Published January 10, 2025 | Published
Journal Article Open

Effective Resistivity in Relativistic Reconnection: A Prescription Based on Fully Kinetic Simulations

  • 1. ROR icon Columbia University
  • 2. Flatiron Institute
  • 3. ROR icon University of Toronto
  • 4. ROR icon Canadian Institute for Theoretical Astrophysics
  • 5. ROR icon Perimeter Institute
  • 6. ROR icon California Institute of Technology

Abstract

A variety of high-energy astrophysical phenomena are powered by the release—via magnetic reconnection—of the energy stored in oppositely directed fields. Single-fluid resistive magnetohydrodynamic (MHD) simulations with uniform resistivity yield dissipation rates that are much lower (by nearly 1 order of magnitude) than equivalent kinetic calculations. Reconnection-driven phenomena could be accordingly modeled in resistive MHD employing a nonuniform, "effective" resistivity informed by kinetic calculations. In this work, we analyze a suite of fully kinetic particle-in-cell (PIC) simulations of relativistic pair-plasma reconnection—where the magnetic energy is greater than the rest mass energy—for different strengths of the guide field orthogonal to the alternating component. We extract an empirical prescription for the effective resistivity, η_(eff) = αB0 | J | p / ( | J | p+1 + (entc)p+1), where B0 is the reconnecting magnetic field strength, J is the current density, nt is the lab-frame total number density, e is the elementary charge, and c is the speed of light. The guide field dependence is encoded in α and p, which we fit to PIC data. This resistivity formulation—which relies only on single-fluid MHD quantities—successfully reproduces the spatial structure and strength of nonideal electric fields and thus provides a promising strategy for enhancing the reconnection rate in resistive MHD simulations.

Copyright and License

© 2025. The Author(s). Published by the American Astronomical Society.

Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

Acknowledgement

We are grateful to Fabio Bacchini, Ashley Bransgrove, Camille Granier, Rony Keppens, Oliver Porth, Sasha Philippov, and Eliot Quataert for useful discussions. L.S. acknowledges support from DoE Early Career Award DE-SC0023015, NASA ATP 80NSSC24K1238, NASA ATP 80NSSC24K1826, and NSF AST-2307202. This work was supported by a grant from the Simons Foundation (MP-SCMPS-00001470) to L.S. and B.R. and facilitated by the Multimessenger Plasma Physics Center (MPPC), grant PHY-2206609 to L.S. and S.S. B.R. and A.L. are supported by the Natural Sciences & Engineering Research Council of Canada (NSERC). B.R. is supported by the Canadian Space Agency (23JWGO2A01). B.R. acknowledges a guest researcher position at the Flatiron Institute, supported by the Simons Foundation. E.R.M. acknowledges support by the National Science Foundation under grants No. PHY-2309210 and AST-2307394 and from NASA's ATP program under grant 80NSSC24K1229. The computational resources and services used in this work were partially provided by Columbia University (Ginsburg HPC cluster) and by facilities supported by the Scientific Computing Core at the Flatiron Institute, a division of the Simons Foundation.

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Additional details

Created:
January 14, 2025
Modified:
January 14, 2025