IMPLICIT AND CONSERVATIVE DIFFERENCE SCHEME FOR THE FOKKER-PLANCK EQUATION

An implicit and fully conservative finite-difference scheme is propose d for solving the Fokker-Planck equation for Coulomb collisions betwee n isotropically distributed like particles in a spatially homogeneous plasma. The scheme extends the standard Chang-Cooper method by providi ng not only number density conservation, but also energy conservation. As a result, time steps much larger than the thermal collision time c an be used to stably and accurately simulate plasmas far from thermal equilibrium. Such a relaxation in time-step constraint has allowed for the successful implementation of the new scheme in multidimensional t ransport Fokker-Planck codes, with a resulting increase in computation al efficiency. (C) 1994 Academic Press, Inc.