NUMERICAL OBSERVATION OF TURBULENCE ENHANCED GROWTH-RATES

An enhancement of the velocity diffusion over the quasilinear value is observed in the regime where the autocorrelation time is much smaller than the linear growth time or resonance broadening time. The diffusi on enhancement occurs when the resonance broadening time is small comp ared with the linear growth time. These simulations are self consisten t and have enough modes to be in the continuous spectrum limit. That i s, even at the initial amplitudes the intermode spacing is sufficientl y small that the resonance overlap parameter is large. A possible mech anism for the enhanced diffusion (spontaneous spectrum discretization) is discussed. (C) 1997 American Institute of Physics.