Magnetic field configurations in binary neutron star mergers. I. Postmerger remnant and disk
Phys. Rev. D 114, 063049 – Published 24 September, 2026
DOI: https://doi.org/10.1103/xlrm-7xr8
Abstract
We present a suite of general relativistic magnetohydrodynamic simulations of binary neutron star mergers performed with the code GR-Athena++. We investigate how a different initial magnetic field configuration, nuclear equation of state, or binary mass ratio affects the magnetic and thermodynamic evolution of the postmerger remnant and disk. We also analyze the impact of the commonly assumed reflection (bitant) symmetry across the equatorial plane. Magnetic field amplification occurs shortly after the merger due to the Kelvin-Helmholtz instability; later, the field keeps evolving with a predominantly toroidal configuration due to winding and turbulence. The initial magnetic field topology leaves an imprint on the field structure and affects magnetic field amplification for the initial magnetic field values commonly assumed in the literature and the limited resolution of the simulations. Enforcing equatorial reflection symmetry partially suppresses the development of turbulence near the equatorial plane and impacts the postmerger magnetic field evolution. Stiffer equations of state produce larger, less compact remnants that may retain memory of the premerger strong poloidal field.
