Magnetic curvature driven Rayleigh-Taylor instability revisited

O A Pokhotelov,O G Onishchenko

doi:10.5194/angeo-29-411-2011

Abstract

Abstract. The problem of incomplete finite ion Larmor radius (FLR) stabilization of the magnetic curvature driven Rayleigh-Taylor instability (RTI) in low beta plasma with homogeneous ion temperature is investigated. For this purpose a model hydrodynamic description of nonlinear flute waves with arbitrary spatial scales compared to the ion Larmor radius is developed. It is shown that the RTI is not stabilized by FLR effects in a plasma with cold electrons when the ratio of characteristic spatial scale of the plasma inhomogeneity to local effective radius of curvature of the magnetic field lines is larger than 1/4. The crucial role in the absence of the complete FLR stabilization plays the contribution of the compressibility of the polarization part of the ion velocity.

Highlights

Microturbulence of drift and magnetic curvature driven flute waves is believed to be plausibly responsible for the anomalous transport in magnetic confinement and astrophysical plasmas
The main purpose of present work is devoted to the problem of incomplete finite ion Larmor radius (FLR) stabilization of the magnetic curvature driven Rayleigh-Taylor instability (RTI) in low-beta plasmas
Our analysis is an extension of the previous study of the RTI that has been limited to consideration of waves with spatial scales larger than the ion Larmor radius ρi

Summary

Introduction

Microturbulence of drift and magnetic curvature driven flute waves is believed to be plausibly responsible for the anomalous transport in magnetic confinement and astrophysical plasmas. The investigation of flute waves with spatial scales compared to the ion Larmor radius are of great importance for the interpretation of laboratory experiments as well as in astrophysical observations. = (ωN ωc/z)1/2 is the maximum value of the RTI growth rate and σ = ωc/ωN = L/R where L = 1/κN is the local scale of the plasma inhomogeneity. Dispersion relation (1) and normalized growth rate (2) in the approximation σ 1 coincide with respective classical relations for the flute waves in a gravity field g (Roberts and Taylor, 1962; Mikhailovskii, 1967) with the substitution vT2 i /R = g, so that vc → vg = −g/ωci, where vg is the ion gravitation drift velocity.

Hydrodynamic description

Linear dispersion relation

Discussion and conclusions