Dynamics of Rotation and Magnetism in the Sun's Convection Zone and Tachocline

 

In this thesis, we assess the theoretical dynamics achieved in the solar interior, with particular focus on the solar tachocline. We use the open-source Rayleigh code on parallel supercomputers to simulate 3-D, rotating spherical shells of convection. First, we discuss how the solar Near-Surface Shear Layer (NSSL) might be generated by fast downflow plumes. Second, we identify a physical mechanism whereby the Sun might establish an internal latitudinal temperature gradient and thus achieve isorotation contours significantly tilted with respect to the rotation axis. Third, we describe how dynamos in convection-zone-only shells display remarkable bistability, in which two distinct magnetic cycles operate simultaneously. Finally, we present an MHD simulation achieving a solid-body-rotating radiative interior and differentially rotating convection zone. This shear layer, similar to the solar tachocline, is dynamically maintained by magnetic torques acting against viscous torques. Our work is thus the first to identify a ``magnetic tachocline confinement scenario" operating in a fully 3-D, nonlinear global simulation. Furthermore, the magnetism is produced by dynamo action, even below the region of convective overshoot. Rather than the classical ``abyssal deep''---i.e., a largely motion-free reservoir that accumulates magnetism pumped in from above---we argue that the Sun's radiative interior may contain inertial oscillations that play an active role in the dynamo.