A bistable pulsar magnetosphere: nulls and mode-changes

TL;DR

This paper investigates the instability in ion-proton pulsar magnetospheres, linking mode transitions to observable phenomena like nulls and mode-changes, and discusses their impact on pulsar emission and spin-down behavior.

Contribution

It introduces a model of pulsar magnetosphere mode transitions involving proton-dominated inverse Compton scattering, explaining nulls and mode-changes in pulsar observations.

Findings

Ion-proton magnetosphere is unstable in certain P-Pdot regions.

Mode transitions affect particle fluxes and spin-down torque.

High Lorentz factors inhibit coherent radio emission.

Abstract

It is shown that the ion-proton magnetosphere is unstable in a limited area of the P - Pdot plane against transitions to a self-sustaining inverse Compton scattering mode in which the particles accelerated are mainly protons with a small component of positrons. It is argued that this mode cannot be absolutely stable. The number density of any outward-moving pair plasma is small and electron and positron Lorentz factors too high to support growth of any collective mode capable of exciting normal pulsar coherent radio emission. Particle fluxes and the position at which they pass through the light cylinder are mode-dependent and in principle, transitions can be accompanied by changes in spin-down torque. The properties of the system are discussed in relation to observations of nulls, mode-changes, and the group of long-term intermittent pulsars.