We report an analysis of timing data for the pulsar B1642 - 03 ( J1645 - 0317 ) gathered over the 40-year time span between 1969 and 2008 .
During this interval , the pulsar experienced eight glitch-like events with a fractional increase in the rotation frequency \Delta \nu / \nu \sim { ( 0.9 - 2.6 ) } \times 10 ^ { -9 } .
We have revealed two important relations in the properties of these peculiar glitches .
The first result shows that there is a strong linear correlation between the amplitude of the glitch and the time interval to the next glitch with a slope of about 0.0026 \times 10 ^ { -9 } Hz day ^ { -1 } .
This relation allows us to predict epochs of new glitches .
The second result shows that the amplitude of the glitches is modulated by a periodic large-scale sawtooth-like function .
As a result of this modulation , the glitch amplitude varies discretely from glitch to glitch with a step of 1.5 \times 10 ^ { -9 } Hz in the range ( 2.4 - 6.9 ) \times 10 ^ { -9 } Hz .
The post-glitch time interval also varies discretely with a step of \sim 600 days in the range 900–2700 days .
An analysis of the data showed that three modulation schemes with modulation periods of 43 years , 53 years and 60 years are possible .
The best model is the 60-year modulation scheme including 12 glitches .
We make a conclusion that the nature of the observed cyclical changes in the timing residuals from PSR B1642 - 03 is a continuous generation of peculiar glitches whose amplitudes are modulated by a periodic large-scale sawtooth-like function .
As the modulation function is periodical , the picture of cyclical timing residuals will be exactly repeated in each modulation period or every 60 years .