  A model for pulsars with polar-cap magnetic flux density B antiparallel with
rotational spin is described. It recognizes the significance of two elementary
processes, proton production in electromagnetic showers and photoelectric
transitions in ions accelerated through the blackbody radiation field, which
must be present at the polar cap in the antiparallel case, but not for pulsars
of the opposite spin direction. The two populations are likely to be
indistinguishable observationally until curvature radiation pair creation
ceases to be possible. The model generates, and provides a physically realistic
framework for, the polar-cap potential fluctuations and their time-scales that
can produce mode-changes and nulls. The RRATs are then no more than an extreme
case of the more commonly observed nulls. The model is also able to support the
basic features of subpulse drift and to some extent the null-memory phenomenon
that is associated with it. Unfortunately, it appears that the most important
neutron-star parameter for quantitative predictive purposes is the
whole-surface temperature, a quantity which is not readily observable at the
neutron-star ages concerned.
