Quasiperiodic microstructure in radio pulsar emissions

A detailed analysis of microstructure in the radio emissions from five pulsars is presented, with particular emphasis on quasi-periodicities of the microstructure. Two objects (PSRs 0950 + 08 and 1133 + 16) show microstructure in only about 5-10 percent of pulse periods whereas the three objects that display drifting subpulses (PSRs 0809 + 74, 1944 + 17, and 2016 + 28) almost always show microstructure. The microstructure for two objects (1944 + 17 and 2016 + 28) is strongest at meter wavelengths and its contribution to the intensity decreases roughly as nu to the -3. The quasi-periods of periodic microstructure vary over a 10:1 range about an average period of 0.5-5 ms. The period can change on timescales as short as the typical subpulse separation, P2 about or equal to 10-60 ms. The significance of microstructure quasi-periodicities is discussed in terms of neutron star oscillation and activity in the pulsar magnetosphere. 54 refs.