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Physical Review Letters 108 (2012) 051105
Low-Energy Break in the Spectrum of Galactic Cosmic Rays
A. Neronov1, D.V. Semikoz2, A.M. Taylor1

Measurements of the low-energy spectrum of Galactic cosmic rays (GCRs) by detectors on or near Earth are affected by solar modulation. To overcome this difficulty, we consider nearby molecular clouds as GCR detectors outside the Solar System. Using γ-ray observations of the clouds by the Fermi telescope, we derive the spectrum of GCRs in the clouds from the observed γ-ray emission spectrum. We find that the GCR spectrum has a low-energy break with the spectral slope hardening by ΔΓ=1.1±0.3 at an energy of E=9±3GeV. Detection of a low-energy break enables a measurement of GCR energy density in the interstellar space U=0.9±0.3eV/cm3.
1 :  ISDC - INTEGRAL Science Data Center
2 :  APC - UMR 7164 - AstroParticule et Cosmologie
Physique/Astrophysique/Phénomènes cosmiques de haute energie

Planète et Univers/Astrophysique/Phénomènes cosmiques de haute energie
Cosmic rays – gamma-ray – Interstellar medium and nebulae in Milky Way
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