Unusual features in high statistics radar meteor studies at EISCAT

We describe results of an experiment conducted with the European Incoherent Scatter (EISCAT) radars during three 8-h runs on consecutive nights in 2008 December aiming to detect and study the high-altitude meteor population along with the meteors detected at classical ∼100-km altitudes. The experiment used coaxial ultra-high-frequency (UHF) and very high-frequency (VHF) radar beams pointed vertically to the zenith of Ramfjordmoen near Tromsø (Norway), and remote UHF receivers at Kiruna (Sweden) and Sodankyla ̈ (Finland) for tristatic observations of a very limited volume at an altitude of 170 km above the transmitter site. The EISCAT VHF radar detected during the 24-h period 22 698 echoes identified as me-teors. The number of UHF echoes in the same period was 2138, most detected also at VHF. Among the VHF meteors, 11 were detected at altitudes higher than 150 km. Of these, the record highest meteor was at 246.9 km. No high-altitude UHF echoes were detected, none was tristatic, and no echoes with a Doppler velocity above ∼60 km s−1 were identified. Given the large number of echoes, which argues in favour of a highly significant characterization of th