Inner-source Pickup Ions Observed in Conjunction with Coronal Mass Ejections

Inner-source pickup ions are singly or doubly charged ions observed in the heliosphere and characterized by a composition and heliospheric extent which is inconsistent with an interstellar gas source. Several sources have been suggested to contribute to the inner-source population, including dust, gas from planets or sun-grazing comets, and solar wind particles that are absorbed by dust grains and then re-emitted. These sources, however, cannot adequately explain some composition measurements of low-charge (low-q) ions. This study examines a population of low-q ions associated with interplanetary coronal mass ejections (ICMEs). These may be of solar origin, presumably related to cold solar filament material, or they may be picked up from inner-source material as the ICME expands outward. A survey of ACE-SWICS composition data indicates that a significant fraction of identified ICMEs are associated with density enhancements in low-q ions. These low-q events are characterized according to their frequency, composition, and their relation to previously identified ICMEs containing cold filament material.