Angular velocity gradients in the solar convection zone

Numerical calculations of Boussinesq nonaxisymmetric convection in a rotating spherical shell are reported which were performed to study how convection in the supergranule layer redistributes angular momentum. It is found that supergranules are at best weakly influenced by rotation and can be largely responsible for the radial gradient of angular velocity observed in the thin supergranule layer below the photosphere. The results indicate that convection in a thin spherical shell weakly influenced by rotation can produce a substantial outward decrease in rotational velocity that approaches the limit predicted for radially moving particles that conserve their angular momentum. This phenomenon is shown to provide a plausible explanation for the observed difference in angular velocity between sunspots and the photospheric plasma.