Classification of subpulse drifting in pulsars

Abstract

In this study we propose a classification scheme for the phenomenon of\nsubpulse drifting in pulsars. We have assembled an exhaustive list of pulsars\nwhich exhibit subpulse drifting from previously published results as well as\nrecent observations using the Giant Meterwave Radio Telescope. We have\nestimated detailed phase variations corresponding to the drifting features.\nBased on phase behaviour the drifting population was classified into four\ngroups : coherent phase-modulated drifting, switching phase-modulated drifting,\ndiffuse phase-modulated drifting and low-mixed phase-modulated drifting. We\nhave re-established the previous assertion that the subpulse drifting is\nprimarily associated with the conal components in pulsar profile. The core\ncomponents generally do not show the drifting phenomenon. However, in core\nemission of certain pulsars longer periodic fluctuations are seen, which are\nsimilar to periodic nulling, and likely arise due to a different physical\nphenomenon. In general the nature of the phase variations of the drifting\nfeatures across the pulsar profile appears to be associated with specific\npulsar profile classes, but we also find several examples that show departures\nfrom this trend. It has also been claimed in previous works that the spin-down\nenergy loss is anti-correlated with the drifting periodicity. We have verified\nthis dependence using a larger sample of drifting measurements.\n