Differences in the O7+/O6+ ratio of magnetic cloud and non-cloud Coronal Mass Ejections

On its trajectory to Jupiter and over the poles of the Sun the Ulysses spacecraft has observed a considerable number of Coronal Mass Ejection (CME) transients in slow and in fast solar wind streams. The analysis of the magnetic field topology and the O7+/O6+ charge state ratio of 56 of these events has yielded strong evidence for a systematic connection between the two features. Coronal mass ejections with magnetic cloud structure have an increased O7+/O6+ ratio with respect to the ambient solar wind whereas non-cloud CMEs do not show enhanced O7+/O6+ ratios. We discuss possible mechanisms based on the freezing-in concept that can account for the observation.