Magnetic topologies of an in vivo FTE observed by Double Star/TC‐1 at Earth's magnetopause

Pu, Z. Y.; Raeder, J.; Zhong, Jun; Bogdanova, Y. V.; Dunlop, M. W.; Xiao, Chijie; Wang, X. G.; Fazakerley, A. N.

doi:10.1002/grl.50714

Cited by 68 publications

(81 citation statements)

References 32 publications

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“…Inside the flux rope, almostisotropic energetic electrons were clearly identified, while the energy flux intensity is weaker than that in the magnetosphere, consisting of the re-closure of the field lines in the flux rope. This is different with large-scale flux rope situations, in which both trapped and untrapped electrons can be observed, suggesting different topologies of magnetic field lines (Pu et al, 2013;Roux et al, 2015). At the sheath side (from 19:58:05.0 to 19:58:06.2 s), energetic electrons only in the antiparallel directions were detected, suggesting the existence of another X line on the north-dusk side to generate these open field lines, and also this X line was formed earlier than the one at the dawn side.…”

Section: Observationcontrasting

confidence: 62%

“…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 (d i ) to a few Earth radii (R E ) (e.g., Hasegawa et al, 2010;Eastwood et al, 2016). Recent in situ observations revealed that flux ropes could be flanked by two converging plasma jets, indicating these flux ropes are still active, and possibly generated by multiple, or even sequential, X-line reconnection (Hasegawa et al, 2010;Øieroset et al, 2011;Pu et al, 2013). Such active flux ropes are relatively less often observed in a statistical study (Zhang et al, 2012); thus, X lines flanking flux ropes might be short-lived once these flux ropes convect away from the generation region.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic depression and electron transport in an ion-scale flux rope associated with Kelvin–Helmholtz waves

Tang

Wang

et al. 2018

Ann. Geophys.

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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.

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Section: Observationcontrasting

confidence: 62%

Section: Introductionmentioning

confidence: 99%

Magnetic depression and electron transport in an ion-scale flux rope associated with Kelvin–Helmholtz waves

Tang

Wang

et al. 2018

Ann. Geophys.

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“…We interpret this sequence of observations as the signature of the successive crossing of the two flux tubes by the spacecraft. These two flux tubes may have been generated by multiple sequential reconnection process, which is expected to occur under strong B Y and negative B Z IMF conditions, as was observed for a long time around the event (e.g., Pu et al, ; Raeder, ). The first flux tube (FT A ) contained trapped electrons.…”

Section: Discussion and Interpretationmentioning

confidence: 88%

“…Aside from large‐scale FTEs often observed at the magnetopause, small‐scale perturbations with magnetic signatures akin to those of FTEs might indicate the existence of very localized magnetic island structures (Hesse et al, ). Such magnetic islands may also be generated by multiple X‐line reconnection (Pu et al, ; Zhong et al, ) (i.e., between two X‐lines created sequentially on the magnetopause) or at a single X‐line owing to rapid variations of the reconnection rate (Huang et al, ). Their typical signatures are an enhancement of the total magnetic field strength and a magnetic bipolar signature (Teh et al, ).…”

Section: Introductionmentioning

confidence: 99%

Magnetic Reconnection at a Thin Current Sheet Separating Two Interlaced Flux Tubes at the Earth's Magnetopause

et al. 2018

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The occurrence of spatially and temporally variable reconnection at the Earth's magnetopause leads to the complex interaction of magnetic fields from the magnetosphere and magnetosheath. Flux transfer events (FTEs) constitute one such type of interaction. Their main characteristics are (1) an enhanced core magnetic field magnitude and (2) a bipolar magnetic field signature in the component normal to the magnetopause, reminiscent of a large‐scale helicoidal flux tube magnetic configuration. However, other geometrical configurations which do not fit this classical picture have also been observed. Using high‐resolution measurements from the Magnetospheric Multiscale mission, we investigate an event in the vicinity of the Earth's magnetopause on 7 November 2015. Despite signatures that, at first glance, appear consistent with a classic FTE, based on detailed geometrical and dynamical analyses as well as on topological signatures revealed by suprathermal electron properties, we demonstrate that this event is not consistent with a single, homogenous helicoidal structure. Our analysis rather suggests that it consists of the interaction of two separate sets of magnetic field lines with different connectivities. This complex three‐dimensional interaction constructively conspires to produce signatures partially consistent with that of an FTE. We also show that, at the interface between the two sets of field lines, where the observed magnetic pileup occurs, a thin and strong current sheet forms with a large ion jet, which may be consistent with magnetic flux dissipation through magnetic reconnection in the interaction region.

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“…Instead, in the original Russell and Elphic [] model a poleward acceleration of the plasma could be detected inside the FTE, but the velocity increase should be observed during the entire FTE and not only at its trailing edge [ Sonnerup , ]. In the multiple X line model [ Lee and Fu , ], two converging reconnection jets at the borders of the FTE are expected if the FTEs are observed during their formation [ Hasegawa et al , ; Trenchi et al , ; Øieroset et al , ; Zhang et al , ; Zhong et al , ; Pu et al , ]. The lack of the southward reconnection jets at the leading edge of the FTEs could be explained possibly also in the context of multiple X line reconnection, if reconnection at the southern X line is more active and reconnection at the northern X line is not active when the FTEs are detected.…”

Section: Discussionmentioning

confidence: 99%

A sequence of flux transfer events potentially generated by different generation mechanisms

et al. 2016

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Flux transfer events (FTEs) are magnetic structures generated by time‐varying reconnection at the dayside magnetopause. Understanding their generation mechanism is important, because it is necessary in order to understand the global contribution of FTEs to the convection process. We present observations of several FTEs sequentially observed by Cluster at the subsolar magnetopause. Cluster detected also several reconnection jets, which seem to be systematically associated with the trailing edge of the FTEs. This association is expected only in the FTEs formed by single X line reconnection but could be compatible also with the multiple X line model, when reconnection at one X line is dominant. Instead, it does not seem compatible with original mechanism proposed by Russell and Elphic (1978). For a large FTE, not associated with any reconnection jet, the Grad‐Shafranov reconstruction obtained from Cluster 1 data recovers a flux rope, indicative of multiple X line reconnection. This same FTE was detected also by Cluster 3, which observed an asymmetric signature in the magnetic field component normal to the magnetopause. We show that this asymmetric signature was caused by an outward motion of the magnetopause. The orientation of the other FTEs, obtained from a Grad‐Shafranov optimization, shows considerable spread, despite the relatively steady conditions. Our interpretation is that a combination of single and multiple X line reconnection generated these FTEs. The FTEs in the first part of the crossing, associated with reconnection jets, are generated by the single X line model and may therefore not satisfy the Grad‐Shafranov assumptions so well. Instead, the last FTE, slower, bigger, and well separated from the previous ones, may be formed by multiple X line reconnection.

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Magnetic topologies of an in vivo FTE observed by Double Star/TC‐1 at Earth's magnetopause

Cited by 68 publications

References 32 publications

Magnetic depression and electron transport in an ion-scale flux rope associated with Kelvin–Helmholtz waves

Magnetic depression and electron transport in an ion-scale flux rope associated with Kelvin–Helmholtz waves

Magnetic Reconnection at a Thin Current Sheet Separating Two Interlaced Flux Tubes at the Earth's Magnetopause

A sequence of flux transfer events potentially generated by different generation mechanisms

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