Effects of a subadiabatic layer on convection and dynamos in spherical wedge simulations

TL;DR

This study investigates how a subadiabatic layer beneath the convection zone influences convection patterns and dynamo behavior in spherical wedge simulations, revealing significant effects on heat transport and magnetic field generation.

Contribution

It introduces a dynamic heat conduction model based on Kramers opacity law, showing how a stable layer affects convection anisotropy and dynamo properties in spherical simulations.

Findings

Convective heat transport is concentrated at equator and poles without a stable layer.

A stable layer reduces radial enthalpy transport anisotropy.

Dynamo solutions are sensitive to convection zone structure, with helicity changing sign at high latitudes.

Abstract

We consider the effect of a subadiabatic layer at the base of the convection zone on convection itself and the associated large-scale dynamos in spherical wedge geometry. We use a heat conduction prescription based on the Kramers opacity law which allows the depth of the convection zone to dynamically adapt to changes in the physical characteristics such as rotation rate and magnetic fields. We find that the convective heat transport is strongly concentrated toward the equatorial and polar regions in the cases without a substantial radiative layer below the convection zone. The presence of a stable layer below the convection zone significantly reduces the anisotropy of radial enthalpy transport. Furthermore, the dynamo solutions are sensitive to subtle changes in the convection zone structure. We find that the kinetic helicity changes sign in the deeper parts of the convection zone at high latitudes in all runs. This region expands progressively toward the equator in runs with a thicker stably stratified layer.