Understanding the radio emission geometry of multi-component radio pulsars from retardation and aberration effects

Abstract

We have conducted a detailed analysis of the emission geometry of a handful of radio pulsars that have prominent, multiple-component profiles at meter wavelengths. From careful determination of the total number of emission components and their locations in pulse longitude, we find that all of the six pulsars show clear evidence for retardation and aberration effects in the conal emission beams. Using this information, coupled with a dipolar field geometry, we obtain estimates of the height and transverse location in the magnetosphere, for each of the emitting cones in these pulsars. These results support our earlier conclusions for PSR B0329+54 in that we find successive outer cones (in cases of multi-cone pulsars) being emitted at higher altitudes in the magnetosphere. The range of inferred heights is from ~200 to ~2200 km. The set of ``active'' field lines from which the conal emissions originate are located in the region from ~0.22 to ~0.74 of the polar cap radius. At the neutron star surface, these conal rings map to radii of a few to several tens of meters and the separation between successive rings is about 10 to 20 meters. We discuss the implications of these findings for the understanding of the pulsar emission geometry and for current theories and models of the emission mechanism.