Toroidal Field Reversals and the Axisymmetric Tayler Instability

TL;DR

This study uses axisymmetric simulations to show how differential rotation induces toroidal magnetic fields that become unstable and reverse, potentially contributing to the solar sunspot cycle without requiring a dynamo.

Contribution

It demonstrates that axisymmetric Tayler instability can cause magnetic field reversals in the solar interior independently of a dynamo process.

Findings

Toroidal fields become unstable to the Tayler instability

Reversals occur without a dynamo or poloidal field change

Reversal behavior depends on initial poloidal field strength

Abstract

We present axisymmetric numerical simulations of the solar interior, including the convection zone and an extended radiative interior. We find that differential rotation in the convection zone induces a toroidal field from an initially purely poloidal field. This toroidal field becomes unstable to the axisymmetric Tayler instability and undergoes equatorward propagating toroidal field reversals. These reversals occur in the absence of a dynamo and without accompanying poloidal field reversals. The nature and presence of such reversals depends sensitively on the initial poloidal field strength imposed, with north-south symmetric reversals only seen at a particular initial field strength. Coupled with a dynamo mechanism which regenerates the poloidal field this could be one ingredient in the sunspot cycle.