DRIFT KELVIN-HELMHOLTZ INSTABILITIES IN SPACE PLASMAS

Drift Kelvin-Helmholtz instabilities are of extreme interest for a variety of astrophysical and space science situations such as the interaction of the solar wind with the boundary of the Earth's magnetosphere, the stream structure of solar wind, and the helical wave motions observed in ionized comet tails. Three cases of these instabilities are discussed in the presence of equilibrium electric and magnetic fields which are perpendicular to each other. A comparison is made with the previous studies. In the first case, the magneto-acoustic instability in a plasma flow of finite beta with homogeneous density and temperature is discussed and a dispersion relation is achieved and the instability criterion is established. In the second case, effect of the density gradient is studied on the electrostatic drift Kelvin-Helmholtz instability of a low-beta plasma in the presence of equilibrium electric and magnetic fields and an instability criterion is obtained. In the third case, we discuss the magneto-acoustic instability of a high-beta plasma with gradients in equilibrium density and magnetic field. Stability conditions are worked out, quantitatively discussed and compared with the previous results. It is shown that the electric field has a stabilizing or destabilizing effect according as the conditions given in this paper.