Experimental Studies of the Effects Observed During the Nonlinear Interaction of Two High-Power Radio Waves in a Magnetoplasma

Abstract

We present the results of experiments on modification of the ionospheric F region by two highpower (P eff ≈ 20 MW) O-mode electromagnetic waves. The experiments were performed at the "Sura" heating facility of the Radiophysical Research Institute (Nizhny Novgorod, Russia) in May 23-27, 1993 at the pump frequencies near the 4th, 5th, or 6th harmonics of the electron gyrofrequency. Ionospheric perturbations were diagnosed by measuring the stationary spectral characteristics of the stimulated electromagnetic emission (SEE) of the ionospheric plasma. We determine the features of variation in the spectral characteristics of particular SEE components during the simultaneous heating of the ionospheric plasma by two radio waves in comparison with the case of a monochromatic pump wave. We observed the effect of enhanced generation of the broad up-shifted maximum (BUM) by the higher-frequency pump wave. This is accompanied by strong suppression of the BUM induced by the lower-frequency pump wave. It is shown that the effects observed during the two-frequency heating of the ionosphere have well pronounced gyroharmonic properties, i.e., depend on both the electron-gyroharmonic number and the frequency detuning of the pump waves from a harmonic of the electron gyrofrequency. We also pointed out that a change in the properties of artificial small-scale ionospheric irregularities (striations) excited by high-power radio waves is not the cause of a change in the properties of the down-shifted maximum and the BUM during the two-frequency modification of the ionospheric plasma. Ways for the further development of these studies are discussed.

On the effects observed during modification of the earth’s upper ionosphere by high-power short radio pulses

“…It is seen that the delay times of the beginning of the ASSI development after the end of the PW radiation exceed the characteristic times of fast processes. It is also important to note that even in the experiments with two-frequency pumping [35], where the regions of resonant interaction of both waves are, to a remarkable degree, overlapped, by far not all of the recorded variations in the DM component intensity were determined by the ASSI influence, and other factors were also required for explaining the reasons for the phenomena observed in such a plasma heating regime.…”

“…For example, for ∆h < 5 km the regions of PW-plasma and DW-plasma resonant interaction can overlap. Such a situation better corresponds to the case of two-frequency action [35] where the conditions of modification of the upper ionosphere and the nature of the observed phenomena are radically changed due to strong interaction between the high-power radio waves themselves and the plasma turbulence they generate. At the same time, the performed experiments permitted us to state that for ∆h ≈ 30 km, the influence of the additional action becomes notably weaker, and for ∆h ≈ 50 km, fast variations in the DSEE intensity at the beginning of the PW radiation are weak and are far from being always recorded.…”