High energy gamma radiation above 300 keV associated with solar activity

The present status of knowledge concerning the production of gamma-ray lines and continuum during the impulsive phase of solar flares is reviewed. The data in this field is based solely on the OSO-7 observations made in 1972, August 4 and August 7. The experimental data is reviewed. These observations along with theoretical work of Ramaty and Lingenfelter (1973) and the charged secondary observations of the Chicago group (Anglin et al., 1973) lead to the investigation of different hypothetical models to explain the production of neutral and charged secondaries in the solar atmosphere. At the present time it is not possible to rule out the preflare and postflare accumulation models if all the data is considered. The outstanding experimental questions to be answered in future investigations are discussed. (Auth.)