Novel parallel-kinetic perpendicular-fluid model for highly magnetized (relativistic) plasmas

Many plasma systems, from pulsar magnetospheres to magnetic confinement devices, are highly magnetized. However, the derivation of large magnetization asymptotic models applicable to this wide variety of plasmas is challenging. Relativistic energies and strong flows both complicate the asymptotics and even if the derivation can be made sufficiently rigorous, the subsequent equations may resist easy discretization via standard numerical methods, especially when one includes the geometry necessary to correctly model the plasma of interest, e.g., field-line following coordinates for magnetic confinement devices or general relativistic effects for extreme astrophysical systems.

This presentation seeks to address these difficulties by considering an alternative approach in which the fundamental kinetic equation, whether incorporating relativistic effects or not, is separated into parallel and perpendicular degrees of freedom and then discretized. The perpendicular degrees of freedom are discretized via a moment expansion with a closure, analogous to spectral methods which have grown in popularity in recent years for gyrokinetics, while the parallel degree of freedom leverages recent advancements in discontinuous Galerkin finite element methods for the “parallel kinetic equation.” This approach then naturally couples to Maxwell’s equations, allowing easy transitions across energy scales. Applications to be shown include simulations of mirror confinement devices and pair plasma discharges.