  It is shown that the time-variability inherent in the ion-proton polar cap
leads naturally to growth of Langmuir modes on narrow bundles of magnetic flux
lines and that the observed size of micropulses is consistent with the smallest
such bundle that can plausibly support the growth of the modes. The
polarization of integrated profiles is revisited, specifically, the pi/2
position-angle jumps that are frequently observed accompanied by a zero in
polarization. The fact that radiation emitted above ion-proton polar caps is
not tangential to the local flux lines but has a finite angular distribution
proves to be the essence of understanding this phenomenon as is a constraint on
the shape of the polar cap. In principle, the behaviour should also be seen if
the form of the polar-cap ion-proton area in a single pulse satisfies certain
conditions which are explained here.
