2024/03/04 by Antoine Bret, Bret, Antoine, Colby Haggerty +3 · 1 citation
Physics and Astronomy · #Dust and Plasma Wave Phenomena #FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE) #Ionosphere and magnetosphere dynamics #Laser-Plasma Interactions and Diagnostics #Plasma Physics (physics.plasm-ph) #Solar and Stellar Astrophysics (astro-ph.SR)
paper · pdf · doi:10.48550/arxiv.2403.01943
openalex publication_date 2024/03/04 · openalex created_date 2024/03/06 · openalex updated_date 2026/08/01
Collisionless shocks are frequently analyzed using the magnetohydrodynamics (MHD) formalism, even though MHD assumes a small mean free path. Yet, isotropy of pressure, fruit of binary collisions and assumed in MHD, may not apply in collisionless shocks. This is especially true within a magnetized plasma, where the field can stabilize an anisotropy. In a previous article \citepBretJPP2022b, a model was presented capable of dealing with the anisotropies that may arise at the front crossing. It was solved for any orientation of the field with respect to the shock front. Yet, for some values of the upstream parameters, several downstream solutions were found. Here, we complete the work started in \citeBretJPP2022b by showing how to pick the physical solution out of the ones offered by the algebra. This is achieved by 2 means: 1) selecting the solution that has the downstream field obliquity closest to the upstream one. This criterion is exemplified on the parallel case and backed up by Particle-in-Cell simulations. 2) Filtering out solutions which do not satisfy a criteria already invoked to trim multiple solutions in MHD: the evolutionarity criterion, that we assume valid in the collisionless case. The end result is a model in which a given upstream configuration results in a unique, or none (like in MHD), downstream configuration. The largest departure from MHD is found for the case of a parallel shock.