Electron Vorticity Indicative of the Electron Diffusion Region of Magnetic Reconnection

Hwang, Kyoung‐Joo; Choi, Eun Jin; Dokgo, K.; Burch, J. L.; Sibeck, D. G.; Giles, B. L.; Goldstein, M. L.; Paterson, W. R.; Pollock, C. J.; Shi, Quanqi; Fu, H. S.; Hasegawa, Hiroshi; Gershman, D. J.; Khotyaintsev, Yuri V.; Torbert, R. B.; Ergun, R. E.; Dorelli, J.; Avanov, L. A.; Russell, C. T.; Strangeway, R. J.

doi:10.1029/2019gl082710

Cited by 28 publications

(32 citation statements)

References 27 publications

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“…A recent study by Hwang et al () reported increased electron vorticity close to an EDR observed in the magnetotail by MMS. The authors concluded that the vorticity is driven by the drift of meandering electrons in the

\overset{M}{true}

direction that changes fast with an increasing distance from the current sheet.…”

Section: Discussionmentioning

confidence: 58%

“…These vortices may work as seeds for the secondary flux ropes as they grow in size and couple with the magnetic field (Fermo et al, 2012;Huang et al, 2015;Zhong et al, 2018). In this event MMS observes the electron vortex closest to the MN plane and the largest shear in the electron velocity inM direction as observed in the magnetotail by Hwang et al (2019), not along the separatrices (LN plane). In this event the electron shear flow inM direction between the current sheet and the magnetic structure (Δv e,M ≈ 840 km/s) fulfills the the instability condition for the electron Kelvin-Helmholtz instability: Δv e,M > v A,eM ∕2, where v A,eM is the electron Alfvén velocity inM direction (Fermo et al, 2012).…”

Section: 1029/2019ja027192mentioning

confidence: 90%

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Electron‐Scale Magnetic Structure Observed Adjacent to an Electron Diffusion Region at the Dayside Magnetopause

et al. 2019

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In this paper, we present observations made by the Magnetospheric Multiscale (MMS) mission of a small-scale magnetic structure adjacent to a reconnecting current sheet at the dayside magnetopause. While MMS crosses the current sheet, it observes signatures of an electron diffusion region (EDR), including crescent shaped electron velocity distribution functions. Right after the EDR crossing, all spacecraft encounter an electron-scale magnetic structure that can roughly be divided into two parts: a force-free flux rope-like part and a nonforce-free magnetic enhancement. Within the leading force-free part of the structure, the magnetic field component normal to the current sheet exhibits a bipolar signature, suggesting that the structure is flux rope-like. In the trailing edge of the bipolar signature, three spacecraft observe a magnetic enhancement that has an amplitude almost twice the ambient magnetic field. The magnetic peak adjacent to an EDR can be associated with an electron vortex, where the perpendicular current is carried by E × B drifting electrons. The structure is advected tailward along the magnetopause while in the plasma frame, it propagates upstream suggesting that this reconnection event is highly three-dimensional. Fluctuations in the plasma density and magnetic field and large peaks in the parallel electric field observed on the magnetospheric side of the EDR suggest that the current sheet is corrugated due to an electromagnetic drift instability. This or another instability of a thin reconnecting current sheet (e.g., tearing) is a likely cause of the formation of the observed magnetic structure.

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\overset{M}{true}

direction that changes fast with an increasing distance from the current sheet.…”

Section: Discussionmentioning

confidence: 58%

Section: 1029/2019ja027192mentioning

confidence: 90%

Electron‐Scale Magnetic Structure Observed Adjacent to an Electron Diffusion Region at the Dayside Magnetopause

et al. 2019

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“…The V e,l, O‐L reversal (250 ± 150 km/s in Figure 4b; marked by the vertical blue line) and the reversal in B l O‐L (Figure 4a; marked by the vertical black line) are separated by ~0.9 s, suggesting the displacement of the stagnant point from the X‐line along the l direction (Hasegawa et al, 2019; Hwang et al, 2019). Around the V e,l, O‐L reversal, the out‐of‐plane V e,m, O‐L (Figure 4b) increases and the parallel heated electron flux is enhanced (red arrow in Figure 4c); J·E′ is negative (Figure 4e), which represents a transfer of energy from the plasma to the fields and has been reported at the outer edge of the EDR (Hwang et al, 2017) or in association with waves (Swisdak et al, 2018; Figure 3k).…”

