Energy source for the magnetic field growth in magnetars driven by the electron-nucleon interaction

TL;DR

This paper proposes a model where electron-nucleon interactions in neutron stars generate magnetic fields by converting thermal energy into magnetic energy, explaining magnetar magnetic fields within 10^4-10^5 years.

Contribution

The study introduces a novel mechanism based on electron-nucleon parity violation for magnetic field generation in neutron stars, supported by numerical solutions of kinetic equations.

Findings

Large-scale magnetic fields (~10^{15} G) can be generated in 10^4-10^5 years.

The model aligns with observed magnetar magnetic field strengths.

Thermal energy from fermions drives magnetic field growth.

Abstract

We study the magnetic field generation in a neutron star within the model based on the magnetic field instability in the nuclear matter owing to the electron-nucleon parity violating interaction. We suggest that the growing magnetic field takes the energy from thermal background fermions in the neutron star matter. The system of kinetic equations for the spectra of the magnetic helicity density and magnetic energy density as well as the chiral imbalance are solved numerically accounting for this energy source. We obtain that, for the initial conditions corresponding to a typical neutron star, the large scale magnetic field $\sim 10^{15}\thinspace\text{G}$ is generated during $(10^4-10^5)\thinspace\text{yr}$. We suggest that the proposed model describes strong magnetic fields observed in magnetars.