ULF waves: Conjugated ground-satellite relationships

The simultaneous occurrence of ULF waves, observed onboard GEOS and at two of its conjugated stations (Husafell, Iceland and Skibotn, Norway) was studied. The authors try to deduce some properties of the regions in which these waves are generated. The small number of simultaneous observations of pearl events indicates that such structured oscillations can occur only in specific conditions, which are not generally met at the geostationary altitude. A new method of measuring time delays between the satellite and the ground is introduced. The time is much higher than would be expected from a simple extrapolation of measurements done at lower latitudes on structured events.