fields, occur in activity belts that are slowly migrating from middle to lower latitudes, finally arriving close to the equator during the cycle maximum phase. While this and other facts about the strong extended magnetic fields have been well known for centuries, much less is known about the solar cycle evolution of small-scale magnetic fields. Thus the question arises if similar principles exist for small-scale magnetic fields.
Aims: To address this question, we study magnetic bright points (MBPs) as proxies for such small-scale, kG solar magnetic fields. This study is based on a homogeneous data set that covers a period of eight years. The number of detected MBPs versus time is analysed to find out if there is an activity cycle for these magnetic features too and, if so, how it is related to the sunspot cycle.
Methods: An automated MBP identification algorithm was applied to the synoptic Hinode/SOT G-band data over the period November 2006 to August 2014, I.e. covering the decreasing phase of Cycle 23 and the rise, maximum, and early decrease of Cycle 24. This data set includes, at the moment of investigation, a total of 4162 images, with about 2.9 million single MBP detections.
Results: After a careful preselection and monthly median filtering of the data, the investigation revealed that the number of MBPs close to the equator is coupled to the global solar cycle but shifted in time by about 2.5 yr. Furthermore, the instantaneous number of detected MBPs depends on the hemisphere, with one hemisphere being more prominent, I.e. showing a higher number of MBPs. After the end of Cycle 23 and at the starting point of Cycle 24, the more active hemisphere changed from south to north. Clear peaks in the detected number of MBPs are found at latitudes of about ±7°, in congruence with the positions of the sunspot belts at the end of the solar cycle.
Conclusions: These findings suggest that there is indeed a coupling between the activity of MBPs close to the equator with the global magnetic field. The results also indicate that a significant fraction of the magnetic flux that is visible as MBPs close to the equator originates from the sunspot activity belts. However, even during the minimum of MBP activity, a percentage as large as 60% of the maximum number of detected MBPs has been observed, which may be related to solar surface dynamo action. 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: Long time variations of Magnetic Bright Points observed by Hinode/SOT Authors: Utz, D.; del Toro Iniesta, J. C.; Bellot-Rubio, L.; Bodnárová, M.; Muller, R.; Bárta, M.; Thonhofer, S.; Hanslmeier, A. Bibcode: 2015CEAB...39...91U Altcode: Magnetic bright points (MBPs) are manifestations of small-scale solar magnetic flux concentrations, best observable due to their high contrast in molecular bands like the G-band. Moreover, they are among the most interesting magnetic features to be studied in high spatial and temporal resolution in the solar photosphere. Their relevance for solar physics is not only given by their contribution to fundamental solar plasma physics on small scales but in addition due to their involvement in processes like the solar atmospheric heating problem (chromosphere and corona), their influence on granulation and hence the convective energy transport, as well as their contribution to the variations in total solar irradiance caused by their higher relative intensity. In this ongoing study we focus on the long-time evolution of statistical parameters of MBPs over the solar cycle. Are parameters like the mean intensity, average size/diameter, and number of MBPs per unit surface element variable with time? If so, how do these parameters vary and is there a relationship to the solar cycle? In the actual contribution we will discuss preliminary results regarding the variation of the number of MBPs with time. We saw a decrease in the number of MBPs for the first years of observation (2006 until 2011) with two distinct local minima in the years 2009 and 2011. After 2011 the number of MBPs is increasing again along with an increase in general solar activity (as seen by the number of sunspots, flares, and CMEs). Title: On Dynamics of G-Band Bright Points Authors: Bodnárová, M.; Utz, D.; Rybák, J. Bibcode: 2014SoPh..289.1543B Altcode: 2013arXiv1312.5464B Various parameters describing the dynamics of G-band bright points (GBPs) were derived from G-band images, acquired by the Dutch Open Telescope (DOT), of a quiet region close to the disk center. Our study is based on four commonly used diagnostics (effective velocity, change in the effective velocity, change in the direction angle, and centrifugal acceleration) and two new ones (rate of motion and time lag between recurrence of GBPs). The results concerning the commonly used parameters are in agreement with previous studies for a comparable spatial and temporal resolution of the used data. The most probable value of the effective velocity is ∼ 0.9 km s−1, whereas we found a deviation of the effective velocity distribution from the expected Rayleigh function for velocities in the range from 2 to 4 km s−1. The change in the effective velocity distribution is consistent with a Gaussian one with FWHM=0.079 km s−2. The distribution of the centrifugal acceleration exhibits a highly exponential nature (a symmetric Gaussian centered at the zero value). To broaden our understanding of the dynamics of GBPs, two new parameters were defined: the real displacement between their appearance and disappearance (rate of motion) and the frequency of their recurrence at the same locations (time lag). For ∼ 45 % of the tracked GBPs, their displacement was found to be small compared to their size (the rate of motion smaller than one). The locations of the tracked GBPs mainly cover the boundaries of supergranules representing the network, and there is no significant difference in the locations of GBPs with small (m<1) and large (m>2) values of the rate of motion. We observed a difference in the overall trend of the obtained distribution for the values of the time lag smaller (slope of the trend line being −0.14) and greater (−0.03) than ∼ 7 min. The time lags mostly lie within the interval of ∼ 2 - 3 min, with those up to ∼ 4 min being more abundant than longer ones. Results for both new parameters indicate that the locations of different dynamical types of GBPs (stable/farther traveling or with short/long lifetimes) are bound to the locations of more stable and long-living magnetic field concentrations. Thus, the disappearance/reappearance of the tracked GBPs cannot be perceived as the disappearance/reappearance of their corresponding magnetic field concentrations. 