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Session 19 - Flares II.
Oral session, Tuesday, July 01
Ballroom A, Chair: Ronald Murphy
Based on SMM/GRS observations of narrow gamma ray lines from solar flares we have previously derived relative abundances of C, O, Ne, Mg, Si and Fe in the solar atmosphere (Ramaty et al. 1995, ApJ, 455, L193). The main results of that analysis were the demonstartion that the FIP effect is already present in the gamma ray production region and that Ne/O in that region is enhanced relative to its coronal value. In the present analysis we use new SMM/GRS data (from Share and Murphy, 1997, ApJ in press) to derive the ambient He abundance in the gamma ray production region. We use the 429 and 478 keV lines resulting from the interactions of accelerated alpha particles with He. Our main results are: (i) we show that the He/H is at least 0.1 and thus much higher than the He abundance is the corona and solar wind, and (ii) we provide an independent confirmation of our previous conclusion on the enhanced Ne abunance. Thus both He/O and Ne/O in the gamma ray production region are enhanced relative to their coronal abundances. We also confirm the conclusion of Share and Murphy that the accelerated alpha particle to proton ratio (alpha/p) has to be as high as 0.5 because the ambient He/H should not exceed 0.1 (from helioseismology). The systematic enhancement of alpha/p has important consequences on acceleration theory.
Program listing for Tuesday