Cyclotron effects on wave dispersion in pulsar plasmas

Extract

Dispersion in an intrinsically relativistic, one-dimensional, electron–positron pair plasma (a pulsar plasma) is treated exactly, generalizing earlier results that applied in the low-frequency limit and that neglected the cyclotron resonance. The general theory involves two additional relativistic plasma dispersion functions, evaluated at the normal and anomalous Doppler resonances. These two functions are associated with the non-gyrotropic and gyrotropic parts of the response respectively. The functions are evaluated for bell-type and Jüttner distributions. Wave dispersion is discussed for a non-gyrotropic pulsar plasma with a highly relativistic Alfvén speed. Emphasis is placed on crossings of the light line, defined in terms of the parallel phase velocity. Subluminal waves exist only for sufficiently small angles of propagation, and are confined to frequencies below about the mean gyrofrequency of the relativistic particles.