Fermi Gamma-ray Space Telescope

Accelerated 3He Reactions in Solar Flares

R. J. Murphy
B.-Z. Kozlovsky, G. H. Share

Abstract:

An important, unsolved problem in solar research that can be addressed with gamma-ray spectroscopy is the relationship of 3He-rich solar energetic particle events and solar flares. If the flare-accelerated ions were shown to also have this enhanced composition, this would directly tie 3He-rich events to solar flares. We have now included accelerated 3He reactions with heavy elements in our nuclear deexcitation-line computer code that calculates the expected gamma-ray spectrum from interactions of accelerated ions with the ambient solar atmosphere. We discuss these reactions and the unique character of the 3He excitation. We identify spectral diagnostics that would reveal the presence of accelerated 3He, including lines that are produced strongly by 3He but only weakly (or not at all) by protons and alpha particles and lines that are also produced by protons or alpha particles, but the excitation by 3He has special properties due to the unique nature of the production cross section. We discuss spectral analysis techniques to derive the accelerated-ion composition (including 3He) and the composition of the ambient solar atmosphere where the ions interact to produce gamma rays.