A5045391979- Solar and Space Plasma Dynamics
- Ionosphere and magnetosphere dynamics
- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- Magnetic confinement fusion research
- Solar Radiation and Photovoltaics
- Oil, Gas, and Environmental Issues
- Atmospheric Ozone and Climate
- Geophysics and Gravity Measurements
- Cholinesterase and Neurodegenerative Diseases
- Gamma-ray bursts and supernovae
- Geomagnetism and Paleomagnetism Studies
- Tropical and Extratropical Cyclones Research
- Particle accelerators and beam dynamics
- Spacecraft and Cryogenic Technologies
- Radiation Therapy and Dosimetry
- Rocket and propulsion systems research
- Laser-Plasma Interactions and Diagnostics
- Nuclear Physics and Applications
- Earthquake Detection and Analysis
- Global Energy and Sustainability Research
- Alzheimer's disease research and treatments
- Neuroscience and Neuropharmacology Research
- Magnetic and Electromagnetic Effects
- Sports and Physical Education Studies
Czech Academy of Sciences, Astronomical Institute
2015-2024
Czech Academy of Sciences
2001-2012
University of California, Berkeley
2012
FHNW University of Applied Sciences and Arts
2012
Czech Academy of Sciences, Institute of Physiology
2001-2003
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...
Context: Solar flares are the result of sudden release magnetic energy in corona. Much this goes into accelerating charged particles to high velocity. These travel along field and is dissipated when density gets enough, primarily solar chromosphere. Modelling region difficult because radiation balance dominated by strong, optically thick spectral lines. Aims: Our aim provide community with realistic simulations a flaring loop an emphasis on detailed treatment chromospheric balance. This will...
Abstract We analyze the spectra of high-temperature Fe xxiv lines observed by Hinode /Extreme-Ultraviolet Imaging Spectrometer (EIS) during impulsive phase X8.3-class flare on 2017 September 10. The line profiles are broad, show pronounced wings, and clearly depart from a single-Gaussian shape. can be well fitted with κ distributions, values varying between ≈1.7 3. regions where we observe non-Gaussian coincide location high-energy (≈100–300 keV) hard X-ray (HXR) sources RHESSI , suggesting...
We investigate whether the so-called kappa distribution, often used to fit electron distributions detected in-situ in solar wind, can describe electrons producing hard X-ray emission flares. Using Ramaty High Energy Solar Spectroscopic imager (RHESSI) flare data we spatially- and feature-integrated spectra, assuming distribution for mean flux spectrum. show that a single generally cannot spatially integrated composed of both footpoint coronal sources. In contrast, is consistent with spectra some
Context. The Spectrometer/Telescope for Imaging X-rays (STIX) is the hard X-ray instrument onboard Solar Orbiter designed to observe solar flares over a broad range of flare sizes. Aims. We report first STIX observations microflares recorded during commissioning phase in order investigate performance at its detection limit. Methods. uses imaging spectroscopy between 4–150 keV diagnose hottest plasma and related nonthermal electrons. This result paper focuses on temporal spectral evolution...
Aims.We investigate the signature of photospheric albedo contribution in solar flare hard X-ray spectra, effect low energy cutoffs electron and directivity emission.
<i>Context. <i/>Observations of hydrogen Balmer lines in solar flares remain an important source information on flare processes the chromosphere during impulsive phase flares. The intensity profiles optically thick are determined by temperature, density, and ionisation structure flaring atmosphere, plasma velocities velocity distribution particles line formation regions.<i>Aims. <i/>We investigate role non-thermal electrons regions H<i>α<i/>, H<i>β<i/>, H<i>γ<i/> order to unfold their...
The Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory has provided unique observations of off-limb flare emission. White-light (WL) continuum enhancements were detected in "continuum" channel Fe 6173 A line during impulsive phase observed flares. In this paper we aim to determine which radiation mechanism is responsible for such an enhancement being seen above limb, at chromospheric heights around or below 1000 km. Using a simple analytical approach, compare two...
