Enhancement and suppression of heat transfer by MHD turbulence

We study the effect of turbulence on heat transfer within magnetized plasmas for energy injection velocities both larger and smaller than the Alfven speed. We find that in the latter regime the heat transfer is partially suppressed, while in the former regime the effects of turbulence depend on the intensity of driving. In fact, the scale l(A) at which the turbulent velocity is equal to the Alfven velocity is an important new parameter. When the electron mean free path lambda is larger than the l(A), stronger the turbulence, the lower the thermal conductivity by electrons. The turbulent motions, however, induce their own advective heat transport, which, for the parameters of intracluster medium, provides effective heat diffusivity that exceeds the classical Spitzer value.