DIFFUSE GALACTIC HARD X-RAY AND LOW-ENERGY GAMMA-RAY CONTINUUM

We summarize some recent results related to observations and interpret ation of hard X-ray and low-energy gamma-ray diffuse Galactic continuu m emission. Combined spectra based on data from OSSE, COMPTEL and EGRE T are presented. In the energy range 1-30 MeV covered by COMPTEL the s pectrum of the diffuse emission has been measured and is consistent wi th a combination of bremsstrahlung and inverse-Compton emission; spati al analysis shows strong evidence for a component with a wide latitude extent which is plausibly identified with inverse-Compton. Molecular hydrogen appears to be only a weak gamma-ray emitter at low energies, which may indicate reduced MeV cosmic-ray electron density in molecula r clouds. New data on the hard X-ray diffuse Galactic emission from OS SE indicates the need for a dramatic low-energy upturn in the electron spectrum, or for some other additional component of gamma-ray emissio n. The interstellar electron spectrum has been computed using a diffus ive halo model and the resulting bremsstrahlung and inverse-Compton em ission is compared with the observations.