The structures of magnetic islands formed during collisionless magnetic reconnections in a force-free current sheet

In this paper, with a two-dimensional particle-in-cell simulation model, we compare the structures of a primary magnetic island to those of a secondary magnetic island, and these islands are formed during collisionless magnetic reconnection in a force-free current sheet. The out-of-plane magnetic field B-y is enhanced in the center of both the primary and secondary islands; however, a quadrupole structure of B-y with a good symmetry may be formed at the ends of the primary island. The in-plane electric field also exists in both the primary and secondary islands. The electric field E-x has a positive value in the left and a negative value in the right of the islands, while the electric field E-z has a positive value in the upper part and a positive value in the lower part of the islands. However, the in-plane electric field exists in the outer part of the primary island, while it exists in the center of the secondary island. Published by AIP Publishing.