Published in

Cambridge University Press (CUP), Journal of Plasma Physics, 1(85), 2019

DOI: 10.1017/s0022377819000114

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Magneto-immutable turbulence in weakly collisional plasmas

Journal article published in 2019 by J. Squire ORCID, A. A. Schekochihin ORCID, E. Quataert ORCID, M. W. Kunz ORCID
This paper was not found in any repository, but could be made available legally by the author.
This paper was not found in any repository, but could be made available legally by the author.

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Abstract

We propose that pressure anisotropy causes weakly collisional turbulent plasmas to self-organize so as to resist changes in magnetic-field strength. We term this effect ‘magneto-immutability’ by analogy with incompressibility (resistance to changes in pressure). The effect is important when the pressure anisotropy becomes comparable to the magnetic pressure, suggesting that in collisionless, weakly magnetized (high-$\unicode[STIX]{x1D6FD}$) plasmas its dynamical relevance is similar to that of incompressibility. Simulations of magnetized turbulence using the weakly collisional Braginskii model show that magneto-immutable turbulence is surprisingly similar, in most statistical measures, to critically balanced magnetohydrodynamic turbulence. However, in order to minimize magnetic-field variation, the flow direction becomes more constrained than in magnetohydrodynamics, and the turbulence is more strongly dominated by magnetic energy (a non-zero ‘residual energy’). These effects represent key differences between pressure-anisotropic and fluid turbulence, and should be observable in the$\unicode[STIX]{x1D6FD}\gtrsim 1$turbulent solar wind.

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