Magnetic helicity evolution in a neutron star accounting for the Adler-Bell-Jackiw anomaly

Understand

We analyze the role of the surface terms in the conservation law for the sum of the magnetic helicity density and the chiral imbalance of the charged particle densities.

• These terms are neglected in the Anomalous MagnetoHydroDynamics (AMHD), where infinite volume is considered typically.
• We discuss a finite volume system, such as a magnetized neutron star (NS), and study the contribution of the surface terms to the evolution of the magnetic helicity.
• Accounting for the fast washing out of the chiral imbalance in a nascent NS, we demonstrate that the surface terms contribution can potentially lead to the reconnection of magnetic field lines and subsequent gamma or X-ray bursts observed from magnetars.