Compressibility in turbulent magnetohydrodynamics and passive scalar transport: Mean-field theory

I. Rogachevskii, N. Kleeorin, A. Brandenburg

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5 Scopus citations

Abstract

We develop a mean-field theory of compressibility effects in turbulent magnetohydrodynamics and passive scalar transport using the quasi-linear approximation and the spectral τ-approach. We find that compressibility decreases the α effect and the turbulent magnetic diffusivity both at small and large magnetic Reynolds numbers, Rm. Similarly, compressibility decreases the turbulent diffusivity for passive scalars both at small and large Péclet numbers, Pe. On the other hand, compressibility does not affect the effective pumping velocity of the magnetic field for large Rm, but it decreases it for small Rm. Density stratification causes turbulent pumping of passive scalars, but it is found to become weaker with increasing compressibility. No such pumping effect exists for magnetic fields. However, compressibility results in a new passive scalar pumping effect from regions of low to high turbulent intensity both for small and large Péclet numbers. It can be interpreted as compressible turbophoresis of non-inertial particles and gaseous admixtures, while the classical turbophoresis effect exists only for inertial particles and causes them to be pumped to regions with lower turbulent intensity.

Original languageEnglish
Article number735840502
JournalJournal of Plasma Physics
Volume84
Issue number5
DOIs
StatePublished - 1 Oct 2018

Keywords

  • Astrophysical plasmas
  • Plasma nonlinear phenomena

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