Poster Abstracts

Name/Affiliation:  Sven Wedemeyer (University of Oslo, Norway)

Title:  Atmospheric dynamics and magnetic activity of M-type dwarf stars 

Three-dimensional radiation magnetohydrodynamic simulations of M-type dwarf stars feature atmospheres with a very dynamic and intermittent structure on small spatial and temporal scales and a wealth of physical processes, which by nature cannot be described by means of one-dimensional static model atmospheres. The presented time-dependent 3D models have different initial magnetic field strengths and thus represent regions with different activity levels, which can be combined into synthetic full stellar disks. A large number of synthetic spectro-polarimetric diagnostics are calculated by using each of these models as input for detailed radiative transfer calculations. These diagnostics, like, e.g., Halpha, Ca II lines, or the continuum intensity from the UV into the millimeter wavelength range, sample various properties of the dynamics, thermal and magnetic structure of the photosphere and the chromosphere and thus provide measures of stellar activity, which can be compared to observations. The complicated magnetic field structure and its imprint in synthetic diagnostics may have important implications for the understanding and characterization of stellar activity and with it possibly for the evaluation of planetary habitability around active M-dwarf stars.