High-energy emission from pulsars: the polar cap scenario

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 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 is 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 magrietospheres: 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. (C) 2004 COSPAR. Published by Elsevier Ltd. All rights reserved.