MMS Observation of Secondary Magnetic Reconnection Beside Ion-Scale Flux Rope at the Magnetopause

Abstract

Using high-resolution data from Magnetospheric Multiscale (MMS) mission, we report an in situ observation of a secondary reconnection electron diffusion region (EDR) beside the leading edge of an ion-scale flux rope at the magnetopause. This reconnection EDR is characterized by strong electron current and electron jet reversal, a normal Hall electric field, unmagnetized electrons with nongyrotropic distributions, a large parallel electric field, and strong energy dissipation. The ion-scale flux rope beside the EDR consists of a force-free structure with diameter of only ~3 ion inertial lengths. Our observation of secondary reconnection beside the flux rope gives further evidence that flux ropes can be created and evolved in the reconnection exhaust region.