Kinetic simulations of the structures of magnetic island in multiple X line guide field reconnection

Magnetic reconnection is one of the most important processes in astrophysical, space, and laboratory plasmas, and magnetic island is an important feature in reconnection. Therefore, identifying the structures of magnetic island is crucial to improving our understanding of magnetic reconnection. Using two-dimensional (2-D) particle-in-cell (PIC) simulations, we demonstrate that the out-of-plane magnetic field has a dip in the center of magnetic island, which is formed during multiple X line guide field reconnection. Such structures are considered to be produced by the current system in the magnetic island. At the edge of the magnetic island, there exists a current anti-parallel to the in-plane magnetic field, while the current is parallel to the in-plane magnetic field inside the magnetic island. Such a dual-ring current system, which is attributed to the electron dynamics in the magnetic island, leads to the dip of the out-of-plane magnetic field in the center of the island. The relevance between our simulations and crater flux transfer events (C-FTEs) is also discussed.