Harmonic generation and anomalous absorption in the case of convective decay instability of a pumping wave into two Langmuir waves

Powerful fluctuations arise as a result of convective instability of pumping wave decay into two Langmuir waves in the neighbourhood of the point of one fourth of the critical density. The theory of such fluctuations has been formulated and their energy calculated. The scattering of pumping wave on such fluctuations leads to arising fractional harmonics ωsub(s/2) = sωsub(o)/2 (s = 1, 3, 5, ωsub(o) is the pumping wave frequency) of the pumping wave frequency in the scattered emission spectrum. Spectral lines of these harmonics have a two-component structure. The spectral distance between doublet components and the spectral width of the components, determined by the electron temperature and the angle of harmonic emission, have been obtained. The intensity of the harmonics generation is found. A considerable anomalous absorption of the pumping wave owing to the convective instability considered may arise under conditions of nonlinear saturation of the w excited Langmuir aves