NON-GAUSSIAN DISTRIBUTIONS IN EXTENDED DYNAMICAL-SYSTEMS

We propose a mechanism for the origin of non-Gaussian tails in the pro bability distribution functions of local variables in nonlinear, diffu sive, dynamical systems including passive scalars advected by chaotic velocity fields: Intermittent fluctuations on appropriate time scales in the amplitude of the (chaotic) noise can lead to exponential tails in certain regimes. We provide numerical evidence for such behavior in deterministic, discrete-time passive scalar models. Different possibi lities for probability distribution functions are also outlined.