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, R.D., Bloom, E.D., Bonamente, E., Bottacini, E., Bouvier, A., Brandt, T.J., Brigida, M., Bruel, P., Buehler, R., Buson, S., Caliandro, G.A., et al.. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 112:15(2014). [10.1103/PhysRevLett.112.151103]

Inferred Cosmic-Ray Spectrum from Fermi Large Area Telescope gamma-Ray Observations of Earth's Limb

FAVUZZI, Cecilia;Giglietto, Nicola;
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.
2014
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, R.D., Bloom, E.D., Bonamente, E., Bottacini, E., Bouvier, A., Brandt, T.J., Brigida, M., Bruel, P., Buehler, R., Buson, S., Caliandro, G.A., et al.. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 112:15(2014). [10.1103/PhysRevLett.112.151103]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11589/656
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