On the dynamics of Travelling Ionospheric Disturbances over Europe

Abstract

Travelling Ionospheric Disturbances (TIDs) are ionospheric signatures of thermospheric surges, commonly generated in the course of geomagnetic storms. Thus they are indicators of rapid changes in the thermosphere (density, composition, wind circulation). The resulting variations of the plasma density can be observed by using estimates of the Total Electron Content (TEC) derived from ground based Global Navigation Satellite System (GNSS) measurements. Consequently, a dense network of GNSS receivers over Europe allows an excellent monitoring and characterization of large scale TIDs. The correlation of TID amplitudes with the auroral electrojet index AE during storm conditions indicates Joule heating as a possible source mechanism of TIDs. Interestingly, TID observations over Europe show a southward shift of the source region of the TIDs. The displacement of the TID source region during the extreme magnetic storm of 20th November 2003 is accompanied by strong dynamics in the thermosphere-ionosphere-magnetosphere system. This is indicated by a co-location of enhanced temporal and spatial changes of TEC, the estimated trough location and the region of the auroral electrojet.