A5052349543- Solar and Space Plasma Dynamics
- Ionosphere and magnetosphere dynamics
- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- Geomagnetism and Paleomagnetism Studies
- Geophysics and Gravity Measurements
- Solar Radiation and Photovoltaics
- Earthquake Detection and Analysis
- Gamma-ray bursts and supernovae
- Atmospheric Ozone and Climate
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- History and Developments in Astronomy
- Oil, Gas, and Environmental Issues
- Spacecraft and Cryogenic Technologies
- Space exploration and regulation
- Adaptive optics and wavefront sensing
- Planetary Science and Exploration
- Meteorological Phenomena and Simulations
- Magnetic confinement fusion research
- Inertial Sensor and Navigation
- Photovoltaic System Optimization Techniques
- Complex Systems and Time Series Analysis
- Reservoir Engineering and Simulation Methods
- Fluid Dynamics and Turbulent Flows
University of Graz
2016-2025
National Solar Observatory
2024
Austrian Academy of Sciences
2011-2023
Space Research Institute
2011-2023
GeoSphere Austria
2023
National University of Malaysia
2023
University of California, Berkeley
2023
Kobe University
2023
Institute of Space and Astronautical Science
2023
Nagoya University
2023
Coronal mass ejections (CMEs) were discovered in the early 1970s when space-borne coronagraphs revealed that eruptions of plasma are ejected from Sun. Today, it is known Sun produces eruptive flares, filament eruptions, coronal and failed eruptions; all thought to be due a release energy stored magnetic field during its drastic reconfiguration. This review discusses observations physical mechanisms behind this activity, with view making an assessment current capability forecasting these...
Aims. The Spectrometer Telescope for Imaging X-rays (STIX) on Solar Orbiter is a hard X-ray imaging spectrometer, which covers the energy range from 4 to 150 keV. STIX observes bremsstrahlung emissions solar flares and therefore provides diagnostics of hottest (⪆10 MK) flare plasma while quantifying location, spectrum, content flare-accelerated nonthermal electrons. Methods. To accomplish this, applies an indirect bigrid Fourier technique using set tungsten grids (at pitches 0.038 1 mm) in...
The Solar MAgnetic Connection HAUS 1 tool (Solar-MACH) is an open-source completely written in Python that derives and visualizes the spatial configuration solar magnetic connection of different observers (i.e., spacecraft or planets) heliosphere at times. For doing this, interplanetary space obtained by classic Parker Heliospheric Magnetic Field (HMF). In close vicinity Sun, a Potential Source Surface (PFSS) model can be applied to connect HMF photosphere. Solar-MACH especially aimed...
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,...
We study two well-observed, fast halo CMEs, covering the full CME kinematics including initiation and impulsive acceleration phase, their associated flares. find a close synchronization between profile flare energy release as indicated by RHESSI hard X-ray flux onsets, well peaks occur simultaneously within 5 minutes. These findings indicate physical connection both phenomena are interpreted in terms of feedback relationship dynamics reconnection process current sheet beneath CME.
Using the potential of two unprecedented missions, STEREO and RHESSI, we study three well observed fast CMEs that occurred close to limb together with their associated high energy flare emissions in terms RHESSI HXR spectra flux evolution. From STEREO/EUVI STEREO/COR1 data full CME kinematics impulsive acceleration phase up 4 Rs is measured a time cadence less equal 2.5 min. For deriving velocity apply test new algorithm based on regularization methods. The maximum achieved at heights h <...
We present first observations of a dome-shaped large-scale extreme-ultraviolet coronal wave, recorded by the Extreme Ultraviolet Imager instrument on board STEREO-B 2010 January 17. The main arguments that observed structure is wave dome (and not mass ejection, CME) are (1) spherical form and sharpness dome's outer edge erupting CME loops inside dome; (2) low-coronal signatures above limb perfectly connecting to on-disk wave; (3) lateral extent expanding which much larger than dimming; (4)...
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...
The "empirical Neupert effect" (ENE) is the observed temporal correlation of hard X-ray (HXR) flux FHXR(t) with time derivative soft (SXR) SXR(t) in many flares. This widely taken to mean that energetic electrons responsible for by thick-target collisional bremsstrahlung are main source heating and mass supply (via chromospheric evaporation) SXR-emitting hot coronal plasma. If this interpretation were correct, one would expect better between beam power Pbeam(t), inferred from HXR spectrum,...
