Cavitons

Cavitons, localized oscillating electric fields with accompanying density cavities, exist in many strong nonlinear interactions when electromagnetic waves or electron beams interact with plasmas. In electromagnetic wave interactions with inhomogeneous plasmas the dominant process is the conversion of electromagnetic waves into electrostatic waves whose field strengths are enhanced by several orders of magnitude in the vicinity of the resonant layer where the incident frequency matches the local plasma frequency. A caviton, once created can decay into several cavitons of even narrower widths. In electron beam plasma interactions a series of cavitons are produced when the unstable beam wave is backscattered from a zero frequency mode. The formation of a standing electron plasma wave and the simultaneous growth of the zero frequency mode lead to a spatial collapse (or spatial narrowing) of both the oscillating fields and the density cavities. Strong scatterings of particles by cavitons are observed. A new collective ion acceleration process is proposed based on the ponderomotive-force-driven ambipolar field