Geometrical Effects on Turbulent Diffusion of Toroidal Plasma

Abstract

Effects of toroidal geometry on the particle diffusion of a turbulent plasma are considered. Using the fluid-like equations obtained by appropriate average of the Klimontovich equation, we derived a formula for the diffusion flux across magnetic surface. The formula is applicable to both turbulent and quiescent plasmas, and reproduces the Pfirsch-Schlüter diffusion in the latter case. The geometrical effect on the turbulent diffusion is found to become substantial when the ratio of the antisymmetric to symmetric part (with respect to the wavenumber parallel to the magnetic field) of the dissipative part of the susceptibility exceeds some critical value. As a specific example, we treat the case of drift wave turbulence. It is shown that the geometrical effect is insignificant unless the perpendicular wavelength is sufficiently large as compared with the ion Larmor radius.