A model for nulling and mode changing in pulsars

TL;DR

This paper presents a model explaining pulsar nulling and mode changing as magnetospheric state switches with different geometries and emission properties, affecting observed emission and spindown rates.

Contribution

It introduces a novel model linking magnetospheric state changes to observable pulsar emission variations and spindown rate differences, supported by theoretical analysis.

Findings

Magnetospheric states have different geometries and emission properties.

Switching states can cause large variations in spindown rate.

Modest beam shape variations can lead to significant spindown rate changes.

Abstract

We propose that in some pulsars the magnetosphere has different states with different geometries or/and different distributions of currents, it occasionally switches between them. These states have different spindown rates and emission beams, in some of the states no radioemission is produced at all. Switching into a different state manifests as a mode change when we see different parts of the emission beam or the beams in different states have significantly different geometries, it manifests as nulling when we either miss the new beam or no radioemission is generated in the new state. We show that modest variations in the beam shape can be accompanied by large variations in the pulsar spindown rate W - the dependence of W on the opening angle of the emission beam $\alpha$ can be as strong as W\propto\alpha^4. We speculate about physical mechanisms which may cause reconfiguration of the magnetosphere.