Turbulent diffusion in the interstellar medium

We have calculated the coefficient of turbulent diffusion in a random flow with time restoration, describing the interstellar medium. Such a flow abru ptly loses its memory at random times, forming a Poisson flow of events. Th e coefficient of turbulent diffusion in the flow is determined by the rms v elocity and correlation time, as in mixing-length theory, but the numerical coefficient differs from that predicted by this theory. The closure equati on derived by us for the transport of the mean concentration of a passive s calar takes a more complicated form than obtained in standard mean-field th eory, but the main properties of the equation retain their validity. The po ssibility of extending the results of this exactly solved problem to the pr oblem of transport in the turbulent interstellar medium is discussed. (C) 2 000 MAIK "Nauka/Interperiodica".