par Ackermann, Markus;Gustafsson, Michael ; [et al.]
Référence Physical review letters, 112, 15, 151103
Publication Publié, 2014-04
Article révisé par les pairs
Résumé : Recent accurate measurements of cosmic-ray (CR) species by ATIC-2, CREAM, and PAMELA reveal an unexpected hardening in the proton and He spectra above a few hundred GeV, a gradual softening of the spectra just below a few hundred GeV, and a harder spectrum of He compared to that of protons. These newly discovered features may offer a clue to the origin of high-energy CRs. We use the Fermi Large Area Telescope observations of the -ray emission from Earthas limb for an indirect measurement of the local spectrum of CR protons in the energy range 90GeV-6TeV (derived from a photon energy range 15 GeV-1 TeV). Our analysis shows that single power law and broken power law spectra fit the data equally well and yield a proton spectrum with index 2.68±0.04 and 2.61±0.08 above 200GeV, respectively. © 2014 American Physical Society.