Vertical propagating signatures of wave-type oscillations (2- and 6.5-days) in the ionosphere obtained from electron-density profiles

We investigate the meteorology of wave-type oscillations in the period range of 2- and 6.5-days observed in the middle latitude ionosphere at the altitude range from 170 to 230 km during 1998, with an emphasis on their vertical propagation characteristics. The true height electron density profiles obtained at the Observatori de l'Ebre station (40.8°N, 0.5°E) have been used for this purpose. We found several events with occurrence of wave packets with periods near 2- and 6.5-days during the summer half-year. These events display a clear vertical progression in the ionospheric F region, with vertical wavelenghts larger than 100 km. The events exist with upward or downward propagation and the different values between the phase and group velocities indicate the degree of dispersion that the ionosphere introduces on their propagation. The potential mechanisms linking the planetary wave activity in the mesosphere/lower thermosphere with the wave events observed in the ionosphere are discussed in order to evaluate the most likely mechanism.