The selection of integrated profiles in Figure 4 shows a rich diversity in morphology including two examples of “interpulses” - a secondary pulse separated by about 180 degrees from the main pulse. The most natural interpretation for this phenomenon is that the two pulses originate from opposite magnetic poles of the neutron star (see however ). Since this is an unlikely viewing angle we would expect interpulses to be a rare phenomenon. Indeed, the fraction of known pulsars in which interpulses are observed in their pulse profiles is only a few percent .Two contrasting phenomenological models to explain the observed pulse shapes are shown in Figure 5. The “core and cone” model  depicts the beam as a core surrounded by a series of nested cones. Alternatively, the “patchy beam” model [202, 109] has the beam populated by a series of randomly-distributed emitting regions. Further work in this area is necessary to improve our understanding of the shape and evolution of pulsar beams and fraction of sky they cover. This is of key importance to the results of population studies reviewed in Section 3.2.
© Max Planck Society and the author(s)