Curvature radiation in rotating pulsar magnetosphere

Abstract

We consider the curvature emission properties from relativistic particles streaming along magnetic field lines and corotating with pulsar magnetosphere. The corotation 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 corotation. 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/γ. The polarization patterns of the emission cone are distorted by the additional rotation, which is 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 emission from density patches, while it has a single sign for the emission from density core and is negligible for the emission from density cone.