Sparking Dynamic, Relativistic Magnetic Reconnection in a Twisted Flux Tube
Abstract
Magnetic reconnection around neutron stars (NSs) forms small-scale currents while transferring energy to electron-positron pairs. These dissipating currents cover a wide range of scales, potentially leaving an imprint on time-variable X-ray bursts and pulsed radio emission. We present a reduced, planar model of internal reconnection in a magnetic flux tube with relativistic magnetization, finite resistivity, and strong guide field. Comparing with realistic NS parameters, this model represents the dynamics of a slender magnetic flux tube that is much thinner than the stellar radius. The seed current profile is smooth and does not spontaneously reconnect; instead, a discrete and localized current perturbation is introduced, representing e.g. localized energy release from a NS crust or magnetosphere. Three high-resolution relativistic magnetohydrodynamics simulations are described: one has uniform resistivity and Lundquist number such that reconnection proceeds in the plasmoid-mediated regime; the other two account for the feedback of charge starvation on the resistivity in current layers, where density is depleted; we provide a more general explanation for this depletion. All simulations produce a few dominant magnetic X-points and a secondary Kelvin-Helmholtz instability that excites high-wavenumber currents. We quantify the reconnection rate, the intermittency of dissipation, and the time profile of current spikes. We further present three-dimensional simulations confirming a limited growth of the ideal kink mode in the strong guide field regime. Applications are discussed, including to radio pulse microstructure and current damping below the magnetar surface during an X-ray flare, leading to mass loss and X-ray afterglow.
Related
- Guide field effects on particle acceleration in three-dimensional relativistic magnetic reconnection
- Are E>B regions essential for particle injection in relativistic magnetic reconnection?
- The Birth of Plasmoids: Weibel-Driven Secondary Tearing and its Suppression in Relativistic Reconnection
- Energy Partition in Relativistic Electron-Positron-Ion Reconnection
- Rapid Variability of Radiative Signatures from Driven Relativistic Reconnection
BibTeX
@misc{grehan2026sparking,
title = {{Sparking Dynamic, Relativistic Magnetic Reconnection in a Twisted Flux Tube}},
author = {Michael P. Grehan and Christopher Thompson and Bart Ripperda and James R. Beattie},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.22653},
eprint = {2610.22653},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.22653},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Sparking Dynamic, Relativistic Magnetic Reconnection in a Twisted Flux Tube
AU - Michael P. Grehan
AU - Christopher Thompson
AU - Bart Ripperda
AU - James R. Beattie
PY - 2026
DA - 2026/10/15
PB - arXiv
DO - 10.48550/arxiv.2610.22653
UR - https://arxiv.org/abs/2610.22653
AB - Magnetic reconnection around neutron stars (NSs) forms small-scale currents while transferring energy to electron-positron pairs. These dissipating currents cover a wide range of scales, potentially leaving an imprint on time-variable X-ray bursts and pulsed radio emission. We present a reduced, planar model of internal reconnection in a magnetic flux tube with relativistic magnetization, finite resistivity, and strong guide field. Comparing with realistic NS parameters, this model represents the dynamics of a slender magnetic flux tube that is much thinner than the stellar radius. The seed current profile is smooth and does not spontaneously reconnect; instead, a discrete and localized current perturbation is introduced, representing e.g. localized energy release from a NS crust or magnetosphere. Three high-resolution relativistic magnetohydrodynamics simulations are described: one has uniform resistivity and Lundquist number such that reconnection proceeds in the plasmoid-mediated regime; the other two account for the feedback of charge starvation on the resistivity in current layers, where density is depleted; we provide a more general explanation for this depletion. All simulations produce a few dominant magnetic X-points and a secondary Kelvin-Helmholtz instability that excites high-wavenumber currents. We quantify the reconnection rate, the intermittency of dissipation, and the time profile of current spikes. We further present three-dimensional simulations confirming a limited growth of the ideal kink mode in the strong guide field regime. Applications are discussed, including to radio pulse microstructure and current damping below the magnetar surface during an X-ray flare, leading to mass loss and X-ray afterglow.
ER -