On the bulk isotopic composition of magnesium and silicon during the May 1998 CME: ACE/SWIMS

Publisher Website
Google Scholar
Abstract
The coronal mass ejection (CME) observed at the Advanced Composition Explorer (ACE) spacecraft on May 2 and 3, 1998, exhibited very high as well as exceptionally low charge states of all ions. In addition, ³He was considerably enhanced by in the bulk material of the CME. High ³He/4He ratios in solar energetic particles have recently been observed in some events to coincide with substantial enrichments in the heavy isotopes of heavy elements. We use data from the Solar Wind Ion Mass Spectrometer (SWIMS) on ACE to investigate whether the enrichment of the heavy isotopes in solar energetic particles is mirrored in the isotopic composition of solar wind Mg and Si. We concentrate on the time period where the unusual mixture of charge states and unusually high ³He/4He was observed to test for isotopic fractionation in such extreme solar wind conditions. We find very little or no enrichment of the neutron‐rich isotopes with respect to the main isotopes. Incidentally, this is also the first report on the isotopic composition of ions with Z > 2 in the bulk material in a CME.