Phase Offsets between Core and Conal Components of Radio Pulsars and Their Emission Altitudes

We present a new and a potentially powerful method for investigating emission altitudes of radio pulsar core and conal components by attributing them different altitudes. We provide a framework for a systematic understanding of resulting longitude offsets between them which are frequently observed. By investigating the contributions to these offsets due to aberration and the magnetic field line sweepback, we show that they are always dominated by aberration for all emission altitudes and inclination angles. This directly leads to the conclusion that the core emission does not necessarily come from the surface. Based on our results, the trends seen in the observational phase offsets imply that for a large number of pulsars the emission altitudes of core and conal components are close when compared to the light cylinder radius but not necessarily relative to the stellar radius. The altitude difference between core and conal components that we find are typically larger than the individual altitudes ascribed to them so far. Our results also allow very widely different but related core/cone altitudes. We find that data supports also this circumstance for some pulsars, which suggests a novel and natural explanation of the precursors in the Crab and similar pulsars. The pre-and post-cursor nature of these components arises because of large offsets caused by correspondingly large differences in the core and conal emission altitudes. We also show that the question of emission altitudes can not be divorced from considerations of the core/cone components' filling factors of the polar flux tube. We propose an empirical '1/3 rule' to concisely describe the observed core/cone morphologies. Combined with the core/cone phase offsets it allows a glimpse into the variation of these filling factors with altitude. Lastly, we outline how the full predictive potential of our results can be realised by combining them with a detailed analysis of the polarization and multifrequency observations.