Inferred cosmic-ray spectrum from fermi large area telescope -Ray Observations of Eartha's Limb

• Main Authors: M. Ackermann, M. Ajello, A. Albert, A. Allafort, L. Baldini, G. Barbiellini, D. Bastieri, K. Bechtol, R. Bellazzini, R. D. Blandford, E. D. Bloom, E. Bonamente, E. Bottacini, A. Bouvier, T. J. Brandt, M. Brigida, P. Bruel, R. Buehler, S. Buson, G. A. Caliandro, R. A. Cameron, P. A. Caraveo, C. Cecchi, E. Charles, R. C.G. Chaves, A. Chekhtman, J. Chiang, G. Chiaro, S. Ciprini, R. Claus, J. Cohen-Tanugi, J. Conrad, S. Cutini, M. Dalton, F. Dammando, A. De Angelis, F. De Palma, C. D. Dermer, S. W. Digel, L. Di Venere, E. Do Couto E Silva, P. S. Drell, A. Drlica-Wagner, C. Favuzzi, S. J. Fegan, E. C. Ferrara, W. B. Focke, A. Franckowiak, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, D. Gasparrini, S. Germani, N. Giglietto, F. Giordano, M. Giroletti, T. Glanzman, G. Godfrey, G. A. Gomez-Vargas, I. A. Grenier, J. E. Grove, S. Guiriec, M. Gustafsson, D. Hadasch, Y. Hanabata, A. K. Harding, M. Hayashida, K. Hayashi, J. W. Hewitt, D. Horan, X. Hou, R. E. Hughes, Y. Inoue, M. S. Jackson, T. Jogler, G. Jóhannesson, A. S. Johnson, T. Kamae
• Other Authors: Deutsche Elektronen-Synchrotron
• Format: Article
• Published: 2018
• Subjects: Physics and Astronomy
• Online Access: https://repository.li.mahidol.ac.th/handle/123456789/34926
• Institution: Mahidol University

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 -ray emission from Earthas limb for an indirect measurement of the local spectrum of CR protons in the energy range 90GeV-6TeV (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 200GeV, respectively. © 2014 American Physical Society.