Particle-in-cell simulations of magnetically driven reconnection using laser-powered capacitor coils

Huang, Kai; Lu, Quanming; Gao, Lan; Ji, Hantao; Wang, Xueyi; Fan, Feibin

doi:10.1063/1.5021147

Cited by 7 publications

(13 citation statements)

References 41 publications

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“…It has been demonstrated that the thickness of the electron diffusion region during fast reconnection is on the electron inertia scale (Huang, Lu, Yang, et al, 2011; Huang, Lu, Gao, et al, 2018; Ji et al, 1998; Olson et al, 2016; Wygant et al, 2005), thus we trace the active region of the x‐line using criterion δ < 2 d e , l , that is triggered when the current sheet half‐thickness is thinner than two local electron inertial length. Figure 1c shows the time stacks of the reconnection electric field E y and the current sheet half‐thickness δ along the x‐line; here we use J y to calculate δ .…”

Section: Overview Of the Internal X‐line Asymmetrymentioning

confidence: 99%

Scaling of Magnetic Reconnection With a Limited X‐Line Extent

Huang

Liu

et al. 2020

Geophysical Research Letters

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Contrary to all the 2-D models, where the reconnection x-line extent is infinitely long, we study magnetic reconnection in the opposite limit. An internal x-line asymmetry along the current direction develops because of the transport of reconnected magnetic flux by electrons beneath the ion kinetic scale, resulting in a suppression region identified in Liu et al. (2019, https://doi.org/10.1029/ 2019JA026539). In this letter, we incorporate the length scale of this suppression region ≃10d i to quantitatively model the reduction of the reconnection rate and the maximum outflow speed observed in the short x-line limit. The average reconnection rate drops because of the limited active region (where the current sheet thins down to the electron inertial scale) within an x-line. The outflow speed reduction correlates with the decrease of the J × B force, that can be modeled by the phase shift between the J and B profiles, also as a consequence of the flux transport. Plain Language Summary Magnetic reconnection is a fundamental physical process that is responsible for releasing the magnetic energy during substorms of planetary magnetotails. Previous studies of magnetic reconnection usually take the two-dimensional (2-D) approach, which assumes that reconnection is uniform in the third direction out of the 2-D reconnection plane. However, observations suggest that reconnection can be limited in the third direction, such as reconnection at Mercury's magnetotail. It turns out that reconnection can be suppressed when reconnection region is very limited in the third direction. Under the guidance of a series of 3-D kinetic simulations, in this work, we write down quantitative models to describe how the reconnection rate and reconnection outflow speed drop in this limit. Notably, these two quantities are most essential in defining the well-being of magnetic reconnection, which can tell us when reconnection shall be suppressed. The models are formulated by considering the transport of reconnected magnetic flux in the third direction, which can weaken the driver of the reconnection process.

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Section: Overview Of the Internal X‐line Asymmetrymentioning

confidence: 99%

Scaling of Magnetic Reconnection With a Limited X‐Line Extent

Huang

Liu

et al. 2020

Geophysical Research Letters

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“…The reason for the formation of J e y is the rapid movement of the magnetic field lines away from the current sheet, and the electrons in the outflow regions are continuously bounced. [30] Electron outflow has been verified as a criterion for reconnection in both simulations and experiments. [49,50] There is no current density in the P-case where no MR occurs.…”

Section: Simulation Resultsmentioning

confidence: 82%

“…Thanks to this experiment configuration, the direct measurement of the nonthermal electrons from MR becomes feasible, [28] which is limited in the dedicated devices like MRX, because of the larger system size compared to the short mean free path and Debye lengths. Experiments [27,29] and kinetic simulations [30,31] depend on this configuration have revealed MR outflow, quadruple magnetic fields, and nonthermal electron acceleration. Different acceleration mechanisms have been studied theoretically and numerically, including direct acceleration of reconnection electric field where the particles drift along the reconnection electric field following the Speiser orbits, [32][33][34] Fermi mechanism that is the particles are reflected in contract magnetic island [35,36] or by the moving magnetic field lines [37,38] and gain kinetic energy, betatron acceleration that is the magnetized electron is accelerated by the perpendicular inductive electric field generated by the enhancement magnetic field, [39][40][41] and parallel electric field acceleration along the magnetic fields.…”

