Spontaneous Emission of a Charged Particle Beam Inside a Plasma: Coherent and Incoherent Aspects

摘要: Injection of charged particle beam into ionospheric plasma has revealed some unexpected behaviour the radio waves emission (Cartwright and Kellog, 1974; Lavergnat et al, 1980). Two kinds in time are observed for wave envelopes: a Continuous emission’ with one to relation between amplitude nominal current “pulsed emission” that reaches maximum few milliseconds after beginning an electron pulse then decreases continuously background value. Along different experiments (Echo 1 2, Araks) both behaviours have been two frequency ranges: whistler mode go ω < ωb, \( {\omega _P} \omega {({\omega _P}^2 + _b}^2)^{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$2$}}}} \) Pulsed will be main topic this paper. Apart from collective processes spontaneous specially Cerenkov is good candidate explain observations. Singh (1973) found by crude computation incoherent electric field values which orders magnitude below value no possible explanation pulsed character. Alekhin Karpman first who suggested infinitely sharp front spread velocity can radiate emission.