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

M. Volwerk (1, 2) , Z. Vörös (1) , W. Baumjohann (1) , R. Nakamura (1) , A. Runov (1) , T. L. Zhang (1) , Karl-Heinz Glassmeier (3) , R. A. Treumann (2) , B. Klecker (2) , A. Balogh (4) , H. Rème (5)

1 IWF - Space Research Institute of Austrian Academy of Sciences
2 MPE - Max-Planck-Institut für Extraterrestrische Physik
3 Technische Universität Braunschweig = Technical University of Braunschweig [Braunschweig]
4 Imperial College London
5 CESR - Centre d'étude spatiale des rayonnements

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 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.

Domaines: Océan, Atmosphère; Sciences de la Terre

M. Volwerk, Z. Vörös, W. Baumjohann, R. Nakamura, A. Runov, et al.. Multi-scale analysis of turbulence in the Earth's current sheet. Annales Geophysicae, 2004, 22 (7), pp.2525-2533. ⟨hal-00329345⟩