1996A&A...314..853G

The charged particles moving along rapidly rotating magnetic field lines get accelerated due to the centrifugal force. They gain energy from the pulsar while moving from magnetic pole to the light cylinder. In the case of a pulsar with non-aligned rotation and magnetic axes, the radio pulses and interpulses are generated near the neutron star surface while those in the X-ray and γ-ray regime are generated within small regions close to the light cylinder, with an optical and UV pulses in the intermediate region. We consider a millisecond pulsar with dipole magnetic field structure and estimate the power emitted by a test charge. Since radiating particles move towards a distant observer along relativistically compressed magnetic field lines, he receives a beamed and transversely compressed radiation pulse. Due to the relativistic compression of field lines in the direction of rotation, near the light cylinder position angle varies smoothly during pulsar rotation in a fashion similar to that which Radhakrishnan and Cooke (1969ApL.....3..225R) expect its variation near magnetic pole. Orthogonal modes could be due to the motion of two charge species along field lines. The fluctuation in particle flux can produce null periods.