Strong anisotropic MHD turbulence with cross helicity

Abstract

This paper proposes a new phenomenology for strong incompressible MHD turbulence with nonzero cross helicity. This phenomenology is then developed into a quantitative Fokker-Planck model that describes the time evolution of the anisotropic power spectra of the fluctuations propagating parallel and antiparallel to the background magnetic field B-0. It is found that in steady state the power spectra of the magnetic field and total energy are steeper than k(perpendicular to)(-5/3) and become increasingly steep as C/epsilon increases, where C = integral d(3)x v . B is the cross helicity, epsilon is the fluctuation energy, and k(perpendicular to) is the wavevector component perpendicular to B-0. Increasing C with fixed epsilon increases the time required for energy to cascade to smaller scales, reduces the cascade power, and increases the anisotropy of the small-scale fluctuations. The implications of these results for the solar wind and solar corona are discussed in some detail.

Department

Physics

Publication Date

9-20-2008

Journal Title

Astrophysical Journal

Publisher

UNIV CHICAGO PRESS

Digital Object Identifier (DOI)

10.1086/589432

Document Type

Article

Rights

© 2008. The American Astronomical Society. All rights reserved.

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