Hybrid fluid-kinetic models for high-energy-density plasmas

Plasma physics in the high-energy-density regime can be dominated by collisional interactions between particles. Particle-in-cell (PIC) based kinetic representations have classically been used to represent these systems in rarefied regimes, however as the density of the plasma increases - or a neutral gas is introduced - the computational costs of particle methods increase. The goal of this research is to develop hybrid representations where the addition of continuum fluid components to the particle solve reduces runtimes in dense plasma simulations while retaining physical accuracy in rarefied regimes. Two approaches will be presented: (1) a species-based coupling where each species is represented by a different discretization (e.g. PIC ions with fluid electrons/neutrals), and (2) a PIC discretization is used to close the fluid model - commonly known as a delta-f method. The current state of our implementation will be presented and the benefits and challenges of these approaches will be discussed.