Comparison of kinetic and a novel hybrid-kinetic scheme for simulating plasma transport and instabilities

Kinetic simulations resolve particles and their collisions individually, so they are computationally expensive. Their alternative, fluid simulations, are less expensive to run but can't capture as much complexity as kinetic models. This work investigates a hybrid model called Parallel Kinetics Perpendicular Moments (PKPM) that is part of the Princeton Plasma Physics Laboratory code, Gkeyll. PKPM uses kinetic methods parallel to the magnetic field and fluid methods otherwise. Its goal is to get kinetic-like results with lower computational cost. This study investigates how PKPM simulations handle plasma transport compared to fully kinetic simulations. The initial conditions of the two simulation types are identical and consist of an initial sinusoidal perturbation in the temperature of the plasma that is parallel to the magnetic field. The perturbation relaxes over time, leading to a reduction in thermal conductivity. This study compares the reduction in thermal conductivity of the plasma between fully kinetic and PKPM simulations for varying levels of collisionality. The PKPM and kinetic results agree, especially for lower collisionality. While more research is needed on how PKPM handles other plasma dynamics, it shows promise as a way to resolve kinetic effects with less computational resources.