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Oughton, S., Matthaeus, W. H., Wan, M., & Parashar, T. N. (2016). Variance anisotropy in compressible 3-D MHD. Journal of Geophysical Research A: Space Physics, 121(6), 5041–5054. http://doi.org/10.1002/2016JA022496
Permanent Research Commons link: https://hdl.handle.net/10289/10572
All Rights Reserved.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 B0; these are distinct effects, although sometimes related. Here we examine the appearance of variance parallel to B0, 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.
This article is published in the Journal of Geophysical Research A: Space Physics. © 2016. American Geophysical Union.