Global distribution of the solar wind during solar cycle 23: ACE observations

The composition of the solar wind can be used to determine its origin at the Sun; e. g., solar wind from coronal holes has demonstrably lower charge states than solar wind of other origins. The O7+/O6+ ratio as measured by Advanced Composition Explorer (ACE) during 1998 2008 is used to divide the solar wind into three categories: non-transient solar wind from coronal holes (hereafter referred to as CHW); non-transient solar wind that originates from outside of coronal holes (hereafter referred to as NCHW), and solar wind associated with transient interplanetary coronal mass ejections (ICMEs). The global distribution of the solar wind relative to the Heliospheric Current Sheet (HCS), as specified by a Potential-Field-Source-Surface model, is then determined. The solar wind from outside of coronal holes is found to originate from a band of about 40 degrees in width about the HCS during solar maximum conditions, and a much smaller band of < 17 degrees during solar minimum. These results are consistent with models for the global transport of the solar magnetic field during the solar cycle, and they are consistent with earlier global flow structure determinations based upon velocity alone. Citation: Zhao, L., T. H. Zurbuchen, and L. A. Fisk (2009), Global distribution of the solar wind during solar cycle 23: ACE observations, Geophys. Res. Lett., 36, L14104, doi:10.1029/2009GL039181.