Inferred cosmic-ray spectrum from \({\it Fermi}\)-LAT \(\gamma\)-ray observations of the Earth's limb

Inferred cosmic-ray spectrum from \({\it Fermi}\)-LAT \(\gamma\)-ray observations of the Earth's limb

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 ne...

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Veröffentlicht in:arXiv.org 2014-03
Hauptverfasser: Ajello, M, Albert, A, Baldini, L, Barbiellini, G, Bechtol, K, Bellazzini, R, Bloom, E D, Bottacini, E, Brigida, M, Buson, S, Caliandro, G A, Cameron, R A, Caraveo, P A, Cecchi, C, Charles, E, Chekhtman, A, Chiaro, G, Ciprini, S, Claus, R, Cohen-Tanugi, J, Conrad, J, D'Ammando, F, Dermer, C D, L Di Venere, E do Couto e Silva, Favuzzi, C, Ferrara, E C, Focke, W B, Franckowiak, A, Fukazawa, Y, Funk, S, Fusco, P, Gargano, F, Gasparrini, D, Germani, S, Giroletti, M, Godfrey, G, Gomez-Vargas, G A, Grenier, I A, Grove, J E, Guiriec, S, Gustafsson, M, Hanabata, Y, Harding, A K, Hayashida, M, Hewitt, J W, Horan, D, Hughes, R E, Inoue, Y, Jogler, T, Jóhannesson, G, Kamae, T, Kawano, T, Kuss, M, Lande, J, Latronico, L, Longo, F, Lubrano, P, Mayer, M, Mehault, J, Michelson, P F, Mitthumsiri, W, Moiseev, A A, Morselli, A, Moskalenko, I V, Murgia, S, Nemmen, R, Nuss, E, Okumura, A, Orienti, M, Paneque, D, Panetta, J H, Perkins, J S, Pesce-Rollins, M, Piron, F, Pivato, G, Razzano, M, Razzaque, S, Reimer, A, Reimer, O, Schaal, M, Schulz, A, Spandre, G, Strong, A W, Takahashi, H, Takeuchi, Y, Thayer, J G, Thayer, J B, Thompson, D J, Tibaldo, L, Tinivella, M, Tosti, G, Troja, E, Usher, T L, Vandenbroucke, J, Vasileiou, V, Vitale, V, Werner, M, Winer, B L, Wood, M
Format: Artikel
Sprache:eng
Schlagworte:
Cosmic rays
Earth limb
Gamma rays
Power law
Spectra
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Zusammenfassung: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 \({\it Fermi}\) Large Area Telescope observations of the \(\gamma\)-ray emission from the Earth's limb for an indirect measurement of the local spectrum of CR protons in the energy range \(\sim 90~\)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 \(2.68 \pm 0.04\) and \(2.61 \pm 0.08\) above \(\sim 200~\)GeV, respectively.
ISSN:2331-8422