  Recent results from the PAMELA satellite indicate the presence of a large
flux of positrons (relative to electrons) in the cosmic ray spectrum between
approximately 10 and 100 GeV. As annihilating dark matter particles in many
models are predicted to contribute to the cosmic ray positron spectrum in this
energy range, a great deal of interest has resulted from this observation.
Here, we consider pulsars (rapidly spinning, magnetized neutron stars) as an
alternative source of this signal. After calculating the contribution to the
cosmic ray positron and electron spectra from pulsars, we find that the
spectrum observed by PAMELA could plausibly originate from such sources. In
particular, a significant contribution is expected from the sum of all mature
pulsars throughout the Milky Way, as well as from the most nearby mature
pulsars (such as Geminga and B0656+14). The signal from nearby pulsars is
expected to generate a small but significant dipole anisotropy in the cosmic
ray electron spectrum, potentially providing a method by which the Fermi
gamma-ray space telescope would be capable of discriminating between the pulsar
and dark matter origins of the observed high energy positrons.
