High-energy gamma rays probing cosmic-ray propagation.

The results of a spectral analysis of the gamma-ray observations made by the COS-B satellite are presented. The gamma-ray spectra of the inner and outer Galaxy are derived from local interstellar cosmic-ray spectra and are presented in graphs. It is concluded that the cosmic-ray proton spectrum between a few GeV and a few tens of GeV is flatter in the outer Galaxy than in the solar vicinity and inner Galaxy. It is suggested that the energy dependence of the cosmic-ray path length is flatter in the outer Galaxy, unless the cosmic-ray source spectrum is flatter.