Fluid and field algorithms for time-implicit plasma simulation

Fluid transport algorithms and implicit electric field computations for particle-fluid hybrid plasma simulation are investigated in the one-dimensional case. Emphasis is placed on acceptable behavior at vacuum interfaces and stable, accurate implicit electric field solutions. A scheme using the FCT method of Boris and Book with all quantities cell centered gives good results for expansion into vacuum, but the resulting banded-matrix field solver admits an unphysical even-odd spatial mode. By defining velocity and electric field at cell boundaries, a diagonal field solver results which eliminates this mode. Advecting momentum defined at cell boundaries gave poor results at vacuum boundaries; acceptable behavior was recovered with momentum advected at cell centers. The field solver uses the exact numerical continuity equation and iterates, so that convergence ensures satisfaction of the Poisson equation. Convergence of the field solver is affected by the choice of advection algorithm. For time steps large compared to the inverse plasma frequency, Δt much-gt ωp-1, the proper ambipolar limit is recovered