Dynamo Confinement of the Solar Tachocline

In the solar interior, strong latitudinal differential rotation persists throughout most of the convective zone (CZ). At the base of the CZ, this differential rotation transitions across a narrow shear layer, known as the "tachocline", to rigid rotation in the radiative zone (RZ) below. The origin of the tachocline is a longstanding mystery of fluid dynamics, given the expected tendency of shear to spread inward relatively quickly compared to the solar age. We explore three-dimensional magnetohydrodynamic simulations of a solar-like CZ-RZ system, in which the magnetic field from the convective dynamo penetrates into the RZ and confines a tachocline. For the first time, our simulations are able to confine tachoclines in the computationally challenging regime of "radiative spread", wherein the large-scale meridional circulation spreads the differential rotation inward, as is expected to occur in the Sun. These new simulations represent a major breakthrough from prior work, which, for computational tractability, was focused on the non-solar regime wherein viscosity (believed to be negligible in the Sun) is the mechanism that spreads the differential rotation inward. We present a summary of this recent progress toward an understanding of tachocline dynamics and outline avenues for further research.