Ackermann, M.M.AckermannAjello, M.M.AjelloAlbert, A.A.AlbertCiprini, StefanoStefanoCipriniCutini, SaraSaraCutiniGasparrini, DarioDarioGasparrini2020-09-172020-09-172014-04-01https://hdl.handle.net/20.500.13025/3853Physical Review Letters, Volume 112, Issue 15, id.151103Recent 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 gamma-ray emission from Earth's limb for an indirect measurement of the local spectrum of CR protons in the energy range ˜90 GeV-6 TeV (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 2.680.04 and 2.610.08 above ˜200 GeV, respectively.10.1103/PhysRevLett.112.151103http://adsabs.harvard.edu/abs/2014PhRvL.112o1103A2014PhRvL.112o1103A