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.