LEPTONIC ORIGIN OF DIFFUSE GALACTIC HIGH-ENERGY GAMMA-RAYS - INDICATIONS FOR A VARYING COSMIC-RAY PROTON-TO-ELECTRON RATIO

The flux of high-energy (> 300 MeV) gamma rays, caused by non-thermal bremsstrahlung and inverse Compton scattering, and the synchrotron flux at 408MHz are calculated with the same power-law spectrum of relativistic electrons. We compare both with the values observed at higher latitudes in the anticentre direction by employing the COS-B data and the 408MHz survey of Haslam et al. (1982). It is shown, that with column densities for the interstellar gas taken from the literature the cosmic ray electron component accounts for nearly the total gamma-flux, provided the magnetic field strength is of the order 3-4-mu-G with an equivalent half-thickness of about 1200pc. These findings demand a decrease of the cosmic ray proton-to-electron ratio at higher latitudes in the anticentre direction compared to the value observed in the solar vicinity.