Statistical study of the proton isotropy boundary

E. A. Lvova (1) , V. A. Sergeev (1) , G. R. Bagautdinova (1)

1 Institute of Physics

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 D_st*, 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, D_st* 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.

Domaines: Océan, Atmosphère; Sciences de la Terre

E. A. Lvova, V. A. Sergeev, G. R. Bagautdinova. Statistical study of the proton isotropy boundary. Annales Geophysicae, 2005, 23 (4), pp.1311-1316. ⟨hal-00317716⟩