Partially ejected flux ropes: Implications for interplanetary coronal mass ejections

Connecting interplanetary coronal mass ejections (ICMEs) to their solar pre-eruption source requires a clear understanding of how that source may have evolved during eruption. Gibson and Fan (2006a) have presented a three-dimensional numerical magnetohydrodynamic simulation of a CME, which showed how, in the course of eruption, a coronal flux rope may writhe and reconnect both internally and with surrounding fields in a manner that leads to a partial ejection of only part of the rope as a CME. In this paper, we will explicitly describe how the evolution during eruption found in that simulation leads to alterations of the magnetic connectivity, helicity, orientation, and topology of the ejected portion of the rope so that it differs significantly from that of the pre-eruption rope. Moreover, because a significant part of the magnetic helicity remains behind in the lower portion of the rope that survives the eruption, the region is likely to experience further eruptions. These changes would complicate how ICMEs embedded in the solar wind relate to their solar source. In particular, the location and evolution of transient coronal holes, topology of magnetic clouds ("tethered spheromak"), and likelihood of interacting ICMEs would differ significantly from what would be predicted for a CME which did not undergo writhing and partial ejection during eruption.