STRUCTURE AND MECHANISM OF HIGH-FREQUENCY OSCILLATION GENERATION IN ABEAM-PLASMA-DISCHARGE

Spectral and statistic characteristics of oscillations generated in a beam-plasma system during the development of a beam-plasma discharge w ith no magnetic field were experimentally investigated. Juxtaposition of properties and characteristics of the beam-plasma discharge excited both by an unmodulated beam, and by a beam initially modulated in vel ocity, has enabled us to establish that, despite the wide-band RF radi ation spectrum, the interaction between the beam and the plasma is a s ingle-mode or few-moded one. The resulting oscillation spectrum arises from chaotic jumps between different modes of the system. A qualitati ve model of a beam-plasma discharge as a stochastic self-oscillating s ystem that has an inherent feedback, was suggested and validated; this allows one to explain the observed discharge properties. The possible correspondence of this model to the effects observed in active geophy sical experiments with electron beam injection into the Earth's upper atmosphere is discussed.