Combined effects of viscosity and a vertical magnetic field on Rayleigh-Taylor instability

The utilization of an external magnetic field greatly enhances the ion temperature and neutron yield from inertial confinement fusion capsule implosions, and viscosity is important in damping the small-scale mixing. In this paper, we present a linear analysis on Rayleigh-Taylor instability in the presence of viscosity and a vertical magnetic field. Unexpectedly, we find that the combined effects may strongly suppress the instability when the ratio S between the viscosity and the magnetic field strength is equal to 0.1, but enhance the instability for sufficiently large S, particularly for perturbations with high wave numbers. Moreover, the growth rate for S = 10 is broadly the same as when the magnetic field is absent, namely, S = 0. Therefore, the suppression or enhancement of the growth rates is greatly dependent on the ratio S. This phenomenon may play an essential role in the dynamics of intracluster gas in astrophysics and the uniformity of the compression target in magnetic inertial fusion. At last, we confirm that the viscosity instead of the electric resistivity plays a more important role to determine the interface motion in relation to inertial confinement fusion.