Magnetic quenching of the inverse cascade in rapidly rotating convective turbulence

TL;DR

This study uses an asymptotic magnetohydrodynamic model to show that strong magnetic fields in rapidly rotating planetary and stellar interiors prevent large-scale vortex formation by saturating the inverse cascade at a finite scale.

Contribution

The paper introduces a quantitative criterion for the transition between finite-size flows and large-scale vortices in magnetized, rapidly rotating fluids.

Findings

Magnetic fields prevent large-scale vortex formation in planetary interiors.

A saturation of the inverse cascade occurs at a finite length-scale due to magnetic effects.

Convection-driven large-scale vortices are unlikely in electrically conducting regions of planets.

Abstract

We present results from an asymptotic magnetohydrodynamic model that is suited for studying the rapidly rotating, low viscosity regime typical of the electrically conducting fluid interiors of planets and stars. We show that the presence of sufficiently strong magnetic fields prevents the formation of large-scale vortices and saturates the inverse cascade at a finite length-scale. This saturation corresponds to an equilibrated state in which the energetics of the depth-averaged flows are characterized by a balance of convective power input and ohmic dissipation. A quantitative criteria delineating the transition between finite-size flows and domain-filling (large-scale) vortices in electrically conducting fluids is found. By making use of the inferred and observed properties of planetary interiors, our results suggest that convection-driven large-scale vortices do not form in the electrically conducting regions of many bodies.