MMS Observation of the Hall Field in an Asymmetric Magnetic Reconnection with Guide Field

Abstract

In this paper, we investigate the structure of out-of-plane magnetic field in the reconnection event observed by Magnetospheric Multiscale Mission at the magnetopause of the Earth magnetosphere on 2015 October 21. We find that the perturbation of out-of-plane magnetic field in this event is different from previous observations of the quadrupolar Hall magnetic field. The distinct out-of-plane magnetic field is interpreted as a part of the hexapolar Hall magnetic field obtained in a recent simulation of asymmetric reconnection with the guide field. This is significant evidence of the hexapolar Hall magnetic field in collisionless magnetic reconnection from the observations in the magnetosphere. High-resolution measurements of particle and field are used to provide a comprehensive description of the features of the hexapolar Hall magnetic field. The results from this study offer an insight into the Hall effect in collisionless magnetic reconnection.