Neutron Production in Solar Flares by Reactions of Accelerated 3He

Previously, we showed that He-3 is enhanced in the ion population accelerated in large solar flares, with a He-3/He-4 ratio of > 0.1; i.e., several orders of magnitude larger than the accepted coronal value. We also showed that when He-3 is enhanced, its nuclear reactions with elements of the solar atmosphere can significantly impact both positron production ( and the subsequent positron-annihilation line) and the gamma-ray de-excitation-line spectrum. Both the 2.223 MeV neutron-capture line and escaping neutrons are important additional flare observables. Neutron production from reactions of He-3 with heavy elements of the solar atmosphere are not currently included in our neutron-production code, and the reliable and consistent analysis of all available solar-flare data requires that neutron-production calculations include these reactions. We evaluate the neutron-production cross sections for these reactions and include them in the code. We then explore how the neutron observables ( the escaping-neutron yield and spectrum and the flux of the neutron-capture line) are affected by He-3 reactions. We find that neutron production by accelerated He-3 reactions with heavy elements is similar to that by accelerated He-4 and so will be significant only for accelerated He-3/He-4 ratios greater than 1.