Building and Maintaining a Solar Tachocline through Convective Dynamo Action

TL;DR

This paper presents the first 3D spherical-shell simulation demonstrating that convective dynamo action can build and sustain the solar tachocline, supporting the dynamo confinement hypothesis in stellar astrophysics.

Contribution

It introduces a novel global 3D simulation showing the solar dynamo can maintain the tachocline, a longstanding problem in stellar physics.

Findings

Dynamo action prevents tachocline viscous spreading in the simulation.

Supports the hypothesis that the solar dynamo confines the tachocline.

First simulation to realize this confinement scenario in a realistic geometry.

Abstract

For more than thirty years, the dynamical maintenance of the thin solar tachocline has remained one of the central outstanding problems of stellar astrophysics. Three main theories have been developed to explain the tachocline's thinness, but so far none of them has been shown to work convincingly in the extreme parameter regime of the solar interior. Here, we present a rotating, 3D, spherical-shell simulation of a combined solar-like convection zone and radiative zone that achieves a tachocline built and maintained by convective dynamo action. Because of numerical constraints, the dynamo prevents the viscous spread of the tachocline instead of the Eddington-Sweet-time-scale radiative spread believed to occur in the Sun. Nonetheless, our simulation supports the scenario of tachocline confinement via the cyclic solar dynamo, and is the first time one of the main confinement scenarios has been realized in a global, 3D, spherical-shell geometry including nonlinear fluid motions and a self-consistently generated dynamo.