Phase offsets between core and conal components of radio pulsars and   their emission altitudes
  We present a new method for investigating emission altitudes of radio pulsar core and conal components by attributing them different altitudes and by providing a framework to understand the 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 allows the conclusion that the core emission does not necessarily come from the surface. Our results and the observational trends 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 core/cone altitude differences that we find are typically larger than the individual altitudes ascribed to them so far. Widely different core/cone altitudes for some pulsars are also supported by data and suggest a novel explanation of the precursors in the Crab and similar pulsars. We 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 describe the observed core/cone morphologies. With it core/cone phase offsets allow a glimpse into the variation of the filling factors with altitude. 
R. C. Kapoor and C. S. Shukre