Tidal resonances in the final seconds of a binary neutron-star inspiral can excite oscillation modes in one or both of the constituents to large amplitudes. Under favorable circumstances, resonant pulsations can overstrain the stellar crust and unleash a torrent of magnetoelastic energy that manifests as a gamma-ray “precursor flare.” We show that for realistic, stratified stars rotating with a spin frequency of $\gtrsim 30\mathrm{Hz}$, the fundamental $g$ mode or its first overtone can also execute a differential rotation in the crust such that a magnetic field of strength $\gtrsim {10}^{13}\mathrm{G}$ is generated via magnetorotational instabilities. This may help to explain observed precursor rates and their luminosities. Premerger magnetic growth would also provide seed magnetic energy for the postmerger remnant.

• Received 6 October 2023
• Accepted 22 April 2024

DOI:https://doi.org/10.1103/PhysRevD.109.103023