Baroclinically-driven flows and dynamo action in rotating spherical fluid shells

TL;DR

This study presents the first non-axisymmetric, time-dependent simulations of baroclinically-driven flows in rotating spherical shells, revealing complex flow bifurcations and potential for magnetic dynamo action in stellar radiative zones.

Contribution

It introduces novel 3D simulations of anelastic flows driven by baroclinic torques, demonstrating flow bifurcations and dynamo possibilities in stellar interior models.

Findings

Flow bifurcations increase flow complexity with baroclinicity.

Polarity of flow shifts towards poloidal components as baroclinicity grows.

Evidence suggests self-sustained dynamo action in baroclinic flows.

Abstract

The dynamics of stably stratified stellar radiative zones is of considerable interest due to the availability of increasingly detailed observations of Solar and stellar interiors. This article reports the first non-axisymmetric and time-dependent simulations of flows of anelastic fluids driven by baroclinic torques in stably stratified rotating spherical shells -- a system serving as an elemental model of a stellar radiative zone. With increasing baroclinicity a sequence of bifurcations from simpler to more complex flows is found in which some of the available symmetries of the problem are broken subsequently. The poloidal component of the flow grows relative to the dominant toroidal component with increasing baroclinicity. The possibility of magnetic field generation thus arises and this paper proceeds to provide some indications for self-sustained dynamo action in baroclinically-driven flows. We speculate that magnetic fields in stably stratified stellar interiors are thus not necessarily of fossil origin as it is often assumed.