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G. H. Share, R. J. Murphy (Naval Research Laboratory), J. Kiener, N. de Sereville, V. Tatischeff (CNRS/University Paris-South)
The energies and widths of gamma-ray lines emitted by ambient nuclei excited by flare-accelerated proton and alpha particles provide information on the particles' angular distributions, compositions, and spectra, and on the uniformity of the interaction region. We have measured the energies and widths of strong lines from de-excitations of 12C, 16O, and 20Ne in solar flares as a function of heliocentric angle. The line energies from all three nuclei exhibit ~1% redshifts at small heliocentric angles, but are not significantly shifted near the limb. The lines at all heliocentric angles have widths from ~2.5 to 4% (FWHM) of their rest energies. These results are suggestive of accelerated particles with a broad angular distribution that preferentially interact in the downward direction. We compare the 12C line measurements with calculations based on recent accelerator measurements and an optical model at higher energies. This work is supported by NASA DPR W-18,995.
The author(s) of this abstract have provided an email address for comments about the abstract: share@gamma.nrl.navy.mil