Analyzing the processes of excitation and decay of plasma turbulence near the fifth electron gyroharmonic using stimulated electromagnetic emission of the ionosphere

Abstract

We present the results concerning the dynamics of stimulated electromagnetic emission (SEE) in the vicinity of the 5th electron gyroharmonic in the ionospheric-modification experiment. Measurements of the dynamic characteristics of different SEE features were performed at the “Sura” heating facility (Radiophysical Research Institute (NIRFI), Nizhny Novgorod) with the use of specialized equipment of the Swedish Institute of Space Physics, Uppsala Division (IRFU) designed for signal spectral analysis with a high temporal-frequency resolution. Based on the measurements performed, we analyzed the following features of nonstationary HF plasma turbulence: the competition between excitation of the Langmuir and upper-hybrid plasma modes for different values of mismatch between the pump frequency and the gyroharmonic, the fine structure of nonstationary energy redistribution over the turbulence spectrum during its excitation and relaxation, and the appearance of anomalously strong collisionless dissipation of turbulence energy with increasing pump duration. Possible mechanisms of the observed phenomena are discussed.