A5027375300- Solar and Space Plasma Dynamics
- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- History and Developments in Astronomy
- Geophysics and Gravity Measurements
- Geomagnetism and Paleomagnetism Studies
- Solar Radiation and Photovoltaics
- Ionosphere and magnetosphere dynamics
- Astronomy and Astrophysical Research
- Space Science and Extraterrestrial Life
- Historical Astronomy and Related Studies
- Astrophysics and Star Formation Studies
- Planetary Science and Exploration
- Astronomical Observations and Instrumentation
- Atmospheric Ozone and Climate
- Gamma-ray bursts and supernovae
- Solar Thermal and Photovoltaic Systems
- Adaptive optics and wavefront sensing
- Earthquake Detection and Analysis
- Spaceflight effects on biology
- Complex Systems and Time Series Analysis
- Galaxies: Formation, Evolution, Phenomena
- Inertial Sensor and Navigation
- Astrophysical Phenomena and Observations
- Fluid Dynamics and Turbulent Flows
University of Graz
2015-2024
Leibniz-Centre General Linguistics
2021
Springer Nature (Germany)
2021
Deutsche Nationalbibliothek
2021
Université Toulouse III - Paul Sabatier
2009-2016
Centre National de la Recherche Scientifique
2009-2016
Nawi Graz
2016
Medical University of Graz
2016
Czech Academy of Sciences, Institute of Physics
2002-2014
Institut d'Estudis Espacials de Catalunya
2006-2009
Low mass M- and K-type stars are much more numerous in the solar neighborhood than solar-like G-type stars. Therefore, some of them may appear as interesting candidates for target star lists terrestrial exoplanet (i.e., planets with mass, radius, internal parameters identical to Earth) search programs like Darwin (ESA) or Terrestrial Planet Finder Coronagraph/Inferometer (NASA). The higher level stellar activity low M stars, compared G well closer orbital distances their habitable zones...
A statistical analysis of almost 50 000 soft X-ray (SXR) flares observed by GOES during the period 1976–2000 is presented. On basis this extensive data set, statistics on temporal properties flares, such as duration, rise and decay times with regard to SXR flare classes Correlations among distinct parameters, i.e. peak flux, fluence characteristic times, frequency distributions occurrence function duration are derived. We discuss results respect models, idea coronal heating nanoflares,...
From sunspot drawings provided by the Kanzelhöhe Solar Observatory, Austria, and Skalnaté Pleso Slovak Republic, we extracted a data catalogue of hemispheric Sunspot Numbers covering time span 1945-2004. The validated includes daily, monthly-mean, smoothed-monthly relative numbers for northern southern hemispheres separately is available scientific use. These then investigated with respect to north-south asymmetries almost 6 entire solar cycles (Nos. 18-23). For all studied, found that...
<i>Aims. <i/>We study the possible atmospheric mass loss from 57 known transiting exoplanets around F, G, K, and M-type stars over evolutionary timescales. For stellar wind induced studies, we estimate position of pressure balance boundary between Coronal Mass Ejection (CME) ram pressures planetary ionosphere for non- or weakly magnetized gas giants at close orbits.<i>Methods. <i/>The thermal atomic hydrogen is calculated by a equation where consider realistic heating efficiency,...
The recently discovered low-density "super-Earths" Kepler-11b, Kepler-11f, Kepler-11d, Kepler-11e, and planets such as GJ 1214b represent the most likely known that are surrounded by dense H/He envelopes or contain deep H₂O oceans also hydrogen envelopes. Although these super-Earths orbiting relatively close to their host stars, they have not lost captured nebula-based hydrogen-rich degassed volatile-rich steam protoatmospheres. Thus, it is interesting estimate maximum possible amount of...
Since the discovery of EIT waves, questions have remained about driver these disturbances and their association with chromospheric Moreton waves. In order to resolve some issues, two flare-associated transient events (1997 November 3 1998 May 2) observed simultaneously in Hα are analyzed. The cospatiality wave fronts is established, a deceleration found both events. case 2, detailed analysis evolution wave, its kinematics, perturbation profile carried out. results—deceleration, broadening,...
Propagating wave-like disturbances associated with solar flares – commonly observed in the chromosphere as Moreton waves have been known for several decades. Recently, phenomenon has come back into focus prompted by observation of coronal SOHO/EIT instrument ("EIT waves"). It suggested that they represent anticipated counterpart to waves, but due some pronounced differences, this interpretation is still being debated. We study 12 flare wave events order determine their physical nature, using...
The study of solar flare waves – globally propagating wave-like disturbances usually observed in Hα as Moreton has recently come back into focus prompted by the observation coronal EUV with SOHO/EIT instrument ("EIT waves"), and several additional wavelength channels. We 12 wave events order to determine their physical nature, using Hα, EUV, helium I, SXR radioheliographic data. In companion Paper we have presented observational data discussed morphology, spatial characteristics kinematics...
Based on a sample of 1114 flares observed simultaneously in hard X-rays (HXR) by the BATSE instrument and soft (SXR) GOES, we studied several aspects Neupert effect its interpretation frame electron-beam-driven evaporation model. In particular, investigated time differences () between maximum SXR emission end HXR emission, which are expected to occur at almost same time. Furthermore, performed detailed analysis peak flux – fluence relationship for complete set events, as well separately...
Stellar coronal mass ejections (CMEs) may play an important role in mass- and angular momentum loss of young Sun-like stars. If occurring frequently, they also have a strong effect on planetary evolution by increasing atmospheric erosion. So far it has not been possible to infer the occurrence frequency stellar CMEs from observations. Based their close relation with flares Sun, we develop empirical model combining solar flare-CME relationships flare rates estimate CME activity late-type...
