Simulations of magnetoconvection in cool main-sequence stars

by Benjamin Beeck
Doctoral thesis
Date of Examination:2014-02-14
Date of issue:2014-05-26
Advisor:Prof. Dr. Ansgar Reiners
Referee:Prof. Dr. Ansgar Reiners
Referee:Prof. Dr. Manfred Schüssler
Referee:Prof. Dr. Robert F. Stein
Persistent Address: http://dx.doi.org/10.53846/goediss-4493

 

 

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Abstract

English

In this thesis, the magnetoconvective processes in the nearsurface layers of cool main-sequence stars were studied in 24 three-dimensional local “box-in-a-star” simulations. For each of six sets of stellar parameters corresponding to spectral types F3V –M2V including the solar case (G2V), one non-magnetic and three magnetic simulations with an initially vertical and homogeneous field of 20, 100, and 500G were performed. A granule segmentation and tracking algorithm was developed and the granulation was analysed for the non-magnetic and some magnetic runs. For a few wavelength passbands, the centre-tolimb variation of the intensity and its rms contrast were calculated on the basis of snapshots from the simulations. Synthetic spectral line profiles were calculated for the simulated stars. A discintegration including differential rotation was carried out in order to study the effects of the three-dimensional atmospheric structure on spectral line profiles. The simulations presented in this thesis are an essential step towards a physically comprehensive description of magnetoconvective processes in stars, which is needed, e. g. for the improvement of inversion methods and the correct interpretation of spectroscopic observations.
Keywords: astrophysics; stellar physics; magnetic fields; convection; hydrodynamcs; magnetohydrodynamics; turbulence; cool stars; main-sequence stars; magnetic activity
 
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