One-dimensional electric field structure of an outer gap accelerator – I. γ-ray production resulting from curvature radiation |
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| Authors: | K Hirotani S Shibata |
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| Institution: | National Astronomical Observatory, Osawa, Mitaka, Tokyo 181-8588, Japan; Department of Physics, Yamagata University, Yamagata 990-8560, Japan |
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| Abstract: | We study the structure of a stationary and axisymmetric charge-deficient region (or potential gap) in the outer magnetosphere of a spinning neutron star. Assuming the existence of global current flow patterns in the magnetosphere, the charge depletion causes a large electric field along the magnetic field lines. This longitudinal electric field accelerates migratory electrons and/or positrons to ultrarelativistic energies. These relativistic electrons/positrons radiate γ -ray photons by curvature radiation. These γ -rays, in turn, produce yet more radiating particles by colliding with ambient X-ray photons, leading to a pair production cascade in the gap. The replenished charges partially screen the longitudinal electric field, which is self-consistently solved together with the distribution of e± and γ -ray photons. We find the voltage drop in the gap as a function of the soft photon luminosity. It is demonstrated that the voltage drop is less than 3×1013 V when the background X-ray radiation is as luminous as Vela . However, this value increases with decreasing X-ray luminosity and attains 3×1015 V when the X-ray luminosity is as low as L X=1031 erg s?1. |
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| Keywords: | magnetic fields pulsars: general gamma-rays: theory |
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