Measures of three-dimensional anisotropy and intermittency in strong Alfvénic turbulence
File(s)
Accepted version
Author(s)
Type
Journal Article
Abstract
We measure the local anisotropy of numerically simulated strong Alfvénic turbulence with respect to two local, physically relevant directions: along the local mean magnetic field and along the local direction of one of the fluctuating Elsasser fields. We find significant scaling anisotropy with respect to both these directions: the fluctuations are ‘ribbon-like’ – statistically, they are elongated along both the mean magnetic field and the fluctuating field. The latter form of anisotropy is due to scale-dependent alignment of the fluctuating fields. The intermittent scalings of the nth-order conditional structure functions in the direction perpendicular to both the local mean field and the fluctuations agree well with the theory of Chandran, Schekochihin & Mallet, while the parallel scalings are consistent with those implied by the critical-balance conjecture. We quantify the relationship between the perpendicular scalings and those in the fluctuation and parallel directions, and find that the scaling exponent of the perpendicular anisotropy (i.e. of the aspect ratio of the Alfvénic structures in the plane perpendicular to the mean magnetic field) depends on the amplitude of the fluctuations. This is shown to be equivalent to the anticorrelation of fluctuation amplitude and alignment at each scale. The dependence of the anisotropy on amplitude is shown to be more significant for the anisotropy between the perpendicular and fluctuation-direction scales than it is between the perpendicular and parallel scales.
Date Issued
2016-04-07
Date Acceptance
2016-04-05
Citation
Monthly Notices of the Royal Astronomical Society, 2016, 459 (2), pp.2130-2139
ISSN
1365-2966
Publisher
Oxford University Press
Start Page
2130
End Page
2139
Journal / Book Title
Monthly Notices of the Royal Astronomical Society
Volume
459
Issue
2
Copyright Statement
© 2016 Royal Astronomical Society. This is a pre-copy-editing, author-produced version of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The definitive publisher-authenticated version A. Mallet, A. A. Schekochihin, B. D. G. Chandran, C. H. K. Chen, T. S. Horbury, R. T. Wicks, C. C. Greenan, Measures of three-dimensional anisotropy and intermittency in strong Alfvénic turbulence, Monthly Notices of the Royal Astronomical Society, Volume 459, Issue 2, 21 June 2016, Pages 2130–2139 is available online at: https://doi.org/10.1093/mnras/stw802
Sponsor
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council [2006-2012]
Identifier
https://academic.oup.com/mnras/article/459/2/2130/2595192
Grant Number
ST/K001051/1
ST/N000692/1
ST/K001051/1
Subjects
Science & Technology
Physical Sciences
Astronomy & Astrophysics
MHD
turbulence
solar wind
SOLAR-WIND TURBULENCE
ORDER STRUCTURE FUNCTIONS
SMALL-SCALE ANISOTROPY
MAGNETOHYDRODYNAMIC TURBULENCE
ALFVENIC TURBULENCE
NUMERICAL SIMULATIONS
CRITICAL BALANCE
astro-ph.SR
astro-ph.SR
Astronomy & Astrophysics
0201 Astronomical and Space Sciences
Publication Status
Published
Date Publish Online
2016-04-07