We report a large-scale coronal wave (so-called EIT wave) observed with high cadence by EUVI on board STEREO in association the GOES B9.5 flare and double CME event 2007 May 19. The instruments provide us unprecedented opportunity to study dynamics of flare/CME associated waves. under reveals deceleration, indicative freely propagating MHD wave. Complementary analysis erupting filament/CME hint at initiation expanding flanks, which drive only over limited distance. is very weak occurs too...
We study the interaction of two successive coronal mass ejections (CMEs) during 2010 August 1 events using STEREO/SECCHI COR and HI data. obtain direction motion for both CMEs by applying several independent reconstruction methods find that head in similar directions. This provides evidence a full takes place between can be observed HI1 field-of-view. The de-projected kinematics faster CME from Sun to Earth is derived combining remote observations with situ measurements at AU. speed profile...
The unusually large active region (AR) NOAA 2192, observed in 2014 October, was outstanding its productivity of major two-ribbon flares without coronal mass ejections. On a scale, predominantly north–south oriented magnetic system arcade fields served as strong top and lateral confinement for series originating from the core AR. initial separation flare ribbons, together with an almost absent growth ribbon separation, suggests confined reconnection site high up corona. Based on detailed...
Forecasting the in situ properties of coronal mass ejections (CMEs) from remote images is expected to strongly enhance predictions space weather, and general interest for studying interaction CMEs with planetary environments. We study feasibility using a single heliospheric imager (HI) instrument, imaging solar wind density Sun 1 AU, connecting observations CMEs. compare speed arrival time 22 (in 2008-2012) corresponding interplanetary ejection (ICME) parameters at observatories (STEREO...
We use high time cadence images acquired by the STEREO EUVI and COR instruments to study evolution of coronal mass ejections (CMEs), from their initiation, through impulsive acceleration propagation phase. For a set 95 CMEs we derived detailed height, velocity profiles statistically analysed characteristic CME parameters: peak acceleration, velocity, duration, initiation height at size source region. The accelerations range 20 6800 m s^2 are inversely correlated duration acceleration. 74%...
Coronal mass ejections (CMEs) are the primary sources of intense disturbances at Earth, where their geo-effectiveness is largely determined by dynamic pressure and internal magnetic field, which can be significantly altered during interactions with other CMEs in interplanetary space. We analyse three successive that erupted from Sun September 4-6, 2017, investigating role CME-CME as source associated geomagnetic storm (Dst_min=-142 nT on 7). To quantify impact (geo-)effectiveness individual...
Abstract The Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory ( SDO ) has been providing high-cadence, high-resolution, full-disk UV-visible/extreme ultraviolet (EUV) images since 2010, with best time coverage among all solar missions. A number of codes have developed to extract plasma differential emission measures (DEMs) from AIA images. Although widely used, they cannot effectively constrain DEM at flaring temperatures data alone. This often results in much higher...
The X8.2 event of 10 September 2017 provides unique observations to study the genesis, magnetic morphology and impulsive dynamics a very fast CME. Combining GOES-16/SUVI SDO/AIA EUV imagery, we identify hot ($T\approx 10-15$ MK) bright rim around quickly expanding cavity, embedded inside much larger CME shell 1-2$ MK). develops from dense set large AR loops ($\gtrsim$0.5 $R_s$), seamlessly evolves into front observed in LASCO C2. strong lateral overexpansion acts as piston initiating wave....
Context. A complex and long-lasting solar eruption on 17 April 2021 produced a widespread energetic particle (SEP) event that was observed by five longitudinally well-separated observers in the inner heliosphere covered distances to Sun from 0.42 1 au: BepiColombo, Parker Solar Probe, Orbiter, STEREO A, near-Earth spacecraft. The second SEP detected cycle 25, it relativistic electrons protons. It associated with hard X-ray flare showed multiple peaks over duration of one hour. further...
Abstract Nonlinear force-free extrapolations are a common approach to estimate the 3D topology of coronal magnetic fields based on photospheric vector magnetograms. The assumption is valid approximation at heights, but for dense plasma conditions in lower atmosphere, this not satisfied. In study, we utilize multiheight field measurements combination with physics-informed neural networks advance solar extrapolations. We include flexible height-mapping, which allows us account different...
We report a new class of solar flare hard X-ray (HXR) sources in which the emission is mainly coronal loop so dense as to be collisionally thick at electron energies up ≳50 keV. In most events previously reported, footpoints, although sometimes with faint high-altitude component. HXR RHESSI data on dimensions and nonthermal parameters GOES soft hot plasma are used model thick-target physics for two "discovery" (2002 April 14 [23:56 UT] 2002 15 [23:05 UT]). show that column densities N...