Re-Reconnection Processes of Magnetopause Flux Ropes: Three-Dimensional Global Hybrid Simulations
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Magnetopause flux ropes (FRs) play a crucial role in the transport of energy and plasma from the solar wind to the Earth's magnetosphere. Once formed by multiple X-line reconnection, the FRs move poleward, during which they can coalesce with each other through a re-reconnection process. The poleward moving FRs eventually coalesce into the cusp regions, through another re-reconnection process. In this paper, using three-dimensional (3-D) global hybrid simulations, we study the two re-reconnection processes of magnetopause FRs by examining the topological changes of magnetic field lines. These re-reconnection processes are essentially 3-D. Two FRs coalesce with each other and form two new FRs (instead of one new FR in the two-dimensional regime). When FRs move close to the cusp region, their field lines can reconnect with the cusp field lines so that the FRs can break into two shorter ones. The two re-reconnection processes increase the plasma energy and the magnetic flux connected to the Earth, which favors particle and energy transport toward the Earth's magnetosphere.