Resistive alignment of a black-hole magnetosphere
Abstract
Recent numerical simulations have shown that black-hole magnetospheres evolve rapidly toward alignment between the magnetic axis and spin axis but the physical origin of this process has remained unclear. We develop an analytic theory of this alignment within resistive relativistic magnetohydrodynamics. Taking the slow-spin Blandford-Znajek monopole solution as the exterior magnetic field, we reduce the induction equation to a relaxation equation for the current-sheet inclination angle. Our analysis shows that alignment results from second-order spin effects in the Blandford-Znajek solution combined with explicit resistive dissipation. We test this prediction using resistive-GRMHD simulations at several spins and resistivities and compare the measured late-time secular decay with the analytic prediction. This alignment timescale hence carries a unique signature which combines plasma dissipation with spacetime rotation.
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BibTeX
@misc{lier2026resistive,
title = {{Resistive alignment of a black-hole magnetosphere}},
author = {Ruben Lier and Oliver Porth},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.13288},
eprint = {2610.13288},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.13288},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Resistive alignment of a black-hole magnetosphere
AU - Ruben Lier
AU - Oliver Porth
PY - 2026
DA - 2026/10/15
PB - arXiv
DO - 10.48550/arxiv.2610.13288
UR - https://arxiv.org/abs/2610.13288
AB - Recent numerical simulations have shown that black-hole magnetospheres evolve rapidly toward alignment between the magnetic axis and spin axis but the physical origin of this process has remained unclear. We develop an analytic theory of this alignment within resistive relativistic magnetohydrodynamics. Taking the slow-spin Blandford-Znajek monopole solution as the exterior magnetic field, we reduce the induction equation to a relaxation equation for the current-sheet inclination angle. Our analysis shows that alignment results from second-order spin effects in the Blandford-Znajek solution combined with explicit resistive dissipation. We test this prediction using resistive-GRMHD simulations at several spins and resistivities and compare the measured late-time secular decay with the analytic prediction. This alignment timescale hence carries a unique signature which combines plasma dissipation with spacetime rotation.
ER -