Abstract
Abstract. We report an ion-scale magnetic flux rope (the size of the flux rope is ∼ 8.5 ion inertial lengths) at the trailing edge of Kelvin–Helmholtz (KH) waves observed by the Magnetospheric Multiscale (MMS) mission on 27 September 2016, which is likely generated by multiple X-line reconnection. The currents of this flux rope are highly filamentary: in the central flux rope, the current flows are mainly parallel to the magnetic field, supporting a local magnetic field increase at about 7 nT, while at the edges the current filaments are predominantly along the antiparallel direction, which induce an opposing field that causes a significant magnetic depression along the axis direction (> 20 nT), meaning the overall magnetic field of this flux rope is depressed compared to the ambient magnetic field. Thus, this flux rope, accompanied by the plasma thermal pressure enhancement in the center, is referred to as a crater type. Intense lower hybrid drift waves (LHDWs) are found at the magnetospheric edge of the flux rope, and the wave potential is estimated to be ∼ 17 % of the electron temperature. Though LHDWs may be stabilized by the mechanism of electron resonance broadening, these waves could still effectively enable diffusive electron transports in the cross-field direction, corresponding to a local density dip. This indicates LHDWs could play important roles in the evolution of crater flux ropes. Keywords. Magnetospheric physics (magnetopause, cusp, and boundary layers; solar wind–magnetosphere interactions)
Highlights
Magnetic flux ropes, characterized by a reversal of the magnetic field in the cross section, are 3-D helical magnetic structures
The magnetic flux rope is usually regarded as the physical model of the flux transfer event (FTE) (Russell and Elphic, 1978) on Earth’s magnetopause, with spatial sizes extending from several ion inertial lengths to a few Earth radii (RE) (e.g., Hasegawa et al, 2010; Eastwood et al, 2016)
An ion-scale magnetic flux rope at the trailing edge of KH waves observed by Magnetospheric Multiscale (MMS) has been investigated, which is probably generated by multiple X-line reconnection
Summary
Magnetic flux ropes, characterized by a reversal of the magnetic field in the cross section, are 3-D helical magnetic structures. The first direct evidence of ongoing magnetic reconnection at the trailing edges of KH waves, where the local magnetic shear is enlarged and the current sheet is compressed to ion scale, is recorded by MMS (Eriksson et al, 2016; Li et al, 2016), and the MMS observations confirm previous studies from both field and particle measurements. Whether such reconnection can result in the generation of flux ropes has not been further examined by MMS. We analyze the lower hybrid drift waves (LHDWs) and their possible roles in plasma transport at the magnetospheric side of this flux rope
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