On the circular polarization of pulsar radiation

We consider the polarization behaviour of radio waves propagating through an ultrarelativistic highly magnetized electron-positron plasma in a pulsar magnetosphere. The rotation of magnetosphere gives rise to the wave mode coupling in the polarization-limiting region. The process is shown to cause considerable circular polarization in the linearly polarized normal waves. Thus, the circular polarization observed for a number of pulsars, despite the linear polarization of the emitted normal waves, can be attributed to the limiting-polarization effect.