Abundances of Trans-Iron Elements in Solar Energetic Particle Events

Abstract

We report the first comprehensive observation of the abundances of heavy elements of atomic number Z in the range 34 ≤ Z ≤ 82 in solar energetic particle (SEP) events as observed on the Wind spacecraft. In large gradual SEP events, abundances of the element groups 34 ≤ Z ≤ 40, 50 ≤ Z ≤ 56, and 70 ≤ Z ≤ 82, relative to Fe, are similar to corresponding coronal abundances within a factor of ∼2 and vary little with time during the events. However, in sharp contrast, abundances of these ions from impulsive flares increase dramatically with Z so that abundances of Fe, 34 ≤ Z ≤ 40, and 50 ≤ Z ≤ 56, relative to O, are seen at ∼10, ∼100, and ∼1000 times their coronal values, respectively.