A total of 660 discrete jumps in the rotation frequency ( ) and the spin-down rate ( ) of about 140 pulsars were studied. Out of the 660 discrete jumps, 394 were classical glitches (the so-called macroglitches) and 266 were microglitches. The objects are grouped into normal radio pulsars, anomalous x-ray pulsars and recycled millisecond pulsars. A bimodal distribution was observed in many of the pulsar glitch parameters, namely the discrete absolute fractional jumps in the rotation frequency ( ), the entire absolute discrete jumps in the spin down rate (|Δ |), cumulative of the absolute jumps in the rotation frequency ( ), cumulative of the absolute fractional jumps in rotation frequency ) for macroglitches may suggest that glitch events may be triggered by dual glitch mechanism. The distribution of the entire absolute discrete fractional jumps in the rotation frequency (| |) cumulative of the absolute jumps in the rotation frequency ( ) and the cumulative of the absolute jumps in spin down rate (∑|Δ |) of microglitches equally suggests that a glitch event is triggered by one mechanism. It was observed that some of the macroglitches have magnitudes in (rotation frequency) which overlapped with the microglitches completely which suggest that some of the rotational jumps that was characterized as macroglitches by previous authors should have been recorded as microglitches since their glitch magnitude . The distribution of the glitches over the spin down parameters shows that pulsars with characteristic age 3 4, rotational frequency of 0.9, spin down rate ) and surface magnetic field strength of 12 13 on logarithmic scales exhibit the highest frequency of macroglitches while those within the characteristic age 5 6 , rotational frequency of 0.4 , spin down rate of and surface magnetic field strength of 11 12 on logarithmic scales exhibit the highest frequency of microglitches. From the regression analysis, it was observed that there was a strong positive linear relationship between ( ) (∑|Δ |)for the macroglitches and microglitches data when analysed separately and jointly. There was no correlation between ( ) data for both samples. On the otherhand, there was a strong ( | | correlation for the macroglitches and microglitches data when analysed separately and jointly.
1.0 An Overview of Rotating Neutron Stars
A neutron star is the core remnant of a supernova event, a violent explosion that marks the death of a massive ( to , where is mass of the sun) star. A typical neutron star is believed to be spherical in structure with a radius of about 12 km (Kaspi et al.,1994) and a mass of about 1.2 to 2.1 (Kramer et al., 2006). Neutron stars rotate and can emit broad band beams of electromagnetic radiations that are detected as pulsars. Pulsars are rapidly rotating highly magnetized neutron stars (Lorimer & Kramer, 2005). The beams of radiation are emitted along the magnetic axis of the pulsar as it spins about the rotation axis. The emitted radiations can be observed when the beam of emission sweeps across the earth much the same way a lighthouse can be seen when it is pointed in the direction of an observer (Lorimer et al., 2005). These pulsed emissions have been detected and studied over the whole electromagnetic spectrum ranging from the high energy gamma rays to the low energy radio waves (Lyne & Graham-Smith, 1998). Pulsars are well known for their stable rotation which allows them to be used as cosmic clocks. According to the data in Australia Telescope National Facility catalogue of pulsars, over 2500 pulsars have being discovered (Manchester et al. 2005).