Non Axi-symmetric Anisotropy of Solar Wind Turbulence

Abstract

A key prediction of turbulence theories is frame-invariance, and in magnetohydrodynamic (MHD) turbulence, axisymmetry of fluctuations with respect to the background magnetic field. Paradoxically the power in fluctuations in the turbulent solar wind are observed to be ordered with respect to the bulk macroscopic flow as well as the background magnetic field. Here, non- axisymmetry across the inertial and dissipation ranges is quantified using in-situ observations from Cluster. The observed inertial range non- axisymmetry is reproduced by a 'fly through' sampling of a Direct Numerical Simulation of MHD turbulence. Furthermore, 'fly through' sampling of a linear superposition of transverse waves with axisymmetric fluctuations generates the trend in non- axisymmetry with power spectral exponent. The observed non-axisymmetric anisotropy may thus simply arise as a sampling effect related to Taylor's hypothesis and is not related to the plasma dynamics itself.

4 pages, 2 figures, accepted for publication in PRL

References in corpus (5)

• Anisotropic scaling of magnetohydrodynamic turbulence
• Anisotropy of Imbalanced Alfvenic Turbulence in Fast Solar Wind
• On the Nature of Incompressible Magnetohydrodynamic Turbulence
• Kolmogorov and Irosnikov-Kraichnan scaling in the anisotropic turbulent solar wind
• Quantifying the Anisotropy and Solar Cycle Dependence of "$1/f$" Solar Wind Fluctuations Observed by Ace

Cited by in corpus (13)

• Solar Wind Turbulence and the Role of Ion Instabilities
• Three-Dimensional Structure of Solar Wind Turbulence
• Spectral Features of Magnetic Fluctuations at Proton Scales from Fast to Slow Solar Wind
• Anisotropy of third-order structure functions in MHD turbulence
• Interpreting Magnetic Variance Anisotropy Measurements in the Solar Wind
• A Generalized Diffusion Tensor for Fully Anisotropic Diffusion of Energetic Particles in the Heliospheric Magnetic Field
• Power Anisotropy in the Magnetic Field Power Spectral Tensor of Solar Wind Turbulence
• Anisotropies of the magnetic field fluctuations at kinetic scales in the solar wind : Cluster observations
• Observational quantification of three-dimensional anisotropies and scalings of space plasma turbulence at kinetic scales
• Simulated Energetic Particle Transport in the Interplanetary Space: The Palmer Consensus Revisited
• Nonaxisymmetric Anisotropy of Solar Wind Turbulence as a Direct Test for the Models of Magnetohydrodynamic Tubulence
• Power Anisotropy, Dispersion Signature and Turbulence Diffusion Region in the 3D Wavenumber Domain of Space Plasma Turbulence
• Magnetic field turbulence in the solar wind at sub-ion scales: in situ observations and numerical simulations