Energetic Radiation from Rapidly Spinning Pulsars. I. Outer Magnetosphere Gaps

Very rapidly spinning magnetized neutron stars such as the Crab and Vela pulsars are strong γ-ray sources with photon energies extending to 10¹²eV and possibly beyond. These special pulsars must contain extremely ultrarelativistic particle accelerators. In this paper the authors consider the origin and structure of particle accelerators in the outer magnetosphere of pulsars characterized by large spindown energy loss rates. The discussion is concerned with the class of (mainly young) pulsars which can sustain pair production in otherwise charge-depleted regions of the outer magnetosphere. The resulting electrostatic accelerating region ("gap") is expected to exist far from the neutron star, where a corotating magnetosphere would be rotating at speeds a significant fraction of c. The size and location of this gap supports the production of energetic radiation beams of quite different character from the usual coherent microwave emission of radio pulsars.