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Astron. Astrophys. 317, 749-751 (1997)

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Anisotropic diffusion and shear instabilities

S. Talon and J.-P. Zahn

Département d'Astrophysique Stellaire et Galactique, Observatoire de Paris, Section de Meudon, F-92195 Meudon, France

Received 5 April 1996 / Accepted 7 June 1996

Abstract

We examine the role of anisotropic turbulence on the shear instabilities in a stratified flow. Such turbulence is expected to occur in the radiative interiors of stars, due to their differential rotation and their strong stratification, and the turbulent transport associated with it will be much stronger in the horizontal than in the vertical direction. It will thus weaken the restoring force which is caused by the gradient of mean molecular weight (µ).

We find that the critical shear which is able to overcome the µ-gradient is substantially reduced by this anisotropic turbulence, and we derive an estimate for the resulting turbulent diffusivity in the vertical direction.

Key words: stars: abundances; evolution; interiors; rotation – diffusion.

Send offprint requests to: S. Talon

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© European Southern Observatory (ESO) 1997

Online publication: July 8, 1998
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