Phenomenology of hydromagnetic turbulence in a uniformly expanding medium
Matthaeus, W. H., Zank, G. P., & Oughton, S. (1996). Phenomenology of hydromagnetic turbulence in a uniformly expanding medium. Journal of Plasma Physics, 56(03), 659-675.
Permanent Research Commons link: https://hdl.handle.net/10289/8631
A simple phenomenology is developed for the decay and transport of turbulence in a constant-speed, uniformly expanding medium. The fluctuations are assumed to be locally incompressible, and either of the hydrodynamic or non-Alfvénic magnetohydrodynamic (MHD) type. In order to represent local effects of nonlinearities, a simple model of the Kaármá-Dryden type for locally homogeneous turbulent decay is adopted. A detailed discussion of the parameters of this familiar one-point hydrodynamic closure is given, which has been shown recently to be applicable to non-Alfvénic MHD as well. The effects of the large-scale flow and expansion are incorporated using a two-scale approach, in which assumptions of particular turbulence symmetries provide simplifications. The derived model is tractable and provides a basis for understanding turbulence in the outer heliosphere, as well as in other astrophysical applications.
©1996 Cambridge University Press.