Differential Rotation and Meridional Flow for Fastrotating SolarType Stars
Abstract
Observations indicate that normalized surface differential rotation decreases for fastrotating stars, that is,  ∆Ω /Ω ~ Ω^{0.3}. An increase of  ∆Ω /Ω is provided, however, by the current Reynolds stress theory of differential rotation in stellar convection zones, without the inclusion of meridional flow. We compute both the poleequator difference of the surface angular velocity and the meridional drift for various Taylor numbers to demonstrate that the inclusion of meridional flow in the computations for fast rotation yields a systematic reduction of the resulting differential rotation. Our model's adiabatic and densitystratified convection zone, with stressfree surfaces and a thickness of 0.3 stellar radii, yields the relation  ∆Ω /Ω ~ Ω^{(0.15 ... 0.30)} for stars with faster rotation than the Sun, in agreement with previous observations. If the Coriolis number rather than the Taylor number is varied, we find a maximum differential rotation of 20%. For stars with fast rotation, exponents of up to n' ~= 0.4 are found. All rotation laws exhibit superrotating equators.
 Publication:

The Astrophysical Journal
 Pub Date:
 February 1998
 DOI:
 10.1086/305216
 Bibcode:
 1998ApJ...494..691R
 Keywords:

 HYDRODYNAMICS;
 STARS: ROTATION;
 TURBULENCE;
 Hydrodynamics;
 Stars: Rotation;
 Turbulence