Classification of Subpulse Drifting in Pulsars

TL;DR

This paper proposes a detailed classification scheme for subpulse drifting in pulsars, analyzing phase variations and their relation to pulsar profile classes, and confirms the anti-correlation between spin-down energy loss and drifting periodicity.

Contribution

It introduces a new classification of subpulse drifting based on phase behavior and expands the analysis of their physical associations and correlations with pulsar properties.

Findings

Four distinct drifting categories identified based on phase behavior.

Subpulse drifting is mainly associated with conal components, not core components.

Confirmed anti-correlation between spin-down energy loss and drifting periodicity.

Abstract

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