Effect of the Reconnection Electric Field on Electron Distribution Functions in the Diffusion Region of Magnetotail Reconnection

Bessho, Naoki; Chen, Li‐Jen; Wang, S.; Hesse, Michael

doi:10.1029/2018gl081216

Cited by 15 publications

(25 citation statements)

References 41 publications

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“…Such stripes can be seen in the inner EDR region (black bars at the bottom of Figures and ) as well as in the Earthward outflow jet region (magenta bars). The results support the conclusion by Bessho et al () that reconnection electric field can be estimated from the second peak in the velocity distribution functions such as shown in Figure d.…”

Section: Change In the Electron Distribution Functionsupporting

confidence: 91%

Structure of the Current Sheet in the 11 July 2017 Electron Diffusion Region Event

et al. 2019

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The structure of the current sheet along the Magnetospheric Multiscale (MMS) orbit is examined during the 11 July 2017 Electron Diffusion Region (EDR) event. The location of MMS relative to the X‐line is deduced and used to obtain the spatial changes in the electron parameters. The electron velocity gradient values are used to estimate the reconnection electric field sustained by nongyrotropic pressure. It is shown that the observations are consistent with theoretical expectations for an inner EDR in 2‐D reconnection. That is, the magnetic field gradient scale, where the electric field due to electron nongyrotropic pressure dominates, is comparable to the gyroscale of the thermal electrons at the edge of the inner EDR. Our approximation of the MMS observations using a steady state, quasi‐2‐D, tailward retreating X‐line was valid only for about 1.4 s. This suggests that the inner EDR is localized; that is, electron outflow jet braking takes place within an ion inertia scale from the X‐line. The existence of multiple events or current sheet processes outside the EDR may play an important role in the geometry of reconnection in the near‐Earth magnetotail.

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Section: Change In the Electron Distribution Functionsupporting

confidence: 91%

Structure of the Current Sheet in the 11 July 2017 Electron Diffusion Region Event

et al. 2019

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“…In most cases, the crescent‐shaped distribution was multiple stripes. Bessho et al () suggested that the multiple stripes were due to multiple meandering bounces caused by the reconnection electric field, and the separation between stripes became larger as the Hall electric field increased in the symmetric reconnection. So the multiple stripes were easily distinguished in the region with the large electric field E N , consistent with our observations.…”

Section: Discussion and Summarymentioning

confidence: 99%

“…A few mechanisms were proposed to interpret such distribution, such as meandering (cusp-like) electron orbits (Hesse et al, 2014;Lapenta et al, 2017;Shay et al, 2016) and a drift-kinetic model (Egedal et al, 2016). Most recently, the crescent-shaped electron distribution was detected in the EDR of a symmetric reconnection in the magnetotail as well Zhou et al, 2019), as predicted by numerical simulations (e.g., Bessho et al, 2018). Moreover, multiple discrete striation of the crescent-shaped and the triangle-shaped in the electron distribution functions were measured and attributed to multiple meandering bounces in the diffusion region (Bessho et al, 2018;Torbert et al, 2018).…”

Section: Introductionmentioning

confidence: 86%

Observation of Nongyrotropic Electron Distribution Across the Electron Diffusion Region in the Magnetotail Reconnection

