The non-zonal effect in the dynamical structure of the midlatitude MLT-region Original Research Article

Ionospheric drift measurements in the LF range, which refer to altitudes between 80 and 100 km, make it possible to permanently monitor the circulation in the upper mesosphere/lower thermosphere region (MLT-region). A long-term (1975–1996) study of the MLT region dynamical structure at stations, well-spaced along 52°N latitude circle has revealed the nonzonality in the MLT dynamical structure. This non-zonality in the nighttime prevailing wind, tidal variability and planetary wave activity is considered including results obtained during the MLTCS, DYANA and CRISTA/MAHRSI Campaigns. The longitudinal variations could be interpreted as sign of “coupling from below” and may be important when empirical and physical upper atmosphere models are being formed.