Sibri Alphonse Sandwidi

In this paper, we presented the effect of moderate geomagnetic storms on the TEC variation at the Koudougou station (Geo Lat 12° 15 N; Geo Long: -2° 20 E) in Burkina Faso (Africa) during the descending phase of solar cycle 24. For this purpose, four moderate geomagnetic storms without storm sudden commencement (SSC) or sudden impulse (SI) that occurred on May 13, 2015 (Dst: -76 nT), June 08, 2015 (Dst: -73 nT), September 11, 2015 (Dst: -80 nT), and May 08-09, 2016 (Dst: -88nT), were considered. These moderate storms were found to be associated with transients induced by fast solar winds. At the Koudougou station, TEC variation shows a positive response to the different moderate geomagnetic storms studied, with increases of order of 2-21 TECU around 1300-1500 UT except for September 11, 2015, TEC variation which shows sometimes negative responses at a few hours (mainly at night). TEC increases observed are a function of geomagnetic parameter (magnitude and polarity) variation. Storm-induced electric field and neutral winds are the main drivers of TEC changes observed during the selected geomagnetic storms. In addition, it was found that the TEC peak on storm day behaves differently compared to the days before and after the storm depending on whether Dst is positive or negative before southward inversion. Indeed, a TEC small peak relative to the days before and after the storm is observed when Dst is negative before southward inversion, and a larger peak occurs in the opposite case. The reasons for these differences are not investigated in this paper.

Every year, millions of dollars are invested in irrigation development in Sahelian African countries. After shifting from governmental organizations to non-governmental organizations (NGOs), the vulnerability of local populations has not changed much over the last 60 years in Africa. In this study, ten 1 ha small-scale irrigation systems—spread over the two driest climatic zones—were investigated in Burkina Faso. The soils and subsoils were characterized using double-ring infiltration measurements and two soil databases. The irrigation systems’ operability was assessed by sampling 10–12 farmers per system. A total of eight pumping tests were performed on a sample of wells. To assess the yield of cultivated onion, 5 to 7 squares were followed up in each of the 10 systems. Results indicated that water availability was ensured nowhere. The 32 wells were dug in clayey subsoils. Six of them yielded available water V_e flows ranging from 0.0 to 6.1 m³/day, far below the 80 m³/(ha·day) required by onion. To solve this issue, the NGOs shifted to a low-pressure drip irrigation solution, but the too-low pressure of 0.1 bar led to clogging. Ultimately, all 10 systems (except Louda) broke down a few months after the project’s end.

This paper deals with recurrent events’ (REs’) impacts on foF2’s diurnal variations at Dakar station (lat: 14.8° N, long: 342.6° E, Senegal) during solar cycles 21 and 22. Data were analyzed by taking in account solar phases and seasons influence. REs generate positive storms in all seasons and on all solar phases and also weak negative storms in all seasons and at minimum and maximum solar phases. The results suggest on the one hand that vertical drift due to strong electrojet currents cannot be considered an important mechanism of positive storms and on the other hand that prereversal enhancement (PRE) phenomenon (with a delay due to Dakar station position) and equatorward thermospheric neutral winds circulation (TNWC) contribute mainly to their generation. The intense positive storms, which appear mostly at night, are observed in decreasing phase and in spring which correspond, respectively, to the solar phase and the season of maximum REs occurrence. Then, positive storms’ strength presents seasonal and solar cycle dependence and it is related to REs days occurrence. REs’ negative storms strength are linked directly with REs days’ occurrence on solar phase scale, while they are not on seasonal scale.