Interactions between magnetohydrodynamic shear instabilities and convective flows in the solar interior

TL;DR

This paper investigates how magnetic fields influence the interactions between shear-driven instabilities and convective flows in the solar interior, revealing how magnetic strength determines the dominant instability and its impact on convection.

Contribution

It provides new insights into the magnetohydrodynamic interactions between shear instabilities and convection, especially how magnetic field strength affects the dynamics in the solar interior.

Findings

Weak magnetic fields have negligible effects on shear-convection interactions.

Strong magnetic fields lead to magnetic buoyancy instabilities and flux emergence.

Magnetic flux concentrations disrupt convective motions in the upper layer.

Abstract

Motivated by the interface model for the solar dynamo, this paper explores the complex magnetohydrodynamic interactions between convective flows and shear-driven instabilities. Initially, we consider the dynamics of a forced shear flow across a convectively-stable polytropic layer, in the presence of a vertical magnetic field. When the imposed magnetic field is weak, the dynamics are dominated by a shear flow (Kelvin-Helmholtz type) instability. For stronger fields, a magnetic buoyancy instability is preferred. If this stably stratified shear layer lies below a convectively unstable region, these two regions can interact. Once again, when the imposed field is very weak, the dynamical effects of the magnetic field are negligible and the interactions between the shear layer and the convective layer are relatively minor. However, if the magnetic field is strong enough to favour magnetic buoyancy instabilities in the shear layer, extended magnetic flux concentrations form and rise into the convective layer. These magnetic structures have a highly disruptive effect upon the convective motions in the upper layer.