An improved ten-moment closure for reconnection and instabilities

Ng, Jonathan; Hakim, Ammar; Wang, Liang; Bhattacharjee, A.

doi:10.1063/5.0012067

Cited by 19 publications

(17 citation statements)

References 60 publications

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“…This difference comes from GRMHD simulations being unaware of the collisionless plasma microphysics, which is important at scales where reconnection happens, i.e., electron skin depth. Incorporating non-ideal effects beyond scalar resistivity (e.g., Ripperda et al 2019b) into GRMHD simulations, such as electron inertia and anisotropic electron pressure tensor effects in the Ohm's law, holds promise of matching the (collisional) GRMHD and collisionless reconnection rates (Ng et al 2020). Radiative kinetic simulations (e.g., Parfrey et al 2019;Crinquand et al 2021Crinquand et al , 2020 are crucial for probing the non-thermal effects and the impact of the higher reconnection rate in collisionless plasma on the flare properties.…”

Section: Discussionmentioning

confidence: 99%

Black hole flares: ejection of accreted magnetic flux through 3D plasmoid-mediated reconnection

Ripperda,

Liska,

Chatterjee

et al. 2021

Preprint

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Magnetic reconnection can power bright and rapid flares originating from the inner magnetosphere of accreting black holes. We conduct extremely high resolution (5376 × 2304 × 2304 cells) generalrelativistic magnetohydrodynamics simulations, capturing plasmoid-mediated reconnection in a 3D magnetically arrested disk for the first time. We show that an equatorial, plasmoid-unstable current sheet forms in a transient, non-axisymmetric, low-density magnetosphere within the inner few Schwarzschild radii. Magnetic flux bundles escape from the event horizon through reconnection at the universal plasmoid-mediated rate in this current sheet. The reconnection feeds on the highlymagnetized plasma in the jets and heats the plasma that ends up trapped in flux bundles to temperatures proportional to the jet's magnetization. The escaped flux bundles can complete a full orbit as low-density hot spots, consistent with Sgr A * observations by the GRAVITY interferometer. Reconnection near the horizon produces sufficiently energetic plasma to explain flares from accreting black holes, such as the TeV emission observed from M87. The drop in mass accretion rate during the flare, and the resulting low-density magnetosphere make it easier for very high energy photons produced by reconnection-accelerated particles to escape. The extreme resolution results in a converged plasmoid-mediated reconnection rate that directly determines the timescales and properties of the flare.

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Section: Discussionmentioning

confidence: 99%

Black hole flares: ejection of accreted magnetic flux through 3D plasmoid-mediated reconnection

Ripperda,

Liska,

Chatterjee

et al. 2021

Preprint

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“…It is well known that the electron non-gyrotropy is essential for breaking the magnetic field frozen-in condition in the electron diffusion region. Wang et al 21 and subsequent works 22,23 used a ten-moment model with the full pressure tensor in their two-fluid (ions and electrons) simulations of magnetic reconnection. They naively applied the original electrostatic Landau closure for the scalar pressure to the full 3 × 3 tensor, which, however, does not have a solid theoretical basis.…”

Section: Discussionmentioning

confidence: 99%

A non-local fluid closure for modeling cyclotron resonance in collisionless magnetized plasmas

Jikei,

Amano

2021

Preprint

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A fluid description for collisionless magnetized plasmas that takes into account the effect of cyclotron resonance has been developed. Following the same approach as the Landau fluid closure, the heat flux components associated with transverse electromagnetic fluctuations are approximated by a linear combination of lower-order moments in wavenumber space. The closure successfully reproduces the linear cyclotron resonance for electromagnetic waves propagating parallel to the ambient magnetic field. In the presence of finite temperature anisotropy, the model gives approximately correct prediction for an instability destabilized via the cyclotron resonance. A nonlinear simulation demonstrates the wave growth consistent with the linear theory followed by the reduction of initial anisotropy, and finally, the saturation of the instability. The isotropization may be understood in terms of quasi-linear theory, which is developed within the framework of the fluid model but very similar to its fully kinetic counterpart. The result indicates that both linear and nonlinear collisionless plasma responses are approximately incorporated in the fluid model.

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“…In this section, we perform direct numerical simulations of the ECDI by integrating the 5-moment equations (1), coupled with the Poisson's equation. The simulations are performed using the multimoment solvers in the Princeton code, Gkeyll [15,16,36], that has been verified extensively for a number of plasma physics problems [3,7,[25][26][27][28][29][30][32][33][34].…”

Section: Numerical Simulationsmentioning

confidence: 99%

Electron cyclotron drift instability and anomalous transport: two-fluid moment theory and modeling

Wang,

Hakim,

Srinivasan

et al. 2021

Preprint

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In the presence of a strong electric field perpendicular to the magnetic field, the electron crossfield (E × B) flow relative to the unmagnetized ions can cause the so-called Electron Cyclotron Drift Instability (ECDI) due to resonances of the ion acoustic mode and the electron cyclotron harmonics. This occurs in, for example, collisionless shock ramps in space, and in E × B discharge devices such as Hall thrusters. A prominent feature of ECDI is its capability to induce an electron flow parallel to the background E field at a speed greatly exceeding predictions by classical collision theory. Such anomalous transport is heavily researched due to its role in particle thermalization at space shocks, and in causing plasma flows towards the walls of E × B devices, leading to unfavorable erosion and performance degradation, etc. The development of ECDI and anomalous transport is often considered to require a fully kinetic treatment. In this work, however, we demonstrate that a reduced variant of this instability, and more importantly, the associated anomalous transport, can be treated self-consistently in a collisionless two-fluid framework without any adjustable collision parameter. By treating both electron and ion species on an equal footing, the free energy due to the inter-species velocity shear allows the growth of an anomalous electron flow parallel to the background E field. We will first present linear analyses of the instability in the two-fluid five-and ten-moment models, and compare them against the fully-kinetic theory. At low temperatures, the two-fluid models predict the fastest-growing mode in good agreement with the kinetic result. Also, by including more (>= 10) moments, secondary (and possibly higher) unstable branches can be recovered. The dependence of the instability on ion-to-electron mass ratio, plasma temperature, and background B field strength is also thoroughly explored. We then carry out direct numerical simulations of the cross-field setup using the five-moment model. The development of the instability, as well as the anomalous transport, is confirmed and in excellent agreement with theoretical predictions. The force balance properties are also studied using the five-moment simulation data. This work casts new insights into the nature of ECDI and the associated anomalous transport and demonstrates the potential of the two-fluid moment model in efficient modeling of E × B plasmas.

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An improved ten-moment closure for reconnection and instabilities

Cited by 19 publications

References 60 publications

Black hole flares: ejection of accreted magnetic flux through 3D plasmoid-mediated reconnection

Black hole flares: ejection of accreted magnetic flux through 3D plasmoid-mediated reconnection

A non-local fluid closure for modeling cyclotron resonance in collisionless magnetized plasmas

Electron cyclotron drift instability and anomalous transport: two-fluid moment theory and modeling

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