Cosmic ray positron to electron ratio in the Galaxy: results of the fractional diffusion approach

The unexpected rise of the positron to electron ratio with energy in the 20 ÷ 100 GeV range has been recently observed by PAMELA. Later, it was also confirmed by Fermi-LAT. In the last experiment it was additionally detected that the positron fraction continues to rise between 100 and 200 GeV. We report the results of new calculations of the positron to electron ratio in the wide energy range. Fractional diffusion model was implemented to describe the particles propagation from sources. It is shown that a self-consistent description of the experimental data can be obtained if we assume that both positrons and electrons are injected into the interstellar medium by the sources with the same spectral exponent p ≈ 2.85. We have also found that the positron to electron ratio increases to a constant value of ∼ 0.22 for energies E > 100 GeV. This flattening of the positron fraction obtained in our model for E > 100 GeV can be examined in the near future by the AMS-02 experiment.