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Title: Magnetohydrodynamic Turbulence Mediated by Reconnection

Abstract

Magnetic field fluctuations in magnetohydrodynamic turbulence can be viewed as current sheets that are progressively more anisotropic at smaller scales. As suggested by Loureiro and Boldyrev and Mallet et al., below a certain critical thickness, λ{sub c}, such current sheets become tearing-unstable. We propose that the tearing instability changes the effective alignment of the magnetic field lines in such a way as to balance the eddy turnover rate at all scales smaller than λ{sub c}. As a result, turbulent fluctuations become progressively less anisotropic at smaller scales, with the alignment angle increasing as θ∼(λ/λ{sub ∗}){sup −4/5+β}, where λ{sub ∗}∼L{sub 0}S{sub 0}{sup −3/4} is the resistive dissipation scale. Here L {sub 0} is the outer scale of the turbulence, S {sub 0} is the corresponding Lundquist number, and 0⩽β<4/5 is a parameter. The resulting Fourier energy spectrum is E(k{sub ⊥})∝k{sub ⊥}{sup −11/5+2β/3}, where k{sub ⊥} is the wavenumber normal to the local mean magnetic field, and the critical scale is λ{sub c}∼S{sub L}{sup −(4−5β)/(7−20β/3)}. The simplest model corresponds to β = 0, in which case the predicted scaling formally agrees with one of the solutions obtained in Mallet et al. from a discrete hierarchical model of abruptly collapsing current sheets, an approach differentmore » from and complementary to ours. We also show that the reconnection-mediated interval is non-universal with respect to the dissipation mechanism. Hyper-resistivity of the form η-tilde k{sup 2+2s} leads (in the simplest case of β = 0) to the different transition scale λ{sub c}∼L{sub 0} S-tilde {sub 0}{sup −4/(7+9s)} and the energy spectrum E(k{sub ⊥})∝k{sub ⊥}{sup −(11+9s)/(5+3s)}, where S-tilde {sub 0} is the corresponding hyper-resistive Lundquist number.« less

Authors:
 [1];  [2]
  1. Department of Physics, University of Wisconsin-Madison, Madison, WI 53706 (United States)
  2. Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge MA 02139 (United States)
Publication Date:
OSTI Identifier:
22875967
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 844; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANISOTROPY; ENERGY SPECTRA; FLUCTUATIONS; MAGNETIC FIELDS; MAGNETIC RECONNECTION; MAGNETOHYDRODYNAMICS; STARS; TEARING INSTABILITY; TURBULENCE

Citation Formats

Boldyrev, Stanislav, and Loureiro, Nuno F. Magnetohydrodynamic Turbulence Mediated by Reconnection. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA7D02.
Boldyrev, Stanislav, & Loureiro, Nuno F. Magnetohydrodynamic Turbulence Mediated by Reconnection. United States. https://doi.org/10.3847/1538-4357/AA7D02
Boldyrev, Stanislav, and Loureiro, Nuno F. 2017. "Magnetohydrodynamic Turbulence Mediated by Reconnection". United States. https://doi.org/10.3847/1538-4357/AA7D02.
@article{osti_22875967,
title = {Magnetohydrodynamic Turbulence Mediated by Reconnection},
author = {Boldyrev, Stanislav and Loureiro, Nuno F.},
abstractNote = {Magnetic field fluctuations in magnetohydrodynamic turbulence can be viewed as current sheets that are progressively more anisotropic at smaller scales. As suggested by Loureiro and Boldyrev and Mallet et al., below a certain critical thickness, λ{sub c}, such current sheets become tearing-unstable. We propose that the tearing instability changes the effective alignment of the magnetic field lines in such a way as to balance the eddy turnover rate at all scales smaller than λ{sub c}. As a result, turbulent fluctuations become progressively less anisotropic at smaller scales, with the alignment angle increasing as θ∼(λ/λ{sub ∗}){sup −4/5+β}, where λ{sub ∗}∼L{sub 0}S{sub 0}{sup −3/4} is the resistive dissipation scale. Here L {sub 0} is the outer scale of the turbulence, S {sub 0} is the corresponding Lundquist number, and 0⩽β<4/5 is a parameter. The resulting Fourier energy spectrum is E(k{sub ⊥})∝k{sub ⊥}{sup −11/5+2β/3}, where k{sub ⊥} is the wavenumber normal to the local mean magnetic field, and the critical scale is λ{sub c}∼S{sub L}{sup −(4−5β)/(7−20β/3)}. The simplest model corresponds to β = 0, in which case the predicted scaling formally agrees with one of the solutions obtained in Mallet et al. from a discrete hierarchical model of abruptly collapsing current sheets, an approach different from and complementary to ours. We also show that the reconnection-mediated interval is non-universal with respect to the dissipation mechanism. Hyper-resistivity of the form η-tilde k{sup 2+2s} leads (in the simplest case of β = 0) to the different transition scale λ{sub c}∼L{sub 0} S-tilde {sub 0}{sup −4/(7+9s)} and the energy spectrum E(k{sub ⊥})∝k{sub ⊥}{sup −(11+9s)/(5+3s)}, where S-tilde {sub 0} is the corresponding hyper-resistive Lundquist number.},
doi = {10.3847/1538-4357/AA7D02},
url = {https://www.osti.gov/biblio/22875967}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 844,
place = {United States},
year = {Tue Aug 01 00:00:00 EDT 2017},
month = {Tue Aug 01 00:00:00 EDT 2017}
}

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Works referencing / citing this record:

The multi-scale nature of the solar wind
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On the Fourier Contribution of Strong Current Sheets to the High‐Frequency Magnetic Power SpectralDensity of the Solar Wind
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Transition from ion-coupled to electron-only reconnection: Basic physics and implications for plasma turbulence
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Diffusion regions and 3D energy mode development in spontaneous reconnection
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Scalings pertaining to current sheet disruption mediated by the plasmoid instability
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3D turbulent reconnection: Theory, tests, and astrophysical implications
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The role of electron heating physics in images and variability of the Galactic Centre black hole Sagittarius A*
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Spectral signatures of recursive magnetic field reconnection
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Two-temperature, Magnetically Arrested Disc simulations of the jet from the supermassive black hole in M87
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Magnetohydrodynamic Turbulence in the Plasmoid-mediated Regime
journal, February 2018


Stochastic Reconnection for Large Magnetic Prandtl Numbers
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Large-scale Compression Acceleration during Magnetic Reconnection in a Low- β Plasma
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Electron and Proton Heating in Transrelativistic Guide Field Reconnection
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Dynamic Evolution of Current Sheets, Ideal Tearing, Plasmoid Formation and Generalized Fractal Reconnection Scaling Relations
journal, August 2019


The Interplay of Magnetically Dominated Turbulence and Magnetic Reconnection in Producing Nonthermal Particles
journal, November 2019


Magnetic Reconnection as a Driver for a Sub-ion-scale Cascade in Plasma Turbulence
journal, November 2017


Turbulence in Magnetized Pair Plasmas
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Properties of the Turbulence Associated with Electron-only Magnetic Reconnection in Earth’s Magnetosheath
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Role of the Plasmoid Instability in Magnetohydrodynamic Turbulence
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Electron and Proton Heating in Transrelativistic Guide Field Reconnection
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3D Turbulent Reconnection: Theory, Tests and Astrophysical Implications
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