Langevin Equation for Guiding Center Motion and its Application to Neoclassical Transport Theory

摘要

Neoclassical transport in toroidal plasmas is addressed by the Langevin equation. To ensure the diffusive nature of a stochastic process, the dynamics of test particles is expressed in terms of the Langevin equation with the assumption of sufficiently small radial orbit width. The transport coefficients are evaluated by the time integration of auto- and cross-correlation functions for each pair of time-reversal expressions of microscopic fluxes. As a test of this method, the neoclassical viscosity coefficients are calculated numerically and are shown to agree with analytical formulas