  Recent multi-frequency measurements of pulse widths W50 for the long-period
pulsar J0250+5854 by Agar et al provide a unique insight to the emission
process owing to its small polar-cap radius. The frequency-dependence of W50
can be simply understood as a consequence of the emitting plasma remaining
under acceleration during the interval of radio emission. This is possible in a
plasma of ions and protons but not in one of high-multiplicity
electron-positron pairs. Extension of the model to the pulse profiles of the
general pulsar population is considered briefly.
