Novel parallel-kinetic perpendicular-moment model for magnetized plasmas

Many astrophysical plasma systems, from pulsar magnetospheres to the solar wind, are highly magnetized. However, the derivation of large magnetization asymptotic models applicable to this wide variety of plasmas is challenging. Relativistic energies, strong flows, and temperature anisotropies complicate the asymptotics and even if the derivation can be made sufficiently rigorous, the subsequent equations may resist easy discretization via standard numerical methods. I will discuss a recent innovation which addresses these challenges by separating the parallel and perpendicular dynamics starting from the kinetic equation while staying agnostic to the inclusion of effects such as relativity or strong flows. The key component of the derivation lies in a spectral expansion of only the perpendicular degrees of freedom, analogous to spectral methods which have grown in popularity in recent years for gyrokinetics, while retaining the complete dynamics parallel to the magnetic field. We thus leverage our intuition that a magnetized plasma’s motion is different parallel and perpendicular to the magnetic field, while allowing for the treatment of complex phase space dynamics parallel to the magnetic field. This approach also naturally couples to Maxwell’s equations, allowing easy transitions across energy scales and I will conclude with a discussion of how this model generalizes to relativistic plasmas.