The mechanisms of electron acceleration in antiparallel and guide field magnetic reconnection

Huang, Can; Lu, Quanming; Wang, Shui

doi:10.1063/1.3457930

Cited by 104 publications

(103 citation statements)

References 31 publications

(35 reference statements)

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“…In this regime, the ion flow is small (V i << V e ), so the contours of toroidal field in Figure 3 are a good approximation to streamlines of the in-plane current, and equivalently the electron flow. It is clear from these patterns that guide field is capable of strongly changing the electron flow dynamics, a result which has been previously studied by simulations [27,28]. The resulting patterns are similar to those of two-fluid simulations [29], and we interpret this qualitative similarity as physical evidence supporting the conclusion that nonlinear interactions between the Hall currents and an applied guide field result in a modified quadrupole field structure.…”

supporting

confidence: 69%

Quantitative Study of Guide-Field Effects on Hall Reconnection in a Laboratory Plasma

Tharp

Lawrence

et al. 2012

Phys. Rev. Lett.

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supporting

confidence: 69%

Quantitative Study of Guide-Field Effects on Hall Reconnection in a Laboratory Plasma

Tharp

Lawrence

et al. 2012

Phys. Rev. Lett.

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“…When the initial guide field is sufficiently large, the parallel electric field in guide field reconnection, which is generated by the gradient of the electron pressure, is found to play an important role to form such structures. The parallel electric field only exists along the separatrix from the upper left to the lower right [20]. Electrons are accelerated by the parallel electric field in the vicinity of the X line, as well as when they move toward the X line along the separatrix from the upper left to the lower right.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

The effects of the guide field on the structures of electron density depletions in collisionless magnetic reconnection

Cao

et al. 2011

Chin. Sci. Bull.

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Two-dimensional particle-in-cell simulations are performed to investigate the formation of electron density depletions in collisionless magnetic reconnection. In anti-parallel reconnection, the quadrupole structures of the out-of-plane magnetic field are formed, and four symmetric electron density depletion layers can be found along the separatrices due to the effects of magetic mirror. With the increase of the initial guide field, the symmetry of both the out-of-plane magnetic field and electron density depletion layers is distorted. When the initial guide field is sufficiently large, the electron density depletion layers along the lower left and upper right separatrices disappear. The parallel electric field in guide field reconnection is found to play an important role in forming such structures of the electron density depletion layers. The structures of the out-of-plane magnetic field B y and electron depletion layers in anti-parallel and guide field reconnection are found to be related to electron flow or in-plane currents in the separatrix regions. In anti-parallel reconnection, electrons flow towards the X line along the separatrices, and are directed away from the X line along the magnetic field lines just inside the separatrices. In guide field reconnection, electrons can only flow towards the X line along the upper left and lower right separatrices due to the existence of the parallel electric field in these regions. Magnetic reconnection is thought to be one of the most important mechanisms that converts rapidly magnetic energy into kinetic energy of plasma. At the same time, the topological configuration of the magnetic field changes. Magnetic reconnection plays an important role in space and laboratory plasma as a driving mechanism for many explosive phenomena, such as solar flares, substorms in the Earth's magnetosphere and disruptions in laboratory fusion experiments [1][2][3][4][5]. At scale lengths greater than the ion inertial length, c/ω pi , magnetohydrodynamic theory is valid, because ions and electrons are both frozen in the magnetic field lines. However, if we study magnetic reconnection at scale lengths between the ion inertial length and electron inertial length *Corresponding author (email: qmlu@ustc.edu.cn) (where the electron inertial length is c/ω pe ), only the electrons are frozen in the magnetic field lines, and ions can move across the magnetic field lines. This ion-electron decoupling causes Hall effects which are very important in collisionless magnetic reconnection [6][7][8]. At scale lengths below c/ω pe , the frozen-in constraint of the electrons is also broken, both ions and electrons can move across the magnetic field lines [7,9]. Sonnerup [6] proposed that the Hall effects can lead to the in-plane Hall current system, and the relations between the Hall current and the out-of-plane magnetic field have recently been studied extensively in anti-parallel reconnection. This can be roughly summarized as follows: Because of the magnetic mirror effect, electrons will flow toward...

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“…Hoshino et al [9] showed that several processes can occur in a single reconnection layer -in the X-line region [50,51] and along the separatrix region [52,53], particles can get accelerated in the nonideal electric field and then further accelerated due to grad-B drift and the curvature drift in the magnetic pileup region [54], where the electric field is mostly ideal E = −v×B/c. Drake et al [11] have further developed the Fermi mechanism inside the magnetic islands as particles get bounced at two ends of islands repeatedly [12].…”

Section: Nonthermal Particle Acceleration In Magnetic Reconnec-timentioning

confidence: 99%

“…The nonideal electric field only contributes to a small fraction of energy conversion in the simulation. The effect of a guide field that is normal to the reconnection plane can significantly alter the dominant acceleration mechanism [12,13,51].…”

Section: Nonthermal Particle Acceleration In Magnetic Reconnec-timentioning

confidence: 99%

Particle acceleration during magnetic reconnection in a low-beta pair plasma

Guo

Daughton

et al. 2016

Physics of Plasmas

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Plasma energization through magnetic reconnection in the magnetically-dominated regime featured by low plasma beta (β = 8πnkT 0 /B 2 1) and/or high magnetizationis important in a series of astrophysical systems such as solar flares, pulsar wind nebula, and relativistic jets from black holes, etc. In this paper, we review the recent progress on kinetic simulations of this process and further discuss plasma dynamics and particle acceleration in a low-β reconnection layer that consists of electron-positron pairs. We also examine the effect of different initial thermal temperatures on the resulting particle energy spectra. While earlier papers have concluded that the spectral index is smaller for higher σ, our simulations show that the spectral index approaches p = 1 for sufficiently low plasma β, even if σ ∼ 1. Since this predicted spectral index in the idealized limit is harder than most observations, it is important to consider effects that can lead to a softer spectrum such as open boundary simulations. We also remark that the effects of 3D reconnection physics and turbulence on reconnection need to be addressed in the future.

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The mechanisms of electron acceleration in antiparallel and guide field magnetic reconnection

Cited by 104 publications

References 31 publications

Quantitative Study of Guide-Field Effects on Hall Reconnection in a Laboratory Plasma

Quantitative Study of Guide-Field Effects on Hall Reconnection in a Laboratory Plasma

The effects of the guide field on the structures of electron density depletions in collisionless magnetic reconnection

Particle acceleration during magnetic reconnection in a low-beta pair plasma

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