A statistical model for the orthogonal modes of polarization in pulsar radio emission

The radio emission from pulsars is modeled as the simultaneous interaction of two modes of orthogonally polarized radiation. Both modes are assumed to be completely linearly polarized, and the flux densities of the modes are represented by random variables to account for the random switching between orthogonally polarized states. Example distributions of total intensity, l inear polarization, fractional linear polarization, and polarization positi on angle are computed with both analytical and numerical versions of the mo del. The model is compared to polarization observations of individual pulse s from PSR B2020+28. Once allowances have been made for interstellar scinti llation, the model distributions compare favorably to observed histograms, except for the position angle histograms that are wider than one would expe ct from a delta function that is broadened by instrumental noise. The flux densities of the orthogonal modes in PSR B2020+28 are found to be highly co rrelated. The depolarization of pulsar radio emission has been attributed t o the orthogonal modes or to the randomization of position angle. A random, or uniform, component of the position angle will arise from superposed mod es that occur with nearly equal frequency. We show that the random componen t of position angle in PSR B2020 + 28 is a consequence of depolarization by the orthogonal modes.