The effect of superfluid hydrodynamics on pulsar glitch sizes and waiting times

TL;DR

This paper integrates quantum vortex simulation results into superfluid hydrodynamics models of pulsars, predicting deviations from simple power-law and exponential distributions in glitch sizes and waiting times, including a small glitch size cutoff.

Contribution

It introduces a macroscopic superfluid hydrodynamics model incorporating quantum vortex effects, explaining observed deviations in pulsar glitch distributions.

Findings

Vortex coupling causes deviations from power-law size distributions.

Predicted cutoff in small glitch sizes.

Explains non-exponential waiting time distributions.

Abstract

Pulsar glitches, sudden jumps in frequency observed in many radio pulsars, may be the macroscopic manifestation of superfluid vortex avalanches on the microscopic scale. Small scale quantum mechanical simulations of vortex motion in a decelerating container have shown that such events are possible and predict power-law distributions for the size of the events, and exponential distributions for the waiting time. Despite a paucity of data, this prediction is consistent with the size and waiting time distributions of most glitching pulsars. Nevertheless a few object appear to glitch quasi-periodically, and exhibit many large glitches, while a recent study of the Crab pulsar has suggested a cut-off deviations from a power-law distribution for smaller glitches. In this paper we incorporate the results of quantum mechanical simulations in a macroscopic scale superfluid hydrodynamics simulation. We show that the effect of vortex coupling to the neutron and proton fluids in the neutron star naturally leads to deviations from power-law distributions for sizes and from exponential distributions for waiting times. In particular we predict a cut-off in the size distribution for small glitches.