Kinetic Effects on the Convective Plasma Diffusion and the Heat Transport

Abstract

Cross field heat and particle transport due to the thermally excited convective cell mode is investigated both by theoretical work and by particle simulations. A parameter range exists where the heat diffusion coefficient is considerably less than the particle diffusion coefficient. This comes from the fact that high energy particles in a velocity distribution diffuse much more slowly than the low energy particles, because the fluctuating electric fields are averaged out over their finite Larmor radii. A velocity dependent diffusion coefficient is obtained by a simple theory, together with an estimate of the heat diffusion coefficient. Good agreement with the simulation results is obtained. The magnetic field scaling of heat diffusion/particle diffusion coefficients is also discussed. The results imply that ions in a thermonuclear reactor should be less affected by turbulence than are electrons, as appears to be the case.