Abstract

The present paper reviews CODG TEC response to the moderate storm of July 26, 2003 and that of July 29 at Niamey station in West African equatorial station (Geo Lat 13° 28'45.3 "N; Geo long: 02° 10'59.5" E) in Niger. These two moderate geomagnetic storms are of solar wind origin. The study showed an increase in CODG TEC values during the initial phase of the storm and a decrease in CODG TEC values during the main and recovery phases of the storm. In general, in the equatorial region, positive and negative storms occurred (increase and decrease in TEC values). Here we highlight the prereversal enhancement (PRE), a particularity of the equatorial ionosphere. Our investigations show M, B and R profiles in addition to the well-known dome profile in the variation of the CODG TEC in Niamey. This work suggests a variation of the equatorial electrojet intensity during the storm recovery phase, the appearance of the counter-electrojet as well as a disturbance of the ExB drift. This study is local, in the equatorial region in the West African sector. Data are needed to corroborate some hypotheses such as changes in profiles associated with the presence or absence of electrojet and counter-electrojet currents. We advocate for a new IHY for Africa and for data exchange between researchers.

Key words: Ionosphere, solar wind, disturbance, total electron content (TEC).