Observations of Electron-Only Magnetic Reconnection Associated With Macroscopic Magnetic Flux Ropes

We report a Magnetospheric Multiscale (MMS) mission observation of magnetic reconnection occurring at the edge of a large-scale magnetic flux rope (MFR), the cross-section of which was about 2 R-E. The MFR was observed at the duskside in the Earth's magnetotail and was highly oblique with its axis approximately along theX(GSM)direction. We find an electron-scale current sheet near the edge of this MFR. The Hall magnetic and electric field, super-Alfvenic electron outflow, parallel electric field, and positive energy dissipation were observed associated with the current sheet, which indicates that MMS detected a reconnecting current sheet with a large guide field. Interestingly, ions were not coupled in this reconnection, akin to the electron-only reconnection observed in the turbulent magnetosheath. We further find that the electron-only reconnection is commonly associated with a macroscopic MFR. This result will shed new light on understanding the multiscale coupling associated with an MFR in space plasmas.