Worldwide atmospheric gravity-wave study 1985–1989

Three campaigns of the Worldwide Atmospheric Gravity-wave Study have taken place in the European sector. On many occasions the onset of auroral activity in the evening and midnight sector, as indicated by EISCAT measurements, was followed after an hour or so by the arrival of a large-scale atmospheric gravity wave over the UK. Similar levels of activity in the early afternoon did not appear to produce waves in the far field, possibly as a result of ion-drag in the daytime ionosphere. The intrinsic time variation of the auroral activity determined the original time variation of the travelling disturbance, but waves with a period of about 30 min were strongly attenuated whereas waves with a period of about 60 min propagated to very great distances.