The Solar Wind Contribution to the Hot Plasma Sheet

The plasma sheet has contributions from both the ionospheric and the solar wind, and the source contributions can be determined by the composition. While H+ can come from both sources, He++ comes from the solar wind, while singly charged heavy ions like O+ come from the ionosphere. If there is no mass discrimination in the entry of the solar wind plasma, the fraction of the plasma that comes from the solar wind can be determined by comparing the He++/H+ ratio in the plasma sheet with the He++/H+ ratio in the solar wind. Using this method, our recent work has shown that during storm times, the composition of the near-earth plasma sheet can quickly change from solar wind dominated to ionosphere dominated. In this study, we will use comparisons of the MMS/HPCA and Wind/SWE He++/H+ measurements to perform a more systematic study of the contribution of the solar wind to the plasma sheet and how it varies in radial distance and MLT for different IMF orientations.