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Variance anisotropy in compressible 3‐D MHD
Author(s) -
Oughton S.,
Matthaeus W. H.,
Wan Minping,
Parashar Tulasi
Publication year - 2016
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2016ja022496
Subject(s) - magnetohydrodynamics , anisotropy , physics , polarization (electrochemistry) , magnetohydrodynamic turbulence , variance (accounting) , turbulence , magnetic field , magnetohydrodynamic drive , compressibility , nonlinear system , statistical physics , computational physics , mechanics , optics , quantum mechanics , chemistry , accounting , business
We employ spectral method numerical simulations to examine the dynamical development of anisotropy of the variance, or polarization, of the magnetic and velocity field in compressible magnetohydrodynamic (MHD) turbulence. Both variance anisotropy and spectral anisotropy emerge under influence of a large‐scale mean magnetic field B 0 ; these are distinct effects, although sometimes related. Here we examine the appearance of variance parallel to B 0 , when starting from a highly anisotropic state. The discussion is based on a turbulence theoretic approach rather than a wave perspective. We find that parallel variance emerges over several characteristic nonlinear times, often attaining a quasi‐steady level that depends on plasma beta. Consistency with solar wind observations seems to occur when the initial state is dominated by quasi‐two‐dimensional fluctuations.