INTERACTION OF A DENSITY MODULATED ELECTRON-BEAM WITH A MAGNETIZED PLASMA - EMISSION OF WHISTLER WAVES

Whistler wave excitation in a magnetized laboratory plasma by a density modulated electron beam is studied for frequency modulation below, but in the range of, the electron gyrofrequency. When the beam velocity differs from the phase velocity of the whistler at the frequency modulation of the beam, a whistler wave, and, by Cerenkov emission, a beam wave at the same frequency are excited as single poles. When both velocities are equal, a resonance occurs leading to a maximum in the emission of whistler waves. The experiment performed in a magnetized plasma (n(p) almost-equal-to 10(11) cm-3, T(e) almost-equal-to 0.2 eV, B almost-equal-to 100 G) with a modulated electron beam (n(b) almost-equal-to 10(9) cm-3 , E(b) almost-equal-to 300 eV) is in agreement with a simple model which predicts the characteristics of the excited waves.