Tidal Variations in the Ionosphere and Mesosphere Over Eastern China During 2014

The sources for the variabilities of the ionospheric tidal oscillations are complex and not totally understood yet. In this paper, both the seasonal and short-term variations of the ionospheric diurnal and semidiurnal oscillations over a meteor radar chain (Wuhan [114.4 degrees E, 30.6 degrees N], Beijing [116.5 degrees E, 39.9 degrees N], and Mohe [121.1 degrees E, 50.1 degrees N]) are investigated with critical frequency of the F2 layer (foF2) observations during 2014. The collocated mesospheric horizontal winds, the daily 10.7-cm solar flux, and the daily Ap index are also examined to determine the sources of the ionospheric tidal variabilities from the lower atmosphere, solar and geomagnetic activities, respectively. We found that the seasonal variations of the ionospheric tidal oscillations at the three sites are consistent, which are not in-phase with the seasonal variations of mesospheric tides at the same location. This indicates that mesospheric tides are unlikely the main cause of the seasonal variations of the ionospheric tides. Besides, the ionospheric tidal oscillations show clear periodical signals, which could correspond well with those in the local mesospheric wind or Ap index. Nevertheless, the periodical solar flux oscillation does not induce similar short-term ionospheric tidal variabilities. We also found that the influence of geomagnetic activities on the ionospheric tidal variabilities is with either enhancement or depression patterns during geomagnetic storms.