Element abundances in solar (He-3) rich events

Abstract

The results of a survey of over 228 (He-3)-rich events, with He-3/H-4 of more than 0.1, observed by the ISEE-3 spacecraft from 1978 August through 1991 April. In these events the elements above C are enhanced relative to the corresponding abundances in the corona and the degree of enhancement increases with Z or A. The flare-to-flare variations in abundances are different in character from those seen in large proton events. For example, using Fe/C as a parameter to describe these variations, the slope of the least-squares fits to ln(X/C) vs ln(Fe/C), where X is the intensity of N, O, Ne, Mg, Si, or S. Slopes of these abundance-correlation lines are much steeper for the (He-3)-rich events than for a sample of 36 large proton events, especially for Ne and heavier ions. The event-to-event variations for the (He-3)-rich events distinguish 3 groups of elements, He-O, Ne-S, and Fe. The abundances of all of the species within each group seem to vary in unison.