During a special experiment in May 1988, coherent echoes were obtained with the UHF EISCAT radar system while the Tromsö antenna was directed to the north at elevation angles between 10° and 13°, with corresponding magnetic aspect angles between 5.8° and 7.6°. The echoes were found to be consistent with scattering from a layer having approximately a Gaussian height profile centered on about 103 km and with an average thickness of about 6 km. This height is considerably lower than most other reports of auroral backscatter height, and the thickness is also smaller than most other reported values. These unusually low heights were confirmed with observations at the remote sites Kiruna and Sodankyla. The heights seem to be independent of aspect angle over the range of aspect angles observed. By modeling the scattering layer and comparing echo intensities at Tromsö and the remote sites, estimates of aspect sensitivity of about 6 dB/deg were obtained, with an indication that the aspect sensitivity decreases with increasing aspect angle.
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