Exact resonance broadening theory of diffusion in random electric fields

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Abstract
Particle motion in random electric fields is considered on the assumption that orbit stochasticity causes the velocity increments at different times to be independent random events with Gaussian probabilities (Wiener process). The resulting resonance broadening term is substantially different from the one derived by Dupree and others [Phys. Fluids 9, 1773 (1966); 1 1, 1977 (1968); 1 5, 1496 (1972); Long Time Prediction in Dynamics (Wiley, New York, 1983), p. 319], and describes the continuous loss of particles from the resonance region. The diffusion coefficient D is time dependent, being quasilinear for t≪td (=diffusion time across resonance region). The validity of D∼(〈E2〉)3/4 in the high‐amplitude case of previous theories is questioned.