Authors: Liang Zhao(U of Michigan), Enrico Landi(U of Michigan), Susan T. Lepri(U of Michigan), Daniel Carpenter (U of Michigan)

The exact coronal origin of the slow-speed solar wind has been under debate for decades in the Heliophysics community. Besides the solar wind speed, the heavy ion composition, including the elemental abundances and charge state ratios, are widely used as diagnostic tool to investigate the coronal origins of the slow wind, because the freeze-in process makes the wind’s composition do not change after it is accelerated from the base of the corona. In this study, we recognize a subset of slow speed solar wind that is located on the upper boundary of the scattered plot in the 2D O7+/O6+ versus C6+/C5+ frame (O-C plot). In addition, in these wind, the heavy ion abundances over the density of proton, such as N/P, O/P, Ne/P, Mg/P, Si/P, S/P, Fe/P, He/P, and C/P are systemically depleted. We compare these winds (“upper depleted wind” or UDW hereafter) with the slow wind that are located in the main stream of the O-C plot and possess comparable Carbon abundance range as the depletion wind (“normal-depletion-wind”, or NDW hereafter). We find that the proton density in the UDW is about 27.5% lower than in the NDW. Charge state ratio of C6+/C5+,  C6+/P,  C5+/P, O7+/O6+,O7+/P, and O6+/P are decreased by 16.8%, 17.8%, 14.5%, 64.4%, 61.7%, and 6.3%, respectively. The occurrence rate of these UDW is anti-correlated with solar cycle: more in solar minimum and less in solar maximum. By tracing the wind along PFSS field lines back to the Sun, we realize that the coronal origins of the UDW are more likely associated with quiet Sun regions, while the NDW are mainly associated with both quiet Sun and active regions.