Institute: MPI für Physik     Collection: YB 2016     Display Documents

ID: 716045.0, MPI für Physik / YB 2016
Inferred cosmic-ray spectrum from ${\\it Fermi}$-LAT $\\gamma$-ray observations of the Earth's limb
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Audience:Not Specified
Intended Educational Use:No
Abstract / Description: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.
Classification / Thesaurus:Fermi
Comment of the Author/Creator:Accepted by PRL for publication; Contact authors: Stefan Funk, Warit Mitthumsiri, Igor Moskalenko; 2 figures
Document Type:Article
Communicated by:MPI für Physik
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