Spectrum in Kinetic Alfvén Wave Turbulence: Implications for the Solar Wind

David, Vincent; Galtier, Sébastien

doi:10.3847/2041-8213/ab2fe6

Cited by 16 publications

(15 citation statements)

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“…IV while we present a numerical simulation in Sec. V. Finally, a discussion is developed around the proximity of this problem with kinetic-Alfvén (or oblique 044603-2 whistler) wave turbulence, an interesting regime for understanding multiscale solar wind turbulence [26], for which the same nonlinear diffusion equation can be found [27,28].…”

Section: Introductionmentioning

confidence: 99%

Inertial/kinetic-Alfvén wave turbulence: A twin problem in the limit of local interactions

Galtier

David

2020

Phys. Rev. Fluids

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Inertial and kinetic-Alfvén wave turbulences have a priori little in common: indeed, the first one concerns rotating hydrodynamics in the limit of a small Rossby number (with 0 the rotating rate) while the second describes high frequency plasmas in the limit of a strong uniform magnetic field B 0 . In this paper we show analytically that, in the limit of local interactions in the perpendicular direction to 0 , the inertial wave turbulence equation converges towards the same nonlinear diffusion equation as for kinetic-Alfvén waves when the same limit is taken; the only difference resides in the constants in front of the equations. Therefore, both systems share the same physical properties for the stationary phase with an energy spectrum in k −5/2 ⊥ ; it is preceded by a self-similar solution of the second kind during the nonstationary phase with a spectrum proportional to k −8/3 ⊥ which propagates explosively towards small scales. It is suggested that the proximity between these two problems may be used to better understand inertial or kinetic-Alfvén wave turbulence.

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Section: Introductionmentioning

confidence: 99%

Inertial/kinetic-Alfvén wave turbulence: A twin problem in the limit of local interactions

Galtier

David

2020

Phys. Rev. Fluids

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“…In the case of plasma turbulence, several popular analytical and numerical models have been developed to describe the turbulence cascade from the magnetohydrodynamic (MHD) to the electron scales, which led to different predictions on the scaling of the magnetic energy spectra (and other quantities, such as electric field spectra, velocity spectra etc). Those include the Iroshnikov-Kraichnan theory for isotropic MHD turbulence (with a k -3/2 spectrum, Iroshnikov, 1963;Kraichnan, 1965), the anisotropic MHD turbulence and the so-called critical balance hypothesis (k ^-5/3 , Goldreich & Sridhar, 1995), the weak turbulence theory of Alfvén waves (k ^-2 , Galtier et al, 2000), the sub-ion scale cascade of whistler or kinetic Alfvén waves (KAW) turbulence (e.g., Biskamp et al 1996;Li et al 2001;Galtier & Bhattacharjee 2003;Galtier & Buchlin, 2007;Howes et al, 2008;Ghosh et al, 1996;Stawicki et al, 2001;David & Galtier, 2019), and an "ultimate" electron scale cascade (Schekochihin et al, 2009, Meyrand & Galtier, 2010Camporeale & Burgess, 2011;Gary et al, 2012;Andrés et al, 2016aAndrés et al, , 2016bZhao et al, 2013，2016), to name a few.…”

Section: Introductionmentioning

confidence: 99%

The Ion Transition Range of Solar Wind Turbulence in the Inner Heliosphere: Parker Solar Probe Observations

Huang

Sahraoui

Andrés

et al. 2021

ApJL

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The scaling of the turbulent spectra provides a key measurement that allows us to discriminate between different theoretical predictions of turbulence. In the solar wind, this has driven a large number of studies dedicated to this issue using in situ data from various orbiting spacecraft. While a semblance of consensus exists regarding the scaling in the magnetohydrodynamic (MHD) and dispersive ranges, the precise scaling in the transition range and the actual physical mechanisms that control it remain open questions. Using the high-resolution data in the inner heliosphere from the Parker Solar Probe mission, we find that the sub-ion scales (i.e., at the frequency f ∼ [2, 9] Hz) follow a power-law spectrum f α with a spectral index α varying between −3 and −5.7. Our results also show that there is a trend toward an anticorrelation between the spectral slopes and the power amplitudes at the MHD scales, in agreement with previous studies: the higher the power amplitude the steeper the spectrum at sub-ion scales. A similar trend toward an anticorrelation between steep spectra and increasing normalized cross helicity is found, in agreement with previous theoretical predictions about the imbalanced solar wind. We discuss the ubiquitous nature of the ion transition range in solar wind turbulence in the inner heliosphere.

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“…However, that mode becomes a Kinetic Alfvénic Wave (KAW) at sub-ion scales, which is inherently compressible since it carries density fluctuations [5,27]. A nearly incompressible whistler mode can develop at high frequency [28], but that mode is unlikely to dominate the sub-ion scales cascade in the solar wind or MS [5,[29][30][31]. These considerations emphasize the crucial need to incorporate density fluctuations in the description of the sub-ion scale cascade, as we will show below using MMS data in the MS.…”

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Energy Cascade Rate Measured in a Collisionless Space Plasma with MMS Data and Compressible Hall Magnetohydrodynamic Turbulence Theory

et al. 2019

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The first complete estimation of the compressible energy cascade rate |εC| at magnetohydrodynamic (MHD) and sub-ion scales is obtained in the Earth's magnetosheath using Magnetospheric MultiScale (MMS) spacecraft data and an exact law derived recently for compressible Hall MHD turbulence. A multi-spacecraft technique is used to compute the velocity and magnetic gradients, and then all the correlation functions involved in the exact relation. It is shown that when the density fluctuations are relatively small, |εC| identifies well with its incompressible analogue |εI| at MHD scales but becomes much larger than |εI| at sub-ion scales. For larger density fluctuations, |εC| is larger than |εI| at every scale with a value significantly higher than for smaller density fluctuations. Our study reveals also that for both small and large density fluctuations, the non-flux terms remain always negligible with respect to the flux terms and that the major contribution to |εC| at sub-ion scales comes from the compressible Hall flux.Introduction. Turbulence is a universal phenomenon observed from quantum to astrophysical scales [see e.g., 1-3]. It is mainly characterized by a nonlinear transfer (or cascade) of energy from a source to a sink. In astrophysical plasmas, fully developed turbulence plays a major role in several physical processes such as accretion flows around massive objects, star formation, solar wind heating or energy transport in planetary magnetospheres [e.g., 4-7]. In particular, the Earth's magnetosheath (MS) -the region of the solar wind downstream of the bow shock [8] -provides a unique laboratory to investigate compressible plasma turbulence. Indeed, a key feature of the MS plasma is the high level of density fluctuations in it, which can reach up to 100% of the background density [9][10][11], in contrast to the solar wind where it is ∼ 20% [12,13]. Thanks to the high time resolution data provided by the Magnetospheric Multi-Scale (MMS) mission in the Earth's MS [14], we are now able for the first time to measure the compressible energy cascade rate ε C from the magnetohydrodynamic (MHD) inertial range down to the sub-ion scales.

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Spectrum in Kinetic Alfvén Wave Turbulence: Implications for the Solar Wind

Cited by 16 publications

References 54 publications

Inertial/kinetic-Alfvén wave turbulence: A twin problem in the limit of local interactions

Inertial/kinetic-Alfvén wave turbulence: A twin problem in the limit of local interactions

The Ion Transition Range of Solar Wind Turbulence in the Inner Heliosphere: Parker Solar Probe Observations

Energy Cascade Rate Measured in a Collisionless Space Plasma with MMS Data and Compressible Hall Magnetohydrodynamic Turbulence Theory

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