Large-scale unpinning and pulsar glitches due to the forced oscillation of vortices

TL;DR

This paper proposes a mechanism where crustquake-induced vibrations cause vortex lines in a pulsar's superfluid interior to oscillate and unpin, providing a natural explanation for large pulsar glitches.

Contribution

It introduces a simple, physically motivated trigger mechanism linking crustquakes to vortex unpinning, unifying crustquake and superfluid vortex models for pulsar glitches.

Findings

Resonance-driven vortex bending leads to unpinning.

Crustquake vibrations can trigger large-scale vortex unpinning.

The model explains the occurrence of large pulsar glitches.

Abstract

The basic framework of the superfluid vortex model for pulsar glitches, though, is well accepted; there is a lack of consensus on the possible trigger mechanism responsible for the simultaneous release of a large number ($\sim 10^{17}$) of superfluid vortices from the inner crust. Here, we propose a simple trigger mechanism to explain such catastrophic events of vortex unpinning. We treat a superfluid vortex line as a classical massive straight string with well-defined string tension stretching along the rotation axis of pulsars. The crustquake-induced lattice vibration of the inner crust can act as a driving force for the transverse oscillation of the string. Such forced oscillation near resonance causes the bending of the vortex lines, disturbing their equilibrium configuration and resulting in the unpinning of vortices. We consider unpinning from the inner crust's so-called {\it strong (nuclear)} pinning region, where the vortices are likely pinned to the nuclear sites. We also comment on vortex unpinning from the interstitial pinning region of the inner crust. We sense that unifying crustquake with the superfluid vortex model can naturally explain the cause of large-scale vortex unpinning and generation of large-size pulsar glitches.