Modelling pulsar glitches with realistic pinning forces : a hydrodynamical approach

Although pulsars are some of the most stable clocks in theUniverse,many of them are observed to ‘glitch’, i.e. to suddenly increase their spin frequency ν with fractional increases that range from ν/ν ≈ 10−11 to 10−5. In this paper, we focus on the ‘giant’ glitches, i.e. glitches with fractional increases in the spin rate of the order of ν/ν ≈ 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.