Cosmic ray gradients in the outer Galaxy

The release of basic cosmic gamma ray data from the COS B satellite experiment has enabled a more detailed analysis than hitherto of the problem of variations of cosmic ray intensity locally and in the Outer Galaxy. It is found that there is still evidence for a modest cosmic ray gradient, particularly at the highest gamma ray energies where the progenitors are mainly protons, the average cosmic ray intensity in the 2nd quadrant is a little higher than that in the 3rd quadrant. Finally, there is a correlation, albeit at a low level of significance, between the longitude dependence of the mean cosmic ray intensity and that expected from the model of cosmic ray acceleration in supernova remnants. The earlier contention that the bulk of the proton component of cosmic rays is of Galactic origin is therefore, if not strongly confirmed, at least not denied.