Differential Rotation and Meridional Flow for Fast‐rotating Solar‐Type Stars

Gunther Rudiger, Brigitta von Rekowski, Robert A. Donahue, Sallie L. Baliunas
1998 Astrophysical Journal  
Observations indicate that normalized surface di †erential rotation decreases for fast-rotating stars, that is, o *) o/) P )~0.3. An increase of o *) o/) is provided, however, by the current Reynolds stress theory of di †erential rotation in stellar convection zones, without the inclusion of meridional Ñow. We compute both the pole-equator di †erence of the surface angular velocity and the meridional drift for various Taylor numbers to demonstrate that the inclusion of meridional Ñow in the
more » ... onal Ñow in the computations for fast rotation yields a systematic reduction of the resulting di †erential rotation. Our modelÏs adiabatic and density-stratiÐed convection zone, with stress-free surfaces and a thickness of 0.3 stellar radii, yields the relation o *) o /) P )~(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 Ðnd a maximum di †erential rotation of 20%. For stars with fast rotation, exponents of up to n@^0.4 are found. All rotation laws exhibit superrotating equators.
doi:10.1086/305216 fatcat:2uoxc5ti5zddxkvdhgkxkuyswu