Global behaviour of the ionosphere electron density using GPS observations Original Research Article

A large number of permanent GPS tracking stations have been established during the past years, most of them under the administration of the International GPS Service (IGS) (Beutler et al., 1999). On April 3, 1995, the MicroLab I (MLI) (Melbourne et al., 1994) satellite with a GPS receiver on board, was launched into a circular orbit of about 775 km of altitude and 60° of inclination. This experiment is named GPS-MET. Apart of other specific applications, the data of the terrestrial and spatial stations can also be used to study the ionosphere. The main goal of this kind of ionosphere research is to exploit the capability of these observations to continuously and routinely monitor the ionosphere at global scale. In particular, we will focus on the estimation of parameters describing the distribution of free electrons in the ionosphere. The electron density profiles introduced in this work are a new input to the ionosphere analysis with GPS observations. The possibility of having a space receiver that gives us information about the total electron content at different heights allows us to bring forward a model for the variation of the electron density with height. This model reflects the average and global behaviour of the ionosphere during the measured interval. We compare our profile with the IRI ones and find that there is better agreement at middle northern latitudes than low and middle southern latitudes.