Section: Introductionmentioning

confidence: 84%

“…[42][43][44] In this paper, we perform two-dimensional (2D) PIC simulations to examine MR and non-MR dynamics based on the experimental configuration by Pei et al [27] We consider two cases, the magnetic fields generated in the middle region by two driving currents are antiparallel and parallel, referred to as AP-case and P-case, respectively, and naturally, there is no reconnection in the latter case. In the paper of Huang et al, [30] the simulation of the AP-case has been performed and found that the electrons are accelerated forming a power-law with an index of 3. We compare the AP-case and P-case and find that they both experience expanding and squeezing phases until the AP-case comes to the reconnection stage, and the Pcase still squeezes.…”

Section: Introductionmentioning

confidence: 99%

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Particle-in-cell simulations of low-β magnetic reconnection driven by laser interaction with a capacitor–coil target

Yuan

Zhou²,

Zhang³

et al. 2023

Chinese Phys. B

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The dynamics of low-$\beta$ magnetic reconnection (MR) driven by laser interaction with a capacitor-coil target are reexamined by simulations in this paper. We compare two cases MR and non-MR (also referred as AP-case and P-case standing for the anti-parallel and parallel magnetic field lines, respectively) to distinguish the different characteristics between them. We find that only in AP-case the reconnection electric field shows up around the X line and the electron jet is directed toward the X line. The quadruple magnetic fields exist in both cases, however, they distribute in the current sheet area in AP-case, and out of the squeezing area in P-case, because electrons are demagnetized in the electron diffusion region in the MR process, which is absent in P-case. The electron acceleration is dominant by the Fermi-like mechanism before the MR process, and by the reconnection electric field when the MR occurs. A power-law electron energy spectrum with an index of 1.8 is found in AP-case. This work proves the significant potential of this experimental platform to be applied in the studies of low-$\beta$ astronomy phenomena.

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“…For these conditions we found through particle tracking studies that the electrons are energized primarily by direct acceleration at the X points, with plasmoid related acceleration contributing only minor additional energy gain. Numerical studies by other groups have shown similar electron acceleration [31][32][33] . Here we extend our study to larger system sizes in terms of the microscopic ion skin depth d i = c/ω pi , which could be produced at megajoule class laser facilities such as NIF.…”

Section: Introductionmentioning

confidence: 62%

Nonthermal electron and ion acceleration by magnetic reconnection in large laser-driven plasmas

et al. 2020

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Magnetic reconnection is a fundamental plasma process that is thought to play a key role in the production of nonthermal particles associated with explosive phenomena in space physics and astrophysics. Experiments at high-energy-density facilities are starting to probe the microphysics of reconnection at high Lundquist numbers and large system sizes. We have performed particle-in-cell (PIC) simulations to explore particle acceleration for parameters relevant to laser-driven reconnection experiments. We study particle acceleration in large system sizes that may be produced soon with the most energetic laser drivers available, such as at the National Ignition Facility. In these conditions, we show the possibility of reaching the multi-plasmoid regime, where plasmoid acceleration becomes dominant. Our results show the transition from X point to plasmoid-dominated acceleration associated with the merging and contraction of plasmoids that further extend the maximum energy of the power-law tail of the particle distribution for electrons. We also find for the first time a system-sizedependent emergence of nonthermal ion acceleration in driven reconnection, where the magnetization of ions at sufficiently large sizes allows them to be contained by the magnetic field and energized by direct X point acceleration. For feasible experimental conditions, electrons and ions can attain energies of max,e /k B T e > 100 and max,i /k B T i > 1000. Using PIC simulations with binary Monte Carlo Coulomb collisions we study the impact of collisionality on plasmoid formation and particle acceleration. The implications of these results for understanding the role reconnection plays in accelerating particles in space physics and astrophysics are discussed.

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Particle-in-cell simulations of magnetically driven reconnection using laser-powered capacitor coils

Cited by 7 publications

References 41 publications

Scaling of Magnetic Reconnection With a Limited X‐Line Extent

Scaling of Magnetic Reconnection With a Limited X‐Line Extent

Particle-in-cell simulations of low-β magnetic reconnection driven by laser interaction with a capacitor–coil target

Nonthermal electron and ion acceleration by magnetic reconnection in large laser-driven plasmas

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