A Self-Consistent Determination of the Temperature Profile and The Magnetic Field Geometry in Winds of Late-Type Stars |
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Authors: | A A Vidotto D Falceta-Gonçalves V Jatenco-Pereira |
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Institution: | 1. Depto. de Astronomia, Univ. de S?o Paulo, Brazil
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Abstract: | Cool giant and supergiant stars generally present low velocity winds with high mass-loss rates. Several models have been proposed
to explain the acceleration process of these winds. Although dust is known to be present in these objects, the radiation pressure
on these particles is uneffective in reproducing the observed physical parameters of the wind. The most promising acceleration
mechanism cited in the literature is the transference of momentum and energy from Alfvén waves to the gas. Usually, these
models consider the wind to be isothermal. We present a stellar wind model in which the Alfvén waves are used as the main
acceleration mechanism, and determine the temperature profile by solving the energy equation taking into account both the
radiative losses and the wave heating. We also determine, self-consistently, the magnetic field geometry as the result of
the competition between the magnetic field and the thermal pressure gradient. As the main result, we show that the magnetic
geometry presents a super-radial index in the region where the gas pressure is increasing. However, this super-radial index
is greater than that observed for the solar corona. |
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Keywords: | stars: mass loss stars: magnetic fields MHD waves |
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