Self-trapping of superfluid vortices and the origin of pulsar glitches

Abstract

This paper gives a physical microscopic interpretation of the capacitor theory or the vortex trap/discharge picture proposed by Alpar & Pines (1993) for pulsar glitches. Vortices exist in the neutron superfluid of the inner crust are mostly pinned but creep outward following pulsar spindown. Pinning is produced by overlapping the vortex core with the nuclei in poly-crystalline nuclear lattice. The crucial point is that the vortex line in a particular region (the frontier region) of strongest pinning can become self-trapped: The vortex core line can produce a nuclear matter rod along the line, and is so strongly trapped that can not creep out to the neighboring pinning centers. The self-trapped vortices block the others creeping from inside of the frontier region. Consequently, there appear a sharp discontinuity in the vortex density. Then the self-trapped vortices in this frontier region experience an extra Magnus force in addition to the conventional coarse-grained force given by the hydrodynamic continuum model. The extra force is the local field correction. We propose that this total Magnus force brings about collective unpinning of the frontier vortices, resulting in a glitch.