Multi-Fluid and Kinetic Models of Partially Ionized Magnetic Reconnection
- Princeton University (PPPL)
Magnetic reconnection in partially ionized plasmas is a ubiquitous and important phenomena 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 Alfv\'en speed, $$v_A^\star$$. These differences are interpreted as the result of operating in different collisional regimes. Multi-fluid simulations are found to maintain $$\nu_{ni}L/v_A^\star \gtrsim 1$$, where $$\nu_{ni}$$ 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 $$\nu_{ni}L/v_A^\star < 1$$, decoupling neutrals from the reconnection outflow. Differences in the way reconnection is triggered may explain these discrepancies.
- Research Organization:
- Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- AC02-09CH11466
- OSTI ID:
- 1814941
- Country of Publication:
- United States
- Language:
- English
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