Electron magnetohydrodynamic turbulence

Biskamp, D.; Schwarz, E. J.; Zeiler, A.; Celani, Antonio; Drake, J. F.

doi:10.1063/1.873312

Cited by 220 publications

(239 citation statements)

References 18 publications

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“…Eqs. (10)- (11) of Biskamp et al (1999)). Differently, in the same β e -range, the equations for KAWs with the Landau fluid closure appear as a fluid reduction of those of Zocco & Schekochihin (2011) (see Loureiro et al (2013) for their numerical simulations in the case of fast collisionless reconnection).…”

Section: Resultsmentioning

confidence: 99%

“…Schekochihin et al (2009)), and can be viewed as the generalization of EMHD for low-frequency anisotropic fluctuations without the assumption of incompressibility. When electron inertia is retained, but not the FLR corrections, the equations for the WWs appear as an extension to the anisotropic three-dimensional regime of the 2.5D equations given in Biskamp et al (1996Biskamp et al ( , 1999.…”

Section: Wws Reduced Modelmentioning

confidence: 99%

“…The regime at scales smaller than d e has been extensively studied mostly for WWs, in the framework of EMHD (Biskamp et al 1996(Biskamp et al , 1999Galtier & Bhattacharjee 2003;Galtier & Meyrand 2015;Lyutikov 2013), of an incompressible bi-fluid model (Andrés et al 2014;Andrés et al 2016a,b) and of extended magnetohydrodynamics (XMHD) (Miloshevich et al 2017). Full particle-in-cell simulations of this regime were performed by Gary et al (2012) and Chang et al (2013).…”

Section: Introductionmentioning

confidence: 99%

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Electron-scale reduced fluid models with gyroviscous effects

2017

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Reduced fluid models for collisionless plasmas including electron inertia and finite Larmor radius corrections are derived for scales ranging from the ion to the electron gyroradii. Based either on pressure balance or on the incompressibility of the electron fluid, they respectively capture kinetic Alfvén waves (KAWs) or whistler waves (WWs), and can provide suitable tools for reconnection and turbulence studies. Both isothermal regimes and Landau fluid closures permitting anisotropic pressure fluctuations are considered. For small values of the electron beta parameter β e , a perturbative computation of the gyroviscous force valid at scales comparable to the electron inertial length is performed at order O(β e ), which requires second-order contributions in a scale expansion. Comparisons with kinetic theory are performed in the linear regime. The spectrum of transverse magnetic fluctuations for strong and weak turbulence energy cascades is also phenomenologically predicted for both types of waves. In the case of moderate ion to electron temperature ratio, a new regime of KAW turbulence at scales smaller than the electron inertial length is obtained, where the magnetic energy spectrum decays like k −13/3 ⊥ , thus faster than the k −11/3 ⊥ spectrum of WW turbulence.

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Section: Resultsmentioning

confidence: 99%

Section: Wws Reduced Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Electron-scale reduced fluid models with gyroviscous effects

2017

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“…Kolmogorov arguments for Electron MHD lead to a ∼ k −7/3 magnetic energy spectrum (Biskamp et al 1996(Biskamp et al , 1999Cho and Lazarian 2004). More recent theories of strong KAW turbulence also predict a -7/3 spectrum for both density and magnetic field (Schekochihin et al 2009).…”

Section: Ion Scale Instabilities Driven By Solar Wind Expansion and Cmentioning

confidence: 99%

“…As with the MHD scale cascade, there are a number of observational and theoretical works, which identify turbulent fluctuations at small scales as having properties of linear wave modes (e.g., Denskat et al 1983;Goldstein et al 1994;Ghosh et al 1996;Biskamp et al 1996Biskamp et al , 1999Leamon et al 1998;Cho and Lazarian 2004;Bale et al 2005;Galtier 2006;Sahraoui et al 2010Howes et al 2006Howes et al , 2008Howes et al , 2012bSchekochihin et al 2009;Gary and Smith 2009;Chandran et al 2009;Chen et al 2010bChen et al , 2013a. A recent analysis by Chen et al (2013c) showed that the ratio of density to magnetic fluctuations in the range between ion and electron scales is very close to that expected for kinetic Alfvén waves, and not whistler waves, and concluded that the fluctuations in this range are predominantly strong kinetic Alfvén turbulence.…”

Section: Ion Scale Instabilities Driven By Solar Wind Expansion and Cmentioning

confidence: 99%

Solar Wind Turbulence and the Role of Ion Instabilities

et al. 2013

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Solar wind is probably the best laboratory to study turbulence in astrophysical plasmas. In addition to the presence of magnetic field, the differences with neutral fluid isotropic turbulence are: (i) weakness of collisional dissipation and (ii) presence of several characteristic space and time scales. In this paper we discuss observational properties of solar wind turbulence in a large range from the MHD to the electron scales. At MHD scales, within the inertial range, turbulence cascade of magnetic fluctuations develops mostly in the plane perpendicular to the mean field, with the Kolmogorov scaling k −5/3 ⊥ for the perpendicular cascade and k −2 for the parallel one. Solar wind turbulence is compressible in nature: density fluctuations at MHD scales have the Kolmogorov spectrum. Velocity fluctuations do not follow magnetic field ones: their spectrum is a power-law with a −3/2 spectral index. Probability distribution functions of different plasma parameters are not Gaussian, indicating presence of intermittency. At the moment there is no global model taking into account all these observed properties of the inertial range. At ion scales, turbulent spectra have a break, compressibility increases and the density fluctuation spectrum has a local flattening. Around ion scales, magnetic spectra are variable and ion instabilities occur as a function of the local plasma parameters. Between ion and electron scales, a small scale turbulent cascade seems to be established. It is characterized by a well defined power-law spectrum in magnetic and density fluctuations with a spectral index close to −2.8. Approaching electron scales, the fluctuations are no more self-similar: an exponential cut-off is usually observed (for time intervals without quasi-parallel whistlers) indicating an onset of dissipation. The small scale inertial range between ion and electron scales and the electron dissipation range can be together described by ∼ k −α ⊥ exp(−k ⊥ d ), with α 8/3 and the dissipation scale d close to the electron Larmor radius d ρ e . The nature of this small scale cascade and a possible dissipation mechanism are still under debate.

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Spectral evolution of helical electron magnetohydrodynamic turbulence

Cho

Kim

2016

JGR Space Physics

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Properties of turbulence in space plasmas above and below the proton gyroscale are very different and different descriptions should be used for the large and the small scales. On scales larger than the proton gyroscale, we can treat the plasmas as conducting fluids and use magnetohydrodynamics (MHD). However, on scales smaller than the proton gyroscale, we cannot use MHD due to various kinetic effects. Electron magnetohydrodynamics (EMHD) is a simple fluid‐like model for small‐scale plasmas. In this paper, we discuss properties of EMHD waves and turbulence. In particular, we focus on inverse cascade in EMHD turbulence. Since EMHD waves are helical and magnetic helicity is a conserved quantity, inverse cascade is expected to be a common phenomenon in EMHD. We first focus on inverse cascade and spectral evolution of completely imbalanced EMHD wave packets, in which all waves are moving in the same direction. Then, we discuss inverse cascade and spectral evolution of driven imbalanced EMHD turbulence. We also discuss “pinning” of energy spectra in imbalanced EMHD turbulence.

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Electron magnetohydrodynamic turbulence

Cited by 220 publications

References 18 publications

Electron-scale reduced fluid models with gyroviscous effects

Electron-scale reduced fluid models with gyroviscous effects

Solar Wind Turbulence and the Role of Ion Instabilities

Spectral evolution of helical electron magnetohydrodynamic turbulence

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