Resonant absorption of electromagnetic waves in a non-uniformly magnetized plasma

Abstract

The propagation and collisionless absorption of electromagnetic waves propagating in non-uniformly magnetized plasmas with regions of cyclotron resonance are computed. The particle dynamics associated with motion in a non-uniform magnetic field near cyclotron resonance is considered explicitly. Above a critical plasma density complete wave absorption is predicted. At high plasma densities particles with high velocities along the field lines are heated preferentially whereas at lower densities the slower particles gain more energy per particle from the wave. At high densities the wave is attenuated by the high energy tail of the velocity distribution; this dissipation is shown to be consistent with the uniform field results of Stix. The lack of heating observed in Princeton ioncyclotron wave absorption experiments is resolved by considering the wave launching efficiency.