The theory of plasma turbulence for strong wave-particle interaction

A perturbation theory is developed, which in first approximation considers the strong interaction between waves and particles near the resonance omega =kv. There follows a useful prescription for the calculation of non-linear interaction. It is shown in what limit the usual approximation of perturbation theory may be applied. The effects of strong wave-particle interaction reduce the non-linear interactions, e.g. in the case of ion-sound turbulence the non-linear interaction with electrons is shown to be always small compared to the quasi-linear interaction, and for the case of Langmuir turbulence the effects of strong interaction become important in the non-linear interaction when the noise-level, w, is sufficiently high, i.e. w>or=nTkr D , where n is the density, T the temperature, k the characteristic wave number and r D the Debye length.