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Modelling the differential rotation of F stars
Author(s) -
Küker M.,
Rüdiger G.
Publication year - 2007
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/asna.200710855
Subject(s) - differential rotation , physics , convection , convection zone , rotation (mathematics) , astrophysics , solar rotation , meridional flow , equator , stars , mechanics , rotation period , stellar rotation , classical mechanics , geometry , latitude , astronomy , solar physics , mathematics
We model stellar differential rotation based on the mean‐field theory of fluid dynamics. DR is mainly driven by Reynolds stress, which is anisotropic and has a non‐diffusive component because the Coriolis force affects the convection pattern. Likewise, the convective heat transport is not strictly radial but slightly tilted towards the rotation axis, causing the polar caps to be slightly warmer than the equator. This drives a flow opposite to that caused by differential rotation and so allows the system to avoid the Taylor‐Proudman state. Our model reproduces the rotation pattern in the solar convection zone and allows predictions for other stars with outer convection zones. The surface shear turns out to depend mainly on the spectral type and only weakly on the rotation rate. We present results for stars of spectral type F which show signs of very strong differential rotation in some cases. Stars just below the mass limit for outer convection zones have shallow convection zones with short convective turnover times. We find solar‐type rotation and meridional flow patterns at much shorter rotation periods and horizontal shear much larger than on the solar surface, in agreement with recent observations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)