Scaling the Ion Inertial Length and Its Implications for Modeling Reconnection in Global Simulations

Journal Article · Sat Oct 21 00:00:00 EDT 2017 · Journal of Geophysical Research. Space Physics

DOI:https://doi.org/10.1002/2017JA024189· OSTI ID:1402087

Tóth, Gábor  ^[1]; Chen, Yuxi ^[1]; Gombosi, Tamas I. ^[1]; Cassak, Paul  ^[2]; Markidis, Stefano ^[3]; Peng, Ivy Bo ^[3]

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1. Center for Space Environment Modeling University of Michigan Ann Arbor MI USA
2. Department of Physics and Astronomy West Virginia University Morgantown WV USA
3. Department for Computational Science and Technology KTH Royal Institute of Technology Stockholm Sweden

Abstract We investigate the use of artificially increased ion and electron kinetic scales in global plasma simulations. We argue that as long as the global and ion inertial scales remain well separated, (1) the overall global solution is not strongly sensitive to the value of the ion inertial scale, while (2) the ion inertial scale dynamics will also be similar to the original system, but it occurs at a larger spatial scale, and (3) structures at intermediate scales, such as magnetic islands, grow in a self‐similar manner. To investigate the validity and limitations of our scaling hypotheses, we carry out many simulations of a two‐dimensional magnetosphere with the magnetohydrodynamics with embedded particle‐in‐cell (MHD‐EPIC) model. The PIC model covers the dayside reconnection site. The simulation results confirm that the hypotheses are true as long as the increased ion inertial length remains less than about 5% of the magnetopause standoff distance. Since the theoretical arguments are general, we expect these results to carry over to three dimensions. The computational cost is reduced by the third and fourth powers of the scaling factor in two‐ and three‐dimensional simulations, respectively, which can be many orders of magnitude. The present results suggest that global simulations that resolve kinetic scales for reconnection are feasible. This is a crucial step for applications to the magnetospheres of Earth, Saturn, and Jupiter and to the solar corona.

• Sponsoring Organization: USDOE
• Grant/Contract Number: AC52-06NA25396
• OSTI ID: 1402087
• Journal Information: Journal of Geophysical Research. Space Physics, Journal Name: Journal of Geophysical Research. Space Physics Vol. 122 Journal Issue: 10; ISSN 2169-9380
• Publisher: American Geophysical Union (AGU)
• Country of Publication: United States
• Language: English