Dynamic response of cusp boundaries to IMF southward turning: global MHD simulation

The geomagnetic cusp is a region that the solar wind plasma can directly enter. Therefore, studying the dynamic response of the cusp to solar wind variations is important. This paper uses global MHD simulation to investigate the spatial and temporal variations of cusp boundaries in response to an IMF  southward turning. It is revealed that the equatorward boundary begins to move toward lower latitudes after the magnetopause reconnection starts, in an intermittent way. Dynamic variations of plasma velocity and thermal temperature in the cusp region are correlated to the distribution of Flux Transfer Events on the day-side magnetopause. The time scale for the equatorward boundary to gradually develop after IMF southward turning is about 20 minutes. The Solar wind Magnetosphere Ionosphere Link Explore (SMILE) is a joint mission between ENA and CAS, due for launch in late 2025. Based on the future observation of SMILE, it's expected that dynamic responses of the cusp region will be directly monitored by soft X-ray imaging.