Interaction of Magnetic Flux Ropes Via Magnetic Reconnection Observed at the Magnetopause

Wang, Rongsheng; Lu, Quanming; Nakamura, R.; Baumjohann, W.; Russell, C. T.; Burch, J. L.; Ergun, R. E.; Lindqvist, Per‐Arne; Wang, Shui; Giles, B. L.; Gershman, D. J.

doi:10.1002/2017ja024482

Cited by 37 publications

(47 citation statements)

References 69 publications

(109 reference statements)

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“…Similarly, at the dayside magnetopause, multiple FTEs are believed to form due to the reconnection process and evolve into larger structure over time (Fu & Lee, ). Previous studies have determined the size distribution and flux content of FTEs (e.g., Eastwood et al, , ; Fermo et al, ; Hasegawa et al, , ; Pu et al, ; Wang et al, , ). These results indicate that FTEs are one to few Earth radii in size and contain 1–10 MWb in magnetic flux.…”

Section: Introductionmentioning

confidence: 99%

MMS Examination of FTEs at the Earth's Subsolar Magnetopause

et al. 2018

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Determining the magnetic field structure, electric currents, and plasma distributions within flux transfer event (FTE)‐type flux ropes is critical to the understanding of their origin, evolution, and dynamics. Here the Magnetospheric Multiscale mission's high‐resolution magnetic field and plasma measurements are used to identify FTEs in the vicinity of the subsolar magnetopause. The constant‐α flux rope model is used to identify quasi‐force free flux ropes and to infer the size, the core magnetic field strength, the magnetic flux content, and the spacecraft trajectories through these structures. Our statistical analysis determines a mean diameter of 1,700 ± 400 km (~30 ± 9 di) and an average magnetic flux content of 100 ± 30 kWb for the quasi‐force free FTEs at the Earth's subsolar magnetopause which are smaller than values reported by Cluster at high latitudes. These observed nonlinear size and magnetic flux content distributions of FTEs appear consistent with the plasmoid instability theory, which relies on the merging of neighboring, small‐scale FTEs to generate larger structures. The ratio of the perpendicular to parallel components of current density, RJ, indicates that our FTEs are magnetically force‐free, defined as RJ < 1, in their core regions (<0.6 Rflux rope). Plasma density is shown to be larger in smaller, newly formed FTEs and dropping with increasing FTE size. It is also shown that parallel ion velocity dominates inside FTEs with largest plasma density. Field‐aligned flow facilitates the evacuation of plasma inside newly formed FTEs, while their core magnetic field strengthens with increasing FTE size.

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Section: Introductionmentioning

confidence: 99%

MMS Examination of FTEs at the Earth's Subsolar Magnetopause

et al. 2018

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“…Kinetic simulations and in situ observations have suggested that, upon generation, flux ropes in three dimensions evolve in response to their environment moving tailward with the magnetosheath flow and expanding as the external pressure relaxes toward solar wind values (e.g., Berchem & Russell, 1984;Rijnbeek et al, 1984;Zhao et al, 2016;Farrugia et al, 2016;Teh, Nakamura, et al, 2017) and coalescence (e.g., Finn & Kaw, 1977;Karimabadi et al, 2011;Pritchett, 1992;Song et al, 2012;Wang et al, 2017;Zhou et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

“…In the other scenario, depicted in Figure 1c, the magnetic islands grow via coalescence. Chains of ion-scale FTEs (Milan et al, 2000;Slavin et al, 2012;Dong et al, 2017;Teh, Denton, et al, 2017;Wang et al, 2017;Hwang et al, 2018) are formed at the dayside magnetopause due to multiple X-line reconnection (Lee & Fu, 1985). In this scenario, the neighboring FTEs are forced to merge, reconnect, and grow into larger The shading of the islands determines the thermal pressure p inside them with the darkest shades indicating the region of largest p. The number of circles per area indicates magnetic field magnitude and the gradient shading inside the islands shows plasma pressure variability across the structure.…”

Section: Introductionmentioning

confidence: 99%

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MMS Multi‐Point Analysis of FTE Evolution: Physical Characteristics and Dynamics

et al. 2019

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Previous studies have indicated that flux transfer events (FTEs) grow as they convect away from the reconnection site along the magnetopause. This increase in FTE diameter may occur via adiabatic expansion in response to decreasing external pressure away from the subsolar region or due to a continuous supply of magnetic flux and plasma to the FTEs' outer layers by magnetic reconnection. Here we investigate an ensemble of 55 FTEs at the subsolar magnetopause using Magnetospheric Multiscale (MMS) multi‐point measurements. The FTEs are initially modeled as quasi‐force‐free flux ropes in order to infer their geometry and the spacecraft trajectory relative to their central axis. The MMS observations reveal a radially‐inward net force at the outer layers of FTEs which can accelerate plasmas and fields toward the FTE's core region. Inside the FTEs, near the central axis, plasma density is found to decrease as the axial net force increases. It is interpreted that the axial net force accelerates plasmas along the axis in the region of compressing field lines. Statistical analysis of the MMS observations of the 55 FTEs indicates that plasma pressure, Pth, decreases with increasing FTE diameter, λ, as Pth,obsv ∝ λ−0.24. Assuming that all 55 FTEs started out with similar diameters, this rate of plasma pressure decrease with increasing FTE diameter is at least an order of magnitude slower than the theoretical rate for adiabatic expansion (i.e., Pth,adiab. ∝ λ−3.3), suggesting the presence of efficient plasma heating mechanisms, such as magnetic reconnection, to facilitate FTE growth.

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“…The Magnetospheric Multiscale (MMS) mission with its unprecedented high-resolution plasma measurements provides a good opportunity to study the structure of ion-scale flux ropes with a duration of a few seconds in the data (e.g., Alm et al, 2018;Eastwood et al, 2016;Teh et al, 2017;Wang et al, 2017), which present observations of current filaments, nonideal ion behaviors, wave activities and even flux rope coalescence. An ion-scale craterlike flux rope has also been resolved by MMS, which is interpreted as a result of the depression of transverse magnetic fields in a flux rope simulation (Teh et al, 2017).…”

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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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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Interaction of Magnetic Flux Ropes Via Magnetic Reconnection Observed at the Magnetopause

Cited by 37 publications

References 69 publications

MMS Examination of FTEs at the Earth's Subsolar Magnetopause

MMS Examination of FTEs at the Earth's Subsolar Magnetopause

MMS Multi‐Point Analysis of FTE Evolution: Physical Characteristics and Dynamics

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

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