Acoustic and magnetic wave heating in stars

I. Theoretical chromospheric models and emerging radiative fluxes

¹ Institut für Theoretische Astrophysik der Universität Heidelberg, Tiergartenstr. 15, 69121 Heidelberg, Germany
² Department of Physics, University of Texas at Arlington, Arlington, TX 76019, USA
³ Warsaw University Observatory, Al. Ujazdowskie 4, 00478 Warszawa, Poland

Corresponding author: P. Ulmschneider, ulmschneider@ita.uni-heidelberg.de

Received: 10 October 2001
Accepted: 18 February 2002

Abstract

We describe a method to construct theoretical, time-dependent, two-component and wave heated chromosphere models for late-type dwarfs. The models depend only on four basic stellar parameters: effective temperature, gravity, metallicity and filling factor, which determines the coverage of these stars by surface magnetic fields. They consist of non-magnetic regions heated by acoustic waves and vertically oriented magnetic flux tubes heated by longitudinal tube waves with contributions from transverse tube waves. Acoustic, longitudinal and transverse wave energy spectra and fluxes generated in stellar convection zones are computed and used as input parameters for the theoretical models. The waves are allowed to propagate and heat both components by shock dissipation. We compute the time-dependent energy balance between the dissipated wave energy and the most prominent chromospheric radiative losses as function of height in the stellar atmosphere. For the flux tube covered stars, the emerging radiative fluxes in the Ca II and Mg II lines are computed by using a newly developed multi-ray radiative transfer method.