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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 27, issue 4
Ann. Geophys., 27, 1407–1411, 2009
https://doi.org/10.5194/angeo-27-1407-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Ninth International Conference on Substorms (ICS9)

Ann. Geophys., 27, 1407–1411, 2009
https://doi.org/10.5194/angeo-27-1407-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.

  01 Apr 2009

01 Apr 2009


Spatial variation of eddy-diffusion coefficients in the turbulent plasma sheet during substorms

M. Stepanova1, E. E. Antonova2,3, D. Paredes-Davis1, I. L. Ovchinnikov2, and Y. I. Yermolaev3 M. Stepanova et al.
  • 1Physics Department, Universidad de Santiago de Chile, Chile
  • 2Sobeltsyn Institute of Nuclear Physics, Moscow State University, Russia
  • 3Space Research Institute, RAS, Russia

Abstract. Study of the plasma turbulence in the central plasma sheet was performed using the Interball-Tail satellite data. Fluctuations of the plasma bulk velocity in the plasma sheet were deduced from the measurements taken by the Corall instrument for different levels of geomagnetic activity and different locations inside the plasma sheet. The events that satisfied the following criteria were selected for analysis: number density 0.1–10 cm−3, ion temperature T≥0.3 keV, and average bulk velocity ≤100 km/s. It was found that the plasma sheet flow generally appears to be strongly turbulent, i.e. is dominated by fluctuations that are unpredictable. Corresponding eddy-diffusion coefficients in Y- and Z-direction in the GSM coordinate system were derived using the autocorrelation time and rms velocity. Statistical studies of variation of the eddy-diffusion coefficients with the location inside the plasma sheet showed a significant increase in these coefficients in the tailward direction. During substorms this dependence shows strong increase of eddy-diffusion in the central part of the plasma sheet at the distances of 10–30 Earth's radii. This effect is much stronger for Y-components of the eddy-diffusion coefficient, which could be related to the geometry of the plasma sheet, allowing more room for development of eddies in this direction.

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