Storm induced Travelling Ionospheric Disturbances observed over Europe

Abstract

Travelling Ionospheric Disturbances (TIDs) are signatures of atmospheric gravity waves. By monitoring the Total Electron Content as a direct result of ground based GNSS measurements one can determine TIDs. A dense network of GNSS receivers over Europe provides allows estimating f wavelength, propagation direction and phase speed of the TIDs. Usually, TIDs are observed after geomagnetic storms and are having wavelengths of the order of about 2000km, a southward orientation and a mean phase speed of about 700 ms-1. A correlation of TID amplitudes with the auroral electrojet index, AE, indicates ionospheric Joule heating, located within the vicinity of the auroral oval, as a possible source of TIDs. The source region of the TIDs is having a similar southward extension as the polar electrojet system during enhanced geomagnetic conditions. Their propagation is discussed in relation to the southward propagation of enhanced ionization fronts and the perturbation induced dilation of the auroral oval towards lower latitudes.