Confinement of the Solar Tachocline by Dynamo Action in the Radiative Interior

Abstract A major outstanding problem in solar physics is the confinement of the solar tachocline, the thin shear layer that separates nearly solid-body rotation in the radiative interior from strong differential rotation in the convection zone. Here, we present the first 3D, global solar simulation that displays a magnetically confined tachocline. The nonaxisymmetric magnetism is initially built in the convection zone and then diffusively imprints downward, similar to the proposed fast magnetic confinement scenario by the Sun’s cyclic dynamo field. Additionally, the field is locally amplified throughout the radiative interior by vigorous horizontal motions that seem to arise from a combination of equatorial Rossby waves and shear, magnetic, and buoyancy instabilities. Our work thus supports prior studies proposing dynamo action in the radiative interior, and suggests that horizontal motions could play a key role in driving this deep dynamo.