NOISE AND SLOW-FAST DYNAMICS IN A 3-WAVE RESONANCE PROBLEM

Recent research on the dynamics of certain fluid-dynamical instabiliti es shows that when there is a slow invariant manifold subject to fast time-scale instability the dynamics are extremely sensitive to noise. The behavior of such systems can be described in terms of a one-dimens ional map, and previous work has shown how the effect of noise can be modeled by a simple adjustment to the map. Here we undertake an in-dep th investigation of a particular set of equations, using the methods o f stochastic integration. We confirm the prediction of the earlier stu dies that the noise becomes important when mu/lnepsilon/ = O(1), where mu is the small time-scale ratio and epsilon is the noise level. In a ddition, we present detailed information about the statistics of the s olution when the noise is a dominant effect; the analytical results sh ow excellent agreement with numerical simulations.