Enrichment of heavy nuclei in ^3He-rich flares

Abstract

Five ^3He-rich solar-flare particle events were observed in 1973-1974 with ^3He/^4He ranging from 0.2 to ~8 at 2.9-12.7 MeV per nucleon. In all five events the (Z ≥ 6)/^1H ratio at ~3 MeV per nucleon was enriched by ~10 to ~100 times and the (Z ~ 6)/^4He ratio was enriched by ~3 to ~30 times, when compared with average solar-particle abundances measured over this 2-year period. It is suggested that the simultaneous enhancement of Z ≥ 6 and ^3He nuclei and the absence of ^2H and ^3H may be partly due to a preferential acceleration process which depends on the Z^2/A of the nuclei.

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