Hydrodynamic simulations of pulsar glitch recovery

TL;DR

This paper uses hydrodynamic simulations of a two-component superfluid model of neutron stars to study how different glitch induction methods and mutual friction strengths affect glitch size and recovery, providing insights into observed pulsar behaviors.

Contribution

It introduces a detailed hydrodynamic simulation framework for pulsar glitches, exploring the effects of mutual friction and glitch induction methods on recovery dynamics.

Findings

Maximum glitch size decreases with stronger mutual friction.

Mutual friction influences the fraction of the glitch that is recovered.

Simulation results may explain diversity in observed glitch recoveries.

Abstract

Glitches are sudden jumps in the spin frequency of pulsars believed to originate in the superfluid interior of neutron stars. Superfluid flow in a model neutron star is simulated by solving the equations of motion of a two-component superfluid consisting of a viscous proton-electron plasma and an inviscid neutron condensate in a spherical Couette geometry. We examine the response of our model neutron star to glitches induced in three different ways: by instantaneous changes of the spin frequency of the inner and outer boundaries, and by instantaneous recoupling of the fluid components in the bulk. All simulations are performed with strong and weak mutual friction. It is found that the maximum size of a glitch that originates in the bulk decreases as the mutual friction strengthens. It is also found that mutual friction determines the fraction of the frequency jump which is later recovered, a quantity known as the 'healing parameter'. These behaviours may explain some of the diversity in observed glitch recoveries.