Gamma-Ray Pulsars: Radiation Processes in the Outer Magnetosphere

We describe an emission model for γ-ray pulsars based on curvature radiation-reaction-limited charges in the outer magnetosphere. We show how pair production on thermal surface flux can limit the acceleration zones; estimates for the efficiency of GeV photon production ηγ and the γ-ray beaming fraction are derived, including their dependence on pulsar parameters. In general, ηγ increases with pulsar age but is decreased for low magnetic fields and for small magnetic inclinations. We argue that this produces GeV pulse profiles, curvature spectra, and detection statistics consistent with the observations. We also describe the optical through X-ray pulsar synchrotron spectrum and the spectral variations with pulsar phase. A test computation for Vela-like parameters reproduces phase-resolved GeV spectra consistent with those observed by EGRET. Finally, we comment on very high energy pulsed emission and particle production and note extensions needed to allow a more complete pulsar model.