MMS FPI Observations of Flux Transfer Events with Cold Ions at the Dayside Magnetopause

The Magnetospheric Multiscale (MMS) spacecraft, launched in March 2015, has been integral to the advancement of the science of solar wind - magnetosphere interaction, including the reconnection physics in the subsolar region. This study uses data from field and particle instruments onboard MMS to investigate the effect of terrestrial, low-energy (<100 eV) ions on the dynamic processes driven by dayside magnetic reconnection. The Fast Plasma Investigation (FPI) dual electron and ion spectrometers (DES and DIS) onboard MMS, has made it possible to investigate transient characteristics of magnetospheric and ionospheric ion populations. The sensitivity of the plasma instruments on MMS allow for direct, 150 ms resolution observations of ionospheric ions coincident with transient sheath plasma. Flux transfer events (FTEs) are an important form of transport of energy and particles associated with magnetospheric dynamics. FTEs enable mixing of magnetosheath and magnetospheric, including ionospheric ions, plasmas. Here we report a series of case studies of FTEs with cold ions. Different techniques, such as flux rope modeling, four spacecraft timing, and comparing velocity distributions, will be used to gain a more complete understanding of how ionospheric ions interact with features near the magnetopause.