Magnetic field decay from the core of neutron stars: Effects of interpinning of 3P2 neutron superfluid and 1S0 proton superconducting fluid

Abstract

We consider a mechanism by which most of the magnetic field in the core of a spinning-down neutron star can be driven out from the core on a time scale of a few million years but will leave a residual field ≥ 108 G on the Hubble time scale (∼3 × 1010 yr). Such a driving force arises from the fact that the magnetized vortices of the 3P2 neutron superfluid are effectively pinned by the magnetic fluxoids of the 1S0 proton superconducting fluid. Despite the strong magnetic pinning energy, ∼10 MeV per intersection, the neutron vortices and the proton fluxoids do not always move out with the same speed because the combined effects of the magnus force, buoyancy force, tension of the fluxoids, drag force, and thermal activation allow the neutron vortices and proton fluxoids to creep through each other in a manner analogous to the creeping phenomenon in a type II superconductor. In this paper, we ignore the collective effects of the drag force and show how the core field decay depends on the decay of the crustal current. In addition to the decay of the pulsar magnetic field such core fluxoid motion may also play a crucial role in other pulsar phenoma.