Capabilities of GNSS based topside reconstructions of the ionosphere

GPS navigation measurements onboard Low Earth Orbiting (LEO) satellites may be used to reconstruct the ionospheric electron density distribution from the LEO satellite orbit height up to GPS orbit heights. We use GPS navigation data obtained onboard CHAMP for reconstructing the plasma density distribution in the ionosphere on a routine basis since 2001. Considering the fact that a tomographic reconstruction is made after each complete revolution of the satellite, 15 reconstructions are obtained per day. Thus, more than 30.000 topside ionosphere/plasmasphere 2D electron density reconstructions have been obtained so far. Considering the fact that such measurements will be available from the Swarm satellites, the potential use of such reconstructions for studying ionosphere/plasmasphere coupling processes is discussed. The reconstructions indicate a great potential for studying vertical plasma redistribution processes during ionospheric storms, and evaluating ionospheric models in the topside ionosphere/plasmasphere altitude range. In a coordinated analysis with other GNSS techniques such as radio occultation measurements for deriving vertical electron density profiles and ground based estimations of the Total Electron Content (TEC) the topside reconstructions provide valuable additional information to understand large scale ionospheric perturbation processes