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Abstract

Glitch is supposed to be a useful probe into pulsar's interior, but the
underlying physics remains puzzling. The glitch activity may reflect a lower
limit of the crustal moment of inertia in conventional neutron star models.
Nevertheless, its statistical feature could also be reproduced in the strangeon
star model, which is focused here. We formulate the glitch activity of normal
radio pulsars under the framework of starquake of solid strangeon star model,
the shear modulus of strangeon matter is constrained to be $\mu\simeq
3\times10^{34}~\rm erg/cm^{3}$, consistent with previous work. Nevertheless,
about ten times the shift in oblateness accumulated during glitch interval is
needed to fulfill the statistical observations. The fact that typical glitch
sizes of two rapidly evolving pulsars (the Crab pulsar and PSR B0540-69) are
about two orders of magnitude lower than that of the Vela pulsar, significantly
lower than the oblateness change they can supply, indicates probably that only
a part of oblateness change is relieved when a pulsar is young. The unreleased
oblateness and stress may relax as compensation in the following evolution. The
small glitch sizes and low glitch activity of the Crab pulsar can be explained
simultaneously in this phenomenological model. Finally, we obtain energy
release to be $\Delta E\sim 2.4\times 10^{40}~\rm erg$ and $\Delta E\sim
4.2\times 10^{41}~\rm erg$ for typical glitch size of $\Delta\nu/\nu\sim
10^{-6}$ (Vela-like) and $\sim 10^{-8}$ (Crab-like). The upcoming SKA may test
this model through the energy release and the power-law relation between the
reduced recovery coefficient $Q/|\dot\nu|^{1/2}$ and $\Delta\nu/\nu$.