FLUIDLIKE ELECTRON AND ION MODES IN INHOMOGENEOUS PLASMAS

Collisionless unstable modes, involving the entire velocity space and not due to Landau damping effects, are shown to exist in two-dimensional configurations in which the particle orbits are periodic along the magnetic field lines, where the magnetic intensity varies along the field, and the particle density gradient is in a perpendicular direction. One mode is associated with the velocity dependence of the electron excursion frequency and one with the trapping of ions in the magnetic field wells. Their relevance to laboratory and space plasmas is pointed out. © 1968 The American Physical Society.