DIFFERENTIAL ROTATION IN SOLAR-TYPE STARS - REVISITING THE TAYLOR-NUMBER PUZZLE

Differential rotation and meridional circulation in a solar-type star are computed. Rotationally-induced anisotropy and quenching of the eddy diffusivities are included. The resulting iso-contours of the angular velocity in the solar convection zone are close to the data of helioseismology. The anisotropy of the convective heat transport prevents the realization of the expected Taylor-Proudman state. The anisotropy produces a latitudinal temperature variation with warm poles and cool equator. The corresponding circulation opposes the meridional flow driven by the centrifugal force hence the net flow is very dow. The model is also applied to the (old) slowly-rotating Sun. The rotation law exhibits only a small latitudinal variation, its angular velocity decreases inwards. This is similar to a model artificially ignoring the meridional flow. The how, however, produces a strong effect for (young) fast rotators decreasing their differential rotation. For sun-like stars, a decrease of the differential rotation with rotation rate is found. Also the model predictions for meridional circulation and differential rotation in a K5-star with deep convection zone are discussed.