2017MNRAS.469.2049Y

We propose and explore a purely magnetospheric model for observed abrupt changes in pulsar radio profile. The flow rate of the magnetospheric plasma is dependent on the magnetospheric state described by the parameter y. We include the effect of the motion of the visible point along its trajectory, whose omission from a 'standard' version of viewing geometry is strictly valid only for align rotation and approximately valid for oblique rotation only in a narrow range of pulsar phase, which decreases as the obliquity increases. Emission is assumed from spots, distributed uniformly around the magnetic axis, so that observable features, such as subpulses, appear to rotate at a rate, ω_R, relative to the visible point. We find that the apparent motion of an individual spot is not constant, and the apparent distribution of emission spots around the trajectory of the visible point is uneven being highest around the centre of the pulse window, where their apparent motion is slowest, allowing more spots to be present simultaneously in the pulse window than in the 'standard' version. An abrupt (or more gradual) change in y implies a change in ω_R, which affects the pulse structure and profile. As a case study, we apply the model to 'swooshing' in PSR B0919+06. We discuss correlated slowing down rate in the model and related time-dependent phenomena in radio pulsars.