Current-vortex-sheet model of the magnetic Rayleigh-Taylor instability.

Abstract

This study investigates the Rayleigh-Taylor instability in the magnetic field applied parallel to the interface. The motion of the interface is described using a current-vortex-sheet model. The growth rate of the interface is obtained from a linear stability analysis of the model. The interface of a single mode k=1 is linearly stable for R_{A}≤1, where R_{A} denotes the Alfvén number. Further, we conduct numerical computations for the evolution of the interface from the model for both regimes of R_{A}≤1 and R_{A}>1. For R_{A}≤1, the interface oscillates vertically but does not intrude into the opposite phase. The amplitude of the interface and the oscillation period decrease with decrease in R_{A}. For 1<R_{A}≲1.5, the interface undergoes some growth at early times and then decreases. This oscillation is repeated, and no roll-ups are observed at the interface. Therefore, the nonlinear growth of the Rayleigh-Taylor instability is stabilized by a sufficiently strong magnetic field. For R_{A}≳3 the interface is unstable and the pattern of the interface evolution differs from the density ratio. In addition, the magnetic field is greatly amplified as R_{A} increases.