Pulsar-wind origin of cosmic-ray positrons

We show that the electron-positron pairs produced in the magnetosphere of a pulsar can be accelerated monoenergetically to relativistic energies in the wind driven by low-frequency electromagnetic waves. The final achievable energy, depending on the surface magnetic field and rotation period of the individual pulsar, is mostly in the range 10(-2) -10(2) GeV. Based on the pair production rate of the individual pulsars and the Galactic pulsar population, the electron-positron flux from the Galactic pulsars is estimated from a statistical analysis of the observed pulsar data. We find that the flux is enough to account for the measured positron fraction and that its energy spectrum well matches the measured one. Our model predicts that the positron fraction will rise with increasing energy until its peak value at 30 GeV and then drop off.