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We discuss the minimum glitch size of Crab observed by Espinoza et al. (2014). Modelling the crustquake as a trigger mechanism, we estimate the size of the broken plate. The plate size obtained, D ~ 100m is comparable to plate size estimates for PSR J1119-6127. The plate size naturally leads to an estimate of the number of unpinned vortices involved in the glitch, N ~ 1013. This number is of the same order in all Crab and Vela pulsar glitches. The minimum glitch relates the constancy of all these numbers among different pulsars to the basic plate size involved in crust breaking. This in turn depends on the critical strain angle θcr of the Coulomb lattice in the neutron star crust. The minimum glitch size implies θcr ~ 10-1 in agreement with theoretical and computational estimates. [ABSTRACT FROM AUTHOR]

The interglitch timing of the Vela pulsar is characterized by a constant second derivative of the rotation rate. This takes over after the post-glitch exponential relaxation and is completed at about the time of the next glitch. The vortex creep model explains the second derivatives in terms of nonlinear response to the glitch. We present interglitch timing fits to the present sample covering 16 large glitches, taking into account the possibility that in some glitches part of the step in the spin-down ratemay involve a 'persistent shift', as observed in the Crab pulsar. Modifying the expression for the time between glitches with this hypothesis leads to better agreement with the observed interglitch time intervals. We extrapolate the interglitch model fits to obtain spin-down rates just prior to each glitch and use these to calculate the braking index n = 2.81 ± 0.12. The next glitch should occur around 2017 December 22, ±197 d if no persistent shift is involved, but could occur as early as 2016 July 27, ±152 d if the 2013 glitch gave rise to a typical Vela persistent shift. Note added: Literally while we were submitting the first version of this paper on 2016 December 12, we saw ATel # 9847 announcing a Vela pulsar glitch which has arrived 138 d after our prediction with a persistent shift, within the 1σ uncertainty of 152 d. [ABSTRACT FROM AUTHOR]

Glitches are sudden changes in rotation frequency and spin-down rate, observed from pulsars of all ages. Standard glitches are characterized by a positive step in angular velocity (ΔΩ > 0) and a negative step in the spin-down rate (ΔΩ <0) of the pulsar. There are no glitch-associated changes in the electromagnetic signature of rotation-powered pulsars in all cases so far. For the first time, in the last glitch of PSR J1119-6127, there is clear evidence for changing emission properties coincident with the glitch. This glitch is also unusual in its signature. Further, the absolute value of the spin-down rate actually decreases in the long term. This is in contrast to usual glitch behaviour. In this paper we extend the vortex creep model in order to take into account these peculiarities. We propose that a starquake with crustal plate movement towards the rotational poles of the star induces inward vortex motion which causes the unusual glitch signature. The component of the magnetic field perpendicular to the rotation axis will decrease, giving rise to a permanent change in the pulsar external torque. [ABSTRACT FROM AUTHOR]