title: In situ observations of a secondary magnetic island in an ion diffusion region and associated energetic electrons.
abstract: Numerical simulations have predicted that an extended current sheet may be unstable to secondary magnetic islands in the vicinity of the X line, and these islands can dramatically influence the reconnection rate. In this Letter, we present the first evidence of such a secondary island near the center of an ion diffusion region, which is consistent with the action of the secondary island instability occurring in the vicinity of the X line. The island is squashed in the z direction with a strong core magnetic field. Energetic electrons with anisotropic or field-aligned bidirectional fluxes are found in the ion diffusion region, and the enhancement of energetic electron fluxes is more obvious inside the secondary island.
authors.affiliation: CAS Key Laboratory of Basic Plasma Physics, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Rongsheng
authors.initials: R
authors.lastname: Wang
authors.forename: Quanming
authors.initials: Q
authors.lastname: Lu
authors.forename: Aimin
authors.initials: A
authors.lastname: Du
authors.forename: Shui
authors.initials: S
authors.lastname: Wang