The Crab pulsar: ion-proton plasma and high-frequency radio spectrum

TL;DR

This paper proposes that the high-frequency band structure in the Crab pulsar's interpulse originates from a one-pass free-electron laser mechanism involving ion-proton plasma interactions in the magnetosphere's current sheet.

Contribution

It introduces a novel model linking the pulsar's spectral features to ion-proton plasma interactions and a free-electron laser mechanism in the magnetosphere.

Findings

Band structure explained by charge-to-mass ratio differences

Current sheet as the emission source

Mechanism involves electron-ion-proton interactions

Abstract

Salient features of the remarkable band structure seen in the high-frequency interpulse of the Crab pulsar are summarized. It is argued that its source must lie in a current sheet, probably coincident with the open-closed magnetosphere separatrix, and that the mechanism is a form of one-pass free-electron laser. An outward moving electron component in the current sheet interacts with the longitudinal electric field of an inward directed ion-proton Lamgmuir mode. The band structure is then a natural consequence of the differing charge-to-mass ratios of the ions, which are a return current component of those accelerated, as in almost all pulsars, from the polar cap to the light cylinder.