Přednášky a semináře
Semináře pořádáme nově s čtvrtletní periodou a s bohatším obsahem.
Příští seminářové odpoledne (od 13h)
23. 03. 2015
Solar spectropolarimetry from 0-D to 3-D geometry
Abstract: Scattering line polarization and the Hanle effect are among the most important mechanisms for diagnostics of the solar and stellar atmospheres. The fact that real stellar atmospheres are horizontally inhomogeneous makes the spectral synthesis and interpretation very challenging because the effect of thermodynamic fluctuations on spectral line polarization is entangled with the action of magnetic fields. This applies to the spatially resolved as well as to the averaged spectra. The necessary step towards the interpretation of such spectra is to study the line formation in sufficiently realistic 3D MHD models and to compare the synthetic spectra with observations. I'll present a brief overview of the relevant mechanisms involved in polarized spectral line formation and the recent progress in the field of 3D NLTE synthesis of polarized spectral lines.
23. 03. 2015
HI shells: why I find them interesting even after 20 years' acquaintance
Abstract: I will give an introduction to HI shells: what they are, where we can find them and why many members of our working group study them. I will focus on the connection between HI shells and other gaseous environment in the Galaxy and will deal with the importance of HI shells in the evolution of galaxies and the Galaxy.
23. 03. 2015
Exoplanets at Ondřejov
Abstract: Since 1995, when the first exoplanet was detected, this scientific field is rapidly developing. Nowadays, we are not only detecting the new worlds but we try to understand how did they evolve and how they do look like. The most recent topic is characterization of exoplanetary atmospheres. Current situation, advances and plans for the future development of the exoplantary research in Ondřejov will be presented.
23. 03. 2015
Bolide Žďár – First results of the recent precisely documented meteorite fall
Abstract: Instrumental observations of fireballs, especially those that can produce meteorites, are of great scientific interest and importance because meteorites provide us with a surviving physical record of the formation of our solar system, and a direct link to their parent asteroids. Last such event occurred over Czech Republic on December 9, 2014 at late dusk. It was
exceptionally well documented because cameras of the Czech part of the European Fireball Network provided us with 10 all-sky photographic images and 21 radiometric records. It enabled us to get very reliable and complex information about position, dynamics, photometry and absolute timing of this extraordinary event. The first results based on the analysis of the best available records and describing fireball trajectory, luminosity, dynamics, fragmentation, orbit, and impact position will be presented. Recovery of meteorites and their analysis will be also shortly mentioned.
Dále se konají menší tématické semináře jednotlivých oddělení:
Semináře slunečního oddělení
Vždy v úterý ve 13:00 (září–červen, s výjimkou úterků po celoústavním semináři) v zasedací místnosti slunečního oddělení pracoviště Ondřejov.
14/04/2015, 13:00
Effect of the electron kappa-distributions on the non-equilibrium ionization in the transition region and solar corona
Abstract:
Many theoretical calculations and several diagnostics support an idea of the
presence of kappa-distributions or distributions exhibiting high-energy tails in the
solar corona and transition region. However, the presence of the kappa-distributions
or distributions exhibiting high-energy tails can be also expected due to particle
acceleration processes arising as a result of “nanoflare” heating in the solar
corona. Generally, the non-Maxwellian distributions change the ionization,
recombination, and excitation rates because they are an integral product of the
cross-section with the electron distribution function. The ionization and
recombination rates influence time what needs plasma to achieve a static
equilibrium. Changes in the non-equilibrium ionization state due to heating and
cooling plasma for the Maxwellian and kappa-distributions for several simple heating
and cooling functions have been modeled. Characteristic times to achieve a static
equilibrium for different types of the distribution, temperature and the other
plasma conditions are compared. Possible consequences of the presence of the
kappa-distributions for impulsive heating are discussed.
Semináře oddělení GPS
Obvykle v pondělí od 14 hod v přednáškové místnosti pracoviště Praha–Spořilov.
15. 04. 2015, 14:00
The Imaging X-ray Polarimetry Explorer (IXPE): An international collaboration
Abstract: The Imaging X-ray Polarimetry Explorer (IXPE) is a mission recently proposed in response to a NASA solicitation announcement for an Astrophysics Small Explorer (SMEX). IXPE will use x-ray polarimetry to expand observation space dramatically, providing fresh insights into x-ray emission mechanisms and geometry of cosmic sources-including pulsar-wind nebulae, isolated and accreting neutron stars, and stellar-mass and supermassive black holes. The two-year mission is very low-risk, utilizing mature flight elements and combining expertise for x-ray optics at NASA Marshall Space Flight Center and for polarization-sensitive x-ray detectors at the Istituto Nazionale di Fisica Nucleare (INFN) Pisa and Istituto Nazionale di Astrofisica (INAF) Istituto di Astrofisica e Planetologia Spaziali (IAPS). The science team is comprised of many interested researchers throughout the world. The expected performance and scientific capability of IXPE will be described.
On behalf of the IXPE collaboration.
On behalf of the IXPE collaboration.
(Takes place at: Sporilov library)
Semináře stelárního oddělení
Ve čtvrtek od 14:00 v seminární místnosti stelárního oddělení.