On the distributions of pulsar glitch sizes and the inter-glitch time intervals

The glitch size, $\Delta\nu/\nu$, inter-glitch time interval, $t_{i}$ and frequency of glitches in pulsars are key parameters in discussing glitch phenomena. In this paper, the glitch sizes and inter-glitch time intervals were statistically analysed in a sample of 168 pulsars with a total of 483 glitches. The glitches were broadly divided into two groups. Those with $\Delta\nu/\nu < 10^{-7}$ are regarded as small size glitches, while those with $\Delta\nu/\nu \geq 10^{-7}$ are regarded as relatively large size glitches. In the ensemble of glitches, the distribution of $\Delta\nu/\nu$ is seen to be bimodal as usual. The distribution of inter-glitch time intervals is unimodal and the inter-glitch time intervals between small and large size glitches are not significantly different from each other. This observation shows that inter-glitch time intervals are size independent. In addition, the distribution of the ratio $\Delta\nu/\nu:t_{i}$ in both small and large size glitches has the same pattern. This observation suggests that a parameter which depends on time, which could be the spin-down rate of a pulsar plays a similar role in the processes that regulate both small and large size glitches. Equally this could be an indication that a single physical mechanism, which could produce varying glitch sizes at similar time-intervals could be responsible for both classes of glitch sizes.