Modification of Weak Turbulence Theory Due to Perturbed Orbit Effects. I. General Formulation

A new formulation is presented to derive a wave-kinetic equation for the spectral function of the fluctuation potential in a weakly turbulent plasma. The theory takes into account both the orbit-modification effect due to strong wave-particle resonant interactions and the wave-scattering effect usually considered in the weak turbulence theory. The effect of a uniform external electric field is also taken into consideration. The method consists in a systematic use of a diagram technique in order to collect secular term contributions. The modified propagator generalized over the previous version by Dupree and Weinstock and the wave-kinetic equation consistent with the usual weak turbulence theory are obtained.