For some time now there has been an interest in the nop. linear interaction of electromagnetic waves in plasma 1,2]. But only in the last few years has the theory of nonlinear wave inter action effects undergone such vigorous development as to result in the formulation of clear phYSical concepts regarding the mech anisms of interaction. This development has been engendered by attempts to solve many of the plasma-physical problems accom panying the tremendous growth of experimental research 3]. The importance of nonlinear effects in modern plasma physics is dis cussed in detail in Chap. I....