Sunspot drawings are provided on a regular basis at the Kanzelhöhe Solar Observatory, Austria, and derived relative sunspot numbers reported to Index Data Center in Brussels. From daily drawings, we northern, Rn, southern, Rs, for time span 1975–2000. In order accord with International Numbers Ri, Rn Rs have been normalized which ensures that relation is fulfilled. For validation, compared international northern southern numbers, available from 1992. The regression analysis performed period...
Three traveling disturbances recorded in the absorption line of Helium I at 10 830 Å (He I), analogous to Hα Moreton waves, are analyzed. The morphology and kinematics wavefronts described detail. He wave appears as an expanding arc increased roughly corresponding disturbance, although not sharply defined. perturbations consist a relatively uniform diffuse component patchy one that enhanced mottles. It leads front by some 20 Mm can be followed considerably larger distances than observations....
We present a new observational campaign, DWARF, aimed at detection of circumbinary extrasolar planets using the timing minima low-mass eclipsing binaries. The observations will be performed within an extensive network relatively small to medium-size telescopes with apertures ~20-200 cm. starting sample objects monitored contains (i) binaries M and K components, (ii) short-period sdB or sdO component, (iii) post-common-envelope systems containing WD, which enable determine high precision....
It is shown that the evolution of planetary atmospheres can only be understood if one recognizes fact radiation and particle environment Sun or a planet’s host star were not always on same level as at present. New insights latest observations research regarding solar radiation, plasma solar/stellar magnetic field derived from proxies with different ages will given. We show extreme environments young Sun/stars have important implications for may responsible planets low gravity like early Mars...
We present a search for stellar activity (flares and mass ejections) in sample of 28 stars the young open cluster Blanco-1. use optical spectra obtained with European Southern Observatory's Visible Multi-Object Spectrograph installed on Very Large Telescope. From total observing time ∼5 h, we find four Hα flares but no distinct indication coronal ejections (CMEs) investigated dK–dM stars. Two show 'dips' their light curves right before impulsive phases which are similar to previous...
We studied the interactions between stellar wind plasma flow of a typical M star, such as GJ 436, and hydrogen-rich upper atmosphere an Earth-like planet "super-Earth" with radius 2 R(Earth) mass 10 M(Earth), located within habitable zone at ∼0.24 AU. investigated formation extended atomic hydrogen coronae under influences XUV flux (soft X-rays EUV), density velocity, shape planetary obstacle (e.g., magnetosphere, ionopause), loss pickup ions on evolution hydrogen-dominated atmospheres....
Solar activity undergoes a variation over time scales of several months known as Rieger-type periodicity, which usually occurs near maxima sunspot cycles. An early analysis showed that the periodicity appears only in some cycles, and is absent other But appearance/absence during different cycles has not been explained. We performed wavelet data from Greenwich Royal Observatory Belgium 14-24. found periods occur all but they are cycle-dependent: shorter stronger Our revealed 185-195 days weak...
Context. Typical uncertainties of ages determined for single star giants from isochrone fitting using single-epoch spectroscopy and photometry without any additional constraints are 30-50 %. Binary systems, particularly double-lined spectroscopic (SB2) binaries, provide an opportunity to study the intricacies internal stellar physics better determine parameters, age. Aims. By binarity asteroseismology, we aim obtain precise age parameters red giant-subgiant binary system KIC 9163796, a with...
The solar corona maintains temperatures of a million Kelvin or more. plasma heating mechanisms responsible for these extreme are still unclear. Large regions magnetic activity in the photosphere cause ultraviolet (EUV) emission corona. Even smaller with bipolar and multipolar fields can generate coronal bright points (CBPs). We performed statistical analysis 346 CBPs. used Solar Dynamics Observatory (SDO) images to track CBPs on continuous basis. Therefore, we were able collect database...
The EXO-UV program is an international, interdisciplinary collaboration between astrophysicists and biologists aimed at expanding the characterization of ultraviolet radiation (UVR) environments on exoplanets. This approach combines astrophysical studies with biological experiments to better understand potential impacts UVR exoplanetary surfaces. particularly relevant because it reaches surface planets can influence their habitability. specific wavelengths within spectrum depend planet's...
The typical uncertainties of ages determined for single star giants from isochrone fitting using single-epoch spectroscopy and photometry without any additional constraints are 30-50,%. Binary systems, particularly double-lined spectroscopic binaries, provide an opportunity to study the intricacies internal stellar physics better determine parameters, age. By binarity asteroseismology, we aim obtain precise age parameters red giant-subgiant binary system a with mass ratio 1.015 but...
A statistical analysis of a large data set Hα flares comprising almost 100 000 single events that occurred during the period January 1975 to December 1999 is presented. We analyzed evolution steps, i.e. duration, rise times, decay times and event asymmetries. Moreover, these parameters characterizing temporal behavior flares, as well spatial distribution on solar disk, N-S E-W asymmetries, are in terms their dependency cycle. The main results are: 1) increase with increasing importance...
A 90 minute time series of high spatial resolution white-light images solar granulation, obtained at the Swedish Vacuum Solar Tower (Observatorio del Roque de los Muchachos, La Palma), was analyzed to study how physical properties granules changed with size. The observational material corrected for global motions and instrumental profile, a subsonic filter applied. definition granular border adopted using inflection points intensity images, cells were defined as areas including, in addition...