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Akademie věd České republiky |
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Akademie věd České republiky |
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Pravidelný seminář 4. 12. 2006
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který se koná v pondělí dne v nové seminární mistnosti AsÚ v Ondřejově PROGRAM: 13:00 Odborná část Solar and stellar
chromospheres
Petr Heinzel Classical stellar atmospheres usually refer to the photospheric layers of stars where the hydrostatic and radiative/convective equilibria prevail in determining the atmospheric structure. However, late-type stars which have developed convective zones exhibit additional layers above the photosphere called chromospheres and coronae. The structure and dynamics of these outermost layers is determined to a large extent by the magnetic fields generated in the convective zone. While the photospheric structure of the Sun and other stars is relatively well understood, the chromospheres are still the subject of controversial debates. By definition, these are the atmospheric layers where the temperature starts to increase, reaching finally millions of degrees in the corona. What is the heating mechanism responsible for such behaviour? I will present the latest high-resolution observations of the solar chromosphere, both from ground and space. Then I will briefly review the radiative-transfer modelling which takes into account strong departures from LTE. Both semi-empirical, as well as latest radiation-hydrodynamical models will be mentioned. The issue of heating is usually related to the observed chromospheric oscillations and I will briefly review some of the latest results which concern the observations and analysis of the accoustic waves in the solar chromosphere. Finally, since only our nearest star – the Sun – can be now studied with unprecedented spatial and temporal resolution, the natural question arises of how we can understand the chromospheres of other late-type stars which are seen without such resolution. Srdečně zve Vladimír Karas vedoucí semináře |