On the mean profiles of radio pulsars I: Theory of the propagation effects

TL;DR

This paper develops a comprehensive theoretical model for radio pulsar profiles, incorporating propagation effects, magnetic field configurations, and plasma dynamics to better understand polarization and profile shapes.

Contribution

It introduces a novel wave propagation approach that includes transition effects, non-dipole fields, and plasma particle drift, enabling detailed pulsar profile modeling.

Findings

Standard S-shape p.a. swing occurs under specific plasma conditions.

The p.a. maximum derivative depends on plasma parameters, not just geometry.

The model predicts a correlation between circular polarization signs and p.a. derivative.

Abstract

We study the influence of the propagation effects on the mean profiles of radio pulsars using the Kravtsov-Orlov method of the wave propagation in the inhomogeneous media. This approach allows us firstly to include into consideration the transition from geometrical optics to vacuum propagation, the cyclotron absorption, and the wave refraction simultaneously. In addition, arbitrary non-dipole magnetic field configuration, drift motion of plasma particles, and their realistic energy distribution are taken into account. The one-to-one correspondence between the signs of circular polarization and position angle (p.a.) derivative along the profile for both ordinary and extraordinary waves is predicted. Using the numerical integration we now can model the main profiles of radio pulsars. It is shown that standard S-shape form of the p.a. swing can be realized for small enough pair production multiplicity and large enough bulk plasma Lorentz factor only. It is also shown that the value of p.a. maximum derivative, that is often used for determination the angle between magnetic dipole and rotation axis, depends on the plasma parameters and could differ from the rotation vector model (RVM) prediction.