Efficient magnetic-field amplification due to the Kelvin-Helmholtz instability in binary neutron star mergers

TL;DR

This study uses high-resolution simulations to show that the Kelvin-Helmholtz instability can amplify magnetic fields in neutron star mergers by over a thousand times, reaching significant energy levels.

Contribution

It provides the first detailed high-resolution simulation demonstrating magnetic-field amplification during neutron star mergers due to Kelvin-Helmholtz instability.

Findings

Magnetic fields are amplified by at least a factor of 10^3.

Magnetic energy saturation exceeds 4 x 10^{50} erg.

Amplification reaches over 0.1% of the binary's kinetic energy.

Abstract

We explore magnetic-field amplification due to the Kelvin-Helmholtz instability during binary neutron star mergers. By performing high-resolution general relativistic magnetohydrodynamics simulations with a resolution of $17.5$ m for $4$--$5$ ms after the onset of the merger on the Japanese supercomputer "K", we find that an initial magnetic field of moderate maximum strength $10^{13}$ G is amplified at least by a factor of $\approx 10^3$. We also explore the saturation of the magnetic-field energy and our result shows that it is likely to be $\gtrsim 4 \times 10^{50}$ erg, which is $\gtrsim 0.1\%$ of the bulk kinetic energy of the merging binary neutron stars.