Inferred Cosmic-Ray Spectrum from Fermi Large Area Telescope γ-Ray Observations of Earth’s Limb

Collaboration
Mar 21, 2014
7 pages
Published in:
  • Phys.Rev.Lett. 112 (2014) 151103
  • Published: Apr 17, 2014
e-Print:
Report number:
  • FERMILAB-PUB-14-378-A
Experiments:

Citations per year

20142016201820202022024681012
Abstract: (APS)

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 90GeV6TeV (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.

Note:
  • Accepted by PRL for publication; Contact authors: Stefan Funk, Warit Mitthumsiri, Igor Moskalenko; 2 figures
  • 96.50.sb
  • 95.85.Pw
  • 95.85.Ry
  • 98.70.Sa
  • p: spectrum
  • cosmic radiation: spectrum
  • photon: energy
  • helium: spectrum
  • gamma ray: emission
  • GLAST