Simulation of the Magnetothermal Instability

Ian Parrish, Princeton University

The magnetothermal instability results from anisotropic conduction along magnetic field lines in an otherwise convectively stable, vertically stratified atmosphere. We have performed a series of two-dimensional magnetohydrodynamic simulations of a model atmosphere to study the linear and non-linear properties of this instability. We have verified the analytical weak-field linear dispersion relation and examined the modifications that result from strong magnetic fields and isotropic conduction. As one would intuitively expect, the atmosphere saturates to an essentially isothermal atmosphere for adiabatic boundary conditions. In cases where we drive continuous vertical heat transport, we find an essentially adiabatic profile with resolution-dependent boundary layers at the conducting walls. We explore the effect of finite magnetic field strength and isotropic conduction on the saturation properties. Finally, we simulate a more realistic atmosphere where the unstable region is surrounded by stable layers.

Abstract Author(s): Ian J. Parrish and James M. Stone