Low-frequency instabilities driven by oxygen ion beams in plasma sheet region

Abstract

Low-frequency instabilities driven by ionospheric oxygen ion beam are studied in the plasma sheet region. In three component cold and uniform plasma consisting of electrons, protons and oxygen ions, the linear dispersion relation is derived with velocity shear in each component. The dispersion relation is solved for the case of uniform as well as nonuniform oxygen ion beam with shear flow passing through stationary electron–ion plasma. It is found that uniform oxygen ion beam can excite the low-frequency instabilities provided the Mach number exceeds a critical value. For the case of nonuniform oxygen ion beam it is found that the velocity shear can give rise to Kelvin–Helmholtz type instabilities. These low-frequency waves may be responsible for the low-frequency turbulence observed in the plasma sheet region.