Suprathermal particle energization in dipolarization fronts: Particle‐in‐cell simulations

Lu, San; Angelopoulos, V.; Fu, H. S.

doi:10.1002/2016ja022815

Cited by 84 publications

(79 citation statements)

References 76 publications

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“…From the observations, we conclude that MMS traversed deep into the electron diffusion region northward of the re‐reconnection X‐line but barely missed the X‐line. Agreement between the observed signatures and Lu et al () PIC simulation results provides the first direct evidence for dissipation of earthward‐moving flux ropes through re‐reconnection. We estimated a rate of reconnection and provided a qualitative argument of the radial profile of the erosion process as the dissipating flux rope propagates earthward.…”

Section: Introductionsupporting

confidence: 77%

“…Magnetic and electric fields, and plasma measurements expected for encounter of the re‐reconnection region (i) northward and (2) southward of the X‐line, respectively. (b) Simulation runs with background guide field of 0.1 B 0 (Lu et al, ). Black lines represent magnetic field lines with color plots representing (top) B Z , (middle) B Y , and (bottom) electron velocity in the z direction V e , Z .…”

Section: Introductionmentioning

confidence: 99%

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Dissipation of Earthward Propagating Flux Rope Through Re‐reconnection with Geomagnetic Field: An MMS Case Study

Poh

Slavin

et al. 2019

JGR Space Physics

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Three‐dimensional global hybrid simulations and observations have shown that earthward‐moving flux ropes (FRs) can undergo magnetic reconnection (or re‐reconnection) with the near‐Earth dipole field to create dipolarization front (DF)‐like signatures that are immediately preceded by brief intervals of negative BZ. The simultaneous erosion of the southward BZ field at the leading edge of the FR and continuous reconnection of lobe magnetic flux at the X‐line tailward of the FR result in the asymmetric south‐north BZ signature in many earthward‐moving FRs and possibly DFs with negative BZ dips prior to their observation. In this study, we analyzed Magnetospheric MultiScale (MMS) observation of fields and plasma signatures associated with the encounter of an ion diffusion region ahead of an earthward‐moving FR on 3 August 2017. The signatures of this re‐reconnection event were (i) +/− BZ reversal, (ii) −/+ bipolar‐type quadrupolar Hall magnetic fields, (iii) northward super‐Alfvénic electron outflow jet of ~1,000–1,500 km/s, (iv) Hall electric field of ~15 mV/m, (v) intense currents of ~40–100 nA/m2, and (vi) J·E′ ~0.11 nW/m3. Our analysis suggests that the MMS spacecraft encounters the ion and electron diffusion regions but misses the X‐line. Our results are in good agreement with particle‐in‐cell simulations of Lu et al. (2016, https://doi.org/10.1002/2016JA022815). We computed a dimensionless reconnection rate of ~0.09 for this re‐reconnection event and through modeling, estimating that the FR would fully dissipate by −16.58 RE. We demonstrated pertubations in the high‐latitude ionospheric currents at the same time of the dissipation of earthward‐moving FRs using ground‐ and space‐based measurements.

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Section: Introductionsupporting

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Dissipation of Earthward Propagating Flux Rope Through Re‐reconnection with Geomagnetic Field: An MMS Case Study

Poh

Slavin

et al. 2019

JGR Space Physics

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“…Electron acceleration processes inside the earthward FPR have been extensively investigated in previous studies [e.g., Ashour‐Abdalla et al ., ; Fu et al ., , ; Khotyaintsev et al ., ; Pan et al ., ; Lu et al ., ], while electron acceleration inside the tailward FPR remains an open issue hitherto. In this study, we particularly focus on the electron acceleration inside the tailward FPR that is formed due to flow rebounce in the near‐Earth region and compare it quantitatively with that inside the earthward FPR.…”

