Elliptically polarized natural modes in pulsar magnetospheres

Some results for the properties of the normal wave modes of a pulsar magnetosphere are presented and applied to the interpretation of these features of the polarization of pulsar radio emission. The magnetosphere is assumed to be populated by a highly relativistic one-dimensional electron-positron gas. The wave properties are calculated assuming that the electrons and positrons have exponential distributions in Lorentz factors with different means. The polarization at frequencies well below the relativistic cyclotron frequency varies from circular at very small angles to the magnetic field, to linear at small angles and back to circular at modest angles. The interpretation of two points is emphasized. The first is the fact that in some pulsars the orthogonal polarizations are elliptical; the second relates explicitly to the assumption that the transitions between orthogonal polarizations are due to different ray paths for the two modes.