JPL pulsar timing observations. III. Pulsar rotation fluctuations.

Pulsar arrival-time data obtained with the NASA Deep Space Network from 1968 to 1982 are subjected to variance and structure function analyses to achieve empirical descriptions of rotational activity for 24 objects. A wide range of activity is seen, including fluctuations caused by identifiable step functions in rotational frequency and frequency derivative in some cases, and by processes with unresolvable events in others. Timing activity is found to be correlated with Pand νbut is uncorrelated with period P. The authors calculate the Allan variance of pulsar rotation frequencies and compare pulsars with terrestrial clocks. Most pulsars are inferior clocks, having a frequency stability worse than 1 part in 10¹¹ on a 1 year time scale.