Role of Coincidental Nonlinear Events in the Saturation of Moderately Damped Modes

Both the level of broadband microturbulence and the behavior of driven waves can be strongly affected by local coincidences that produce nonlinear levels of the total fluctuation amplitude. We evaluate the rate at which such coincidences occur, for moderately damped modes which frequently reset their phases. They can produce significant nonlinear effects and can limit the amplitude of individual modes to low levels. These effects, which involve very many modes, are inherently difficult to observe using standard Fourier space or particle simulation techniques. copyright 1998 The American Physical Society