@article{84f44b57d7c847c082b005ed42066dc6,
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 Alfv{\'e}n 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. ",
author = "J. Jara-Almonte and Murphy, {N. A.} and H. Ji",
note = "Funding Information: Some kinetic simulations were performed on computational resources managed and supported by Princeton Research Computing, a consortium of groups including the Princeton Institute for Computational Science and Engineering (PICSciE) and the Office of Information Technology{\textquoteright}s High Performance Computing Center and Visualization Laboratory at Princeton University. An award of computer time was also provided by the Innovative and Novel Computational Impact on Theory and Experiment (INCITE) program. This research used resources of the Argonne Leadership Computing Facility, which is a DoE Office of Science User Facility supported under Contract No. DE-AC02–06CH11357. Funding Information: The authors thank W. S. Daughton for helpful discussion and V. S. Lukin, E. T. Meier, J. Leake, and L. Ni for code development on HiFi and its plasma–neutral module and past simulation efforts that made this work possible. This research was supported by NASA Grant No. H-TIDES NNH15AB29I, with corresponding subcontract S014981-F from Princeton University to the Smithsonian Astrophysical Observatory (SAO). J.J-A. acknowledges partial support by Max Planck Princeton Center for Plasma Physics (MPPC) funded by DoE through Contract No. DE-AC0209CH11466. N.A.M. acknowledges partial support from NSF Grant No. 1931388, NASA Grant Nos. 80NSSC18K1124 and 80NSSC20K0174, and NASA Contract No. NNM07AB07C to SAO. This research made use of PlasmaPy version 0.3.1,42 an open source Python package for plasma physics developed with support from NSF, DoE, and NASA. The multi-fluid simulations performed for this paper were conducted on the Smithsonian Institution High Performance Cluster.43 This research has made use of NASA{\textquoteright}s Astrophysics Data System Bibliographic Services. Publisher Copyright: {\textcopyright} 2021 Author(s).",
year = "2021",
month = apr,
day = "1",
doi = "10.1063/5.0039860",
language = "English (US)",
volume = "28",
journal = "Physics of Plasmas",
issn = "1070-664X",
publisher = "American Institute of Physics Publising LLC",
number = "4",
}