CIRCULAR-POLARIZATION IN PULSAR INTEGRATED PROFILES

We present a systematic study of the circular polarization in pulsar i ntegrated profiles, based on published polarization data. For core com ponents, we find no significant correlation between the sense change o f circular polarization and the sense of linear position-angle variati on. Circular polarization is not restricted to core components and, in some cases, reversals of circular polarization sense are observed acr oss the conal emission. In conal double profiles, the sense of circula r polarization is found to be correlated with the sense of position-an gle variation. Pulsars with a high degree of linear polarization often have one hand of circular polarization across the whole profile. For most pulsars, the sign of circular polarization is the same at 50-cm a nd 20-cm wavelengths, and the degree of polarization is similar, albei t with a wide scatter. However, at least two cases of frequency-depend ent sign reversals are known. This diverse behaviour may require more than one mechanism to generate circular polarization.