Sub‐ion‐scale Dynamics of the Ion Diffusion Region in the Magnetotail: MMS Observations

Zhou, Meng; Man, H. Y.; Zhong, Zhihong; Deng, Xiaohua; Pang, Y.; Huang, Suming; Khotyaintsev, Yuri V.; Russell, C. T.; Giles, B. L.

doi:10.1029/2019ja026817

Cited by 11 publications

(9 citation statements)

References 63 publications

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“…A zoom‐in of the MMS observations at the magnetosheath separatrix is presented in Figure 2, where the variation of the magnetic field and the plasma density is identified (Figures 2a1 and 2b1). An electric field normal to this boundary ( E N⊥ ) is also revealed, with a magnitude of 5–10 mV m −1 (Figure 2d1), and similar electric field structures have also been reported in another reconnection separatrix (Yu et al, 2019; Zhou et al, 2019). In this event, this electric field is primarily balanced by the electron drift motion, suggesting that electrons are almost magnetized.…”

Section: Observationssupporting

confidence: 80%

Lower Hybrid Waves at the Magnetosheath Separatrix Region

Tang

Graham

et al. 2020

Geophysical Research Letters

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Lower hybrid waves are investigated at the magnetosheath separatrix region in asymmetric guide field reconnection by using the Magnetospheric Multiscale (MMS) mission. Three of the four MMS spacecraft observe clear wave activities around the lower hybrid frequency across the magnetosheath separatrix, where a density gradient is present. The observed waves are consistent with generation by the lower hybrid drift instability. The characteristic properties of these waves include the following: (1) the waves propagate toward the x-line in the spacecraft frame due to the large out-of-plane magnetic field, which is in the same direction of the diamagnetic drift of the x-line; (2) the wave potential is about 20% of the electron temperature. These drift waves effectively produce cross-field particle diffusion, enabling the transport of magnetosheath electrons into the exhaust region. At last, we suggest that the lower hybrid waves at the magnetosheath separatrix region represent some unique features of asymmetric guide field reconnection, which is different from that widely observed at the magnetospheric side of magnetopause reconnection. Plain Language Summary Magnetic reconnection is a fundamental process of explosive energy conversion in space, and one important unresolved issue during this process is how plasma waves impact the magnetic reconnection. Different types of waves have been found and investigated during reconnection, including kinetic Alfvén waves, lower hybrid waves, whistler waves, upper hybrid waves, and parallel electrostatic waves. Among these waves, lower hybrid waves, taken as a basic feature of 3-D asymmetric reconnection, are frequently observed at the magnetospheric side. In this study, we present new observations from the Magnetospheric Multiscale (MMS) mission, showing that the lower hybrid waves can also be found at the magnetosheath separatrix in asymmetric guide field reconnection, which enable the cross-field particle diffusion from the magnetosheath to the exhaust. These results can help deepen our understanding of the roles of plasma waves in reconnection.

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Section: Observationssupporting

confidence: 80%

Lower Hybrid Waves at the Magnetosheath Separatrix Region

Tang

Graham

et al. 2020

Geophysical Research Letters

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“…Which mechanism is responsible for the abnormal E n can not be determined in this work. However, positive E n observed by MMS2 is significantly smaller than of others (Figure 7 of Zhou, Man et al, 2019). MMS2 is separated from other MMS (nearly same position) in the N direction, and the distance between MMS2 and the other three MMS is less than 2 d e (not shown here).…”

Section: Discussionmentioning

confidence: 62%

“…The patchy parallel electric fields are shown in green arrows in Figure 2s. As for the explanation of the positive E n in n1, Yu et al (2019) considered it as a result of a new electron jet instability developed in the perpendicular direction (Divin et al, 2012), and Zhou, Man et al (2019 thought that electron physics caused the positive E n . Which mechanism is responsible for the abnormal E n can not be determined in this work.…”

Section: Discussionmentioning

confidence: 99%

“…(2019), and Zhou, Man et al. (2019) thought that electron physics caused the positive E n . Which mechanism is responsible for the abnormal E n can not be determined in this work.…”

