On Stellar Rotation: I. The Rotation of Upper Main-Sequence Stars

The centrifugal perturbation to the thermal field drives meridional circulation in radiative zones of rotating stars. Transport of angular momentum by the circulation changes the angular velocity field and hence the circulation itself. We here assume that the system approaches a steady state in which there is no meridional circulation, and calculate that distribution of angular velocity that does not upset radiative equilibrium, assuming that the star has no internal magnetic field. Results are obtained for two upper main-sequence stellar models: one with the opacity given by a modified Kramer's law, the other with electron scattering. The angular velocity is found to be a monotonically decreasing function of distance from the centre of the star and to be independent of latitude, so that the star rotates in spherical shells. The solution is shown to be dynamically stable.