Articles | Volume 22, issue 7
Ann. Geophys., 22, 2525–2533, 2004

Special issue: Spatio-temporal analysis and multipoint measurements in space...

Ann. Geophys., 22, 2525–2533, 2004

  14 Jul 2004

14 Jul 2004

Multi-scale analysis of turbulence in the Earth's current sheet

M. Volwerk1,3, Z. Vörös1, W. Baumjohann1, R. Nakamura1, A. Runov1, T. L. Zhang1, K.-H. Glassmeier2, R. A. Treumann3, B. Klecker3, A. Balogh4, and H. Rème5 M. Volwerk et al.
  • 1IWF, ÖAW, Graz, Austria
  • 2TU Braunschweig, Germany
  • 3MPE Garching, Germany
  • 4Imperial College, London, UK
  • 5CESR, Toulouse, France

Abstract. A multi-scale analysis of magnetotail turbulence in the Earth's tail current sheet is presented based on Cluster magnetometer observations. Both Fourier and wavelet analysis is used to describe the spectral index and scaling indices of the turbulence for different frequency regions. Flows in the tail are very important for driving the observed turbulence. There is a strong correlation between the maximum perpendicular flow velocity and the turbulence power for maximum velocities $150{leq}v_{perp, {rm max}}{leq}400$km/s. At higher maximum flow velocities the turbulence power levels out, showing a saturation of the generation mechanism. The suspected presence of breaks in the slope of the spectrum at two frequencies (f1 and f2) can be confirmed for f1≈0.08Hz, but based on the data analysis the second break at f2 is expected at a frequency higher than 12.5Hz, where the data cannot significantly be evaluated. A schematic turbulence power spectrum is presented based on the Cluster magnetic field measurements. Dependent on the presence of BBFs the spectral index or scaling index varies significantly.