Ion and electron heating during magnetic reconnection in weakly collisional plasmas

Numata, Ryusuke; Loureiro, Nuno

doi:10.1017/s002237781400107x

Cited by 55 publications

(78 citation statements)

References 25 publications

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“…We reiterate that the key feature of equation (48) is not the precise value of the predicted Q p /Q e , but rather the transition from Q p Q e for β p ≫ 1 to Q p ≪ Q e for β e ≪ 1. This qualitative transition is much more robust than the specific functional form in equation (48) (e.g., Quataert & Gruzinov 1999;Numata & Loureiro 2015).…”

Section: Electron Parameter Choicesmentioning

confidence: 97%

Electron thermodynamics in GRMHD simulations of low-luminosity black hole accretion

Ressler

Tchekhovskoy

Quataert

et al. 2015

Mon. Not. R. Astron. Soc.

171

238

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Simple assumptions made regarding electron thermodynamics often limit the extent to which general relativistic magnetohydrodynamic (GRMHD) simulations can be applied to observations of low-luminosity accreting black holes. We present, implement, and test a model that self-consistently evolves an entropy equation for the electrons and takes into account the effects of spatially varying electron heating and relativistic anisotropic thermal conduction along magnetic field lines. We neglect the back-reaction of electron pressure on the dynamics of the accretion flow. Our model is appropriate for systems accreting at ≪ 10 −5 of the Eddington accretion rate, so radiative cooling by electrons can be neglected. It can be extended to higher accretion rates in the future by including electron cooling and proton-electron Coulomb collisions. We present a suite of tests showing that our method recovers the correct solution for electron heating under a range of circumstances, including strong shocks and driven turbulence. Our initial applications to axisymmetric simulations of accreting black holes show that (1) physically-motivated electron heating rates that depend on the local magnetic field strength yield electron temperature distributions significantly different from the constant electron to proton temperature ratios assumed in previous work, with higher electron temperatures concentrated in the coronal region between the disc and the jet; (2) electron thermal conduction significantly modifies the electron temperature in the inner regions of black hole accretion flows if the effective electron mean free path is larger than the local scale-height of the disc (at least for the initial conditions and magnetic field configurations we study). The methods developed in this work are important for producing more realistic predictions for the emission from accreting black holes such as Sagittarius A* and M87; these applications will be explored in future work.

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Section: Electron Parameter Choicesmentioning

confidence: 97%

Electron thermodynamics in GRMHD simulations of low-luminosity black hole accretion

Ressler

Tchekhovskoy

Quataert

et al. 2015

Mon. Not. R. Astron. Soc.

171

238

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“…By averaging over the gyromotion of the particles, gyrokinetics reduces the dimensionality of the kinetic system from six (three dimensions in coordinate space, three dimensions in velocity space (3D-3V)) to five (three dimensions in coordinate space, two dimensions in velocity space (3D-2V)). The gyrokinetic formalism describes damping via the Landau (n = 0) resonance, ) and resolves the kinetic microphysics of collisionless magnetic reconnection in the large-guide-field limit (TenBarge et al 2014a;Numata & Loureiro 2015). Mechanisms such as cyclotron damping and stochastic heating due to low-frequency Alfvénic turbulence are not included, the former due to the exclusion of high-frequency behaviour and the latter due to conservation of the magnetic moment enforced by the gyroaveraging procedure.…”

Section: Gyrokinetic Simulations Of Low-frequency Turbulencementioning

confidence: 99%

Diagnosing collisionless energy transfer using field–particle correlations: gyrokinetic turbulence

2017

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Determining the physical mechanisms that extract energy from turbulent fluctuations in weakly collisional magnetized plasmas is necessary for a more complete characterization of the behaviour of a variety of space and astrophysical plasmas. Such a determination is complicated by the complex nature of the turbulence as well as observational constraints, chiefly that in situ measurements of such plasmas are typically only available at a single point in space. Recent work has shown that correlations between electric fields and particle velocity distributions constructed from single-point measurements produce a velocity-dependent signature of the collisionless damping mechanism. We extend this work by constructing field-particle correlations using data sets drawn from single points in strongly driven, turbulent, electromagnetic gyrokinetic simulations to demonstrate that this technique can identify the collisionless mechanisms operating in such systems. The velocity-space structure of the correlation between proton distributions and parallel electric fields agrees with expectations of resonant mechanisms transferring energy collisionlessly in turbulent systems. This work motivates the eventual application of field-particle correlations to spacecraft measurements in the solar wind, with the ultimate goal to determine the physical mechanisms that dissipate magnetized plasma turbulence.

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“…The scale-to-scale transfers (equation (31)) are obtained by integrating over all mediator scales. Here, rather than doing so, we will characterize the exchanges between two scales p and k as a function of the values taken by the mediators q, and integrate accordingly over q to obtain a conditional form of the scale-to-scale transfers.…”

Section: The Impact Made By the Separation Of Scales On The Ion Scalementioning

confidence: 99%

“…Perpendicular plasma structures, generated through nonlinear interactions, can be damped in the parallel direction through Landau damping, if a balance between the damping rates and the nonlinear turnover time can be achieved. While this is a problem that is receiving more interest within the community [23,[28][29][30][31] and is far from being solved, analyzing the effective perpendicular cascade in position space can offer an important insight into the properties of kinetic turbulence.…”

Section: Introductionmentioning

confidence: 99%

Gyrokinetic turbulence: between idealized estimates and a detailed analysis of nonlinear energy transfers

2017

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Using large resolution numerical simulations of gyrokinetic (GK) turbulence, spanning an interval ranging from the end of the fluid scales to the electron gyroradius, we study the energy transfers in the perpendicular direction for a proton-electron plasma in a slab equilibrium magnetic geometry. The plasma parameters employed here are relevant to kinetic Alfvén wave turbulence in solar wind conditions. In addition, we use an idealized test representation for the energy transfers between two scales, to aid our understanding of the diagnostics applicable to the nonlinear cascade in an infinite inertial range. For GK turbulence, a detailed analysis of nonlinear energy transfers that account for the separation of energy exchanging scales is performed. Starting from the study of the energy cascade and the scale locality problem, we show that the general nonlocal nature of GK turbulence, captured via locality functions, contains a subset of interactions that are deemed local, are scale invariant (i.e. a sign of asymptotic locality) and possess a locality exponent that can be recovered directly from measurements on the energy cascade. It is the first time that GK turbulence is shown to possess an asymptotic local component, even if the overall locality of interactions is nonlocal. The results presented here and their implications are discussed from the perspective of previous findings reported in the literature and the idea of universality of GK turbulence.

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Ion and electron heating during magnetic reconnection in weakly collisional plasmas

Cited by 55 publications

References 25 publications

Electron thermodynamics in GRMHD simulations of low-luminosity black hole accretion

Electron thermodynamics in GRMHD simulations of low-luminosity black hole accretion

Diagnosing collisionless energy transfer using field–particle correlations: gyrokinetic turbulence

Gyrokinetic turbulence: between idealized estimates and a detailed analysis of nonlinear energy transfers

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