Section: Summary and Discussionmentioning

confidence: 99%

Suprathermal electron acceleration in the near‐Earth flow rebounce region

Liu

et al. 2017

JGR Space Physics

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Flux pileup regions (FPRs) are traditionally referred to the strong‐Bz bundles behind dipolarization fronts (DFs) in the Earth's magnetotail and can appear both inside earthward and tailward bursty bulk flows. It has been widely reported that suprathermal electrons (40–200 keV) can be efficiently accelerated inside earthward FPRs, leaving the electron acceleration inside tailward FPRs as an open question. In this study, we focus on the electron acceleration inside a tailward FPR that is formed due to the flow rebounce in the near‐Earth region (XGSM ≈ −12 RE) and compare it quantitatively with the acceleration inside an earthward FPR. By examining the Cluster data in 2008, we sequentially observe an earthward FPR and a tailward FPR in the near‐Earth region, with the earthward one belonging to decaying type and the tailward one belonging to growing type. Inside the earthward FPR, Fermi acceleration and betatron cooling of suprathermal electrons are found, while inside the tailward FPR, Fermi and betatron acceleration occur. Whistler‐mode waves are observed inside the tailward FPR; their generation process may still be at the early stage. We notice that the suprathermal electron fluxes inside the tailward FPR are about twice as large as those inside the earthward FPR, suggesting that the acceleration of suprathermal electrons is more efficient in the flow rebounce region. These acceleration processes have been successfully reproduced using an analytical model; they emphasize the role of flow rebounce in accelerating suprathermal electrons and further reveal how the MHD‐scale flow modulates the kinetic‐scale electron dynamics in the near‐Earth magnetotail.

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“…[19][20][21] With a 1-D PIC simulation model, we have successfully reproduced two types of E-t channels. The 1-D PIC simulation model is performed in a homogeneous and collisionless electron-proton plasma, which only allows the spatial variation in the x direction.…”

Section: Simulation Model and Initial Setupmentioning

confidence: 98%

Theoretical analysis on lower band cascade as a mechanism for multiband chorus in the Earth’s magnetosphere

Gao

Wang

et al. 2018

AIP Advances

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Whistler-mode waves play a crucial role in controlling electron dynamics in the Earth’s Van Allen radiation belt, which is increasingly important for spacecraft safety. Using THEMIS waveform data, Gao et al. [X. L. Gao, Q. Lu, J. Bortnik, W. Li, L. Chen, and S. Wang, Geophys. Res. Lett., 43, 2343-2350, 2016] have reported two multiband chorus events, wherein upper-band chorus appears at harmonics of lower-band chorus. They proposed that upper-band harmonic waves are excited through the nonlinear coupling between the electromagnetic and electrostatic components of lower-band chorus, a second-order effect called “lower band cascade”. However, the theoretical explanation of lower band cascade was not thoroughly explained in the earlier work. In this paper, based on a cold plasma assumption, we have obtained the explicit nonlinear driven force of lower band cascade through a full nonlinear theoretical analysis, which includes both the ponderomotive force and coupling between electrostatic and electromagnetic components of the pump whistler wave. Moreover, we discover the existence of an efficient energy-transfer (E-t) channel from lower-band to upper-band whistler-mode waves during lower band cascade for the first time, which is also confirmed by PIC simulations. For lower-band whistler-mode waves with a small wave normal angle (WNA), the E-t channel is detected when the driven upper-band wave nearly satisfies the linear dispersion relation of whistler mode. While, for lower-band waves with a large WNA, the E-t channel is found when the lower-band wave is close to its resonant frequency, and the driven upper-band wave becomes quasi-electrostatic. Through this efficient channel, the harmonic upper band of whistler waves is generated through energy cascade from the lower band, and the two-band spectral structure of whistler waves is then formed. Both two types of banded whistler-mode spectrum have also been successfully reproduced by PIC simulations.

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Suprathermal particle energization in dipolarization fronts: Particle‐in‐cell simulations

Cited by 84 publications

References 76 publications

Dissipation of Earthward Propagating Flux Rope Through Re‐reconnection with Geomagnetic Field: An MMS Case Study

Dissipation of Earthward Propagating Flux Rope Through Re‐reconnection with Geomagnetic Field: An MMS Case Study

Suprathermal electron acceleration in the near‐Earth flow rebounce region

Theoretical analysis on lower band cascade as a mechanism for multiband chorus in the Earth’s magnetosphere

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