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Magneto-immutable turbulence in weakly collisional plasmas

Squire, J. and Schekochihin, A. A. and Quataert, E. and Kunz, M. W. (2019) Magneto-immutable turbulence in weakly collisional plasmas. Journal of Plasma Physics, 85 (1). Art. No. 905850114. ISSN 0022-3778.

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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-β) 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 β ≳ 1 turbulent solar wind.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Squire, J.0000-0001-8479-962X
Schekochihin, A. A.0000-0003-4421-1128
Quataert, E.0000-0001-9185-5044
Kunz, M. W.0000-0003-1676-6126
Additional Information:© 2019 Cambridge University Press. Published online by Cambridge University Press: 18 February 2019. We thank S. Cowley, P. Kempski, R. Meyrand, and M. Strumik for enlightening discussions. Support for J.S. was provided by the Marsden Fund grant UOO1727 managed through the Royal Society Te Aparangi, and by the Gordon and Betty Moore Foundation through Grant GBMF5076 to Lars Bildsten, Eliot Quataert and E. Sterl Phinney. The work of A.A.S was supported in part by grants from UK STFC (ST/N000919/1) and EPSRC (EP/M022331/1). E.Q. was supported by Simons Investigator awards from the Simons Foundation and NSF grants AST 13-33612 and AST 17-15054. M.W.K. was supported in part by NASA grant NNX17AK63G, US DOE Contract DE-AC02-09-CH11466, and an Alfred P. Sloan Research Fellowship. This work used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation Grant No. ACI-1548562. Computations were carried out on the Comet system at the San Diego Supercomputing Center, through allocation TG-AST160068. Some of the numerical calculations presented in this work were done on Caltech's Wheeler cluster.
Funding AgencyGrant Number
Royal SocietyUOO1727
Gordon and Betty Moore FoundationGBMF5076
Science and Technology Facilities Council (STFC)ST/N000919/1
Engineering and Physical Sciences Research Council (EPSRC)EP/M022331/1
Simons FoundationUNSPECIFIED
Department of Energy (DOE)DE-AC02-09-CH11466
Alfred P. Sloan FoundationUNSPECIFIED
Issue or Number:1
Record Number:CaltechAUTHORS:20190725-080511515
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Official Citation:Squire, J., Schekochihin, A., Quataert, E., & Kunz, M. (2019). Magneto-immutable turbulence in weakly collisional plasmas. Journal of Plasma Physics, 85(1), 905850114. doi:10.1017/S0022377819000114
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:97399
Deposited By: Tony Diaz
Deposited On:25 Jul 2019 16:07
Last Modified:03 Oct 2019 21:31

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