Turbulent transport in stellar interiors (Q1271802)

The authors consider differential rotation as a major cause of turbulence in stably stratified stellar interiors. It is shown that for an anisotropy \(A\) of horizontal to vertical velocities, the vertical diffusivity is a factor \(A^2\) less than the horizontal diffusivity. Transport by meridional circulation is also reduced, as well as the efficiency of a composition gradient in suppressing meridional circulation. These effects of anisotropy explain the very small upper limit that observations of concentrations of chemical elements impose on the vertical transport in stars.