Ultrahigh performance three-dimensional electromagnetic relativistic kinetic plasma simulation

Simulations of decaying magnetohydrodynamic (MHD) turbulence are performed with a fluid and a kinetic code. The initial condition is an ensemble of long-wavelength, counterpropagating, shear-Alfvén waves, which interact and rapidly generate strong MHD turbulence. The total energy is conserved and the rate of turbulent energy decay is very similar in both codes, although the fluid code has numerical dissipation whereas the kinetic code has kinetic dissipation. The inertial range power spectrum index is similar in both the codes. The fluid code shows a perpendicular wavenumber spectral slope of k −1.3 ⊥ . The kinetic code shows a spectral slope of k −1.5 ⊥ for smaller simulation domain, and k −1.3 ⊥ for larger domain. We estimate that collisionless damping mechanisms in the kinetic code can account for the dissipation of the observed nonlinear energy cascade. Current sheets are geometrically characterized. Their lengths and widths are in good agreement between the two codes. The length scales linearly with the driving scale of the turbulence. In the fluid code, their thickness is determined by the grid resolution as there is no explicit diffusivity. In the kinetic code, their thickness is very close to the skin-depth, irrespective of the grid resolution. This work shows that kinetic codes can reproduce the MHD inertial range dynamics at large scales, while at the same time capturing important kinetic physics at small scales.

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“…VPIC integrates the coupled Maxwell-Boltzmann equations [22]. We consider a pair plasma for the sake of computational ease.…”

Section: Setup Of Numerical Simulationsmentioning

confidence: 99%

“…We simulate decaying turbulence with the use of two codes -the MHD code PLUTO [21], and the particle-in-cell code VPIC [22]. PLUTO solves the ideal MHD equations with a finite-volume technique.…”

Section: Setup Of Numerical Simulationsmentioning

confidence: 99%

Energy dynamics and current sheet structure in fluid and kinetic simulations of decaying magnetohydrodynamic turbulence

Makwana

Zhdankin

et al. 2015

Physics of Plasmas

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“…As we vary the plasma β, we keep the ratio of injected energy (in the waves) to background magnetic field energy at a constant level of around 0.2. The simulations are performed with the state-of-the-art PIC code VPIC [15].…”

Section: Setup Of Simulations and Energy Spectramentioning

confidence: 99%

Dissipation and particle energization in moderate to low beta turbulent plasma via PIC simulations

Makwana

Guo

et al. 2017

J. Phys.: Conf. Ser.

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“…During this transition, the reconnection electric field ex ceeds the runaway limit leading to a collapse of the dif fusion region current sheet to the electron kinetic scale. These electron layers form elongated current sheets which are also unstable to the formation of new plasmoids in a manner similar to the collisionless limit [8, 18, 19J . The simulations were performed with the kinetic plasma simulation code VPIC [20] which has been modi fied to include Coulomb collisions and benchmarked care fully against transport theory [17]. The initial condition is a Harris sheet with magnetic field Bx = Bo tanh(z/.\) and density n = nosech2(z/.\) provided by drifting The Fokker-Planck treatment of Coulomb collisions gives rise to a number of complications not normally con sidered in the fluid calculations [17].…”

Section: Transition From Collisional To Kinetic Reconnection In Largementioning

confidence: 99%

“…The simulations were performed with the kinetic plasma simulation code VPIC [20] which has been modi fied to include Coulomb collisions and benchmarked care fully against transport theory [17]. The initial condition is a Harris sheet with magnetic field Bx = Bo tanh(z/.\) and density n = nosech2(z/.\) provided by drifting Maxwellian distributions with uniform temperature Te = Ti = To (.\ = 2d i is the half-thickness of the current sheet and Bo is the asymptotic field).…”

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confidence: 99%

Transition from collisional to kinetic regimes in large-scale reconnection layers

et al. 2009

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Using first-principles fully kinetic simulations with a Fokker-Planck collision operator, it is demon strated that Sweet-Parker reco=ection layers are unstable to a chain of plasmoids (secondary is lands) for Lundquist numbers beyond S ;C; 1000. The instability is increasingly violent at higher Lundquist number, both in terms of the number of plasmoids produced and the super-Alfvenic growth rate. A dramatic enhancement in the reconnect ion rate is observed when the half-thickness of the current sheet between two plasmoids approaches the ion inertial length. During this transi tion, the reconnection electric field rapidly exceeds the runaway limit, resulting in the formation of electron-scale current layers that are unstable to the continual formation of new plasmoids.PACS numbers: 52.35. Vd, 52.35.Py, The conversion of magnetic energy into kinetic energy through the process of magnetic reconnect ion remains one of the most challenging and far reaching problems in plasma physics. One key issue is the scaling of the recon nection dynamics for applications where the system size is vastly larger than the kinetic scales. The magnetohy drodynamics (MHD) model should provide an accurate description of collisional reconnect ion where the resis tive layers are larger than the ion kinetic scale. tween islands approach the ion kinetic scale. This regime is typically referred to as kinetic or fast reconnection since a variety of two-fluid and kinetic models predict rates that are weakly dependent on the system size and dis sipation mechanism [6,7] (the precise scalings are still a subject of controversy [8,9]). In neutral sheet geom etry, both two-fluid simulations [10,11] and theory [12J predict an abrupt transition from the collisional to the kinetic regime when 8 sp ::; d i where d i is the ion inertial length. In this geometry, d i is comparable to the ion gy roradius, and in the kinetic regime d i is also compa.rable to the ion crossing orbit scale.Recently, this transition between collisional and kinetic reconnection was proposed as the central mechanism in regulating coronal heating [13-15J. However, these es timates were based on the assumption of a stable SP layer within the collisional regime. To properly describe the dynamics at high Lundquist number, it is crucial to consider how plasmoid formation ma.y influence the tran sition. To address this problem, this work employs fully kinetic particle-in-cell (PIC) simulations with a Monte Carlo treatment [16] of the Fokker-Planck collision op erator. For Lundquist numbers where the SP layers are stable 5 ;s 1000, this powerful first-principles approach has demonstrated a clear transition between the colli sional and kinetic regimes near the expected thresholdHere we demonstrate that SP layers are in creasingly unstable to plasmoid formation in large-scale systems. The observed growth rate is super-Alfvenic, al lowing the islands to grow to large amplitude before they are convected downstream. A dramatic enhancement in the reconnection rate is observed when the current...

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Ultrahigh performance three-dimensional electromagnetic relativistic kinetic plasma simulation

Cited by 425 publications

References 19 publications

Energy dynamics and current sheet structure in fluid and kinetic simulations of decaying magnetohydrodynamic turbulence

Energy dynamics and current sheet structure in fluid and kinetic simulations of decaying magnetohydrodynamic turbulence

Dissipation and particle energization in moderate to low beta turbulent plasma via PIC simulations

Transition from collisional to kinetic regimes in large-scale reconnection layers

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