Fermion zero-mode influence on neutron-star magnetic field evolution

TL;DR

This paper explores how fermion zero-modes and spectral flow phenomena influence magnetic flux expulsion in neutron stars, affecting their magnetic field evolution during different phases.

Contribution

It introduces the role of spectral flow and fermion zero-modes in controlling vortex dynamics and magnetic flux expulsion in neutron star cores, linking laboratory superfluid phenomena to astrophysical processes.

Findings

Spectral flow controls vortex drift velocity in neutron star cores.

Flux expulsion rates are low during early active phases of pulsars.

Normal neutrons can limit flux expulsion during rapid spin-down.

Abstract

The quantum phenomenon of spectral flow which has been observed in laboratory superfluids, such as 3He-B, controls the drift velocity of proton type II superconductor vortices in the liquid core of a neutron star and so determines the rate at which magnetic flux can be expelled from the core to the crust. In the earliest and most active phases of the anomalous X-ray pulsars and soft-gamma repeaters, the rates are low and consistent with a large fraction of the active crustal flux not linking the core. If normal neutrons are present in an appreciable core matter-density interval, the spectral flow force limits flux expulsion in cases of rapid spin-down, such as in the Crab pulsar or in the propeller phase of binary systems.