Comparison of the IRI-2007 Topside Electron density with CHAMP and COSMIC/Formosat-3 Data

Abstract

Reported are results of a comparison of the topside electron density of the IRI-2007 model with data obtained from the CHAMP and the COSMIC/Formosat-3 satellite missions. Starting from 2001 we have collected on average 15 tomographic reconstructions of the topside electron density every day using GPS data of the zenith-viewing antenna onboard CHAMP. These data sets form the basis of a comparative study with IRI-2007 topside data. While this long-term data basis enables us to study solar cycle dependent effects in the upper ionosphere/plasmasphere, the electron density profiles derived from COSMIC/Formosat-3 offer an up to now unprecedented temporal and spatial resolution with up to 2500 profiles per day. As more and more of the COSMIC satellites approach their design orbits in about 800km height, the upper part of the electron density profiles can provide valuable information about the transition region between the ionosphere and the plasmasphere. Starting from F2-layer height we fit a combination of a Chapman layer function and a topside approximation with a linearly variable scale height to the COSMIC profiles and compare the results with the IRI-2007 model.