Magnetohydrodynamics of superfluid and superconducting neutron star cores

TL;DR

This paper develops a multifluid hydrodynamic model for the outer core of neutron stars, incorporating superfluid neutrons, superconducting protons, and magnetic fields to understand their complex interactions and astrophysical implications.

Contribution

It introduces a comprehensive multifluid framework accounting for vortices, fluxtubes, and forces in neutron star cores, advancing the understanding of superfluid and superconducting dynamics.

Findings

Model includes vortex and fluxtube interactions

Analyzes the effects of entrainment and magnetic fields

Provides insights into neutron star oscillations and magnetic evolution

Abstract

Mature neutron stars are cold enough to contain a number of superfluid and superconducting components. These systems are distinguished by the presence of additional dynamical degrees of freedom associated with superfluidity. In order to consider models with mixtures of condensates we need to develop a multifluid description that accounts for the presence of rotational neutron vortices and magnetic proton fluxtubes. We also need to model the forces that impede the motion of vortices and fluxtubes, and understand how these forces act on the condensates. This paper concerns the development of such a model for the outer core of a neutron star, where superfluid neutrons co-exist with a type II proton superconductor and an electron gas. We discuss the hydrodynamics of this system, focusing on the role of the entrainment effect, the magnetic field, the vortex/fluxtube tension and the dissipative mutual friction forces. Out final results can be directly applied to a number of interesting astrophysical scenarios, e.g. associated with neutron star oscillations or the evolution of the large scale magnetic field.