Observations O Stimulated Electromagnetic Emissions in Ionospheric Heating Experiments

摘要

Induced sideband modes, due to stimulated electromagnetic emissions in the ionosphere, were observed around the frequency of a high-intensity HF radio wave transmitted from an ionospheric modification facility. The received HF spectrum was analyzed without diagnostic radar. The parametric decay instability, and, possibly, the stimulated Brillouin backscattering of the strong HF pump wave were identified. A series of narrow spectral peaks induced in the upper sideband by a transmission in extraordinary mode indicate the excitation of ion Bernstein modes. Very strong spectral features, upshifted from the 5.4 MHz pump by 20 to 45 kHz, are observed. By monitoring fixed frequencies in the lower and the upper sidebands of the ionospherically reflected modifying wave the intensity of the stimulated emissions is found to exhibit a conspicuous long as well as short-term variability.