Random Polarization Position Angle Behaviors across Bursts of Repeating Fast Radio Bursts

Abstract Fast radio bursts (FRBs) are highly polarized and mostly show a nearly constant polarization position angle (PA) during each burst. Their PAs are observed to vary from burst to burst, with the statistical properties remaining stable across different observation sessions. We found that the intrinsic PAs of repeating FRBs are approximately Gaussian distributed with a stable mean PA. This suggests that the magnetic field line sampled by the emission does not vary randomly across the magnetosphere but instead remains confined to a limited range of viewing geometries, consistent with emission arising from a localized region. A periodicity search of the PA time series using the Lomb–Scargle periodogram reveals no credible periodic signal in the period range from 10 to 10 7 ms, and similar analyses of several active observations also yield null detections. We interpret these properties by extending the rotating vector model to include a dynamically evolving magnetosphere, in which the effective magnetic axis varies from burst to burst due to stochastic perturbations. In this framework, the observed PA distributions can naturally arise from geometric projection effects, and the absence of periodicity reflects the random wandering of the magnetic axis within a confined region. This scenario provides a natural explanation for both repeating and apparently nonrepeating FRBs.