Kinetic-scale flux ropes: Observations and applications of kinetic equilibrium models

Abstract

Magnetic flux ropes with helical field lines and strong core field are ubiquitous structures in space plasmas. Recently, kinetic-scale flux ropes have been identified by high-resolution observations from Magnetospheric Multiscale (MMS) spacecraft in the magnetosheath, which have drawn a lot of attention because of their non-ideal behavior and internal structures. Detailed investigation of flux rope structure and dynamics requires development of realistic kinetic models. In this paper, we generalize an equilibrium model to reconstruct a kinetic-scale flux rope previously reported via MMS observations. The key features in the magnetic field and electron pitch-angle distribution measurements of all four satellites are simultaneously reproduced in this reconstruction. Besides validating the model, our results also indicate that the anisotropic features previously attributed to asymmetric magnetic topologies in the magnetosheath can be alternatively explained by the spacecraft motion in the flux rope rest frame.