DISPERSIVE PROPERTIES OF A MAGNETIZED PLASMA WITH A FIELD-ALIGNED DRIFT AND INHOMOGENEOUS TRANSVERSE FLOW

Electrostatic fluctuations driven by the combination of a magnetic-fie ld-aligned electron current and a localized transverse electric field are investigated. Characteristic parameters, such as scale length and magnitude of the sheared ExB velocity, magnitude of the magnetic-field -aligned current, and temperature ratio tau T-i/T-e are varied to incl ude conditions associated with electrostatic waves driven entirely by magnetic-field-aligned current, driven entirely by transverse electric field, and driven by a combination of magnetic-field-aligned current and transverse electric field. It is shown that, in contrast to the ho mogeneous case of current-driven modes, the modes in the presence of a transverse-velocity shear can be unstable in a wider range of tempera ture ratio tau and they are broadband in frequency. Using a simplified model, numerical solutions of the nonlocal dispersion relation, and p hysical arguments, cases of stabilization and destabilization due to t he inhomogeneous energy-density driven instability mechanism are studi ed for the ion-cyclotron, ion-acoustic and drift modes. The response o f the plasma to transverse-velocity shear can be categorized as reacti ve or dissipative and conditions corresponding to the predominance of either one are evaluated. Possible applications of these results to sp ace and laboratory plasma are discussed. (C) 1996 American Institute o f Physics.