The average seasonal and local time variations at Argentine Islands

Figure 1. The average seasonal and local time variations in ln(N/N0), at Argentine Islands (650 S) for 1971-1981, taken from Rodger et al. (1989).






Image showing a, b, and c The equatorial extent of the “composition bulge” at 1200 UT, for equivalent storms in the northern hemisphere for summer, winter, and equinox


Figure 2. The equatorial extent of the “composition bulge” at 1200 UT, for equivalent storms in the northern hemisphere for a) summer, b) winter, and c) equinox conditions.






A comparison of the observed f0F2 and the monthly mean

a comparison between the observed
            and CTIM modeled ratio of storm to quiet foF2 values

The variations in the geomagnetic index ap


Figure 3a. Numerical simulation of a period during November and December of 1997 for the winter hemisphere. The top panel shows a comparison of the observed f0F2 and the monthly median. The middle panel is a comparison between the observed and CTIM modeled ratio of storm to quiet foF2 values. The lower panel shows the variations in the geomagnetic index ap.



A comparison of the observed f0F2 and the monthly mean for the summer hemisphere

a comparison between the observed
            and CTIM modeled ratio of storm to quiet foF2 values for the summer hemisphere

The variations in the geomagnetic index ap for the summer hemisphere


Figure 3b. Same as Figure 3a except for summer hemisphere.






A plot showing the evolution
of the ionosphere at mid-latitude over South America


Time history of the ap index over a five day interval from June 5th 1981

Figure 4. Time history of the ap index over a five day interval from June 5th 1981, and the evolution of the ionosphere at mid-latitude over South America.






Filter shape, F(t), representing the relationship between the geomagnetic
    index ap and the ionospheric storm-time response at summer mid-latitudes.


Figure 5. Filter shape, F(t), representing the relationship between the geomagnetic index ap and the ionospheric storm-time response at summer mid-latitudes.






The seasonal/latitude response of the storm-to-quiet foF2 as a
function of filtered ap, X(t0)


Figure 6. The seasonal/latitude response of the storm-to-quiet foF2 as a function of filtered ap, X(t0).






Observed and empirical model
  FoF2 ratios for the event that occurred on November 22/23 at Grahamstown in the southern hemisphere
  (summer)

Observed and empirical model
FoF2 ratios for the event that occurred on November 22/23 at Rome in
the northern hemisphere (winter)


Figure 7. Observed and empirical model FoF2 ratios for the event that occurred on November 22/23 at two sites, Rome in the northern hemisphere (winter) and Grahamstown in the southern hemisphere (summer).






Illustration of the local time
dependence in the residual of the foF2
storm-to-quiet ratio


Figure 8. Illustration of the local time dependence in the residual of the foF2 storm-to-quiet ratio.