Rapid Variability of Radiative Signatures from Driven Relativistic Reconnection
Abstract
Rapid variability in energetic flares is a distinctive feature of high-energy emission from many magnetically dominated astrophysical sources. We investigate the radiative variability of driven relativistic magnetic reconnection using Particle-in-Cell simulations of strongly magnetized flux tubes pushed to merge at driving speed vpush. This setup captures the onset of reconnection and provides a controlled model for single reconnection-driven flares near compact objects, where magnetic structures can be twisted, sheared, and forced to merge by turbulent accretion flows or relativistic frame dragging. We find that the merger efficiently accelerates particles into nonthermal distributions, producing synchrotron emission whose variability tracks the reconnection phases. We identify two regimes: a quasi-steady, weakly driven regime for vpush≤0.1 c, and strongly driven regime for vpush>0.1 c. The transition occurs when the driving exceeds the typical inflow-to-outflow velocity ratio of ∼0.1 in steady collisionless relativistic reconnection, i.e., the average rate at which reconnection can process incoming flux, potentially providing an additional source of variability. The lightcurves rise on $1−−3$ light-crossing times of the reconnecting region, and the particle spectra develop power laws with index p≃1.8--$2.4$. These timescales are compatible with observed variability in high-energy sources, including the very-high-energy flares of M87* and the γ-ray flares of the Crab Nebula, making this model a viable framework for rapid flaring in active galactic nuclei and pulsar wind nebulae.
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BibTeX
@misc{mora2026rapid,
title = {{Rapid Variability of Radiative Signatures from Driven Relativistic Reconnection}},
author = {Clarissa Mora and Fabio Bacchini and Camille Granier and Daniel Groselj},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.28034},
eprint = {2610.28034},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.28034},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Rapid Variability of Radiative Signatures from Driven Relativistic Reconnection
AU - Clarissa Mora
AU - Fabio Bacchini
AU - Camille Granier
AU - Daniel Groselj
PY - 2026
DA - 2026/10/20
PB - arXiv
DO - 10.48550/arxiv.2610.28034
UR - https://arxiv.org/abs/2610.28034
AB - Rapid variability in energetic flares is a distinctive feature of high-energy emission from many magnetically dominated astrophysical sources. We investigate the radiative variability of driven relativistic magnetic reconnection using Particle-in-Cell simulations of strongly magnetized flux tubes pushed to merge at driving speed v_push. This setup captures the onset of reconnection and provides a controlled model for single reconnection-driven flares near compact objects, where magnetic structures can be twisted, sheared, and forced to merge by turbulent accretion flows or relativistic frame dragging. We find that the merger efficiently accelerates particles into nonthermal distributions, producing synchrotron emission whose variability tracks the reconnection phases. We identify two regimes: a quasi-steady, weakly driven regime for v_push≤0.1 c, and strongly driven regime for v_push>0.1 c. The transition occurs when the driving exceeds the typical inflow-to-outflow velocity ratio of ∼0.1 in steady collisionless relativistic reconnection, i.e., the average rate at which reconnection can process incoming flux, potentially providing an additional source of variability. The lightcurves rise on $1−−3$ light-crossing times of the reconnecting region, and the particle spectra develop power laws with index p≃1.8--$2.4$. These timescales are compatible with observed variability in high-energy sources, including the very-high-energy flares of M87^* and the γ-ray flares of the Crab Nebula, making this model a viable framework for rapid flaring in active galactic nuclei and pulsar wind nebulae.
ER -