Beam instabilities induced by pulsed RF field

RF sounder experiments on board L-3H-9 rocket were carried out in order to investigate the generation mechanism of plasma resonances produced by electrostatic electron cyclotron harmonic (ESCH) waves. The spectrum of the stimulated plasma resonances suggested that there are ESCH waves generated by the instability due to an electron beam, which is caused by antenna charging by an impressed RF field. The observed frequency range of the generated ESCH waves is in agreement with the range theoretically predicted for ESCH wave instabilities triggered by low energy electron beams. The generation of an electron beam is verified by a space simulation chamber experiment. When an RF pulse is applied from a sounder antenna in the chamber plasma, a clear signature of an electron burst was observed. The characteristics of the beam type instability are also verified by K-9M-61 sounding rocket experiment. In the space plasma, beam type instability generates the same branches of the ESCH waves as the plasma resonances by the L-3H-9 plasma sounder experiment. (author)