Articles | Volume 23, issue 4
Ann. Geophys., 23, 1311–1316, 2005
https://doi.org/10.5194/angeo-23-1311-2005
Ann. Geophys., 23, 1311–1316, 2005
https://doi.org/10.5194/angeo-23-1311-2005

  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.