During three days of quiet geomagnetic conditions in August 1988, both the EISCAT UHF radar and the NOAA digital ionospheric sounder (Dynasonde) were operated from 12:00 to 22:00 U.T. Sporadic-E layers were observed on all three days, controlled by the action of the semi-diurnal tide. Gravity wave activity was very evident in both data sets, and particularly visible in the changes in intensity and position of the layers. By combining the two sets of measurements it is possible to build up a spatial picture of the phase fronts passing over Tromsø, with sporadic-E layers acting as tracers for them in the E-region. It is observed that structures in the electron density associated with gravity waves descend from the F-region through the E-region to merge with the increases in the layer intensity. The enhancements in the layers, which we suggest are produced by horizontal convergence, are ribbon-like and aligned along the gravity wave phase fronts in the E-W direction, travelling southwards at 60 km h−1 and about 50 km apart.
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Authors: Lanchester, B.S., Nygrén, T., Huuskonen, A., Turunen, T., Jarvis, Martin J.