A5016137167- Solar and Space Plasma Dynamics
- Ionosphere and magnetosphere dynamics
- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Magnetic confinement fusion research
- Geomagnetism and Paleomagnetism Studies
- Fluid Dynamics and Turbulent Flows
- Geophysics and Gravity Measurements
- Astronomical Observations and Instrumentation
- Cosmology and Gravitation Theories
- Calibration and Measurement Techniques
- Astrophysical Phenomena and Observations
- Congenital Heart Disease Studies
- Aerodynamics and Fluid Dynamics Research
- Electromagnetic Scattering and Analysis
- Astrophysics and Cosmic Phenomena
- Advanced Differential Equations and Dynamical Systems
- History and Developments in Astronomy
- Historical Astronomy and Related Studies
- Superconducting Materials and Applications
- Nonlinear Waves and Solitons
- Plasma Diagnostics and Applications
- Black Holes and Theoretical Physics
Czech Academy of Sciences, Astronomical Institute
2014-2024
Max Planck Institute for Solar System Research
2019
Max Planck Society
2019
Czech Academy of Sciences
2013-2017
Utrecht University
2005-2012
Nickel Institute
2008
University of Bonn
2006
Astronomical Institute of the Slovak Academy of Sciences
2006
Context. Blue supergiant stars are known to display photometric and spectroscopic variability that is suggested be linked stellar pulsations. Pulsational activity in massive strongly depends on the star’s evolutionary stage assumed connected with mass-loss episodes, appearance of macroturbulent line broadening, formation clumps wind.
The appearance of the B[e] phenomenon in evolved massive stars such as supergiants is still a mystery. While these are generally found to have disks that cool and dense enough for efficient molecule dust condensation, origin disk material unclear. We aim at studying kinematics eccentric binary system GG Car, whose primary component proposed be supergiant. Based on medium- high-resolution near-infrared spectra we analyzed CO-band emission detected from Car. complete structure delivers...
Our aim is to model the three-dimensional magnetic field structure of upper solar atmosphere, including regions non-negligible plasma beta. We use high-resolution photospheric measurements from SUNRISE/IMaX as boundary condition for a magneto-static model. The high resolution IMaX allows us resolve interface region between photosphere and corona, but modeling this challenging following reasons. While coronal thought be force-free (the Lorentz force vanishes), not case in mixed β environment...
We aim to improve our knowledge on the structure and dynamics of circumstellar disk LMC B[e] supergiant LHA 120-S 73. High-resolution optical near-IR spectroscopic data were obtained over a period 16 7 years, respectively. The spectra cover diagnostic emission lines from [CaII] [OI], as well CO bands. These features trace at different distances star. analyzed kinematics individual regions by modeling their profiles. A low-resolution mid-infrared spectrum was well, which provides information...
Abstract Magneto-static models may overcome some of the issues facing force-free magnetic field extrapolations. So far they have seen limited use and faced problems when applied to quiet-Sun data. Here we present a first application an active region. We solar vector measurements gathered by IMaX polarimeter during flight S unrise balloon-borne observatory in 2013 June as boundary conditions for magneto-static model higher atmosphere above The data are embedded region magnetograms observed...
Abstract The Galactic object MWC 137 has been suggested to belong the group of B[e] supergiants. However, with its large-scale optical bipolar ring nebula and high-velocity jet knots, it is a rather atypical representative this class. We performed multiwavelength observations spreading from radio regimes. Based on imaging long-slit spectroscopic data, we found that northern parts are predominantly blueshifted, while southern regions appear mostly redshifted. developed geometrical model...
Context. Application of the magnetic-reconnection theory onto large-scale events, such as solar flares, requires formation very thin (kinetic-scale) current sheets within rather thick flare layer. Hence, some fragmentation/filamentation mechanisms has to be in action.
Aims. We numerically study a formation of the return current generated in solar flares.
Strong gradients in plasma flows play a major role space and astrophysical plasmas. A typical situation is that static equilibrium surrounded by flow, which can lead to strong flow at the separatrices between field lines with different magnetic topologies, e.g., planetary magnetospheres, helmet streamers solar corona, or boundary heliosphere interstellar medium. Within this work we make first step understand influence of these towards occurrence current sheets stationary state situation. We...
