This plot shows comparisons between COSMIC observations of the annual asymmetry in F2-region electron density (global electron densities are lower at the June solstice than they are at the December solstice) and NCAR-TIEGCM calculations of this asymmetry (bottom). The left hand side gives its local time variations and the right hand side gives its longitudinal variations. The TIEGCM reproduces the local time variations seen in the data very well and the longitudinal variations reasonably. The TIEGCM results were then used to determine the causes of the annual asymmetry (see Zeng et al., 2007).

Zeng, Z., A. G. Burns , W. Wang , J. Lei , S. C. Solomon , S. Syndergaard, L. Qian , Y.-Hwa Kuo, Ionospheric annual asymmetry observed by the COSMIC radio occultation measurements and simulated by the TIEGCM, J. Geophys. Res., 113, doi:10.1029/2007JA012897, 2008

This plot shows the F2 peak electron densities at local midnight averaged for a period around the December solstice. High electron densities occur in an oval over the Weddell Sea. An odd feature of this anomaly is that peak electron densities occur at night over this sea.