Journal
ASTRONOMY & ASTROPHYSICS
Volume 553, Issue -, Pages -Publisher
EDP SCIENCES S A
DOI: 10.1051/0004-6361/201220936
Keywords
convection; hydrodynamics; instabilities; turbulence
Categories
Funding
- Swiss National Fund
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Aims. We examine the interactions of various instabilities in rotating stars, which usually are considered as independent. Methods. An analytical study of the problem is performed accounting for radiative losses, mu-gradients, and horizontal turbulence. Results. The diffusion coefficient for an ensemble of instabilities is not given by the sum of the specific coefficients for each instability, but by the solution of a general equation. We find that thermohaline mixing is possible in low-mass red giants only if the horizontal turbulence is very weak. In rotating stars the Rayleigh-Taylor and the shear instabilities need simultaneous treating. This leads to rotation laws of the form 1/r(alpha) being predicted to be unstable for alpha > 1.6568, while the usual Rayleigh criterion only predicts instability for alpha > 2. Also, the shear instabilities are somehow reduced in main sequence stars by the effect of the Rayleigh-Taylor criterion. Various instability criteria should be expressed differently in rotating stars than in simplified geometries.
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