Geometry of radio pulsar signals: The origin of pulsation modes and nulling

TL;DR

This paper proposes a new geometric model for radio pulsar signals, explaining diverse pulse behaviors and nulling as effects of a simple, sector-structured beam influenced by magnetospheric charge distribution and drift, challenging the carousel model.

Contribution

It introduces a novel geometric interpretation of pulsar emission, linking pulse variability to a sector beam structure and magnetospheric charge distribution, moving beyond traditional carousel models.

Findings

Single pulse complexity arises from viewing a simple sector beam.

Drift of the beam causes observed pulsation mode changes and nulling.

The model suggests inward particle flow and emission, contradicting conal beam symmetry.

Abstract

Radio pulsars exhibit an enormous diversity of single pulse behaviour that involves sudden changes in pulsation mode and nulling occurring on timescales of tens or hundreds of spin periods. The pulsations appear both chaotic and quasi-regular, which has hampered their interpretation for decades. Here I show that the pseudo-chaotic complexity of single pulses is caused by the viewing of a relatively simple radio beam that has a sector structure traceable to the magnetospheric charge distribution. The slow ExB drift of the sector beam, when sampled by the line of sight, produces the classical drift-period-folded patterns known from observations. The drifting azimuthal zones of the beam produce the changes in pulsation modes and both the intermodal and sporadic nulling at timescales of beating between the drift and the star spin. The axially symmetric conal beams are thus a superficial geometric illusion, and the standard carousel model of pulsar radio beams does not apply. The beam suggests a particle flow structure that involves inward motions with possible inward emission.