Simulation of Coulomb collisions is important for plasma computation in which the Knudsen number is of moderate size. This talk will describe several methods for performing and accelerating these simulations. The first is a drag and diffusion method, in which the collisions are described as occurring between test particles and a field. The test particles experience drag and diffusion, which can be formulated as a stochastic differential equation. The second method uses a binary collision model, which follows the DSMC method, except that the "collisions" are not physical collisions but are each an accumulation of many interactions. The resulting Monte Carlo method can be computationally complex, and we present two acceleration strategies. The first is the delta-f method in which the velocity distribution function is written as a perturbation of a Maxwellian. The second is a hybrid method in which the binary collision method is combined with a continuum method based on the MHD equations.
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