Curvature Radiation in Rotating Pulsar Magnetosphere

TL;DR

This paper investigates how rotation influences curvature radiation and polarization in pulsar magnetospheres, revealing effects on polarization patterns, sign reversals, and the impact of emission height and density models.

Contribution

It introduces a detailed model of curvature radiation considering co-rotation effects, polarization distortion, and density gradients, advancing understanding of pulsar emission mechanisms.

Findings

Polarization patterns are distorted by rotation, especially at higher emission heights.

Circular polarization can reverse sign depending on density gradients.

Total emission profiles are dominated by a specific emission height.

Abstract

We consider the curvature emission properties from relativistic particles streaming along magnetic field lines and co-rotating with pulsar magnetosphere. The co-rotation affects the trajectories of the particles and hence the emission properties, especially the polarization. We consider the modification of the particle velocity and acceleration due to the co-rotation. Curvature radiation from a single particle is calculated using the approximation of a circular path to the particle trajectory. Curvature radiation from particles at a given height actually contains the contributions from particles streaming along all the nearby field lines around the tangential point, forming the emission cone of 1/{\gamma}. The polarization patterns from the emission cone are distorted by the additional rotation, more serious for emission from a larger height. Net circular polarization can be generated by the density gradient in the emission cone. For three typical density models in the form of core, cone and patches, we calculate the polarization profiles for emission generated at a given height. We find that the circular polarization could have a single sign or sign reversal, depending on the density gradient along the rotation phase. The polarization profiles of the total curvature radiation from the whole open field line region, calculated by adding the emission from all possible heights, are similar to that from a dominating emission height. The circular polarization of curvature radiation has sign reversals in the patchy emission, while it has a single sign for the core emission, and is negligible for the cone emission.