Wang

et al. 2019

Geophysical Research Letters

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Using measurements by the Magnetospheric Multiscale spacecraft in the magnetotail, we studied electron distribution functions across an electron diffusion region. The dependence of the nongyrotropic distribution on the energy and vertical distance from the electron diffusion region midplane was revealed for the first time. The nongyrotropic distribution was observed everywhere except for an extremely narrow layer right at the electron diffusion region midplane. The energy of the nongyrotropic distribution increased with growth of the vertical distance from the midplane. For the electrons within certain energy range, they exhibited the nongyrotropic distribution at the distance further away from the midplane than that expected from the meandering motion. The correlation between the crescent-shaped distribution with multiple stripes and the large Hall electric field was established. It appears that the measured nongyrotropic distribution and the crescent-shaped distribution were caused by the meandering motion and the Hall electric field together. Plain Language SummaryThe Magnetospheric Multiscale mission is designed to study electron physics of magnetic reconnection, a key process for many explosive phenomena in solar flares and magnetosphere. Understanding electron motion is highly important in the study of magnetic reconnection, and the electron velocity distribution is an intuitive and effective way to study the electron dynamics. In this paper, we present a complete electron diffusion region crossing by Magnetospheric Multiscale during a nearly symmetric magnetic reconnection in the magnetotail and show the evolution of the electron velocity distributions across the electron diffusion region. In addition, the relationship between Hall electric field and crescent-shaped electron distribution is also shown in this paper. Key Points:• The electron nongyrotropic distribution depended on the energy and the normal distance from the midplane of the electron diffusion region • The electron crescent distributions were caused by the meandering motion and the Hall electric field together • The fine substructures were observed in the narrow electron diffusion region

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“…During the MMS encounter with an electron diffusion region described in Torbert et al (2018), highly non-Maxwellian electron distribution functions were observed close to the x-point. These velocity distributions have been studied in detail (Bessho et al, 2018), and it has been shown that the combination of the electron meandering motion and reconnection electric field is important for setting the structure of the distribution functions. These distributions are used to identify regions in the simulation for study and provide a link to reality.…”

Section: Reconstruction Of Distributions In Reconnection Regionsmentioning

confidence: 99%

“…In particular, for magnetic reconnection regions in the magnetotail, strongly anisotropic electron velocity distributions with p ‖ > p ⊥ are found in inflow regions (Øieroset et al, 2002), while triangular distributions with accelerated electrons are found within the electron diffusion region and close to the x-point during antiparallel reconnection (Torbert et al, 2018). The formation of these distributions can be explained by electron trapping in the inflow (Egedal et al, 2013), while in the electron diffusion region, the meandering electron orbits in the magnetic field reversal explains the striated and counterstreaming populations (Bessho et al, 2014(Bessho et al, , 2018Fujimoto & Sydora, 2009;Ng et al, 2011Ng et al, , 2012.…”

Section: Introductionmentioning

confidence: 99%

Reconstruction of Electron and Ion Distribution Functions in a Magnetotail Reconnection Diffusion Region

Chen

Hakim

et al. 2020

JGR Space Physics

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In the diffusion region of magnetotail reconnection, particle distributions are highly structured, exhibiting triangular shapes and multiple striations that deviate dramatically from the Maxwellian distribution. Fully kinetic simulations have been demonstrated to be capable of producing the essential structures of the observed distribution functions, yet are computationally not feasible for 3D global simulations. The fluid models used for large‐scale simulations, on the other hand, do not have the kinetic physics necessary for describing reconnection accurately. Our study aims to bridge fully kinetic and fluid simulations by quantifying the information required to capture the non‐Maxwellian features in the distributions underlying the closures used in the fluid code. We compare the results of fully kinetic simulations with observed electron velocity distributions in a magnetotail reconnection diffusion region and use the maximum entropy model to reconstruct electron and ion distributions using various numbers of moments obtained from the simulation. Our results indicate that using only local moments, the maximum entropy model can reproduce many of the features of the distributions: (1) the electron outflow distribution with a tilted triangular structure is reproduced with 21 or more moments in agreement with Ng et al. (2018, https://doi.org/10.1063/1.5041758) and (2) counterstreaming distributions can be captured with the 35‐moment model when the separation in velocity space between the populations is large.

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Effect of the Reconnection Electric Field on Electron Distribution Functions in the Diffusion Region of Magnetotail Reconnection

Cited by 15 publications

References 41 publications

Structure of the Current Sheet in the 11 July 2017 Electron Diffusion Region Event

Structure of the Current Sheet in the 11 July 2017 Electron Diffusion Region Event

Observation of Nongyrotropic Electron Distribution Across the Electron Diffusion Region in the Magnetotail Reconnection

Reconstruction of Electron and Ion Distribution Functions in a Magnetotail Reconnection Diffusion Region

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