SPECTRAL STRUCTURE OF STIMULATED ELECTROMAGNETIC EMISSIONS BETWEEN ELECTRON-CYCLOTRON HARMONICS

Experimental results concerning the spectrum of stimulated electromagn etic emissions (SEE) in the sidebands of a powerful high-frequency ele ctromagnetic ordinary mode pump wave are presented. The pump wave was vertically injected into the ionospheric F region from the Sura ionosp heric modification facility in Russia. We report detailed measurements of the commonly observed continuum, downshifted maximum, and broad up shifted maximum emissions for pump frequencies ranging from the fourth to above the seventh electron cyclotron harmonic in the ionospheric p lasma as well as observations of a new wideband emission occurring pri marily in the upper sideband. The dependence of the SEE spectral struc ture on the pump frequency in relation to electron cyclotron harmonics is emphasized. All spectral features in the sidebands of the pump exh ibit cyclotron harmonic effects.