Ii. Radio Astronomy Academic and Research Staff

High time resolution observations at 115 MHz and 150 MHz have confirmed the marching subpulse behavior of CP1919 and AP2015+28 reported by Drake and Craft,I and have revealed similar behavior in MP0031 and CP0808 (Fig. II-1). The marching patterns for all four pulsars slope in the same sense; i. e., subpulses occur slightly earlier within the average pulse window with each succeeding pulse. Similar, but more ambiguous, results have been obtained for CP0834. Drake and Craft described the phenomenon by a single parameter, the Class 2 Period P2', which is the mean separation of the marching or Class 2 pulses and is much shorter than the basic pulsar period P 1 and incommensurate with it. We define a third period, the pattern period P 3, as the time between successive appearances of Class 2 pulses in a given time window of the average pulse. Values of P', P2, and P 3 are given in Table I-i. Each of the marching patterns in Fig. II-1 can be represented by a series of sloping lines connecting the Class 2 pulses in consecutive pulses. The average separations of these lines, P 2 and P3' are approximately unchanged from day to day and month to month, but the slopes and separations of individual lines show variations of ~+20%. In the case of MP0031, the width of the Class 2 pulses is approximately 0. 2 P 2, which shows that the modulation process is not sinusoidal. The pulsars MP0031 and CP1919 also exhibit periodicities in pulse intensity of the order of 2 min and 6 min, respectively. The slow periodic variations were first noted in MP0031, as illustrated in Fig. 11-2. On this strip chart record the pulse intensities vary, with a period of ~2 min. Examination of several hours of MP0031 data suggests that the effect is often, but not always, evident, and that the period sometimes varies 20% or more over several minutes. The day-to-day variation does not appear to be