Polarization Sweeps in Rotation‐powered Pulsars

We reexamine the characteristic polarization angle sweep of rotation-powered pulsars and calculate the expected deviations from this sweep caused by aberrational effects and by polar-cap current flow. We find that in addition to the previously known phase shift of the entire sweep by ΔΦ = -4 r / R L (when R L is the light cylinder distance), aberration shifts the polarization angle itself by ΔΨ = -(10/3)( r / R L ) cos α. Similarly, current flow above the polar cap shifts the polarization sweep by ΔΨ = (10/3)( r / R L )( J / J GL ) cos α, potentially providing a method of directly measuring the magnitude of the current. The competition between these two effects produces a potentially observable signature in the polarization angle sweep. Although these effects may appear similar to orthogonal mode shifts, they are an independent phenomenon with distinct observational characteristics.