F-region vertical drift measurements at Ebro, Spain

Eighteen months values of vertical drift velocity measured with a Digisonde 256 at the mid-latitude station of Ebro Observatory (40.5°N, 0.5°E) have been analyzed in order to establish the typical daily variations. The daily pattern of the vertical drift velocity can easily be represented by the main daily harmonics. The summer and winter patterns are quite different. The diurnal component is most prominent for each month, with a practically constant phase and larger equinoctial amplitudes. The semidiurnal component displays the same seasonal amplitude variation as the diurnal one, but its phase is sun-synchronous. The terdiurnal component displays a constant phase and it plays a role during the summer half year, with amplitudes larger than those of the semidiurnal component. The variability is larger at nighttime than at daytime, and in general winter shows a larger variability. The usefulness of monitoring the vertical F-region drift motions with Digisonde drift measurements is discussed.