Production sites and mechanisms of discrete gamma-ray components of the Vela and Crab light curves

New results on the temporal and spectral characteristics of the high-energy (50 MeV to 5 GeV) gamma-ray emission from the Vela pulsar have become available from an new analysis of COS-B data. The total pulsed flux is found to exhibit longterm variability. Five discrete emission regions within the pulsar lightcurve have been identified, with the spectral characteristics and long-term behaviour being different. These characteristics differ significantly from those reported earlier for the gamma-ray emission from the Crab pulsar. The identification of the different components in the Vela gamma-ray lightcurve and different components, noted earlier, in the Crab X-ray lightcurve supports the idea that several source regions exist in different parts of the pulsars magnetospheres. The different spectral characteristics of these components indicate that different generating processes exist in each source. Geometrical pulsar models could explain many of these features.