MMS Study of the Structure of Ion-Scale Flux Ropes in the Earth's Cross-Tail Current Sheet

摘要

This study analyzes 25 ion-scale flux ropes in the Magnetospheric Multiscale (MMS) observations to determine their structures. The high temporal and spatial resolution MMS measurements enable the application of multispacecraft techniques to ion-scale flux ropes. Flux ropes are identified as quasi-one-dimensional (quasi-1-D) when they retain the features of reconnecting current sheets; that is, the magnetic field gradient is predominantly northward or southward, and quasi-2-D when they exhibit circular cross sections; that is, the magnetic field gradients in the plane transverse to the flux rope axis are comparable. The analysis shows that the quasi-2-D events have larger core fields and smaller pressure variations than the quasi-1-D events. These two types of flux ropes could be the result of different processes, including magnetic reconnection with different dawn-dusk magnetic field components, temporal transformation of flattened structure to circular, or interactions with external environments.