F3 layer occurrence as a function of (a) local time, (b) geographic position of the F3 layer during 06:00–18:00 LT
in boreal summer (blue) and winter (red), (c) dip latitude, (d) geographic longitude during boreal summer, and (e) winter.
ROCSAT‐1 derived equatorial vertical drift V⊥ (gray) were superimposed on Figures 3d and 3e.

Associate professor ZHAO Biqiang and his team have published a paper on extraction of ionospheric global scale hierarchical structure information. They use global observations of electron density profile (EDP) from the COSMIC/FORMOSAT‐3 satellites.

This paper presents a statistical work to infer the F3 layer structure directly from COSMIC RO data. Basic morphology and properties of F3 layer occurrence during 2006–2010 are investigated.

The major findings presented herein are summarized as follows: it is the first time the stratification structure of the F2 region is investigated by the COSMIC EDPs. The location of the F3 layer occurrence on a global scale are presented, which clearly shows the existence of the F2 stratification as a regular phenomenon at all the longitudes and have delineated its rapid variation with latitude in a narrow zone of occurrence. Meanwhile, the longitude difference of the F3 layer, which shows WN4 pattern in boreal summer, provides an indirect clue that the DE3 of lower atmosphere changes not only a single parameter in the ionosphere but also the whole altitude structure of the F region.

These results indicate that the RO soundings are of sufficient high accuracy to differentiate the variation of very local and subtle structure, although more RO events are needed to derive the refined structure of the ionospheric profiles at the low and equatorial latitudes.

Zhao et al. Global characteristics of occurrence of an additional layer in the ionosphere observed by COSMIC/FORMOSAT‐3. Geophys. Res. Lett.，2011，38，L02101，doi:10.1029/2010GL045744