2003ApJ...590.1026M

Polarization observations of the radio emission from PSR B2016+28 at 1404 MHz reveal properties that are consistent with two very different interpretations of the pulsar's viewing geometry. The pulsar's average polarization properties show a rapid change in position angle (P.A.) near the pulse center, suggesting that the observer's sight line nearly intersects the star's magnetic pole. But single-pulse polarization observations of the pulsar show nearly orthogonal modes of polarization following relatively flat and parallel P.A. trajectories across the pulse, suggesting that the sight line is far from the pole. Additionally, P.A. histograms reveal a modal connecting bridge of unknown origin, joining the modal P.A. trajectories over much of the pulse and following the rapid P.A. change shown in the average data. The nonorthogonality of polarization modes is incorporated in a statistical model of radio polarization to account for the deviations from mode orthogonality that are observed in the pulsar. The model is used to interpret the rapid P.A. change and modal connecting bridge as a longitudinally resolved transition between modes of nonorthogonal polarization. Thus, the modal P.A. trajectories are argued to reflect the pulsar's true viewing geometry. This interpretation is consistent with the pulsar's morphological classification, preserves the Radhakrishnan & Cooke model of pulsar radio emission, and avoids the complication that the modal connecting bridge might be produced by some other emission mechanism. The statistical model's ability to simulate the rich variety of polarization properties observed in the emission lends additional support to the model's applicability and its underlying assumption that the polarization modes occur simultaneously.