  The study of pulsars in the three and a half decades since their discovery
has highlighted a handful of issues critical to their understanding. To date
there is no consensus on the physical mechanism for their radio radio emission,
despite a rapid increase in the observed population due to the Parkes
Multi-Beam survey and prospects for similar growth in the radio population
database in the near future. The small subset of pulsars that emit at X-ray to
gamma-ray wavelengths are critical to refining the pulsar paradigm since this
energy band (i) is where the vast majority of radiative luminosity is observed,
and (ii) is intimately connected to the pair winds that form the dominant mode
of energy deposition in the circum-pulsar environment. The most crucial point
of contention pertaining to the high energy astrophysics of pulsars is the
location of the acceleration region in their magnetospheres: is an outer gap
model or a polar cap scenario (or both) the most appropriate picture. Radiative
signatures provide the clues to this current enigma. This review focuses on
salient characteristics of the polar cap scenario; these form the basis for
discriminating observational diagnostics that should drive pulsars studies in
the GLAST era just three years away.
