An inverse Compton scattering (ICS) model of pulsar emission: III. polarization

Abstract

Qiao and his collaborators recently proposed an inverse Compton Scattering (ICS) model to explain radio emission of pulsars. In this paper, we investigate the polarization properties of pulsar emission in the model. First of all, using the lower frequency approximation, we derived the analytical amplitude of inverse Compton scattered wave of a single electron in strong magnetic field. We found that the out-going radio emission of a single relativistic electron scattering off the ``low frequency waves'' produced by gap-sparking should be linearly polarized and have no circular polarization at all. However, considering the coherency of the emission from a bunch of electrons, we found that the out-going radiation from the inner part of emission beam, i.e., that from the lower emission altitudes, prefers to have circular polarization. Computer simulations show that the polarization properties, such as the sense reversal of circular polarization near the pulse center, S-shape of position angle swing of the linear polarization, strong linear polarization in conal components, can be reproduced in the ICS model.