Modulational instability of Langmuir wave packets

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Abstract
The broad spectra of random waves in unmagnetized plasmas are considered. A universal nonlinear formalism is developed for description of the nonlinear effects (modulational instability, etc.) in which random plasma waves take part. The integral equations for perturbations of wave field correlation functions are obtained. In a description of the modulational instability of random wave packets these equations play the same role as the set of coupled equations for the fields of modulational perturbations in the case of a single monochromatic pump wave. On the basis of these integral dispersion equations the modulational instability of broad wave spectra is investigated for the one‐dimensional situation (when directions of propagation of the random waves coincide with that of the modulational perturbations) and for isotropic wave turbulence.