Living Reviews in Solar Physics: "Space–time structure and wavevector anisotropy in space plasma turbulence"
Narita, Yasuhito, "Space–time structure and wavevector anisotropy in space plasma turbulence", Living Rev Sol Phys (2018) 15: 2. https://doi.org/10.1007/s41116-017-0010-0
Open Access | Review Article
First Online: 21 February 2018
Abstract:
Space and astrophysical plasmas often develop into a turbulent state and exhibit nearly random and stochastic motions. While earlier studies emphasize more on understanding the energy spectrum of turbulence in the one-dimensional context (either in the frequency or the wavenumber domain), recent achievements in plasma turbulence studies provide an increasing amount of evidence that plasma turbulence is essentially a spatially and temporally evolving phenomenon. This review presents various models for the space–time structure and anisotropy of the turbulent fields in space plasmas, or equivalently the energy spectra in the wavenumber–frequency domain for the space–time structures and that in the wavevector domain for the anisotropies. The turbulence energy spectra are evaluated in different one-dimensional spectral domains; one speaks of the frequency spectra in the spacecraft observations and the wavenumber spectra in the numerical simulation studies. The notion of the wavenumber–frequency spectrum offers a more comprehensive picture of the turbulent fields, and good models can explain the one-dimensional spectra in the both domains at the same time. To achieve this goal, the Doppler shift, the Doppler broadening, linear-mode dispersion relations, and sideband waves are reviewed. The energy spectra are then extended to the wavevector domain spanning the directions parallel and perpendicular to the large-scale magnetic field. By doing so, the change in the spectral index at different projections onto the one-dimensional spectral domain can be explained in a simpler way.
The authors:
Yasuhito Narita is a Group Leader at the Space Research Institute of the Austrian Academy of Sciences, and Lecturer at the TU Braunschweig, Germany, and the University of Graz, Austria. His research interests include plasma turbulence (theory and observation) and signal processing.
Dr. Narita is the author of the book "Plasma Turbulence in the Solar System" (Springer 2012) and Editorial Board member of the open-access journals Earth, Planets and Space and Frontiers in Physics.