GENERALIZED LOWER-HYBRID-DRIFT INSTABILITY

The theory of lower-hybrid-drift instability is extended to include a finite k|| (the component of wave vector k parallel to the ambient magnetic field B0) so that the analysis bridges the usual lower-hybrid-drift instability of flute modes and the modified-two-stream instability. The present theory also includes electromagnetic and ambient magnetic field-gradient effects. It is found that in the cold-electron limit the density and magnetic gradients can qualitatively modify the conclusion obtained in the early theory of the modified-two-stream instability. For example, even if the relative drift far exceeds the Alfvén speed of the plasma, the instability may still persist. This result is in contrast to that established in the literature. When the electron temperature is finite, the problem is complicated. Numerical solutions are obtained for a number of cases. Results indicate that when k|≠0, the growth rate is not always reduced. © 1979 American Institute of Physics.