Multi-fluid and kinetic models of partially ionized magnetic reconnection

J. Jara-Almonte, N. A. Murphy, H. Ji

Research output: Contribution to journalArticlepeer-review

Abstract

Magnetic reconnection in partially ionized plasmas is a ubiquitous and important phenomenon in both laboratory and astrophysical systems. Here, simulations of partially ionized magnetic reconnection with well-matched initial conditions are performed using both multi-fluid and fully-kinetic approaches. Despite similar initial conditions, the time-dependent evolution differs between the two models. In multi-fluid models, the reconnection rate locally obeys either a decoupled Sweet-Parker scaling, where neutrals are unimportant, or a fully coupled Sweet-Parker scaling, where neutrals and ions are strongly coupled, depending on the resistivity. In contrast, kinetic models show a faster reconnection rate that is proportional to the fully-coupled, bulk Alfvén speed, v A ⋆. These differences are interpreted as the result of operating in different collisional regimes. Multi-fluid simulations are found to maintain ν n i L / v A ∗ ≳ 1, where νni is the neutral-ion collision frequency and L is the time-dependent current sheet half-length. This strongly couples neutrals to the reconnection outflow, while kinetic simulations evolve to allow ν n i L / v A ∗ < 1, decoupling neutrals from the reconnection outflow. Differences in the way reconnection is triggered may explain these discrepancies.

Original languageEnglish (US)
Article number042108
JournalPhysics of Plasmas
Volume28
Issue number4
DOIs
StatePublished - Apr 1 2021

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics

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