Flows and dynamos in a model of stellar radiative zones

TL;DR

This study uses numerical simulations to explore how flows and magnetic fields develop in stellar radiative zones, revealing complex dynamics and dynamo action driven by baroclinic effects and varying physical parameters.

Contribution

It introduces a 3D, time-dependent model of stellar radiation zones showing flow transitions and dynamo generation influenced by baroclinic torque and parameter variations.

Findings

Flow regimes with non-axisymmetric components can generate magnetic fields.

Decreasing Prandtl and Ekman numbers leads to more complex, time-dependent flows.

Dynamo action occurs at lower magnetic Prandtl numbers with increased flow complexity.

Abstract

Stellar radiative zones are typically assumed to be motionless in standard models of stellar structure but there is sound theoretical and observational evidence that this cannot be the case. We investigate by direct numerical simulations a three-dimensional and time-dependent model of stellar radiation zones consisting of an electrically-conductive and stably-stratified anelastic fluid confined to a rotating spherical shell and driven by a baroclinic torque. As the baroclinic driving is gradually increased a sequence of transitions from an axisymmetric and equatorially-symmetric time-independent flow to flows with a strong poloidal component and lesser symmetry are found. It is shown that all flow regimes characterised with significant non-axisymmetric components are capable of generating self-sustained magnetic field. As the value of the Prandtl number is decreased and the value of the Ekman number is decreased flows become strongly time-dependent with progressively complex spatial structure and dynamos can be generated at lower values of the magnetic Prandtl number.