RELATIVISTIC CYCLOTRON INSTABILITIES

A velocity space instability was observed in plasmas produced by electron cyclotron resonance heating which causes greatly enhanced diffusion into the mirror loss-cones. The instability occurs at frequencies slightly above the second harmonic of the nonrelativistic cyclotron frequency omega , and is observed only if a relativistic runaway component is present in a dense, finite temperature background plasma. Since the unstable waves have frequencies above 2 omega c while the second harmonic 2 omega 0, of the relativistic electron gyrofrequency occurs below 2 omega c, the fully relativistic condition for resonant wave-particle interaction omega -2 omega 0-k/sub ///v/sub ///=0 must be used in the stability analysis.