Pulsar glitches: The crust is not enough

TL;DR

This paper argues that the crust superfluid alone cannot account for pulsar glitches due to entrainment effects, suggesting the need for additional angular momentum reservoirs or revised models.

Contribution

It demonstrates that crust entrainment reduces the superfluid's effective moment of inertia, challenging the traditional crust-based glitch explanation.

Findings

Crust superfluid's moment of inertia is insufficient to explain observed glitches.

Entrainment coupling significantly reduces superfluid mobility.

Additional reservoirs or mechanisms are needed to account for glitches.

Abstract

Pulsar glitches are traditionally viewed as a manifestation of vortex dynamics associated with a neutron superfluid reservoir confined to the inner crust of the star. In this Letter we show that the non-dissipative entrainment coupling between the neutron superfluid and the nuclear lattice leads to a less mobile crust superfluid, effectively reducing the moment of inertia associated with the angular momentum reservoir. Combining the latest observational data for prolific glitching pulsars with theoretical results for the crust entrainment we find that the required superfluid reservoir exceeds that available in the crust. This challenges our understanding of the glitch phenomenon, and we discuss possible resolutions to the problem.