M. Hernandez-Pajares, J.M. Juan, J.Sanz, M. Martinez-Garcia Universitat Politecnica de Catalunya, c/ Gran Capita s/n, Mod. C-3 Campus Nord, Barcelona, E08940-Spain (manuel@mat.upc.es)

The electron distribution in the ionosphere is derived from global models using GPS data, during the January 10th 1997 geomagnetic storm, with data gathered from the International GPS Service for Geodynamics (IGS). The adopted strategy consists on using the ionospheric combination to estimate the electron distribution with a tomographic model, in a inertial reference frame, with ground data. As it is known, the vertical information contained provided by this kind of data is weak, and the reconstruction of the vertical distribution can be affected by great correlations. Nevertheless, it is possible to obtain the vertical structure with low resolution. In our model we can separate the contribution to the Total Electron Content whitin three spherical layers. The Kalman filtering approach is applied to take into account the time dependences.