A predictor-corrector scheme for hybrid fluid-PIC electrostatic plasma simulation

Computational plasma physicists typically must choose between fluid models, which are fast but can fail in certain physical regimes, and particle models, which are slower and noisier but more widely applicable. Many hybrid schemes have been developed to combine the two models. Notably, delta-f schemes model deviations from a Maxwellian distribution as particles. However, this introduces negative-weight particles to the simulation, complicating collisional models. In this work, we present a hybrid scheme for simulations of electrostatic plasmas utilizing both a discontinuous Galerkin discretization of the Euler fluid equations and a particle-in-cell (PIC) method. We implement this in the hPIC2 unstructured PIC code leveraging the MFEM finite element method library, perform verification studies, and evaluate its performance on massively parallel, heterogeneous computers. The hybrid coupling allows hPIC2 to model the Maxwellian bulk of a species as a fluid and kinetic perturbations as PIC, all while allowing typical collisional models.