Section: Reconnection Occurring In/around the Flux Ropementioning

confidence: 99%

Magnetic Reconnection Inside a Flux Rope Induced by Kelvin‐Helmholtz Vortices

et al. 2020

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On 5 May 2017, MMS observed a crater-type flux rope on the dawnside tailward magnetopause with fluctuations. The boundary-normal analysis shows that the fluctuations can be attributed to nonlinear Kelvin-Helmholtz (KH) waves. Reconnection signatures such as flow reversals and Joule dissipation were identified at the leading and trailing edges of the flux rope. In particular, strong northward electron jets observed at the trailing edge indicated midlatitude reconnection associated with the 3-D structure of the KH vortex. The scale size of the flux rope, together with reconnection signatures, strongly supports the interpretation that the flux rope was generated locally by KH vortex-induced reconnection. The center of the flux rope also displayed signatures of guide-field reconnection (out-of-plane electron jets, parallel electron heating, and Joule dissipation). These signatures indicate that an interface between two interlinked flux tubes was undergoing interaction, causing a local magnetic depression, resulting in an M-shaped crater flux rope, as supported by reconstruction.Plain Language Summary Magnetic reconnection and Kelvin-Helmholtz instability (KHI), two of the most fundamental physical processes occurring within the heliosphere and throughout the Universe, often occur simultaneously on the Earth's magnetopause. Previous studies indicate the importance of nonlinearly developed KH waves, which produce multiple kinetic layers facilitating reconnection both in and out of the velocity shear plane and resulting in the magnetic flux rope. However, these studies significantly lacked detailed in situ observations in quantity as well as appropriate 3-D analyses of the structure of the KH vortex-induced flux rope. In this paper, we use detailed observations by the MMS spacecraft to investigate both 2-D and 3-D structures of the flux rope developed along the KH waves. We found that two flux tubes interact through reconnection to form a single combined structure, which can explain the occurrence of M-shaped crater flux rope.

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“…To confirm this speculation, Figure 3b shows the four‐spacecraft averaged magnetic field ( B ml ) in black, a hyperbolic tangent function ( B hl ) fitting to the averaged magnetic field in cyan, and the sum of B hl and the magnetic field from the contribution of electron vortex ( B vl ) in magenta. The contribution of the electron vortex to the magnetic field is calculated following the approach of Hwang et al (2019). Ampere's law predicts that the electron vorticity can generate perturbations in magnetic field, B vl = − μ 0 n e e (▽ × V e ) l (Δ s mn ) 2 , where μ 0 is the vacuum magnetic permeability, n e is the electron density, e is the electric charge, and Δ s is the spatial scale of the electron vortex, which is estimated by V e /▽ V e .…”

Section: Observationsmentioning

confidence: 99%

Observations of Electron Vortex at the Dipolarization Front

Jiang

Huang

Yuan

et al. 2020

Geophysical Research Letters

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Dipolarization front (DF), embedded in fast plasma flow, is a sharp structure with the increase of Bz in a short time and plays an important role in the energy dissipation and particle accelerations in the magnetotail. However, detailed physics at the small scales is still unclear in the DF due to the limitation of the previous mission. In the present study, an electron‐scale plateau in Bz is observed at the DF by Magnetospheric Multiscale (MMS) mission. By analyzing the velocity of the electrons, we find that the electron‐scale plateau is surrounded by a sub‐ion‐scale electron vortex, which is the first observation of electron vortex at the DF as far as we know. The magnetic field generated by the electron vortex cancels parts of the increase of Bz and causes the plateau. Strong asymmetric electric field and demagnetization of electrons and ions are observed at the boundary of the electron vortex. These results shed new light on that small‐scale structures can develop within the ion‐scale DF and affect the evolution and kinetic effects at the DF.

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Electron Vorticity Indicative of the Electron Diffusion Region of Magnetic Reconnection

Cited by 28 publications

References 27 publications

Electron‐Scale Magnetic Structure Observed Adjacent to an Electron Diffusion Region at the Dayside Magnetopause

Electron‐Scale Magnetic Structure Observed Adjacent to an Electron Diffusion Region at the Dayside Magnetopause

Magnetic Reconnection Inside a Flux Rope Induced by Kelvin‐Helmholtz Vortices

Observations of Electron Vortex at the Dipolarization Front

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