Simulating the Ion-trapping Acceleration at Rippled Reconnection Fronts

Bai, Kun; Yu, Yiqun; Huang, H.; Cao, Jinbin

doi:10.3847/1538-4357/ac3a08

Cited by 4 publications

(3 citation statements)

References 64 publications

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“…(2013) indicated that the pre‐DF oscillations in 3D PIC simulations is produced by interchange instability and/or lower hybrid drift instability (LHDI). Theses instabilities can lead to the generation of fine structures, such as wavy DF that is associated with interchange instability (Wu et al., 2018), and rippled DF associated with LHDI (Pan et al., 2018), and further regulate the particle acceleration process (Bai, Yu, Huang, & Cao, 2022; Bai, Yu, Huang, Tian, & Cao, 2022). Nevertheless, the B z dip ahead of the DF is still present in these observed DF events with fine structures (Wu et al., 2018).…”

Section: Discussionmentioning

confidence: 99%

On the Magnetic Dip Ahead of the Dipolarization Fronts

Huang

Chen

et al. 2022

JGR Space Physics

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Dipolarization front (DF), a transient structure that is associated with the earthward plasma flow, is widely considered as a result of magnetic reconnection. It is often characterized with a sharp increase in the northward magnetic field Bz preceded by a minor decrease of it. However, the small magnetic dip ahead of the DF is not always present, the reason of which is not well known. By analyzing in site Magnetospheric MultiScale spacecraft measurements at the magnetotail, we present two events of DF with and without a dip ahead of it. It is found that the magnetic dip ahead of DF is accompanied by a guide field By. To investigate the physical mechanism that determines the appearance of the dip, we perform kinetic simulations of symmetric single X line magnetic reconnection under various guide fields. The simulation results show that the dip is generated due to the separation of the gyro‐motion between ions and electrons under the influence of the guide field. Ions are reflected at the DF and further deviated by the guide field away from the neutral sheet, while more electrons remain in the neutral sheet due to their small gyroradius. In the absence of a compensating ion current, a dawnward current thus is formed, carried by the electrons, and generates the dip. Our results bring in a new perspective on the formation of the dip in single X line reconnection.

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Section: Discussionmentioning

confidence: 99%

On the Magnetic Dip Ahead of the Dipolarization Fronts

Huang

Chen

et al. 2022

JGR Space Physics

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“…Such fingerlike structures are found to play a role in modulating the electron acceleration process (Wu et al 2018). Bai et al (2022) also reported significant ion trapping acceleration at the RF with ionscale ripples. Unlike these surface structures with ion or ionelectron hybrid scales, Liu et al (2018b) recently reported that the RF layer has electron-scale density gradients, currents, and electric fields, based on the MMS mission, which consists of four spacecraft separated by 30 km.…”

Section: Introductionmentioning

confidence: 93%

Electron Surfing Acceleration at Rippled Reconnection Fronts

Bai

Huang

et al. 2022

ApJ

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The reconnection front (RF), one of the most efficient accelerators of particles in the terrestrial magnetosphere, is a sharp plasma boundary resulting from transient magnetic reconnection. It has been both theoretically predicted and observationally confirmed that electron-scale substructures can develop at the RFs. How such electron-scale structures modulate the electron energization and transport has not been fully explored. Based on high-resolution data from MMS spacecraft and particle tracing simulations, we investigate and compare the electron acceleration across two typical RFs with or without rippled electron-scale structures. Both observations and simulations reveal that high-energy electron flux behind the RF increases more dramatically if the electrons encounter a rippled RF surface, as compared to a smooth RF surface. The main acceleration mechanism is electron surfing acceleration, in which electrons are trapped by the ripples, due to the large local magnetic field gradient, and therefore undergo surfing motion along the motional electric field.

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“…Otherwise, the guiding center approximation can be readily applied. In this study, we trace ions in the global electromagnetic field by solving motion equations with a fourth-order Runge-Kutta scheme (Northrop 1963; Brizard & Chan 1999; Cary & Brizard 2009;Bai et al 2022aBai et al , 2022b. To determine the energy flux at a location of interest, we trace the particle backward in time to its initial location.…”

Section: Ion Accelerationmentioning

confidence: 99%

The Role of Magnetic Flux Rope in Ion Acceleration: MHD Simulations and Test-particle Tracing

Bai

et al. 2022

ApJ

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Magnetic flux ropes (MFRs), playing a crucial role in particle energization and energy transport in the solar–terrestrial space, are helical structures produced by magnetic reconnection. It has been both theoretically predicted and observationally confirmed that MFRs and associated processes are inherently three-dimensional in space. Although such structures have been widely suggested as a favorable place for electron acceleration, whether large-scale MFRs can lead to ion acceleration has been rarely investigated. In this study, an MHD model is used to examine the evolution of large-scale MFRs in the magnetotail, and a test-particle simulation is further employed to study the associated ion energization. Results show that magnetic reconnections take place at multiple X-lines in the magnetotail current sheet, generating a twisted MFR with a scale of about 10 R e in azimuth. It propagates earthward following the tail reconnection but its east and west wings are significantly distorted azimuthally. Test-particle tracing reveals that ions (0.1–100 keV) can be trapped within the rope while being effectively accelerated. The rope therefore brings in energetic plasma sources into the inner magnetosphere as it transports earthward. These results demonstrate that the MFR is an important source carrier for the ring-current formation in the inner magnetosphere.

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Simulating the Ion-trapping Acceleration at Rippled Reconnection Fronts

Cited by 4 publications

References 64 publications

On the Magnetic Dip Ahead of the Dipolarization Fronts

On the Magnetic Dip Ahead of the Dipolarization Fronts

Electron Surfing Acceleration at Rippled Reconnection Fronts

The Role of Magnetic Flux Rope in Ion Acceleration: MHD Simulations and Test-particle Tracing

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