Enhancement and Suppression of Heat Transfer by MHD Turbulence

We study of the effect of turbulence on heat transfer within magnetizedplasmas for energy injection velocities both larger and smaller that the Alfvenspeed. We find that in the latter regime the heat transfer is partiallysuppressed, while in the former regime the effects of turbulence depend on theintensity of driving. In fact, the scale l at which the turbulent velocity isequal the Alfven velocity is a new important parameter. When the electron meanfree path is larger than l, the stronger the the turbulence, the lower thermalconductivity by electrons is. The turbulent motions, however, induces their ownadvective heat transport, which, for the parameters of intracluster medium(ICM) provides effective heat diffusivity that exceeds the classical Spitzervalue.Comment: 4 pages, misprint corrected, published ApJL version is correc