MMS observations of electron‐scale filamentary currents in the reconnection exhaust and near the X line

Phan, T. D.; Eastwood, J. P.; Cassak, P. A.; Øieroset, M.; Gosling, J. T.; Gershman, D. J.; Mozer, F. S.; Shay, M. A.; Fujimoto, M.; Daughton, W.; Drake, J. F.; Burch, J. L.; Torbert, R. B.; Ergun, R. E.; Chen, Li‐Jen; Wang, S.; Pollock, C. J.; Dorelli, J.; Lavraud, B.; Giles, B. L.; Moore, T. E.; Saito, Y.; Avanov, L. A.; Paterson, W. R.; Strangeway, R. J.; Russell, C. T.; Khotyaintsev, Yuri V.; Lindqvist, Per‐Arne; Oka, M.; Wilder, F. D.

doi:10.1002/2016gl069212

Cited by 104 publications

(122 citation statements)

References 28 publications

(34 reference statements)

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“…Good agreement is found between two measures, both showing considerable structure and variability in the current density of the flux rope with a maximum value of ∼ 900 nA m −2 , while the current from plasma measurements is more structured, as shown by Phan et al (2016). Therefore, this current is transformed to the directions parallel and perpendicular to the magnetic field (Fig.…”

Section: Observationmentioning

confidence: 78%

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: Observationmentioning

confidence: 78%

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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“…<Ω e > represents the direction of Ω e averaged over the interval including the times when Ω e peaks (the blue arrows in Figure 1a, P and Q). Instead of a simple average, which gives the result that is very sensitive to the period selection of averaging, we performed a minimum variance analysis (Paschmann & Daly, 1998) Red, green, cyan, blue, and magenta arrows present m vort n vort -plane projected electron velocity vectors at 2234:01.9, 2.0, 2.1, 2.2, and 2.3 UT, respectively. They predominantly points to −m at all four-spacecraft locations.…”

Section: Origin Of the Enhanced Electron Vorticitymentioning

confidence: 99%

Electron Vorticity Indicative of the Electron Diffusion Region of Magnetic Reconnection

Hwang

Choi

Dokgo

et al. 2019

Geophysical Research Letters

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While vorticity defined as the curl of the velocity has been broadly used in fluid and plasma physics, this quantity has been underutilized in space physics due to low time resolution observations. We report Magnetospheric Multiscale (MMS) observations of enhanced electron vorticity in the vicinity of the electron diffusion region of magnetic reconnection. On 11 July 2017 MMS traversed the magnetotail current sheet, observing tailward‐to‐earthward outflow reversal, current‐carrying electron jets in the direction along the electron meandering motion or out‐of‐plane direction, agyrotropic electron distribution functions, and dissipative signatures. At the edge of the electron jets, the electron vorticity increased with magnitudes greater than the electron gyrofrequency. The out‐of‐plane velocity shear along distance from the current sheet leads to the enhanced vorticity. This, in turn, contributes to the magnetic field perturbations observed by MMS. These observations indicate that electron vorticity can act as a proxy for delineating the electron diffusion region of magnetic reconnection.

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“…Commonly, it is attributed to the current sheets with a plateau in B L during reconnection (e.g., Karimabadi et al, 2005;Phan et al, 2006). The ECSs are often associated with the electron diffusion region and the separatrices during magnetic reconnection (Baumjohann et al, 2007;Burch et al, 2016;Ji et al, 2008;Phan et al, 2016;Wang et al, 2017). The ECSs are often associated with the electron diffusion region and the separatrices during magnetic reconnection (Baumjohann et al, 2007;Burch et al, 2016;Ji et al, 2008;Phan et al, 2016;Wang et al, 2017).…”

Section: Geophysical Research Lettersmentioning

confidence: 99%

An Electron‐Scale Current Sheet Without Bursty Reconnection Signatures Observed in the Near‐Earth Tail

Wang

Nakamura

et al. 2018

Geophysical Research Letters

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Observations of a current sheet as thin as the electron scale are extremely rare in the near‐Earth magnetotail. By measurement from the novel Magnetospheric Multiscale mission in the near‐Earth magnetotail, we identified such an electron‐scale current sheet and determined its detailed properties. The electron current sheet was bifurcated, with a half‐thickness of nine electron inertial lengths, and was sandwiched between the Hall field. Because of the strong Hall electric field, the super‐Alfvénic electron bulk flows were created mainly by the electric field drift, leading to the generation of the strong electron current. Inevitably, a bifurcated current sheet was formed since the Hall electric field was close to zero at the center of the current sheet. Inside the electron current sheet, the electrons were significantly heated while the ion temperature showed no change. The ions kept moving at a low speed, which was not affected by this electron current sheet. The energy dissipation was negligible inside the current sheet. The observations indicate that a thin current sheet, even as thin as electron scale, is not the sufficient condition for triggering bursty reconnection.

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MMS observations of electron‐scale filamentary currents in the reconnection exhaust and near the X line

Cited by 104 publications

References 28 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

Electron Vorticity Indicative of the Electron Diffusion Region of Magnetic Reconnection

An Electron‐Scale Current Sheet Without Bursty Reconnection Signatures Observed in the Near‐Earth Tail

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