Title: Multi-fluid and kinetic models of partially ionized magnetic reconnection

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, $$v^*_A$$. In this work, these differences are interpreted as the result of operating in different collisional regimes. Multi-fluid simulations are found to maintain $$ν_{ni}L/v^*_A$$ ≳1, where $$ν_{ni}$$ 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 $$ν_{ni}L/v^*_A$$ <1, decoupling neutrals from the reconnection outflow. Differences in the way reconnection is triggered may explain these discrepancies.

Authors:

Jara-Almonte, J.  ^[1];

• Search DOE PAGES for author "Jara-Almonte, J."
• Search DOE PAGES for ORCID "0000-0003-0760-6198"

Murphy, N. A.  ^[2];

• Search DOE PAGES for author "Murphy, N. A."
• Search DOE PAGES for ORCID "0000-0001-6628-8033"

Ji, H.  ^[1]

• Search DOE PAGES for author "Ji, H."
• Search DOE PAGES for ORCID "0000-0001-9600-9963"

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+ Show Author Affiliations

1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
2. Harvard and Smithsonian, Cambridge, MA (United States)

Publication Date:

Tue Apr 13 00:00:00 EDT 2021

Research Org.:

Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States); Argonne National Laboratory (ANL), Argonne, IL (United States). Argonne Leadership Computing Facility (ALCF)

Sponsoring Org.:

National Aeronautics and Space Administration (NASA); National Science Foundation (NSF); USDOE Office of Science (SC)

OSTI Identifier:

1804609

Alternate Identifier(s):

OSTI ID: 1776994

Grant/Contract Number:  

AC02-09CH11466; H-TIDES NNH15AB29I; S014981-F; 1931388; 80NSSC18K1124; 80NSSC20K0174; NNM07AB07C; AC02-06CH11357; AC0209CH11466.

Resource Type:

Accepted Manuscript

Journal Name:

Physics of Plasmas

Additional Journal Information:

Journal Volume: 28; Journal Issue: 4; Journal ID: ISSN 1070-664X

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Atomic and molecular collisions; Thermodynamic states and processes; Computational fluid dynamics; Energy equations; Charge exchange reactions; Particle-in-cell method; Plasma properties and parameters; Magnetic reconnection; Collisional processes; Partially ionized plasma