Gamma rays in L-B coordinates at CORONAS-I altitude

Abstract. We present here observations of gamma rays in the energy range between 3.0 and 8.3 MeV gathered by the SONG instrument aboard low-altitude polar-orbiting satellite CORONAS-I throughout the period March-June 1994. We concentrate on the emissions related to the trapped particles and organize CORONAS-I measurements in the magnetic L–B coordinate system. The spatial distribution of the average gamma-ray counts reveals that the most intense fluxes were observed under the inner radiation belt, at L<2, and that they are exclusively confined into the region of stably trapped particles, where daughter gamma rays could result from the interactions within the spacecraft and instrumental matter. In the outer radiation zone (L~4), the enhanced gamma radiation, also detected outside the stably trapping region, shows pronounced longitudinal variations. The observed eastward increase in the gamma-ray count rate suggests quasi-traped energetic (megavolt) electrons as a source of the gamma rays both in the upper atmosphere and in the satellite matter, most likely, through the bremsstrahlung process in the studied energy domain.

Keywords. Magnetospheric physics (Energetic particles, precipitating; Energetic particles, trapped; Magnetosphereionosphere interactions)