The Solar Connection of Enhanced Heavy Ion Charge States in the Interplanetary Medium: Implications for the Flux-Rope Structure of CMEs

Abstract

We investigated a set of 54 interplanetary coronal mass ejection (ICME) events whose solar sources are very close to the disk center (within 15 degrees from the central meridian). The ICMEs consisted of 23 magnetic cloud (MC) events and 31 non-MC events. Our analyses suggest that the MC and non-MC ICMEs have more or less the same eruption characteristics at the Sun in terms of soft X-ray flares and CMEs. Both types have significant enhancements in charge states, although the non-MC structures have slightly lower levels of enhancement. The overall duration of charge state enhancement is also considerably smaller than that than that in MCs as derived from solar wind plasma and magnetic signatures. We find very good correlation between the Fe and O charge state measurements and the flare properties such as soft X-ray flare intensity and flare temperature for both MCs and non-MCs. These observations suggest that both MC and non-MC ICMEs are likely to have a flux-rope structure and the unfavorable observational geometry may be responsible for the appearance of non-MC structures at 1 AU. We do not find any evidence for active region expansion resulting in ICMEs lacking a flux rope structure because the mechanism of producing high charge states and the flux rope structure at the Sun is the same for MC and non-MC events.