Origin of Cosmic Ray Electrons and Positrons

Abstract

With experimental results of AMS on the spectra of cosmic ray (CR) e^−, e^+, e^− + e^+ and positron fraction, as well as new measurements of CR e^− + e^+ flux by HESS, one can better understand the CR lepton (e^− and e^+) spectra and the puzzling electron–positron excess above ∼10 GeV. In this article, spectra of CR e^− and e^+ are fitted with a physically motivated simple model, and their injection spectra are obtained with a 1D propagation model including the diffusion and energy loss processes. Our results show that the electron–positron excess can be attributed to uniformly distributed sources that continuously inject into the galactic disc electron–positron with a power-law spectrum cutting off near 1 TeV and a triple power-law model is needed to fit the primary CR electron spectrum. The lower energy spectral break can be attributed to propagation effects giving rise to a broken power-law injection spectrum of primary CR electrons with a spectral hardening above ∼40 GeV.