Glitches due to quasineutron-vortex scattering in the superfluid inner crust of a pulsar

Abstract

We revisit the mechanism of vortex unpinning caused by the neutron-vortex scattering [B. Layek and P. R. Yadav, Mon. Not. R. Astron. Soc. 499, 455 (2020)] in the inner crust of a pulsar. The strain energy released by the crustquake is assumed to be absorbed in some part of the inner crust and causes pair-breaking quasineutron excitations from the existing free neutron superfluid in the bulk of the inner crust. The scattering of these quasineutrons with the vortex core normal neutrons unpins a large number of vortices from the thermally affected regions and results in pulsar glitches. We consider the geometry of a cylindrical shell of the affected pinning region to study the implications of the vortex unpinning in the context of pulsar glitches. We find that a pulsar can release about ∼1011–1013 vortices by this mechanism. These numbers are equivalent to the glitch size of orders ∼10−11–10−9 for Vela-like pulsars with the characteristic age τ≃104 years. We also suggest a possibility of a vortex avalanche triggered by the movement of the unpinned vortices. A rough estimate of the glitch size caused by an avalanche shows an encouraging result.