Analysis of Turbulent Particle Fluxes in Reduced MHD Simulation

Abstract

Some local turbulence analyses in tokamaks have shown that inward particle fluxes are induced in inversed density gradient regions. To evaluate the particle transport effect, we carry out global simulations using a 5-field reduced MHD model with an inversed density gradient near the plasma edge. Outward particle fluxes in the steeper gradient region are dominant, which mainly determine the evolution of the density profile. On the other hand, inward particle fluxes are also induced in the inversed gradient region. The electron drift modes are possible to become unstable with negative density gradients. The contribution of the inward particle fluxes is found to be present and its fraction is increased with nonlinear excitation of low n modes in the nonlinear phase, where n is the toroidal mode number.