A multi-frequency fluctuation spectrum analysis of the pulse to pulse intensity variations in nine pulsars

A fluctuation spectrum analysis of single pulse sequences from nine pulsars measured at radio frequencies ranging from 0.43 GHz to 2.7 GHz has been carried out. It is shown that a gradual growth of the quasi-steady component of the pulsar emission with increasing radio frequency is a common feature of these sources. A theoretically predicted radio frequency independence of the P3 periods is found to hold in both the systematic and the erratic drifters, except for PSR 2016+28 and possibly PSR 2020+28. It is suggested that a slow intensity modulation generated by the quasi-steady component may explain the break frequency found in the modulation index/radio frequency relationship for some pulsars and that the phenomena observed in our data may be directly related to the pulse emission constituents described as the core and the conal emissions. (orig.)