The Evolution of a Double Diffusive Magnetic Buoyancy Instability

TL;DR

This paper investigates the long-term nonlinear evolution of a double diffusive magnetic buoyancy instability, revealing how three-dimensional perturbations develop and expand over time in simulated conditions.

Contribution

It demonstrates the nonlinear evolution of a double diffusive magnetic buoyancy instability and highlights the increasing three-dimensional nature of the instability over time.

Findings

A quasi two-dimensional interchange instability develops.

Three-dimensional perturbations remain unstable and expand.

The instability's activity region grows and becomes more three-dimensional.

Abstract

Recently, Silvers, Vasil, Brummell, & Proctor (2009), using numerical simulations, confirmed the existence of a double diffusive magnetic buoyancy instability of a layer of horizontal magnetic field produced by the interaction of a shear velocity field with a weak vertical field. Here, we demonstrate the longer term nonlinear evolution of such an instability in the simulations. We find that a quasi two-dimensional interchange instability rides (or "surfs") on the growing shear-induced background downstream field gradients. The region of activity expands since three-dimensional perturbations remain unstable in the wake of this upward-moving activity front, and so the three-dimensional nature becomes more noticeable with time.