34th Solar Physics Division Meeting, June 2003
Session 15 Flares and Microflares I
Oral, Wednesday, June 18, 2003, 1:30-3:30pm, Auditorium

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[15.09] Gamma-Ray Spectral Evolution in the Solar Flare of 11 June 1991

J.M. Ryan (U. New Hampshire)

Three distinct phases of particle acceleration appear to be present in the COMPTEL data of the 11 June 1991 solar flare. The first and third phases both have hard components with gamma-ray emission above 10 MeV that we associate with either bremsstrahlung or pion decays. However, the intermediate, second, phase is characterized by an unusual spectrum that is rich in a lingering and prolonged emission from the formation of deuterium from free neutrons but relatively poor in the emission of lines from heavy nuclei, such as carbon and oxygen. We conclude that this is a result of an unusually soft ion population in the flare that is also relatively rich in heavy nuclei. Such a spectrum would produce many free neutrons that would take long to be captured and radiate but would produce little emission from inelastic collisions of heavy nuclei.


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Bulletin of the American Astronomical Society, 35 #3
© 2003. The American Astronomical Soceity.