Saturation of the Tayler instability in a cylindrical annulus

As stars evolve beyond their core-hydrogen-burning phase, angular momentum conservation suggests their contracting cores should spin up and their expanding envelopes should spin down. However, asteroseismic observations show a much smaller core-envelope rotation difference than expected, indicating some angular momentum transport in the stably-stratified region between the core and envelope. One proposed source of this transport is MHD turbulence driven by the Tayler instability, which combines with differential rotation to form the Tayler-Spruit dynamo. However, conflicting reduced models have been put forth to predict the efficiency of this transport and how it varies with properties of the star. These conflicting predictions stem from different assumptions regarding the saturation mechanism of the Tayler instability.

We present a suite of 3D MHD simulations of the Tayler instability in a rotating, stratified, cylindrical annulus to model the local dynamics near the rotation axis of a star. To test the assumptions of different reduced models, we investigate how this instability saturates, and how the saturated state varies for different field configurations and across different parameter regimes relevant to stellar interiors.