Pulsar emissions

The standard model for radio pulsars implies that the 'pulsar plasma' in the source region is a highly relativistic, strongly magnetized, one-dimensional, electron-positron pair plasma. Relativistic quantum effects lead to a correction of first order in h to the linear response of a pulsar plasma due to its spin dependence, but this is small for highly relativistic particles. Wave dispersion in the radio range involves the X-mode, Alfven mode and L-O mode. It is argued that the most plausible radio emission mechanism involves a nonresonant beam instability due to a beam mode that couples to the L-O mode. It is suggested that 'orthogonal modes' in the observed radio emission arise from mode coupling at sharp gradients at the edges of ducts, and that the observed circular polarization is associated with gyrotropy (a difference in the electron and positron distributions) and it develops as a propagation effect.