Elemental Abundances of Prominence Material inside ICMEs

Abstract

A small number of interplanetary coronal mass ejections (ICMEs) have been identified that contain measurable contributions from prominence plasma. In situ measurements from during these events are marked by the presence of unusually low-charge states of C, O, and Fe, representing ionization equilibrium formation temperatures of ∼10 4 –10 5 K, consistent with prominence material observed at the Sun. We present a thorough analysis of the elemental abundances of a wide variety of heavy ions, measured by Advanced Composition Explorer/SWICS, in prominence material observed in the solar wind. We find that prominence material observed in situ tends to be more enriched in heavy ions than the surrounding ICME plasma and the fast and slow solar wind. We also find that the material is on average moderately enhanced in low first ionization potential elements compared to photospheric abundances, with values that lie between fast and slow solar wind. In rare instances, where in situ prominence material is observed to have clear, persistent, low-charge states over longer periods of time, it exhibits elemental abundances that are photospheric in nature. However, in most prominence events we see indications that the associated material contains a mixture of prominence and adjacent ICME plasma. The anomalous behavior of the elemental and ionic composition in ICMEs with and without prominence material can be used to study physical processes that occur during CME initiation and release.