Large scale ionospheric gradients over Europe observed in October 2003

Kurzfassung

It is well known that ionospheric perturbations are characterized by strong horizontal gradients and rapid changes of the ionization. Thus, space weather induced severe ionosphere perturbations can cause serious technological problems in Global Navigation Satellite Systems (GNSS) such as GPS. During the severe ionosphere storm period of 29-31 October 2003, reported were several significant malfunctions due to the adverse effects of the ionosphere perturbations such as interruption of the WAAS service and degradation of mid-latitudes GPS reference services. To warn users of such services in a proper way, a quick evaluation of the current signal propagation conditions effectively expressed in a suitable ionospheric perturbation index would be of great benefit. To investigate possibilities of describing ionospheric perturbations by such an index, a task force group was established in the COST 296 activity. Preliminary results of a comparative study of ionospheric gradients including vertical sounding and TEC data are presented. Strong enhancements of latitudinal gradients and temporal changes of the ionization are observed over Europe during the 29-30 October storm period. The potential use of spatial and temporal gradients for characterizing the actual perturbation degree of the ionosphere is discussed.