Physics of radio emission in gamma-ray pulsars

TL;DR

This paper reviews the propagation of radio emission in gamma-ray pulsars, analyzing polarization, scattering, and plasma diagnostics, and presents observational data linking plasma densities to radio and gamma-ray emission characteristics.

Contribution

It introduces a detailed analysis of radio emission propagation effects in gamma-ray pulsars and provides plasma density profiles derived from polarization data, linking radio and gamma-ray emission features.

Findings

Plasma densities vary with radio pulse timing relative to gamma-ray peaks.

Radio pulse components with flat polarization angles may result from induced scattering.

Radio quietness is due to resonant absorption, while radio loudness relates to beam escape.

Abstract

Propagation of radio emission in pulsar magnetosphere is reviewed. The effects of polarization transfer, induced scattering and reprocessing to high energies are analysed with an especial emphasis on the implications for the gamma-ray pulsars. The possibilities of the pulsar plasma diagnostics based on the observed radio pulse characteristics are outlined as well. As an example, the plasma number density profiles obtained from the polarization data for the Vela and the gamma-ray millisecond pulsars J1446-4701, J1939+2134 and J1744-1134 are presented. The number densities derived tend to be the highest/lowest when the radio pulse leads/lags the gamma-ray peak. In the PSR J1939+2134, the plasma density profiles for the main pulse and interpulse appear to fit exactly the same curve, testifying to the origin of both radio components above the same magnetic pole and their propagation through the same plasma flow in opposite directions. The millisecond radio pulse components exhibiting flat position angle curves are suggested to result from the induced scattering of the main pulse by the same particles that generate gamma-rays. This is believed to underlie the wide-sense radio/gamma-ray correlation in the millisecond pulsars. The radio quietness of young gamma-ray pulsars is attributed to resonant absorption, whereas the radio loudness to the radio beam escape through the periphery of the open field line tube.