Propagator methods for plasma simulations: application to breakdown

Summary form only given. Accurate simulation of plasmas often requires a solution of the kinetic equation, either directly by solving the Boltzmann Equation (BE) or indirectly by means of ´particle´ simulations. However, kinetic simulations are still too computationally intensive for many large 3-D simulations. In this work we examine the matching between a kinetic simulation and fluid models which are used in conjunction to form a ´hybrid´ plasma model of the breakdown process. The kinetic model is tested for convergence with respect to mesh size, /spl Delta/x, and time step, /spl Delta/t. We then implement fluid models in an attempt to reproduce the results of the kinetic mode. To do this it is necessary to have a fluid model which provides accurate simulations with a wide range of /spl Delta/x and /spl Delta/t. We accomplish this by means of a propagator (or Green´s function) approach. The propagator method reduces to a finite difference scheme at small /spl Delta/x and /spl Delta/t and gives correct results across a wide range of parameters. For intermediate /spl Delta/x, /spl Delta/t, it is necessary to take considerable care to derive the correct propagator. We apply the propagator in two forms, one of which explicitly conserves energy locally and exactly, and show that the details of the fluid model employed make a profound difference to the predicted breakdown. The breakdown phase of dielectric barrier discharge of Nitrogen at atmospheric pressure is simulated by employing an energy conserving fluid scheme.