Yellow hypergiants are evolved massive stars that were suggested to be in post-red supergiant stage. Post-red supergiants evolve back the blue, hot side of Hertzsprung-Russell diagram can intersect a temperature domain which their atmospheres become unstable against pulsations (the Void or Wall), and experience outbursts with short, but violent mass eruptions. The yellow hypergiant Rho Cas is famous for its historical recent outbursts, during star develops cool, optically thick wind very...
Context.A stellar wind passing through the reverse shock is deflected into astrospheric tail and leaves system either as a sub-Alfvénic or super-Alfvénic flow. An example our own heliosphere its heliotail.
Context. HD 50138 presents the B[e] phenomenon, but its nature is not clear yet. This star known to present spectral variations, which have been associated with outbursts and shell phases.
Abstract. Magnetohydrodynamic configurations with strong localized current concentrations and vortices play an important role in the dissipation of energy space astrophysical plasma. Within this work we investigate relation between sheets vortex incompressible, stationary equilibria. For approach it is helpful that similar mathematical structure magnetohydrostatics incompressible hydrodynamics allows us to transform static equilibria into ones. The main control function for such a...
Abstract In this work we describe a numerical optimization method for computing stationary MHD equilibria. The newly developed code is based on nonlinear force-free principle. We apply our to model the solar corona using synoptic vector magnetograms as boundary condition. Below about two radii plasma $\beta $ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>β</mml:mi> </mml:math> and Alfvén Mach number $M_{A}$ <mml:msub> <mml:mi>M</mml:mi> <mml:mi>A</mml:mi> </mml:msub> are...
We consider a magnetic configuration consisting of an arcade structure and detached plasmoid, resulting from reconnection process, as is typically found in connection with solar flares. study spontaneous current fragmentation caused by shear vortex plasma flows. An exact analytical transformation method was applied to calculate self-consistent solutions the nonlinear stationary MHD equations. The assumption incompressible field-aligned flows implies that both Alfven Mach number mass density...
The Galactic B[e] supergiant MWC 137 is surrounded by a large-scale optical nebula. To shed light on the physical conditions and kinematics of nebula, we analyze forbidden emission lines [NII] 6548,6583 [SII] 6716,6731 in long-slit spectra taken with ALFOSC at Nordic Optical Telescope. radial velocities display complex behavior but, general, northern nebular features are predominantly approaching while southern ones mostly receding. electron density shows strong variations across nebula...
Massive stars expel large amounts of mass during their late evolutionary phases. We aim to unveil the physical conditions within warm molecular environments B[e] supergiants (B[e]SGs) and yellow hypergiants (YHGs), which are known be embedded in circumstellar shells disks. present K-band spectra two B[e]SGs from Large Magellanic Cloud four Galactic YHGs. The CO band emission detected LHA 120-S 12 134 suggests that these surrounded by stable rotating rings. YHGs display a rather diverse...
Context. Magnetic fields and flows in coronal structures, for example, gradual phases flares, can be described by 2D 3D magnetohydrostatic (MHS) steady magnetohydrodynamic (MHD) equilibria.
The paradigm of ideal MHD is investigated in the vicinity null points flows and magnetic fields.These determine location geometrical shape heliopause (or other astropauses).We investigate question whether regular stable solutions equations flow field exist.This done to test validity plasma boundaries stellar winds their local interstellar medium.We calculate general use standard form stagnation point analyse all possible time evolutions these environments.We show that solution space 2-D...
Structures in circumstellar matter reflect both fast processes and quasi-equilibrium states. A geometrical diversity of emitting is observed around evolved massive stars, particular B[e] supergiants. We recapitulate classical analytical tools linear non-linear potential theory, such as Cole-Hopf transformations Grad-Shafranov develop them further to explain occurrence the structures their dynamics. use theory formulate hydrodynamical equations test dilatations initial conditions. find that a...
Abstract Structures in circumstellar matter reflect both fast processes and quasi-equilibrium states. A geometrical diversity of emitting is observed around evolved massive stars, particular B[e] supergiants. We recapitulate classical analytical tools linear nonlinear potential theory, such as Cole–Hopf transformation Grad–Shafranov develop them further to explain the occurrence structures their dynamics. use theory formulate hydrodynamical equations test dilatations initial conditions. find...
The geometrical shapes and the physical properties of stellar wind -- interstellar medium interaction regions form an important stage for studying winds their embedded magnetic fields as well cosmic ray modulation. Our goal is to provide a proper representation classification counter-flow configurations interfaces in frame fluid theory. In addition we calculate flows large-scale electromagnetic based on which dynamics its role possible background particle acceleration, e.g. anomalous rays,...