Magnetic energy production by turbulence in binary neutron star mergers

TL;DR

This paper demonstrates that turbulence in neutron star mergers can generate magnetar-level magnetic fields rapidly, and suggests this process could produce detectable electromagnetic signals during mergers.

Contribution

It provides high-resolution simulations showing turbulence amplifies magnetic fields to magnetar strength and links this to potential electromagnetic observables.

Findings

Turbulent dynamo converts 60% of kinetic energy into magnetic fields.

Magnetic fields reach ~10^16 G during the merger.

Reconnection events could produce detectable gamma-ray signals.

Abstract

The simultaneous detection of electromagnetic and gravitational wave emission from merging neutron star binaries would aid greatly in their discovery and interpretation. By studying turbulent amplification of magnetic fields in local high-resolution simulations of neutron star merger conditions, we demonstrate that magnetar-level (~10^16) G fields are present throughout the merger duration. We find that the small-scale turbulent dynamo converts 60% of the randomized kinetic energy into magnetic fields on a merger time scale. Since turbulent magnetic energy dissipates through reconnection events which accelerate relativistic electrons, turbulence may facilitate the conversion of orbital kinetic energy into radiation. If 10^-4 of the ~ 10^53 erg of orbital kinetic available gets processed through reconnection, and creates radiation in the 15-150 keV band, then the fluence at 200 Mpc would be 10^-7 erg/cm^2, potentially rendering most merging neutron stars in the advanced LIGO and Virgo detection volumes detectable by Swift BAT.