We present here the results of a statistical study of the ionospheric trough observed in 2003 by means of satellite tomography. We focus on the seasonal morphology of the trough occurrence and investigate the trough latitude, width and the horizontal gradients at the edges, at different magnetic local times, as well as their relations to geomagnetic activity and the interplanetary magnetic field. A seasonal effect is noticed in the diurnal variation

Measurements of midlatitude E region coherent backscatter obtained during four summers with SESCAT, a 50 MHz Doppler system operating in Crete, Greece, and concurrent ionosonde recordings from the same ionospheric volume obtained with a CADI for one of these summers, are used to analyse the long-term variability in echo and Es occurrence. Echo and Es layer occurrences, computed in percent of time over a 12-h nighttime interval, take the form of time

In this paper a large database of midlatitude E region coherent backscatter, obtained with a 50 MHz Doppler system, is used to investigate the long-term variability in echo occurrence. The backscatter is found to be dominated by pronounced quasi-periodic variations with periods in the range from about 2 to 9 days that persist for time intervals from about 10 to maybe more than 20 days and have no relation to geomagnetic activity. The most commonly

Experimental findings have shown that travelling planetary waves modulate the occurrence of mid-latitude sporadic-E-layers. Using a simple quantitative model, we analyse the effects of the linear interaction between tides and planetary waves on ion motion. Besides an expected variation of the dumping height, it is found that the boundaries of the oscillations induced by the descending semidiurnal tide are significantly modified by the presence of

A seasonally dependent total neutral wind model obtained from experimental data is used to evaluate the diurnal variation of the vertical ion velocity in the E-region at a high-latitude location (Tromsø), for each season, in the presence of an electric field with a typical diurnal variation for quiet auroral days. The diurnal variation and spatial locations of the vertical convergence of ions are analyzed and the effect of the total wind on the