Abstract

The Tayler-Spruit dynamo is a subcritical dynamo driven by the Tayler instability in a stably stratified shear flow. This mechanism is of particular interest to astrophysics as the generated strong large-scale magnetic field could explain angular momentum transport during stellar evolution and the formation of very magnetized neutron stars called magnetars. Due to its subcritical nature and stable stratification, this dynamo has remained elusive in numerical simulations until the recent studies of Petitdemange et al. and Barrère et al. I will present the results of 3D numerical simulations of the Tayler-Spruit dynamo and their implications for astrophysical problems. Our results demonstrate the existence of different subcritical branches showing distinct magnetic field geometries and dynamical behaviours, which were not predicted by previous analytical studies. The strongest branch harbours magnetic fields which are consistent with the observation of magnetars with low magnetic dipoles and in global agreement with analytical prescription for angular momentum transport in stellar radiative zones. Thus, beyond capturing an unexpected rich dynamics of the Tayler-Spruit dynamo, our work provides a better understanding of the formation of magnetars and the physics in stellar interiors.