2012MNRAS.420..658H

Although pulsars are some of the most stable clocks in the Universe, many of them are observed to `glitch', i.e. to suddenly increase their spin frequency ν with fractional increases that range from Δ_ν/ν≈10<sup>–11</sup> to 10<sup>–5</sup>. In this paper, we focus on the `giant' glitches, i.e. glitches with fractional increases in the spin rate of the order of Δ_ν/ν≈10^–11 to 10^–6, that are observed in a subclass of pulsars including the Vela. We show that giant glitches can be modelled with a two-fluid hydrodynamical approach. The model is based on the formalism for superfluid neutron stars of Andersson & Comer and on the realistic pinning forces of Grill & Pizzochero. We show that all stages of Vela glitches, from the rise to the post-glitch relaxation, can be reproduced with a set of physically reasonable parameters and that the sizes and waiting times between giant glitches in other pulsars are also consistent with our model.