Effects of External Magnetic Fields on the Multi-mode Rayleigh-Taylor Instability

TL;DR

This study uses resistive MHD simulations to explore how external magnetic fields affect the nonlinear evolution of multi-mode Rayleigh-Taylor instability, revealing that field orientation and strength significantly influence instability growth and plasma mixing.

Contribution

The paper provides new insights into the nonlinear behavior of multi-mode mRTI under external magnetic fields through comprehensive 2D and 3D resistive MHD simulations, highlighting the role of magnetic tension.

Findings

Weak parallel fields increase mixing-zone growth.

Stronger parallel fields suppress instability.

Perpendicular fields initially inhibit then enhance growth.

Abstract

The magneto-Rayleigh-Taylor instability (mRTI) is a key process in inertial confinement fusion and is thought to be widespread in the interstellar medium, where it can concentrate plasma into discrete structures. We present resistive MHD simulations of the nonlinear evolution of multi-mode mRTI in both two and three dimensions, examining the effects of uniform external magnetic fields oriented either parallel or perpendicular to the initial interface. In both 2-D and 3-D, weak parallel fields enhance mixing-zone growth, whereas stronger fields suppress it. For perpendicular fields, growth is initially inhibited but becomes enhanced at later times. These behaviors arise from magnetic tension, which modifies flow anisotropy, buoyancy, drag, and vortex dynamics. The interplay of these mechanisms governs the distinct ways in which magnetic fields influence mRTI evolution.