Pulsar-Wind Origin of Cosmic-Ray Positrons

Abstract

We show that the electron-positron pairs produced in the magnetosphere of a pulsarcan be accelerated monoenergetically to relativistic energies inthe wind driven by low-frequency electromagnetic waves. The finalachievable energy, depending on the surface magnetic field and rotationperiod of the individual pulsar, is mostly in the range 10-2--102 GeV.Based on the pair production rate of the individual pulsars and theGalactic pulsar population, the electron-positron flux from the Galacticpulsars is estimated from a statistical analysis of the observed pulsardata. We find that the flux is enough to account for the measuredpositron fraction and that its energy spectrum well matches the measuredone. Our model predicts that the positron fraction will rise withincreasing energy until its peak value at 30 GeV and then drop off.