Articles | Volume 21, issue 1
Nonlin. Processes Geophys., 21, 41–47, 2014
https://doi.org/10.5194/npg-21-41-2014

Special issue: Nonlinear waves and chaos in space plasmas

Nonlin. Processes Geophys., 21, 41–47, 2014
https://doi.org/10.5194/npg-21-41-2014

Research article 09 Jan 2014

Research article | 09 Jan 2014

Four-dimensional energy spectrum for space–time structure of plasma turbulence

Y. Narita1,2 Y. Narita
  • 1Space Research Institute, Austrian Academy of Sciences, Schmiedlstr. 6, 8042 Graz, Austria
  • 2Institut für Geophysik und extraterrestrische Physik, Technische Universität Braunschweig, 38106 Braunschweig, Germany

Abstract. A parametric model of the inertial-range energy spectrum is constructed for plasma turbulence in the four-dimensional wave vector and frequency domain. The model is based on that of the Eulerian wavenumber-frequency spectrum developed for describing fluid turbulence, and includes wave vector anisotropies in the three-dimensional wave vector domain by approximating the spectrum to a set of ellipses. The shape of the four-dimensional spectrum is determined by the Doppler shift, the Doppler broadening, and anisotropy coefficients. The model is applied to the magnetic energy spectrum in the near-Earth solar wind measured by four Cluster spacecraft, and the set of the spectral parameters are determined observationally. In this way, space–time structure of plasma turbulence can be condensed into a small number of parameters, which is suitable for evaluating the energy spectra in observational and numerical studies on the quantitative basis.