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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 23, issue 4 | Copyright
Ann. Geophys., 23, 1311-1316, 2005
https://doi.org/10.5194/angeo-23-1311-2005
© Author(s) 2005. This work is distributed under
the Creative Commons Attribution 3.0 License.

  03 Jun 2005

03 Jun 2005

Statistical study of the proton isotropy boundary

E. A. Lvova, V. A. Sergeev, and G. R. Bagautdinova E. A. Lvova et al.
  • Institute of Physics, St. Petersburg State University, St. Petersburg, Russia

Abstract. Based on a large data set of polar NOAA-type satellite observations we studied the latitude-MLT shape of the 80keV proton isotropy boundary (IB) as a function of the solar wind parameters and magnetic activity. Using "snapshots" of isotropy boundaries near-simultaneously crossed at four points we found that its equatorward expansion, as well as its dawn-dusk shift, depends mostly on the AE-index and on the corrected Dst*, whereas the amplitude of the IB daily variation is mostly controlled by the solar wind dynamic pressure. Applying a nonlinear, multi-parametric, least-square regression procedure, the empirical relationship describing the IB latitude as a function of MLT and AE, Pd, Dst* parameters was obtained. Comparing it with the predictions from the Tsyganenko-2001 model we found a good agreement during the quiet time but some important differences during the disturbed periods. Interpretation of these results in terms of the properties of the magnetospheric configuration is briefly discussed.

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