Solution comparisons of models of an expanding ambipolar plasma

A common phenomenon in plasma transport is ambipolar expansion; the ambipolar expansion rate is the typical rate at which a neutral plasma will expand into a vacuum. This expansion is particularly important, for example, in understanding how quickly a plasma will fill a gap in high power electronics or in understanding how energy is transported in intense laser-driven plasmas. Often times, a plasma simulation must accurately capture the ambipolar expansion of a neutral plasma. We present simulation benchmarks for three codes: one plasma fluid code1 and two kinetic plasma codes - one of the kinetic codes using an unstructured mesh and the other a structured mesh. We compare results from these codes to analytic models and previously published simulation results. We discuss speed and accuracy for these three different approaches, specifically including a discussion of particle splitting and combining algorithms in the kinetic approaches.