Small-scale dipolarization fronts in the Earth′s magnetotail

Huang, Jing; Zhou, Meng; Li, Huimin; Deng, Xiaohua; Liu, Jiang; Huang, Suming

doi:10.26464/epp2019036

Cited by 5 publications

(3 citation statements)

References 36 publications

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“…For the ion scale of the DF, statistical studies have shown that the thickness of the DF was ∼1.7–1.8 ion inertial length (e.g., Fu et al., 2012b; J. Liu et al., 2013; Schmid et al., 2011). DFs with ion‐scale in the dawn‐dusk direction were also reported recently (J. Huang et al., 2019). Runov et al.…”

Section: Introductionsupporting

confidence: 76%

Electron Pitch Angle Distributions Around Dipolarization Fronts at the Off Magnetic Equator

2021

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The pitch angle distributions of energetic electrons (10 s–200 keV) around the dipolarization front (DF) have been studied extensively. However, the pitch angle distributions of energetic electrons around the DF at the off magnetic equator have been unclear so far. In this study, we present the observations of the DF at the off magnetic equator in the near‐Earth tail. Some properties of the DF at the off magnetic equator are presented. Importantly, the triple‐peaked pitch angle distribution of energetic electrons around the DF is found. Such a new type of distribution is a peak at around 22.5°, 90°, and 157.5°, which is a combinational consequence of betatron acceleration, Fermi acceleration, and magnetic mirror effect. Using an analytical model, we quantitatively reproduce the processes of betatron acceleration, Fermi acceleration, and magnetic mirror effect. These results will further enhance our understanding of the electron dynamics around DFs.

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Section: Introductionsupporting

confidence: 76%

Electron Pitch Angle Distributions Around Dipolarization Fronts at the Off Magnetic Equator

2021

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“…We should note that our simulation is 2.5‐D, which neglects any variations in the Y direction (the out‐of‐plane direction). However, significant variations in the Y direction are seen on the DF due to the cross‐tail instabilities developed on the front surface (Huang et al, 2019; Lapenta et al, 2014; Pritchett, 2016), which leads to an alternative sign of J · E along the surface of the DF. This 3‐D effect may also lead to the sign change of Pi‐D in Y.…”

Section: Discussion and Summarymentioning

confidence: 99%

Force and Energy Balance of the Dipolarization Front

Song

Zhou

et al. 2020

JGR Space Physics

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We have performed a particle-in-cell simulation to understand the dynamic evolution of the dipolarization front during its early stage after ejected by magnetic reconnection, focusing on the force and energy balance around the dipolarization front. We track the temporal evolution of the force and different energy channels in the Lagrangian frame of the dipolarization front. We find that the curvature force continuously accelerates the dipolarization front moving outward, while the thermal pressure gradient force hinders the movement of the DF. The DF is accelerated outward because the total force is positive. The maximum value of B z at the DF gradually increases during the outward propagation of the front. Although the dipolarization front is the site with significant energy conversion from the magnetic field to plasma, that is, J • E > 0, the compression of the magnetic field by the convergent flow at the front leads to the gradual enhancement of B z. The released magnetic energy bulk accelerates and heats the plasma. The plasma thermal energy increases at the front that is primarily due to the work of the pressure gradient (v • (∇ • P) > 0), while the enthalpy flux emitted from the front reduces the thermal energy. Both the pressure-strain interaction −(P′ • ∇) • v and the pressure dilation p∇ • v contribute to the ion and electron temperature enhancement. Our results are important for revealing the dynamic evolution of the dipolarization fronts and will aid us to understand the energy transport in the disturbed magnetotail. Plain Language Summary Dipolarization front is a common structure in Earth's magnetotail. As a derivant of magnetic reconnection, the dipolarization front is generated at the X-line and propagates earthward. Scientists believe that dipolarization fronts play important roles in the energetics of the magnetotail; however, many details of this process are missing. Using particle simulation, we are able to study the force and energy balance around the dipolarization front in detail. We find that it is the curvature force that accelerates the dipolarization front moving away from the reconnection site. At the dipolarization front, different energy channels exchange. Poynting flux feeds the magnetic energy, which is dissipated to heat plasma around the front. The energy exchange and transport at the dipolarization front will shed new light on understanding the energy cycle in our magnetosphere.

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“…Similar events have also been reported in simulations (Haynes et al, 2015; Roytershteyn et al, 2015) and observations (Huang SY et al, 2017a, b). These structures, including recently reported kinetic‐scale flux ropes (Huang SY et al, 2016; Matsui et al, 2019; Sun WJ et al, 2019; Wang SM et al, 2019; Yao ST et al, 2020b) and kinetic‐scale magnetic dips and peaks (Hellinger and Štverák, 2018; Stawarz et al, 2018; Yao ST et al, 2018a; Hoilijoki et al, 2019), are new types of coherent structures found in turbulent plasmas, and play important roles in the cascade of turbulence from ion to electron scales (e.g., Huang J et al, 2019; Lucek et al, 2005; Karimabadi et al, 2014; Sahraoui et al, 2020; Shang WS et al, 2020). Yao ST et al (2019a) found that these KSMHs are coupled with electron cyclotron waves, electrostatic solitary waves, and whistler mode waves (Li Z et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Statistical properties of kinetic-scale magnetic holes in terrestrial space

Yao

Yue

Shi

et al. 2021

Earth and Planetary Physics

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Most KSMHs are locally generated in the magnetosheath, rather than advected with the solar wind. q KSMHs are more likely to be generated downstream of the quasi-parallel shock, indicating the importance of turbulence in their generation. q The scale-size of KSMHs is smaller near the subsolar magnetosheath than along the flanks, indicating they may be affected by the magnetosheath pressure environment.

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Small-scale dipolarization fronts in the Earth′s magnetotail

Cited by 5 publications

References 36 publications

Electron Pitch Angle Distributions Around Dipolarization Fronts at the Off Magnetic Equator

Electron Pitch Angle Distributions Around Dipolarization Fronts at the Off Magnetic Equator

Force and Energy Balance of the Dipolarization Front

Statistical properties of kinetic-scale magnetic holes in terrestrial space

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