Cosmic-ray positrons produced by pulsar winds from mature gamma-ray pulsars

Abstract

In the frame of the γ-ray pulsar outer gap model, e± pairs in the pulsar magnetosphere are produced by the cascade of e± pairs through synchrotron radiation of the return current from the outer gap. These pairs are accelerated mono-energetically to relativistic energies in the pulsar wind driven by low-frequency electromagnetic waves. Using Monte Carlo simulations, we generate a sample of the mature γ-ray pulsars in our Galaxy and calculate the positron production rate from these pulsars. With a simple leaky box model, we calculate the ratio of cosmic-ray positron to total electrons. Our result indicates that the pulsar contribution to the cosmic-ray positron peaks at about 40 GeV and the observed e+/(e- + e+) ratio can be explained by this model.