Interpretations Of Rapid Gamma-ray Variability In The Crab Nebula

Recent observations of the Crab Nebula with FGST and AGILE have exhibited remarkable variability at 70-2000MeV energy on timescales as short as an hour. There is little evidence for correlated variation at other wavelengths. The ways in which these observations challenge our understanding of particle acceleration in four candidate emission sites - the wind, its shock, the jet and the torus - will be described. A new critique of electrostatic acceleration as a means of emitting high energy photons will be presented. It will be argued that the first option now seems indicated by the available evidence. Some particular models will be outlined and their observable implications discussed relating especially to the recently reported observation of 150 GeV pulsation from the pulsar.