Effective Resistivity in Relativistic Collisionless Reconnection

Magnetic reconnection can power spectacular high-energy astrophysical phenomena by producing nonthermal energy distributions in highly magnetized regions around compact objects. By means of two-dimensional fully kinetic particle-in-cell (PIC) simulations, we investigate relativistic collisionless pl...

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Bibliographic Details
Published in:The Astrophysical journal 2023-06, Vol.950 (2), p.169
Main Authors: Selvi, S., Porth, O., Ripperda, B., Bacchini, F., Sironi, L., Keppens, R.
Format: Article
Language:English
Subjects:
Astronomy & Astrophysics
Astrophysics
Compact objects
Electric fields
Electrical resistivity
High energy astrophysics
Magnetic fields
Magnetic reconnection
Magnetohydrodynamics
Ohm's Law
Plasma astrophysics
Relativistic effects
Relativity
Statistical analysis
Tensors
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Summary:Magnetic reconnection can power spectacular high-energy astrophysical phenomena by producing nonthermal energy distributions in highly magnetized regions around compact objects. By means of two-dimensional fully kinetic particle-in-cell (PIC) simulations, we investigate relativistic collisionless plasmoid-mediated reconnection in magnetically dominated pair plasmas with and without a guide field. In X-points, where diverging flows result in a nondiagonal thermal pressure tensor, a finite residence time for particles gives rise to a localized collisionless effective resistivity. Here, for the first time for relativistic reconnection in a fully developed plasmoid chain, we identify the mechanisms driving the nonideal electric field using a full Ohm law by means of a statistical analysis based on our PIC simulations. We show that the nonideal electric field is predominantly driven by gradients of nongyrotropic thermal pressures. We propose a kinetic physics motivated nonuniform effective resistivity model that is negligible on global scales and becomes significant only locally in X-points. It captures the properties of collisionless reconnection with the aim of mimicking its essentials in nonideal magnetohydrodynamic descriptions. This effective resistivity model provides a viable opportunity to design physically grounded global models for reconnection-powered high-energy emission.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/acd0b0