Laboratory experiment on the excitation of electron cyclotron harmonic waves observed in the topside RF sounder experiment

An experiment is performed to study the interaction of a high power microwave pulse with a magnetized dense plasma, in relation to topside RF sounder experiments in the ionosphere. Electron cyclotron harmonic waves similar to the emissions observed in the ionospheric experiment are excited after the complete termination of a pumping microwave pulse when the frequency of the pumping wave is equal to harmonics of the electron cyclotron frequency and is near the plasma frequency. The excitation of the wave is explained by an anisotropic velocity distribution of hot electrons produced by the high power microwave pulse. The experimental results imply that some of the VLF emissions observed in the magnetosphere are excited by the electrostatic instabilities.