NONQUASILINEAR DIFFUSION FAR FROM THE CHAOTIC THRESHOLD

The diffusion coefficient for particles in a field of randomly phased waves was calculated numerically. Spectra broad in wave number and broad in frequency exhibit identical behavior for the diffusion coefficient as a function of the overlap parameter. The diffusion coefficient exceeds the quasilinear value by a factor of about 2.5 at near 18. Differences greater than 25% between the two values exist far above the chaotic threshold (60). A mapping-based model with a small number of random phases qualitatively reproduces the results of the simulations. © 1990 The American Physical Society.