Field‐aligned currents associated with dipolarization fronts

Sun, W.; Fu, S. Y.; Parks, G. K.; Liu, Jiang; Yao, Zhonghua; Shi, Quanqi; Zong, Qiugang; Huang, Suming; Pu, Z. Y.; Xiao, Ting

doi:10.1002/grl.50902

Cited by 53 publications

(74 citation statements)

References 25 publications

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“…Different from previous studies that suggested that parallel currents and perpendicular currents are generally uniform across the DF (e.g., Fu et al, 2012a;Runov et al, 2011;Sun et al, 2013;Yao et al, 2013), we find that strong parallel currents only exist in the high-density side of the DF and perpendicular currents feature multiple peaks at the DF. Different from previous studies that suggested that parallel currents and perpendicular currents are generally uniform across the DF (e.g., Fu et al, 2012a;Runov et al, 2011;Sun et al, 2013;Yao et al, 2013), we find that strong parallel currents only exist in the high-density side of the DF and perpendicular currents feature multiple peaks at the DF.…”

Section: Summary and Discussioncontrasting

confidence: 99%

“…Such difference may stem from the fact that at electron scale, DF may be more like a nonlinear structure (e.g., Balikhin et al, 2014), as seen from the conspicuous fluctuation of currents. This is different from previous studies that suggested that parallel currents are generally uniform across the whole DF layer (e.g., Sun et al, 2013). Figures 3e and 3f show the parallel and perpendicular currents at the DF.…”

Section: 1029/2018gl077928contrasting

confidence: 94%

“…Interestingly, we see that J m also shows a localized positive value (in the dusk-dawn direction) in the low-density side of the DF. J l also shows a finite value at the front, with a peak approaching 13 nA/m 2 and a valley near À11 nA/m 2 (Figure 2d), indicating field-aligned/parallel currents that are expected to be associated with the DF (e.g., Balikhin et al, 2014;Liu et al, 2018;Sun et al, 2013;Yao et al, 2016). This is different from previous studies that suggested that DF may be a tangential discontinuity at subproton scale (e.g., Fu et al, 2012a;Khotyaintsev et al, 2011).…”

Section: 1029/2018gl077928contrasting

confidence: 69%

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Electron‐Scale Measurements of Dipolarization Front

Liu

et al. 2018

Geophysical Research Letters

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Dipolarization front (DF)—a sharp boundary with scale of ion inertial length (c/ωpi) in the Earth's magnetotail—can also have fine structures at electron scale (c/ωpe). Such electron‐scale structures, determining the local energy conversion, have not been revealed by multispacecraft observations so far, due to the large separation of spacecraft in previous studies. Here we report the first electron‐scale multispacecraft measurements of DF, using data from the recent Magnetospheric Multiscale mission. We find strong parallel currents only in the high‐density side of the DF but strong perpendicular currents across the whole DF. We find no parallel electric fields during the DF interval. Although DF is primarily an energy‐load region (E·J > 0), the electron‐scale currents could lead to a localized energy generation (E·J < 0). Such features are different from those reported in previous multispacecraft studies, where the currents, electric fields, and energy conversion are uniform across the DF; they also shed lights on the study of substorm current wedge, which is crucial in the magnetosphere‐ionosphere coupling.

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Section: Summary and Discussioncontrasting

confidence: 99%

Section: 1029/2018gl077928contrasting

confidence: 94%

Section: 1029/2018gl077928contrasting

confidence: 69%

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Electron‐Scale Measurements of Dipolarization Front

Liu

et al. 2018

Geophysical Research Letters

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“…The formation of DFs is associated with unsteady magnetic reconnection (e.g., , spontaneous formation , interchange ballooning instability (e.g., Pritchett & Coroniti, 2010), or jet braking (Birn et al, 2011). The electric field at the DF layer is mainly normal to the DF (Fu et al, 2012b;Sun et al, 2014), and the current is mainly along the DF from dawnside to duskside (Fu et al, 2012b;Sun et al, 2013). Huang, Fu, Vaivads, et al (2015) estimated that the scale of DF in the dawn-dusk direction is about 3.6 R E (R E is Earth's radius).…”

Section: Introductionmentioning

confidence: 99%

Periodical Dipolarization Processes in Earth's Magnetotail

Huang

Jiang

et al. 2019

Geophysical Research Letters

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Using high-resolution data of Magnetospheric Multiscale mission, we observed a gradual but periodical dipolarization process (DPs) in the Earth's magnetotail for the first time. These sub-DPs, characterized by increase of B z component and magnetic magnitude B t , have a period of~16 s. The electrons have a cigar distribution in the first three sub-DPs but have a pancake distribution in the last sub-DP, which excites two oppositely propagating whistler waves. At the trailing boundary of the last sub-DP, B z decreases sharply. Meanwhile, strong tailward and duskward plasma flow, intense current, ion and electron demagnetization, and positive energy conversion from the fields to the plasmas are observed at this boundary. By comparing the motion of this boundary with the plasma flow, we infer that the flow rebounds in longer period of the last DP and causes perpendicular electron acceleration. The periodical sub-DPs and kinetic effects on the DP could improve our understanding of substorm and the magnetotail dynamics.

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“…The current disruption started at the leading edge of the flow, as a sharp dipolarization front (DF) with a magnetic dip ahead of the front layer. The magnetic dip current, which is of Region 2 sense, has been studied recently [Liu et al, 2013a[Liu et al, , 2013bYao et al, 2013b;Sun et al, 2013]. Those studies presented the FAC features ahead of the DF, while this paper has studied the cross-tail current density evolution ahead of earthward flow.…”

Section: Discussionmentioning

confidence: 99%

Current reduction in a pseudo‐breakup event: THEMIS observations

Yao

Owen³

et al. 2014

JGR Space Physics

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Pseudo-breakup events are thought to be generated by the same physical processes as substorms. This paper reports on the cross-tail current reduction in an isolated pseudo-breakup observed by three of the THEMIS probes (THEMIS A (THA), THEMIS D (THD), and THEMIS E (THE)) on 22 March 2010. During this pseudo-breakup, several localized auroral intensifications were seen by ground-based observatories. Using the unique spatial configuration of the three THEMIS probes, we have estimated the inertial and diamagnetic currents in the near-Earth plasma sheet associated with flow braking and diversion. We found the diamagnetic current to be the major contributor to the current reduction in this pseudo-breakup event. During flow braking, the plasma pressure was reinforced, and a weak electrojet and an auroral intensification appeared. After flow braking/diversion, the electrojet was enhanced, and a new auroral intensification was seen. The peak current intensity of the electrojet estimated from ground-based magnetometers,~0.7 × 10 5 A, was about 1 order of magnitude lower than that in a typical substorm. We suggest that this pseudo-breakup event involved two dynamical processes: a current-reduction associated with plasma compression ahead of the earthward flow and a current-disruption related to the flow braking/diversion. Both processes are closely connected to the fundamental interaction between fast flows, the near-Earth ambient plasma, and the magnetic field.

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Field‐aligned currents associated with dipolarization fronts

Cited by 53 publications

References 25 publications

Electron‐Scale Measurements of Dipolarization Front

Electron‐Scale Measurements of Dipolarization Front

Periodical Dipolarization Processes in Earth's Magnetotail

Current reduction in a pseudo‐breakup event: THEMIS observations

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