f Variation Of The Ionospheric Equatorial Anomaly With Solar Cycle In The Brazilian Region During Autumn Equinox Condition

An investigation of the equatorial anomaly dependence<br>on solar activity is carried out using a sophisticated<br>theoretical model, the Sheffield University<br>Plasmasphere Ionosphere Model (SUPIM). Measurements<br>of the ionospheric electron content (TEC)<br>over Cachoeira Paulista (22.5° S, 45° W and dip lat.=<br>15°), which is near the southern anomaly crest, have<br>shown a decrease for F10.7 solar flux greater than<br>180. SUPIM results have revealed that this behaviour<br>of TEC is a consequence of an increased equatorial<br>E´B drift. An increase in the upward equatorial E´B<br>drift causes the equatorial anomaly to expand, i.e, the<br>position of the anomaly crests move poleward, so that<br>Cachoeira Paulista is in the anomaly trough rather<br>than at the southern crest.