On the morphology of Stimulated Electromagnetic Emission spectra in a wide pump wave frequency range Original Research Article

Results of systematic study of Stimulated Electromagnetic Emission (SEE) steady state spectrum dependence on the pump wave frequency f0 are presented. Investigations of the HF-pumped ionosphere were performed at the SURA facility for the frequency range 4.3 < f0 < 9.5 MHz with stepping of 1–50 kHz including the vicinities of the electron gyroharmonics nfce from n = 4 to 7. The results are based on the data collected during 1996–2004. The main tendencies in a behavior of the most prominent SEE spectral features (their peak and total intensities, and positions in the spectrum) versus f0 are established and studied in detail. A comparative analysis of peculiarities of different spectral features allows to improve a determination of the electron gyrofrequency in the ionosphere from the SEE spectra, as well as provides a base for deeper understanding nonlinear processes in the pump-driven upper hybrid turbulence responsible for the SEE generation.