KINETIC EIGENMODES AND DISCRETE SPECTRUM OF PLASMA OSCILLATIONS IN A WEAKLY COLLISIONAL PLASMA

The damping of plasma oscillations in a weakly collisional plasma is revisited using a Fokker-Plan collision operator. It is shown that the Case–Van Kampen continuous spectrum is eliminated in limit of zero collision frequency and replaced by a discrete spectrum. The Landau-damped solutions recovered in this limit, but as true eigenmodes of the weakly collisional system. For small but nonz collision frequency, the spectra and eigenmodes are qualitatively different from their counterparts in collisionless theory. These results are consistent with recent experimental findings.