High resolution simulations of positive streamers discharges at high pressure*

Particle-in-cell codes are a common approach to simulation of streamer discharges.  In this work we utilize EMPIRE a Sandia National Laboratories electromagnetic/electrostatic particle-in-cell (PIC), Direct Simulation Monte Carlo (DSMC) code.  Furthermore, we utilize Sandia computing resources that allow us to perform computations on >1000 computation cores.   Since explicit PIC simulations require Debye length to be resolved by the mesh size such that no artificial numerical heating is present, access to significant computing resources is required.  Use of mesh sizes greater than Debye length can at times be violated if there is no evidence of excess heating when lower resolution simulations are performed. Here we perform high resolution (Δx≪λ_D) simulations of positive streamer discharges at atmospheric pressure and centimeter-scale electrode gaps.  These high resolution simulations are compared to simulations using lower resolution grids to determine the effects of the grid size on streamer parameters such as velocity, density, temperature, etc.  In addition, we will compare simulations using lower resolution and higher number of particles.  Using these results we determine the minimum mesh grid size required to properly resolve all of the relevant physics.  In general, sensitivity of streamer discharge properties to grid size will not be consistent and as such different studies might require different minimum grid size cells.