8 - Nonlinear Electromagnetic Waves in Flowing Plasma

Summary

INTRODUCTION.

In the nonlinear plasma electrodynamics the wide range of phenomena is connected with the ponderomotlve Miller force [1-3]. Already the beginning of the theoretical research in this direction has predicted the original self-focussed states of the electromagnetic field in plasmas [4-8], In paper [5>], it was shown that the hysteresis nonlinear picture of strong electromagnetic field increases in plasma. A special interest connected with the ponderomotive Miller force influence onto the plasma density changes has grown in connection with the problem of the strong p-polarized radiation transformation in space nonuniform plasmas [10-14]. Here it is necessary to underline that a number of authors (see, for example [15-25]) have investigated numerically the nonlinear dynamics of plasmas that are subjected to strong radiation interaction. Alongside the numerical results let us note the description of the strikingly nonstationary picture of fields in space nonuniform flowing plasmas. This picture is connected with the creation and with the disappearance of the cavitons—the density caves into which is created the high intensity field that accounts for the anomalous growth of the field absorption rate. Recently, this picture was corroborated once again in paper [26]. For the purpose of our paper, it is important to note the results of paper [27] based on numerical simulation. In [27] the effect of the suppression of hot electrons in the transition from subsonic to supersonic plasma flow was found. It turned out that such suppression was connected with caviton suppression and therefore, it was connected with the strong plasma field suppression that gave us the reduction of the reflected harmonics of the pumping radiation [25,28]. Meanwhile, it is necessary to underline that similar phenomena have been predicted only for the case of the p—polarized field irradiation interaction with plasmas. The experimental results [29,30] are of interest. They indicate the suppression of harmonics generation due to the transition from subsonic to supersonic regime, not only in the case of p-polarized fields, but also in the case of s-polarization. To explain the last result in paper [29], a thesis about the field self-restriction phenomena was suggested.