HR: 1340h
AN: SH23A-0311    [Abstracts]
TI: Gamma-Ray Observations of the 2005 January 20 Solar Flare
AU: * Murphy, R J
EM: murphy@ssd5.nrl.navy.mil
AF: Naval Research Laboratory, E.O. Hulburt Center for Space Research, Washington, DC 20375 United States
AU: Share, G H
EM: share@ssd5.nrl.navy.mil
AF: University of Maryland, Dept. of Astronomy, College Park, MD 20742 United States
AU: Smith, D M
EM:
AF: University of California at Santa Cruz, Inst. for Particle Physics, Santa Cruz, CA 95064 United States
AU: Shih, A H
EM:
AF: University of California at Berkeley, Space Science Laboratory, Berkeley, CA 94720 United States
AU: Lin, R L
EM:
AF: University of California at Berkeley, Space Science Laboratory, Berkeley, CA 94720 United States
AB: The RHESSI spectrometer observed the entire impulsive phase of the flare. The measured spectrum was dominated by the positron-electron annihilation line at 511 keV and neutron-capture line at 2223 keV above a continuum formed by electron bremsstrahlung and nuclear continuum. There is only weak evidence for narrow nuclear de-excitation lines. We show that such a gamma-ray spectrum can be produced by a population of accelerated particles with a very hard spectrum. We use the 511-keV/2222-keV line flux ratio to infer that the power-law index of accelerated particles >30 MeV was ~2.2. This index is similar to the event-averaged index observed in particles at 1 AU. We show that our calculations also suggest an impulsive SEP composition of accelerated particles with an alpha/p ratio > 0.1. This work has been funded by NASA DPR13,777G and ONR.
DE: 2139 Interplanetary shocks
DE: 7513 Coronal mass ejections (2101)
DE: 7514 Energetic particles (2114)
DE: 7519 Flares
DE: 7554 X-rays, gamma rays, and neutrinos
SC: SPA-Solar and Heliospheric Physics [SH]
MN: Fall Meeting 2005