Magnetospheric ion influence at the dayside magnetopause

Magnetospheric ions have the potential to affect magnetic reconnection at the magnetopause. The results of a survey of magnetospheric ions near the magnetopause are reported here. Composition measurements from the Magnetospheric Multiscale (MMS) mission are used to determine the total mass density of all magnetospheric ions and distinguish two populations of magnetospheric ions: the warm plasma cloak and the plasmaspheric drainage plume. The warm plasma cloak can contain substantial O+, and the plasmaspheric plume can contain substantial He+. The results of the survey show that, for nominal magnetospheric activity, the warm plasma cloak and plasmaspheric plume will reduce the normalized reconnection rate at the magnetopause by greater than 20% only a few percent of the time. Plain Language Summary Magnetic reconnection is the interconnection of magnetic fields that results in energy release. At the Earth's boundary with the solar wind, the magnetopause, reconnection occurs between the solar wind magnetic field and the Earth's magnetic field. Magnetic reconnection can be affected by the presence of high densities of cold ions that originate from the Earth's high latitude ionosphere. However, this study shows that under normal conditions in near-Earth space, the ion densities are too low to have a significant effect on the reconnection process.