Statistic Properties of Flux Ropes and Flux Transfer Events Observed by MMS spacecraft

Observationally, flux transfer events (FTEs) are characterized by an enhancement of the magnetic field strength, a bipolar magnetic field in the direction transverse to the direction of motion of the structure, a dominant field-aligned current throughout the structure and the mixture of plasma from both magnetosphere and magnetosheath. FTEs are important for the space environment since they provide a means for the solar wind plasma, momentum and energy to be transferred into the terrestrial magnetosphere. In phase 1a of magnetospheric multiscale mission (MMS) we found 47 flux transfer events. However, during the same period, we also found another 52 flux ropes (FRs) which share the same magnetic topology as FTEs but have no signature of plasma from either magnetosphere and magnetosheath. With the help of the tetrahedron of the MMS spacecraft, it is possible to accurately calculate the cross-sectional radius, the total flux content, the speed of the FTEs and FRs as well as the expansion/contraction rates. In this paper, we will compare the properties of the FTE and the FR. In addition, the solar wind conditions associated with these events are also compared in order to test whether the FTEs and FRs are related to the southward IMF conditions, and hence magnetic reconnection.