학술논문
Inferred cosmic-ray spectrum from Fermi large area telescope γ-ray observations of Earth's limb.
Document Type
article
Author
Ackermann, M; Ajello, M; Albert, A; Allafort, A; Baldini, L; Barbiellini, G; Bastieri, D; Bechtol, K; Bellazzini, R; Blandford, RD; Bloom, ED; Bonamente, E; Bottacini, E; Bouvier, A; Brandt, TJ; Brigida, M; Bruel, P; Buehler, R; Buson, S; Caliandro, GA; Cameron, RA; Caraveo, PA; Cecchi, C; Charles, E; Chaves, RCG; Chekhtman, A; Chiang, J; Chiaro, G; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; Cutini, S; Dalton, M; D'Ammando, F; de Angelis, A; de Palma, F; Dermer, CD; Digel, SW; Di Venere, L; do Couto e Silva, E; Drell, PS; Drlica-Wagner, A; Favuzzi, C; Fegan, SJ; Ferrara, EC; Focke, WB; Franckowiak, A; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Germani, S; Giglietto, N; Giordano, F; Giroletti, M; Glanzman, T; Godfrey, G; Gomez-Vargas, GA; Grenier, IA; Grove, JE; Guiriec, S; Gustafsson, M; Hadasch, D; Hanabata, Y; Harding, AK; Hayashida, M; 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; Longo, F; Loparco, F; 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
Source
Physical review letters. 112(15)
Subject
Language
Abstract
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.