- Main
Inferred Cosmic-Ray Spectrum from Fermi Large Area Telescope γ-Ray Observations of Earth’s Limb
- Ackermann, M;
- Ajello, M;
- Albert, A;
- Allafort, A;
- Baldini, L;
- Barbiellini, G;
- Bastieri, D;
- Bechtol, K;
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- Blandford, RD;
- Bloom, ED;
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- Brandt, TJ;
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- Caliandro, GA;
- Cameron, RA;
- Caraveo, PA;
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- do Couto e Silva, E;
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- Ferrara, EC;
- Focke, WB;
- Franckowiak, A;
- Fukazawa, Y;
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- Hayashi, K;
- Hewitt, JW;
- Horan, D;
- Hou, X;
- Hughes, RE;
- Inoue, Y;
- Jackson, MS;
- Jogler, T;
- Jóhannesson, G;
- Johnson, AS;
- Kamae, T;
- Kawano, T;
- Knödlseder, J;
- Kuss, M;
- Lande, J;
- Larsson, S;
- Latronico, L;
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- Lovellette, MN;
- Lubrano, P;
- Mayer, M;
- Mazziotta, MN;
- McEnery, JE;
- Mehault, J;
- Michelson, PF;
- Mitthumsiri, W;
- Mizuno, T;
- Moiseev, AA;
- Monte, C;
- Monzani, ME;
- Morselli, A;
- Moskalenko, IV;
- Murgia, S;
- Nemmen, R;
- Nuss, E;
- Ohsugi, T;
- Okumura, A;
- Orienti, M;
- Orlando, E;
- Ormes, JF;
- Paneque, D;
- Panetta, JH;
- Perkins, JS;
- Pesce-Rollins, M;
- Piron, F;
- Pivato, G;
- Porter, TA;
- Rainò, S;
- Rando, R;
- Razzano, M;
- Razzaque, S;
- Reimer, A;
- Reimer, O;
- Ritz, S;
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- Strong, AW;
- Takahashi, H;
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- Thayer, JG;
- Thayer, JB;
- Thompson, DJ;
- Tibaldo, L;
- Tinivella, M;
- Torres, DF;
- Tosti, G;
- Troja, E;
- Tronconi, V;
- Usher, TL;
- Vandenbroucke, J;
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- Yang, Z
- et al.
Published Web Location
https://doi.org/10.1103/physrevlett.112.151103Abstract
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 γ-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 2.68±0.04 and 2.61±0.08 above ∼200 GeV, respectively.
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