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Session 12 - Stellar Evolution - Theory.
Display session, Wednesday, January 07
We present self-consistent and time-dependent MHD heating models for chromospheres of magnetically active stars. We investigate the propagation and dissipation of longitudinal flux tube waves in K2V stars with different rotation rates implying different photospheric and chromospheric magnetic filling factors. These filling factors are critical for determining the number of flux tubes on the stellar surface and the spreading of the tubes with height, which is relevant for the propagation and dissipation of the magnetic energy. The photospheric filling factors are estimated using a relationship between the magnetic field strength B_o multiplied by the photospheric magnetic filling factor f_o and the stellar rotation P_rot in accord with very recent magnetic field measurements. We also consider revised computations for the initial magnetic energy fluxes generated by turbulent motions (Ulmschneider amp; Musielak 1997, Aamp;A, submitted). Our models show increased shock strengths and energy dissipation rates in stars of faster rotation due to the narrower spreading of the tubes. This also leads to increased chromospheric emission particularly in Mg II in stars of faster rotation. We consider these results as a first step toward a theoretical derivation of chromospheric emission --- stellar rotation relations for stars of different masses and evolutionary status.
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