SOUSY Svalbard radar observed the first Polar Mesospheric Summer Echos (PMSE) of the season. SOUSY is a MST radar, which is co-located with the EISCAT Svalbard Radar (ESR) outside Longyearbyen, Svalbard, and it is operated by the University of Tromsø, Norway.
In summer, the polar mesopause region is extremely cold. Interesting phenomena are observed in that region, namely so-called noctilucent clouds (NLC) and strong radar echos (PMSE) between 80 and 95 km altitude. PMSE have first been observed by Ecklund and Balsley (J. Geophys. Res., 86, 7775–7780, 1981).
In the cold mesopause region, ice particles form and create noctilucent clouds. The surrounding atmosphere, i.e. the lower ionosphere, is ionised and free electrons attach to the ice particles. At the same time, gravity waves propagate upwards in the atmosphere. The part of the atmosphere where the ice particles occur coincides with the region in which these gravity waves become unstable and thereby produce turbulence. This turbulence leads to small-scale structures in the distribution of the charged ice particles, which, in turn, can be seen by radars as strong, coherent echos (PMSE).
The EISCAT_3D radar will not only be able to see these echos, but it will provide three-dimensional, high time-resolution images of PMSE. These and other Atmospheric Science topics were discussed at the recent 3rd EISCAT_3D User Meeting in Uppsala, Sweden. Most of the presentations are available for download now at the EISCAT_3D project site.
You can watch the measurements of the SOUSY radar in real-time on-line.