We present a modular and highly versatile test particle-radiative hydrodynamic code which simultaneously models the particle beam energy transport deposition, corresponding explosive response of flare atmosphere NLTE (NLTE, plasma radiation out local thermodynamic equilibrium) radiative transfer for partly ionized hydrogen in chromosphere photosphere. The computational domain covers photosphere, chromosphere, transition region, corona with initial hydrostatic preflare atmosphere. To...
The Spectrometer Telescope for Imaging X-rays (STIX) is one of 10 instruments on board Solar Orbiter, a confirmed Mclass mission the European Space Agency (ESA) within Cosmic Vision program scheduled to be launched in 2017. STIX applies Fourier-imaging technique using set tungsten grids (at pitches from 0.038 1 mm) front 32 pixelized CdTe detectors provide imaging spectroscopy solar thermal and non-thermal hard X-ray emissions 4 150 keV. status instrument reviewed this paper based design...
We focus on the non-thermal components of electron distribution in keV range and analyse high-energy resolution X-ray spectra detected by RESIK RHESSI for three solar flares.In 2-4 we assume that can be modelled an n-distribution. Using a method line-intensity ratios, allowed satellite lines Si observed estimate parameters this At higher energies explore bremsstrahlung spectra. Adopting forward-fitting approach thick-target approximation, determine characteristics injected beams. component...
Abstract Drifting pulsation structures (DPSs) are important radio fine usually observed at the beginning of eruptive solar flares. It has been suggested that DPSs carry information on energy release processes in We study DPS an X8.2-class flare 2017 September 10 context spatial and spectral diagnostics provided by microwave, EUV, X-ray observations. describe its substructures were for first time. use a new wavelet technique to reveal characteristic periods their frequency bands. Comparing...
Particle acceleration is a fundamental process arising in many astrophysical objects, including active galactic nuclei, black holes, neutron stars, gamma-ray bursts, accretion disks, solar and stellar coronae, planetary magnetospheres. Its ubiquity means energetic particles permeate the Universe influence conditions for emergence continuation of life. In our system, Sun most particle accelerator, its proximity makes it unique laboratory which to explore acceleration. However, despite...
Influence of non-thermal collisional rates, related to an electron beam, on hydrogen Balmer line profiles is investigated. Semi-empirical temperature structure the flare model F1 has been used for computing non-LTE Hα, Hβ, and Hγ. Contribution functions their change due different values beam parameters are shown. Unlike core intensity, intensity wings considerably depends it significantly enhanced typical energy flux. The ratio intensities at a selected wavelength proposed be diagnostics...
We study two modifications of the collisional thick-target model (CTTM) based on global and local re-acceleration non-thermal electrons by static stochastic electric fields during their transport from coronal acceleration site to region in chromosphere. concentrate a comparison electron distribution functions, chromospheric energy deposits, HXR spectra obtained for both considered with CTTM itself. The results were using relativistic test-particle approach. simulated power-law spectrum...
Aims. We investigate the X-ray, UV, and also radio continuum arising from plasmas with a non-Maxwellian distribution of electron energies. The two investigated types distributions are κ- n-distributions.
First a problem of the transport electron beams with high energy fluxes into cold chromosphere during flare is presented. Then it shown that might be solved by return current formed superthermal (runaway) electrons. In such case electrons could influence hydrogen excitations and ionizations. Therefore, we computed collisional rates compared them those thermal plasma monoenergetic (10 keV) beam flux penetrating atmosphere described F1 model (Machado et al. [CITE]). We show in this situation...
Context. Hard X-ray bremsstrahlung continuum spectra, such as from solar flares, are commonly described in terms of power-law fits, either to the photon spectra themselves or electron responsible for them. In applications various approximate relations between and spectral indices often used energies both above below low-energy cutoffs.