Cyclotron resonance phenomena in a non-neutral plasma

Abstract

A kinetic theory of electrostatic cyclotron waves in a single component plasma slab of density n0(x) immersed in a uniform magnetic field B0ẑ is presented. The space charge electric field E0(x)x̂ in such a plasma modifies the single particle gyrofrequency from Ω=qB0/mc to Ω1(x)=[Ω2−ω2p(x)]1/2 in the limit rc/L ≪1 (where rc is the orbit size and L−1=d ln E0/dx), causing the upper hybrid frequency to have the value (Ω21+ω2p)1/2 =Ω. Finite Larmor radius effects introduce a velocity dependence into the single particle gyrofrequency Ω1, leading to energy transfer to the particles located at the resonant layers where ω−kyvE(x) =Ω1(x) [vE(x)ŷ being the E×B drift velocity]. This energy transfer mechanism is operative even when kz =0. Another nonzero Larmor radius effect is the appearance of thermal modes that are the analogs of Bernstein modes of neutral plasmas. When driven by an external capacitor plate antenna, these modes exhibit behavior similar to Tonks–Dattner resonances.