A. Neronov, D. V. Semikoz, A. M. Taylor
Measurements of the low energy spectrum of Galactic Cosmic Rays (GCR) by
detectors at or near the Earth are affected by Solar modulation. To overcome
this difficulty, we consider nearby molecular clouds as GCR detectors outside
the Solar system. Using gamma-ray observations of the clouds by the Fermi
telescope we derive the spectrum of GCRs in the clouds from the observed
gamma-ray emission spectrum. We find that the GCR spectrum has a low energy
break with the spectral slope hardening by 1.1+/-0.3 at an energy of 9+/-3 GeV.
Detection of a low-energy break enables a measurement of GCR energy density in
the interstellar space 0.9+/-0.3 eV/cm3.
View original:
http://arxiv.org/abs/1112.5541
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