Large Scale TIDs Observed in GPS Derived Differential TEC

Abstract

In this study we focus on deriving measures of the activity of wavelike perturbation processes in the ionosphere, called Travelling Ionospheric Disturbances (TIDs). The TID activity has a significant impact on the accuracy and reliability of precise Global Positioning System (GPS) reference network applications. Because of its dual frequency, signals received from GPS satellites enable extracting information of the dispersive ionosphere. The European area is covered with dense networks of GPS receivers providing data with frequencies of 1/30 to 1Hz. The good data coverage of more than 150 ground stations enables calculating maps of the ionospheric disturbance activity with high accuracy. It is shown that in the course of several storms significant wave packets may be generated at high latitudes. These waves are assigned to large scale TIDs propagating equatorwards. Typical wave parameters such as velocity, wave length and direction can be estimated from the maps. The results support recent findings by other authors. In this study, additionally ionospheric radio occultation data will be used to detect the proven large scale TIDs. The differential TEC derived from low earth orbiting satellites is supposed to reveal information about the vertical spreading of these TIDs.