COMPARISON OF RESULTS OF NONLINEAR ACTION ON THE F-LAYER OF THE IONOSPHERE AT

wave was continuously emitted at a nearby frequency. The experiments were conducted in FebruaryMarch of 1974 during the night, when the critical frequency of the F-layer varied between 1.9 and 2.8 MI-Iz; there was no absorption in the D-layer, and there were no reflections from the sporadic E S layer. The probe was linearly polarized, but since its working frequency was close to the electron cyclotron frequency, the extraordinary component was always heavily absorbed. When the pump was turned on, aware (1.5-3)-fold reduction in the intensity of the reflected probewave signal was observed having a characteristic time of about 20 sec in the 1.25-1.45-MHz range. Figure 1 shows the intensity variation (in relative units) of probe waves reflected from the ionosphere with a powerful 1.34-MHz radio wave acting on the ionosphere; A and B are the times at which the powerful transmitter was turned on and turned off, respectively. Each point represents the result of averagingover five successive operating cycles of the high-power transmitter. Probe-wave frequencies of; a) f