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 gamma-ray emission from Earth's limb for an indirect measurement of the local spectrum of CR protons in the energy range similar to 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 similar to 200 GeV, respectively.
Inferred Cosmic-Ray Spectrum from Fermi Large Area Telescope gamma-Ray Observations of Earth's Limb / 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; DAmmando F; de Angelis A; de Palma F; Dermer CD; Digel SW; Di Venere L; Silva EDE; 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; Johannesson G; Johnson AS; Kamae T; Kawano T; Knodlseder 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; 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; Raino S; Rando R; Razzano M; Razzaque S; Reimer A; Reimer O; Ritz S; Roth M; Schaal M; Schulz A; Sgro C; Siskind EJ; Spandre G; Spinelli P; Strong AW; Takahashi H; Takeuchi Y; Thayer JG; Thayer JB; Thompson DJ; Tibaldo L; Tinivella M; Torres DF; Tosti G; Troja E; Tronconi V; Usher TL; Vandenbroucke J; Vasileiou V; Vianello G; Vitale V; Werner M; Winer BL; Wood KS; Wood M; Yang Z. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - STAMPA. - 112:15(2014), pp. 151103.1-151103.7. [10.1103/PhysRevLett.112.151103]
Inferred Cosmic-Ray Spectrum from Fermi Large Area Telescope gamma-Ray Observations of Earth's Limb
D'AMMANDO, FILIPPO;
2014
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 gamma-ray emission from Earth's limb for an indirect measurement of the local spectrum of CR protons in the energy range similar to 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 similar to 200 GeV, respectively.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
