The Meissner effect in neutron stars

TL;DR

This paper models how the Meissner effect influences magnetic fields in young neutron stars, revealing multiple possible magnetic configurations and energy release mechanisms during superconductivity onset.

Contribution

It introduces the first model of magnetic field expulsion in neutron stars, highlighting the role of fluid motions and reconnection during superconductivity onset.

Findings

Complete Meissner expulsion is one of four generic magnetic configurations.

Magnetic reconnection can release up to 5×10^{46} erg of energy.

Reconnection occurs only within specific early-phase magnetic field strengths.

Abstract

We present the first model aimed at understanding how the Meissner effect in a young neutron star affects its macroscopic magnetic field. In this model, field expulsion occurs on a dynamical timescale, and is realised through two processes that occur at the onset of superconductivity: fluid motions causing the dragging of field lines, followed by magnetic reconnection. Focussing on magnetic fields weaker than the superconducting critical field, we show that complete Meissner expulsion is but one of four possible generic scenarios for the magnetic-field geometry, and can never expel magnetic flux from the centre of the star. Reconnection causes the release of up to $\sim 5\times 10^{46}\,\mathrm{erg}$ of energy at the onset of superconductivity, and is only possible for certain favourable early-phase dynamics and for pre-condensation fields $10^{12}\,\mathrm{G}\lesssim B\lesssim 5\times 10^{14}\,\mathrm{G}$. Fields weaker or stronger than this are predicted to thread the whole star.