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Determination of the Abundances of Subcoronal He and of Solar Flare Accelerated He-3 and He-4 from Gamma-Ray Spectroscopy  

Natalie Mandzhavidze   Submitted: 1999-11-04 18:01

A series of narrow gamma-ray lines at 0.339, 0.429, 0.478, 0.937, 1.00, 1.04, 1.05, and 1.08 result almost exclusively from the bombardment of ambient He, O, and Fe by accelerated α particles and He-3 nuclei. Study of these lines, combined with the Fe-56 line at 0.847 MeV and the O-16 line at 6.129 MeV, allows the determination of the abundances of α particles and He-3 accelerated in solar flares and of the ambient He in the gamma-ray production region in the solar atmosphere. Using the Solar Maximum Mission/GRS and Compton Gamma Ray Observatory/OSSE data for 20 flares, we find that with significance not exceeding about 2.5 sigma there are flares that exhibit α particle abundance enhancements α p>0.1), show evidence for the presence of accelerated He-3, and indicate ambient He abundance enhancements. In some cases the accelerated He-3/He-4 ~ 1 , and for essentially all of the flares He-3/He-4 could be 0.1, consistent with our earlier conclusion that in both impulsive and gradual flares the particles that interact and produce gamma rays are always accelerated by the same mechanism that operates in impulsive flares, namely, stochastic accelerati- acceleration through gyroresonant wave-particle interactions. The ambient He abundance enhancements suggest that there are chromospheric regions where He/O exceeds its photospheric value, a result that could have important implications for solar atmospheric dynamics.

Authors: N. Mandzhavidze, R. Ramaty, B. Kozlovsky
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Publication Status: ApJ, 1999, 518, 918
Last Modified: 1999-11-04 18:01
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Determination of the Abundances of Subcoronal He and of Solar Flare Accelerated He-3 and He-4 from Gamma-Ray Spectroscopy

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