The Effect of Compressibility on the Kelvin-Helmholtz Instability in Plasmas.

A. G. GONZÁLEZ; J. GRATTON

Anales AFA

Asociación Física Argentina

Año: 2001 vol. 13 p. 67 - 70

0327-358X

    The Kelvin-Helmholtz instability occurs in many natural and laboratory plasmas, in complex configurations with magnetic shear and density and temperature jumps across the velocity. The addition of compressibility effects leads to notable complexities since the dispersion relation yields apolynomial of tenth degree that depends on 6 in dependent parameters. Then, the results of the incompressible theory are usually employed while interpreting experimental data since in this approximation the stability condition has an analytical form, and it is as sumed that compressibilitytends to stabilize the Kelvin-Helmholtz modes, an assumption based on the Newcomb?s well-known theorems. Nevertheless these theorems cannot be applied in our case because perturbations with negative energy are possible in configurations with mass flow, and in consequence new instabilities may develop if new modes appear due to compressibility. In this paper we show that the effect of compressibility destabilizes the plasma for low relative velocities in cases that were stable in theincompressible limit .