Heavy Ions in the October 1989 Solar Flares Observed on the Galileo Spacecraft

Abstract

Composition measurements were made of the energetic particles produced in the series of large flares which began on 19 October 1989, using the Galileo Heavy Ion Counter which is sensitive to nuclei ranging from carbon (Z=6) to nickel (Z=28) over an energy range from about 5 MeV/nucleon to >70 MeV/nucleon. The observations are unique in that clean, statistically well-measured abundances are available for heavy ions for an unusually large flare. For elements with low First Ionization Potential (FIP), these results show the same correlation of relative abundances with the ion charge to mass ratio as the earlier Voyager observations of solar energetic particles 1 . After correction for selection on the basis of this charge to mass ratio, the abundances of all the elements measured show the expected step-function correlation with FIP, when compared to the spectroscopic photspheric abundances.