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Magnetohydrodynamic Turbulence Revisited

Goldreich, P. and Sridhar, S. (1997) Magnetohydrodynamic Turbulence Revisited. Astrophysical Journal, 485 (2). pp. 680-688. ISSN 0004-637X. doi:10.1086/304442.

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In 1965, Kraichnan proposed that MHD turbulence occurs as a result of collisions between oppositely directed Alfvén wave packets. Recent work has generated some controversy over the nature of nonlinear couplings between colliding Alfvén waves. We find that the resolution to much of the confusion lies in the existence of a new type of turbulence, intermediate turbulence, in which the cascade of energy in the inertial range exhibits properties intermediate between those of weak and strong turbulent cascades. Some properties of intermediate MHD turbulence are the following: (1) in common with weak turbulent cascades, wave packets belonging to the inertial range are long-lived; (2) however, components of the strain tensor are so large that, similar to the situation in strong turbulence, perturbation theory is not applicable; (3) the breakdown of perturbation theory results from the divergence of neighboring field lines due to wave packets whose perturbations in velocity and magnetic fields are localized, but whose perturbations in displacement are not; (4) three-wave interactions dominate individual collisions between wave packets, but interactions of all orders n ≥ 3 make comparable contributions to the intermediate turbulent energy cascade; (5) successive collisions are correlated since wave packets are distorted as they follow diverging field lines; (6) in common with the weak MHD cascade, there is no parallel cascade of energy, and the cascade to small perpendicular scales strengthens as it reaches higher wavenumbers; (7) for an appropriate weak excitation, there is a natural progression from a weak, through an intermediate, to a strong cascade.

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Additional Information:© 1997 American Astronomical Society. Received 1995 September 5; accepted 1997 March 25. Financial support for this research was provided by NSF grant 94-14232. P. G. benefited from visits to the Institute for Advanced Study and the Canadian Institute for Theoretical Astrophysics. We thank Omer Blaes for comments that improved the clarity of the manuscript.
Group:UNSPECIFIED, Division of Geological and Planetary Sciences
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Subject Keywords:ISM: general - MHD - turbulence
Issue or Number:2
Record Number:CaltechAUTHORS:20130227-073328900
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Official Citation:Magnetohydrodynamic Turbulence Revisited P. Goldreich and S. Sridhar 1997 ApJ 485 680
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37160
Deposited By: Ruth Sustaita
Deposited On:28 Feb 2013 15:51
Last Modified:09 Nov 2021 23:27

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