|
|
 |
|
|
Ann. Geophys., 22, 2525-2533, 2004
www.ann-geophys.net/22/2525/2004/
© European Geosciences Union 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
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
 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.
Full Article in PDF (2912 KB) |
|
|
