The inside-out view on neutron star magnetospheres

TL;DR

This paper develops a unified model of neutron star interiors and magnetospheres, allowing for non-zero exterior currents, which bridges previous models that treated these regions separately, especially relevant for slowly rotating stars like magnetars.

Contribution

It introduces a novel inside-out modeling approach that couples neutron star interiors with their magnetospheres, extending previous work by including non-zero exterior currents.

Findings

Magnetosphere configurations similar to those of magnetars and pulsars are achievable.

The models demonstrate equilibrium states with interior and exterior magnetic fields in harmony.

The approach is adaptable to rotating neutron stars, promising broader applications.

Abstract

We construct hydromagnetic neutron star equilibria which allow for a non-zero electric current distribution in the exterior. The novelty of our models is that the neutron star's interior field is in equilibrium with its magnetosphere, thus bridging the gap between previous work in this area which either solves for the interior assuming a vacuum exterior or solves for the magnetosphere without modelling the star itself. We consider only non-rotating stars in this work, so our solutions are most immediately applicable to slowly-rotating systems such as magnetars. Nonetheless, we demonstrate that magnetospheres qualitatively resembling those expected for both magnetars and pulsars are possible within our framework. The "inside-out" approach taken in this paper should be more generally applicable to rotating neutron stars, where the interior and exterior regions are again not independent but evolve together.