Section: Discussionmentioning

confidence: 99%

“…Intense particle heating and high‐velocity jets are usually observed along with reconnection (e.g., S. Y. Huang et al., 2010; S. Y. Huang et al., 2020; Torbert et al., 2018). Observations of reconnection at different environments, like magnetopause (Burch et al., 2016; Deng & Matsumoto, 2001; S. Y. Huang et al., 2021; Mozer et al., 2002; Paschmann et al., 1979; R. Wang et al., 2017; Zhong et al., 2021; Zhou et al., 2017), magnetotail (S. Y. Huang, Fu et al., 2016; S. Y. Huang, Retino et al., 2016; S. Y. Huang, Vaivads et al., 2012; S. Y. Huang, Zhou et al., 2012; S. Y. Huang et al., 2017, 2018; 2022; Jiang et al., 2019; Øieroset et al., 2001; Torbert et al., 2018; R. Wang et al., 2010; Zhou, Deng et al., 2019; Zhou, Man et al., 2019), magnetosheath (e.g., Phan et al., 2018; Retinò et al., 2007; S. Wang et al., 2021), and foreshock (Jiang et al., 2021), have been widely reported.…”

Section: Introductionmentioning

confidence: 99%

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Sub‐Structures of the Separatrix Region During Magnetic Reconnection

Jiang

Huang

Yuan

et al. 2022

Geophysical Research Letters

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Utilizing data from the Magnetospheric Multiscale mission, the sub‐structures of the separatrix region during reconnection are investigated. A small current system in the separatrix region is embedded in the large Hall current system, which appears as a quadrupole current. This small current system has an opposite direction to the Hall current and cancels part of the Hall magnetic field. The formation of the quadrupole current is possibly related to the patchy parallel electric field. The electric field in the separatrix region can be divided into three sub‐layers according to the electron frozen‐in condition. En enhances in two outside sub‐layers, where the strong En is supported by the Hall term and electron pressure gradient term, and the nearly zero En, separating the enhanced electric fields, is caused by a small flow and electron density gradient. Our observations imply complex dynamics in the separatrix region during magnetic reconnection.

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Kinetic scale magnetic holes in the terrestrial magnetosheath: A review

Shi,

Yao,

Hamrin

et al. 2024

Sci. China Earth Sci.

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Magnetic holes at the ion-to-electron kinetic scale (KSMHs) are one of the extremely small intermittent structures generated in turbulent magnetized plasmas. In recent years, the explorations of KSMHs have made substantial strides, driven by the ultra-high-precision observational data gathered from the Magnetospheric Multiscale (MMS) mission. This review paper summarizes the up-to-date characteristics of the KSMHs observed in Earth’s turbulent magnetosheath, as well as their potential impacts on space plasma. This review starts by introducing the fundamental properties of the KSMHs, including observational features, particle behaviors, scales, geometries, and distributions in terrestrial space. Researchers have discovered that KSMHs display a quasi-circular electron vortex-like structure attributed to electron diamagnetic drift. These electrons exhibit noticeable non-gyrotropy and undergo acceleration. The occurrence rate of KSMH in the Earth’s magnetosheath is significantly greater than in the solar wind and magnetotail, suggesting the turbulent magnetosheath is a primary source region. Additionally, KSMHs have also been generated in turbulence simulations and successfully reproduced by the kinetic equilibrium models. Furthermore, KSMHs have demonstrated their ability to accelerate electrons by a novel non-adiabatic electron acceleration mechanism, serve as an additional avenue for energy dissipation during magnetic reconnection, and generate diverse wave phenomena, including whistler waves, electrostatic solitary waves, and electron cyclotron waves in space plasma. These results highlight the magnetic hole’s impact such as wave-particle interaction, energy cascade/dissipation, and particle acceleration/heating in space plasma. We end this paper by summarizing these discoveries, discussing the generation mechanism, similar structures, and observations in the Earth’s magnetotail and solar wind, and presenting a future extension perspective in this active field.

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Sub‐ion‐scale Dynamics of the Ion Diffusion Region in the Magnetotail: MMS Observations

Cited by 11 publications

References 63 publications

Lower Hybrid Waves at the Magnetosheath Separatrix Region

Lower Hybrid Waves at the Magnetosheath Separatrix Region

Sub‐Structures of the Separatrix Region During Magnetic Reconnection

Kinetic scale magnetic holes in the terrestrial magnetosheath: A review

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