Numerical Studies of Solar Evolution with Rotation and Comparison With Stellar Rotation Data

Abstract

Models of rotating stars involve a number of assumptions regarding initial rotation, surface angular momentum losses (due to winds), and internal angular momentum redistribution (due to convective flows, fluid instabilities, magnetic torques, etc.). Such models can be used to predict surface rotational velocities, which may be compared to the rotation rates observed for stars at various masses and ages. These comparisons are useful for checking the assumptions in the models and, more indirectly, inferring the physical mechanisms which govern the internal rotation of the Sun and other stars. Recent improvements in the observational data allow more meaningful comparisons to the model predictions. In young clusters, the K dwarfs rotate much more rapidly that the G dwarfs, suggesting that the convective envelopes are spun down more easily than the radiative interiors. This creates a shear layer at the core-envelope interface. Post-main-sequence stars show clear evidence for strong rotational braking at the onset of deep envelope convection. These observations are reviewed in the context of models for rotating stars.