Characteristics of Low-Frequency Radiation Excited by the Impact of an Oscillating, High-Frequency Beam on the Ionosphere According to In Situ Measurements

— The results of experimental studies of the characteristics of low-frequency (LF) radiation excited by the impact of two frequency-shifted, unmodulated pump waves emitted by spatially separated antenna subarrays of the EISCAT high-latitude heating facility on the Earth’s ionosphere are presented. In situ measurements of the characteristics of the generated LF signals have been carried out at altitudes of ∼660 km with the onboard equipment of the DEMETER microsatellite. The spatial and amplitude characteristics of LF radiation are determined. It is shown that the detected values of the electric-field strength of the excited radiation (~3 µV/m in the daytime and ~50 µV/m in the nighttime) under this generation scheme, even if the combination of impact parameters is far from optimal, are comparable to the levels of signals during heating with powerful, amplitude-modulated, high-frequency radiation, which offers the potential to significantly increase the efficiency of LF wave radiation.