Global-scale hybrid simulation of cusp precipitating ions associated with magnetopause reconnection under southward IMF

With a 3-D global-scale hybrid simulation model, we investigate the energy spectra of cusp precipitating ions and issues associated with magnetopause reconnection under a southward IMF. Both the spatial and temporal energy spectra of cusp precipitating ions are computed by tracing trajectories of the transmitted magnetosheath ions. The spatial spectrum shows a dispersive feature consistent with satellite observations, with higher energy particles at lower latitudes and lower energy particles at higher latitudes. The simulation reveals (1) how and where particles are transmitted from the solar wind into the magnetosphere via direct magnetic reconnection on the dayside; (2) how the features of the spectra are related to ongoing magnetic FTEs; and (3) how the motion of the cusp, particularly the latitudinal variation of the open/closed field line boundary, is correlated with the dayside reconnection and reflected in the energy flux spectra of the precipitating ions as a function of time.