Slide 46 of 59
Notes:
For periodic pulses to appear from a rotating neutron star, it is necessary that the radiation is highly directional.
We also have to take into account the coherence of radio emission (at least) and possibly differences in the location of the source of radiation at different frequencies (eg radio and X-ray emission may not be emitted from the same regions).
There are essentially two models :
1. Magnetic poles. Supporting evidence from this model comes from radio beam widths and polarization of the emission. Another possibility is magnetic braking where waves are emitted from the polar caps.
2. Light cylinder. The evidence for this theory is from the fact that high energy radiation is only observed from young pulsars with short periods.