Parametric rotation of the principal polarization axes and other effects due to four transverse waves in a plasma

Abstract

Four elliptically polarized waves acting in a cold and unmagnetized plasma are shown to be responsible for the parametric evolution in time of the rotation of the principal polarization axes (the precession frequency) and some other nonlinear effects in two evolving waves by two other powerful waves. The investigation requires the transition from the macroscopic to a new type of more general and vivid microscopic study of parametric processes due to transverse waves in continuous media. The parametric precession frequency (PPF), when complex, is a new source of instability in plasmas. Complex PPF and complex parametric frequency shift occur in some near-resonant interactions in which the sum or difference between two frequencies is close to the characteristic frequency of electrons in a plasma. It is found that when the plasma is subjected to two strong fields, sharp bands of monochromatic noise transform into growing continuous spectra.