Parametric Excitation of Nonneutral-Plasma Surface Ripples

Parametric excitation of the equilibrium surface ripples of a drifting, magnetically confined, nonneutral plasma is investigated by passing it through a spatially periodic magnetic field. Resonances are observed at 2..cap omega../sub 0/, ..cap omega../sub 0/, and ..cap omega../sub 0//2 (..cap omega../sub 0/ is the natural frequency for the ripple). The ripple amplitude of the equilibrium surface is measured as a function of the phase angle of the excitation, the number of pump periods, and the magnitude of the magnetic field perturbations. (AIP)