Results of the experimental study of narrow continuum features in stimulated ionospheric emission spectra

Spectral and dynamical characteristics of the narrow continuum feature observed in the stimulated ionospheric emission spectra for small detunings from the pumping wave frequency are presented. It is found that the generation of the narrow continuum in the initial stage of interaction of a strong high-frequency o-mode pumping wave with an F-region ionospheric plasma is determined by the parametric decay instability whereas the radiation observed in the stationary stage of artificial turbulence results from the thermal parametric instability. Generation models of narrow continumm in different stages of its evolution are discussed. Radiophysical Research Institute, Nizhny Novgorod, Russia; Swedish Institute of Space Physics, Uppsala Division, Sweden. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 9, pp. 1091–1112, September, 1997.