Comparison of Ionospheric Bite-Outs Between Observations From Beidou GEO TEC and Ionosonde Over East Asia

In this study, the daytime bite-outs were systematically compared between the total electron content (TEC) and peak electron density of F2 layer (NmF2) data using observations from Beidou GEO receivers and ionosondes over East Asia. Moreover, the Thermosphere-Ionosphere Electrodynamics Global Circulation Model simulations were also employed to analyze the underlying physical mechanisms. There was an obvious difference in the occurrence rate of bite-outs between TEC and NmF2, although bite-outs from both data sets showed similar seasonal and latitudinal dependences. Interestingly, the differences in the bite-out occurrence rates also varied with season and latitude. Their difference, which showed the opposite trend to the occurrence rates themselves, became prominent in equinoxes and less evident in June solstice, peaking at the equatorial ionization anomaly crest. In addition, the occurrence times of bite-outs were different as observed in TEC and NmF2 sometimes. Bite-out in TEC tended to start earlier than that in NmF2 at middle latitudes, whereas an opposite pattern was seen at low latitudes. On the contrary, TEC bite-out often died away earlier than NmF2 bite-out regardless of the latitudes. The simulations suggested that the vertical E x B drifts associated with zonal equatorial electric fields and the meridional neutral winds could play crucial roles in the characteristics of both bite-outs.