Radiation Reaction in Relativistic Magnetized Shocks of Neutron Star Magnetospheres
Abstract
The steepening of fast magnetosonic waves in the inner magnetospheres of magnetars can produce monster shocks, whose precursor emission may account for fast radio bursts (FRBs). For sufficiently bright bursts, particles crossing the shock radiate their energy within a single gyration period, raising the question of how radiation reaction affects the shock structure and its coherent emission. We investigate strongly cooled, relativistically magnetized shocks using a stationary multifluid model generalized to include the Landau-Lifshitz radiation-reaction force, together with particle-in-cell simulations of monster-shock dynamics. We show that the kinetic-scale shock transition is governed by only two dimensionless parameters: the Alfvénic Mach number and a cooling parameter τ that measures radiative losses over a gyration period. Coherent precursor emission is triggered above a critical Mach number that increases with τ, at which the beam dynamics becomes chaotic. Above this threshold, radiative cooling shifts the peak frequency of the precursor to higher values, scaling as τ2/7. Remarkably, monster shocks remain far above the emission threshold even under strong radiative cooling. Radiation reaction therefore does not quench the precursor emission; instead, it primarily shifts the spectral peak into the kinetic regime. The luminosity of the precursor wave is determined solely by the luminosity of the driving kHz wave and the conversion efficiency, εX∼ 10−3 − 10−2.
Related
- Landau-Zener formula and resonant axion conversion in neutron star magnetospheres
- Superluminal Wave Activation at Relativistic Magnetized Shocks
- Structural quasi-universality in highly magnetized, differentially rotating neutron stars
- Effects of Ambient Medium Profiles on the Evolution of Relativistic Magnetized Jets
- Breaking the symmetry: X-ray polarization from a spreading layer on a tilted weakly magnetized neutron star
BibTeX
@misc{vanthieghem2026radiation,
title = {{Radiation Reaction in Relativistic Magnetized Shocks of Neutron Star Magnetospheres}},
author = {Arno Vanthieghem and Amir Levinson},
howpublished = {HAL},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.05386},
eprint = {2610.05386},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05835124v1},
}
RIS
TY - UNPB
TI - Radiation Reaction in Relativistic Magnetized Shocks of Neutron Star Magnetospheres
AU - Arno Vanthieghem
AU - Amir Levinson
PY - 2026
DA - 2026/10/04
PB - HAL
DO - 10.48550/arxiv.2610.05386
UR - https://hal.science/hal-05835124v1
AB - The steepening of fast magnetosonic waves in the inner magnetospheres of magnetars can produce monster shocks, whose precursor emission may account for fast radio bursts (FRBs). For sufficiently bright bursts, particles crossing the shock radiate their energy within a single gyration period, raising the question of how radiation reaction affects the shock structure and its coherent emission. We investigate strongly cooled, relativistically magnetized shocks using a stationary multifluid model generalized to include the Landau-Lifshitz radiation-reaction force, together with particle-in-cell simulations of monster-shock dynamics. We show that the kinetic-scale shock transition is governed by only two dimensionless parameters: the Alfvénic Mach number and a cooling parameter τ that measures radiative losses over a gyration period. Coherent precursor emission is triggered above a critical Mach number that increases with τ, at which the beam dynamics becomes chaotic. Above this threshold, radiative cooling shifts the peak frequency of the precursor to higher values, scaling as τ^2/7. Remarkably, monster shocks remain far above the emission threshold even under strong radiative cooling. Radiation reaction therefore does not quench the precursor emission; instead, it primarily shifts the spectral peak into the kinetic regime. The luminosity of the precursor wave is determined solely by the luminosity of the driving kHz wave and the conversion efficiency, ε_X∼ 10^−3 − 10^−2.
ER -