3-Dimensional Global Hybrid Simulation of the Magnetospheric Polar Cusp Region in Response to the Passage of a Solar Wind Rotational Discontinuity

Solar wind directional discontinuities, such as rotational discontinuities (RDs), have a significant influence on the energy and transport processes in the Earth's magnetosphere. This process is studied in a global hybrid simulation case of the magnetosphere in response to a solar wind RD. The simulation shows strong variances in the magnetopause, boundary layer, and cusp caused by the passing RD. After the RD arrives at the low latitude of the northern cusp region, ion precipitation intensifies, and a double cusp structure varying in latitude occurs near the noonside and lasts for several minutes. We find a connection between this double cusp region and ion injection from both high-latitude and low-latitude X-line regions. This suggests that the double cusp structure may be a signature of magnetic reconnection occurring at both high and low latitudes due to the dominant IMF By after RD arrival. Additionally, we observe other phenomena related to the passing RD, such as periodic stronger ion outflow from the southern cusp region related to pre-noon ion precipitation into the northern hemisphere. On the By-dominated interplanetary magnetic field condition, cold plasma would pile up in southern cusp region. As the invation of dense cold plasma into lower altitude (~4Re) of the cusp, the ions would suddenly be accelerated to energy~keV and propagate out to the equator along with strong Alfven variations in the route. The mechanism of acceleration remains to be analyzed.