Evidence of long-term cyclic evolution of radio pulsar periods

The derived statistical relations as well as “anomalous” values of ν¨ are well described by assuming the existence of long-time variations of the spin-down rate. The pulsar frequency evolution, therefore, consists of secular change of νev(t), ν˙ev(t) and ν¨ev(t) according to the power law with n ≈ 5, the irregularities, observed within the timespan as timing noise, and the non-monotonous variations on the timescale of several tens of years, which is larger than that of the timespan. It is possible that the nature of long-term variations is similar to that of short-term ones. The idea of non-constant secular pulsars' braking index n is also analysed.