Three‐Dimensional Electron‐Scale Magnetic Reconnection in Earth's Magnetosphere

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Despite a growing number of observations of whistler waves in/around the reconnection diffusion region, the origin of the whistler waves in the diffusion region and their role in reconnection remain elusive. This paper investigates the whistler‐mode waves within an electron‐scale reconnecting current sheet observed by the Magnetospheric Multiscale mission on 23 December 2016. These whistlers were observed in both the electron diffusion region (EDR) and the immediate inflow region of the electron‐scale magnetic reconnection site. The dispersion relation of these whistlers is measured and compared to predictions from linear theory for the first time in these regions. The comparison shows that the field‐aligned drifting electron component critically modifies the dispersion relation of whistlers in the EDR due to the Doppler‐shift effects. We demonstrate that these whistlers propagated into the EDR from outside rather than locally excited, however, they did not provide sufficiently large anomalous dissipation in this EDR.

Section: Event Overviewmentioning

confidence: 99%

“…A detailed comparison between the MMS observations and a particle‐in‐cell simulation is illustrated in Zhong, Zhou, et al. (2021). The black and red rectangles in Figures 1a–1i mark the area of the EDR and the immediate inflow region, respectively, while the magenta dashed line marks the location of the active X‐line.…”

Section: Event Overviewmentioning

confidence: 99%

Evidence for Whistler Waves Propagating Into the Electron Diffusion Region of Collisionless Magnetic Reconnection

Zhong

Zhou

Graham

et al. 2022

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“…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%

Sub‐Structures of the Separatrix Region During Magnetic Reconnection

Jiang

Huang

Yuan

et al. 2022

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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.

“…These intense energy conversions usually occur within kinetic‐scale structures, most of which are reconnecting current sheets (Burch et al., 2016; Dong et al., 2020; Genestreti et al., 2017; Khotyaintsev et al., 2016; Zhou et al., 2016, 2018). Some of the reconnecting current sheets are in the exhaust of the large‐scale magnetopause reconnection, that is, they are secondary reconnections (Øieroset et al., 2016; Wang et al., 2017, 2020; Zhong et al., 2021; Zhou et al., 2017). Recent observations also identified kinetic‐scale reconnection induced by the Kelvin‐Helmholtz vortex (KHV; Eriksson et al., 2016), which is also likely important for energy conversion and transport through multiscale processes (Hasegawa et al., 2009; Moore et al., 2016; Nykyri et al., 2006).…”

Section: Introductionmentioning

confidence: 99%

Intense Energy Conversion Events at the Magnetopause Boundary Layer

Man

Zhou

Zhong

et al. 2022

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This paper investigates intense energy conversion events (IECEs) at the dayside magnetopause boundary layer (MBL) using high-resolution data from the Magnetospheric Multiscale (MMS) spacecraft. Most events were detected by MMS in a duration less than 0.5 s, corresponding to a thickness below one ion inertia length. About three-quarters of the events occurred in local reconnecting current sheets. Interestingly, there are more electron-only reconnections than standard reconnections. Most of the reconnection IECEs are within the exhaust of the primary reconnection and the Kelvin-Helmholtz vortices, suggesting that secondary reconnections are important building blocks for the overall energy conversion at the magnetopause. The nonreconnection events are also primarily within the reconnection exhaust and the Kelvin-Helmholtz vortices, highlighting the importance of reconnection and Kelvin-Helmholtz instability in regulating the energy conversion at the MBL.Plain Language Summary Solar wind-magnetosphere coupling is one of the long-standing questions in magnetosphere physics. Part of the input energy from the solar wind is converted and dissipated at the magnetopause boundary layer. Identifying where does energy conversion occurs is valuable for understanding the solar wind-magnetosphere coupling. Here we picked up hundreds of intense energy conversion events using high precision data from Magnetospheric Multiscale at the magnetopause boundary layer to study their locations and fundamental properties. It is found that most events are associated with magnetic reconnection and are more likely located in the reconnection exhaust and Kelvin-Helmholtz vortices. An interesting finding is that most of these intense energy conversion events are associated with reconnection in which only electrons participate, that is, without ion coupling.MAN ET AL.