| Autor: |
Squire J; Physics Department, University of Otago, 730 Cumberland St., Dunedin 9016, New Zealand.; TAPIR, Mailcode 350-17, California Institute of Technology, Pasadena, CA 91125, USA., Schekochihin AA; The Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford, OX1 3P4, UK.; Merton College, Oxford OX1 4JD, UK., Quataert E; Astronomy Department and Theoretical Astrophysics Center, University of California, Berkeley, CA 94720, USA., Kunz MW; Department of Astrophysical Sciences, Princeton University, Peyton Hall, Princeton, NJ 08544, USA.; Princeton Plasma Physics Laboratory, PO Box 451, Princeton, NJ 08543, USA. |
| Abstrakt: |
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 MHD turbulence. However, in order to minimize magnetic-field variation, the flow direction becomes more constrained than in MHD, and the turbulence is more strongly dominated by magnetic energy (a nonzero "residual energy"). These effects represent key differences between pressure-anisotropic and fluid turbulence, and should be observable in the β ≳ 1 turbulent solar wind. |