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: New insights into the temporal evolution of MBPs Authors: Utz, D.; del Toro Iniesta, J. C.; Bellot Rubio, L. R.; Jurčak, J.; Thonhofer, S.; Bodnárová, M.; Hanslmeier, A.; Lemmerer, B.; Piantschitsch, I.; Guttenbrunner, S. Bibcode: 2014CEAB...38...73U Altcode: Magnetic bright points (MBPs) are among the most fascinating and interesting manifestations of small-scale solar magnetic fields. In the present work the temporal evolution of MBPs is followed in data sets taken by the Hinode satellite. The analysed data and obtained results confirm a recently presented study done with Sunrise/IMaX data, namely that MBPs are features undergoing fast evolution with magnetic fields starting around the equipartition field strength, then showing strong downflows (between 2 to 4 km/s) causing the magnetic field to amplify into the kG range (700 to 1500 G) before dissolving again. Furthermore the initial field inclinations depend on the initial magnetic field strengths and show an evolution with more vertical angles at some point during the evolution. 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: Dynamika fotosférických jasných bodov v G-páse odvodená použitím dvoch plne automatických algoritmov Title: Dynamika fotosférických jasných bodov v G-páse odvodená použitím dvoch plne automatických algoritmov Title: Dynamics of photospheric bright points in G-band derived from two fully automated algorithms. Authors: Bodnárová, M.; Rybák, J.; Hanslmeier, A.; Utz, D. Bibcode: 2010nspm.conf...25B Altcode: Concentrations of small-scale magnetic field in the solar photosphere can be identified in the G-band of the solar spectrum as bright points. Studying the dynamics of the bright points in the G-band (BPGBs) can also help in addressing many issues related to the problem of the solar corona heating. In this work, we have used a set of 142 specled images in the G-band taken by the Dutch Open Telescope (DOT) on 19 October 2005 to make a comparison of two fully automated algorithms identifying BPGBs: an algorithm developed by Utz et al. (2009, 2010), and an algorithm developed following the work of Berger et al. (1995, 1998). We then followed in time and space motion of the BPGBs identified by both algorithms and constructed the distributions of their lifetimes, sizes and speeds. The results show that both algorithms give very similar results for the BPGB lifetimes and speeds, but their results vary significantly for the sizes of the identified BPGBs. This difference is due to the fact that in the case of the Berger et al. identification algorithm no additional criteria were applied to constrain the allowed BPGB sizes. As a result in further studies of the BPGB dynamics we will prefer to use the Utz algorithm to identify and track BPGBs. Title: Slnečná aktivita a kozmické 'iarenie: magnetické pole Slnka a úroveň kozmického žiarenia Title: Slnečná aktivita a kozmické 'iarenie: magnetické pole Slnka a úroveň kozmického žiarenia Title: Solar activity and cosmic radiation: Sun's magnetic field and cosmic radiation levels. Authors: Bodnárová, M.; Rybák, J.; Gömöry, P.; Kudela, K. Bibcode: 2010nspm.conf..175B Altcode: In this work we have analyzed the correlation of the Sun's magnetic activity and cosmic radiation levels during the period 1951-2004. As a solar magnetic activity indicator, affecting the cosmic radiation, we have chosen open magnetic field configurations which we characterized by an open magnetic flux factor (OMFF). The OMFF was calculated from the intensity measurements of the green coronal line. In calculations leading to the relation between the OMFF and galactic cosmic radiation (GCR) levels the cross-correlation of these datasets was used. The goal of this contribution was to find mainly time-dependent changes in the evolution of the OMFF and GCR correlation. In order to do so,besides the correlation calculations based on the long time series of the OMFF and GCR data covering the entire period 1951-2004 we have also calculated the correlation of the OMFF and GCR data from shorter periods (180 days). We have found that the cross-correlation evolution varies depending on the phase of the solar cycle. During the minimum the evolution is characterized by conspicuous periodicity with a period ~ 14 days and the cross-correlation function takes statistically significant values. During the maximum the period of the variations is not clear and the cross-correlation function takes low values that are not statistically significant. Title: Dynamics of G-band bright points derived using two fully automated algorithms Authors: Bodnárová, M.; Utz, D.; Rybák, J.; Hanslmeier, A. Bibcode: 2010CEAB...34...25B Altcode: Small-scale magnetic field concentrations (∼ 1 kG) in the solar photosphere can be identified in the G-band of the solar spectrum as bright points. Study of the G-band bright points (GBPs) dynamics can help us in solving several questions related also to the coronal heating problem. Here a set of 142 G-band speckled images obtained using the Dutch Open Telescope (DOT) on October 19, 2005 are used to compare identification of the GBPs by two different fully automated identification algorithms: an algorithm developed by Utz et al. (2009a, 2009b) and an algorithm developed according to papers of Berger et al. (1995, 1998). Temporal and spatial tracking of the GBPs identified by both algorithms was performed resulting in distributions of lifetimes, sizes and velocities of the GBPs. The obtained results show that both algorithms give very similar values in the case of lifetime and velocity estimation of the GBPs, but they differ significantly in case of estimation of the GBPs sizes. This difference is caused by the fact that we have applied no additional exclusive criteria on the GBPs identified by the algorithm based on the work of Berger et al. (1995, 1998). Therefore we conclude that in a future study of the GBPs dynamics we will prefer to use the Utz's algorithm to perform identification and tracking of the GBPs in G-band images.