Dynamic Evolution of Dayside Magnetopause Reconnection Locations and Their Dependence on IMF Cone Angle: 3‐D Global Hybrid Simulation.

We study the dynamic evolution of dayside magnetopause reconnection locations and their dependence on the interplanetary magnetic field (IMF) cone angle via 3‐D global‐scale hybrid simulations. Cases with finite IMF Bx and Bz but IMF By = 0 are investigated. It is shown that the dayside magnetopause reconnection is unsteady under quasi‐steady solar wind conditions. The reconnection lines during the dynamic evolution are not always parallel to the equatorial plane even under purely southward IMF conditions. Magnetopause reconnection locations can be affected by the generation, coalescence, and transport of flux ropes (FRs), reconnection inside the FRs, and the magnetosheath flow. In the presence of an IMF component Bx, the magnetopause reconnection initially occurs in high‐latitude regions downstream of the quasi‐perpendicular bow shock, followed by the generation of multiple reconnection regions. In the later stages of the simulation, a dominant reconnection region is present in low‐latitude regions, which can also affect reconnection in other regions. The global distribution of reconnection lines under a finite IMF Bx is found to not be limited to the region with maximum magnetic shear angle. Plain Language Summary: The channel of solar wind energy transfer into the magnetosphere is widely believed to be controlled by magnetic reconnection at the dayside magnetopause. Understanding the location of dayside magnetopause reconnection is crucial to comprehending the energy coupling process between the solar wind and the magnetosphere. Magnetopause reconnection has been intensively investigated by numerical simulations and space observations. Nevertheless, the locations and dynamic evolution of reconnection sites in the 3‐D magnetopause reconnection under different interplanetary magnetic field (IMF) conditions are barely scrutinized. In this paper, we investigate the effects of IMF Bx on the motion of magnetopause reconnection locations by using 3‐D global hybrid simulations under a southward IMF Bz. We find that the reconnection is highly variable due to local magnetopause processes associated with the generation, coalescence, and transport of flux ropes (FRs), as well as reconnection inside the FRs. Under southward IMF conditions with IMF Bx, the magnetopause reconnection initially occurs downstream of the quasi‐perpendicular bow shock but eventually dominates in low‐latitude regions, including the magnetopause downstream of the quasi‐parallel bow shock. Key Points: Dayside magnetopause reconnection is highly variable but the reconnection locations eventually maintain quasi‐steady in the low latitudeIn the presence of interplanetary magnetic field Bx, high‐latitude dayside reconnection can be inhibited by reconnection near the equator and magnetosheath flowVariations of reconnection locations are also controlled by the generation, coalescence, and transport of flux ropes (FRs), and reconnection inside FRs [ABSTRACT FROM AUTHOR]