The statistics of a passive scalar in field-guided magnetohydrodynamic turbulence |
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| Authors: | J Mason S Boldyrev F Cattaneo JC Perez |
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| Institution: | 1. College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, EX4 4QFUK.;2. Department of Physics, University of Wisconsin at Madison, 1150 University Ave, Madison, WI, 53706USA.;3. Department of Astronomy &4. Astrophysics, University of Chicago, 5640 S. Ellis Ave, Chicago, IL, 60637USA.;5. Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Morse Hall, 8 College Road, Durham, NH, 03824USA. |
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| Abstract: | A variety of studies of magnetised plasma turbulence invoke theories for the advection of a passive scalar by turbulent fluctuations. Examples include modelling the electron density fluctuations in the interstellar medium, understanding the chemical composition of galaxy clusters and the intergalactic medium, and testing the prevailing phenomenological theories of magnetohydrodynamic turbulence. While passive scalar turbulence has been extensively studied in the hydrodynamic case, its counterpart in MHD turbulence is significantly less well understood. Herein we conduct a series of high-resolution direct numerical simulations of incompressible, field-guided, MHD turbulence in order to establish the fundamental properties of passive scalar evolution. We study the scalar anisotropy, establish the scaling relation analogous to Yaglom’s law, and measure the intermittency of the passive scalar statistics. We also assess to what extent the pseudo Alfvén fluctuations in strong MHD turbulence can be modelled as a passive scalar. The results suggest that the dynamics of a passive scalar in MHD turbulence is considerably more complicated than in the hydrodynamic case. |
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| Keywords: | Magnetic fields Magnetohydrodynamics Turbulence |
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