Collisions in multi-dimensional plasma simulations

Collisions in multi-dimeniosnal plasma simulation models using finite-size particles are studied numerically and analytically. Drag and diffusion of particles in velocity space are measured and are compared with the theoretical predictions for two-, two-and-a-half-, and three-dimensional models. For two- and three-dimensional models, the measurement agrees reasonably well with the Balescu–Lenard theory. For the two-and-a-half-dimensional model, it is shown that the collisions strongly depend on the choice of the angle between magnetic field and wave vector due to the limited phase space available in the model. For a strongly magnetized plasma with Ωe≳ωpe, the effective collisions are significantly reduced for a simulation plasma when a≳ρe (where a is particle size, and ρe is the gyroradius) in contrast to a real plasma where the effective collisions depend weakly on the magnetic field.