NEW IONOSPHERIC MODELS FOR MONITORING AND FORECASTING IONOSPHERIC WEATHER

The ionospheric plasma may cause range errors of up to 100m at L-band signals used in Global Navigation Satellite Systems (GNSS). Hence, correction of ionospheric propagation errors is an important task for single frequency users and related augmentation systems such as WAAS in US and EGNOS in Europe. In a first order approximation the range error is proportional to the integral of the electron density along the ray path (Total Electron Content - TEC). Therefore, knowledge of the ionospheric TEC can effectively be used to correct ionospheric errors. In this talk we review new ionospheric models we have recently developed for imaging the ionospheric behaviour. The modelled parameters such as TEC and electron density are functions of geographic/geomagnetic location, local time and solar flux as a measure of solar activity. The model coefficients are deduced from input data by least squares methods. The models are used in the operational space weather and ionosphere data service SWACI (http://swaciweb.dlr.de ) at DLR Neustrelitz for calibrating, mapping and forecasting TEC and for starting 3D reconstructions of the ionospheric plasma density. Furthermore, basic features of the models for TEC and F2 layer peak density NmF2 including preliminary validation results are reported. The multifunctional use of the models in the SWACI service is described.