Superconductivity and Magnetism at Nuclear-matter Densities: An Astronomical Challenge

TL;DR

This paper investigates the evolution of magnetic fields in neutron stars by modeling flux expulsion from the proton superconducting core, highlighting uncertainties in fluxoid dynamics and boundary behaviors.

Contribution

It provides a theoretical analysis of magnetic flux expulsion in neutron stars, addressing complex forces and boundary effects in superconducting nuclear matter.

Findings

Flux expulsion rate depends on fluxoid forces and boundary conditions

Uncertainties remain in fluxoid behavior within neutron star cores

Implications for magnetic field evolution in neutron stars

Abstract

We report on a study of the evolution of magnetic fields of neutron stars, driven by the expulsion of magnetic flux out of the proton superconducting core of the star. The rate of expulsion, or equivalently the velocity of outward motion of flux-carrying proton-vortices is determined from a solution of their equation of motion. A determination of the effective forces on the fluxoids moving through the quantum liquid interior of neutron stars is however confronted with many ambiguities about the properties of this special case of superconductivity in the nature. Also, the behaviour of the fluxoids at the core boundary, and the subsequent evolution of the expelled flux within the highly conductive surrounding crust, are other related issues that have not been so far explored in any great details.