Gamma ray lines from solar flares and cosmic transients

Gamma-ray line emission processes in solar flares and cosmic transients are reviewed and the implications of recent line observations are discussed. For solar flares, neutron, positron, and deexcitation line production is addressed, presenting results of new numerical calculations based on more detailed and accurate nuclear cross sections. The application of the theory is illustrated by considering the June 7, 1980 flare, and the structure of the interaction region is discussed. For gamma-ray bursts and transients, the processes of positron production and annihilation and nuclear line emission are emphasized. The possible origin of the gamma-ray lines observed in a longer duration transient which is a particularly strong gamma-ray line emitter is also considered