Angular momentum flow in the sun

Abstract

Theories of the solar core rotation are first reviewed. The sun's surface rotation rate being relatively low as stars go has led many authors to believe the sun has lost most of its angular momentum and has this low rotation rate throughout. This low rotation rate is supported by heliometer observations of the roundness of the sun around the turn of the century as well as by recent experiments of Hill and colleagues. Dicke and Goldenberg, however, observe a more oblate appearance indicative of a rapidly rotating solar core. This rapid rotation appears to be explicable in terms of angular momentum released as the solar core contracts due to hydrogen burning. Three calculations of solar core rotation rates yield values of the pierod near one day. The author contends that the sun has a rapidly rotating core, but not fast enough to favour the Brans-Dicke theory of general relativity over the Einstein theory. The surface rotation of the sun is also reviewed. Four theories which appear as candidates for the explanation of the sun's differential rotation are anisotropic viscosities, Rossby waves, giant cell convection, and solar wind drag at the poles. All appear reasonable and there does not appear to be overwhelming support for any one.