ELECTROMAGNETIC-RADIATION EMITTED BY SUPERSONIC LANGMUIR TURBULENCE IN ACTIVE EXPERIMENTS IN SPACE

Experimental evidence of supersonic Langmuir turbulence has been reported by Pulinets and Selegey (1986; J. atmos. terr. Phys. 48, 149) and Shuiskaya et al. (1987; Report, Space Research Institute of the U.S.S.R.) in the vicinity of a satellite when high-power radio waves were transmitted for topside sounding of the ionosphere. It is shown that, in the presence of supersonic Langmuir turbulence, electromagnetic radiation near the local electron plasma frequency can be emitted through the electromagnetic parametric instabilities driven by intense Langmuir waves. The growth rates of these electromagnetic parametric instabilities are shown to be identical to the corresponding growth rates of the electrostatic Langmuir parametric instabilities. It is suggested that the stimulated electromagnetic emission can become a useful diagnostic technique for active experiments in space.