Correlation between arrival directions and sources of cosmic ray positrons (AMS-02)

Since the high-precision measurement of the cosmic ray positron component was published in 2014, the astrophysical community has yet to agree on the source of the positron population at kinetic energies above a few GeV. The two most popular explanations assume either an astrophysical acceleration mechanism around pulsar magnetospheres, or understand these positrons as a product of dark matter annihilation processes; and it is currently believed that a clear distinction can be made by the analysis of the dipole anisotropy in positron flux. In particular, it is currently assumed that the pulsar hypothesis is falsifiable if the anisotropy of positrons relative to electrons lies below 1% (for energies 16 to 350 GeV). We demonstrate that the state of knowledge of close-by pulsars is sufficiently uncertain to construct various pulsar scenario explanations for the present AMS-02 measurement that show a significantly smaller degree of anisotropy. Moreover, the propagation of positrons throughout the local environment further increases the uncertainty in anisotropy prediction considerably.