# Thermospheric Neutral Wind Measurements and Investigations across the African Region--A Review
###### Abstract  
This paper briefly reviews studies of thermospheric neutral wind dynamics over the African region. The literature includes a review of the observations of neutral winds over five African locations using the Fabry-Perot Interferometer (FPI), and the comparison between the FPI observations and predictions of the horizontal wind model (HMM-14). So far, there are reports of FPI thermospheric wind measurements in South Africa and Morocco representing the mid-latitude regions in the southern and northern hemispheres, respectively. Within the low latitudes, FPI instruments are installed in the Ivory Coast, Ethiopia, and Nigeria. For the literature reviewed, the years covered in the FPI data are 2018-2019 (South Africa), 2016-2017 (Nigeria), 2015-2016 (Ethiopia), 2013-2016 (Morocco), and 1994-1995 (Ivory Coast). Overall, the HWM-14 reproduces the climatological behavior of the meridional and zonal winds, with varying levels of fidelity for the different regions. The HWM-14 is more accurate in the stations located in the northern hemisphere of the African region; a result attributed to the presence of data during the development of this empirical model. F 4 May 20220 20 May 2022 20 May 2022 2020 20 May 20220 2020 20 May 2022  
magnetically active periods are partly affected by thermospheric neutral winds [4]. Thermospheric neutral winds were established to play vital roles in the dynamics of the ionosphere and in the generation of the evening anomalies of electron concentrations [5; 6; 7]. The configuration of the equatorial ionization anomaly (EIA), for instance, can be significantly modulated by thermospheric neutral winds [8; 9; 10]. Thermospheric neutral winds were also shown to play important roles in determining the thermospheric composition (e.g., [11]). Despite this importance, thermospheric neutral winds are generally inadequately studied globally. This is obviously due to the general paucity of thermospheric neutral wind measurements. Neutral winds are difficult to measure remotely and space-based measurements are also hard to come by. However, with recent advances in imaging technologies, the ability to field robust and reliable wind-measuring instruments has allowed for easier and more reliable deployments. Fabry-Perot Interferometers (FPIs) are commonly used to measure thermospheric neutral winds (e.g., [12; 13; 14; 15; 16; 17]). They monitor the Doppler shift and the broadening of thermospheric nightglow emissions, from which the neutral wind and temperatures are deduced [18]. Ground-based FPIs typically make observations of nightglow emissions (usually at 630 nm wavelength) in different alternating directions, and the observations are analyzed individually to estimate the Doppler shift (neutral wind) and Doppler broadening (neutral temperature) [4; 19] along the line of sight of the observation. The nighttime 630.0 nm redline emissions are naturally produced through the dissociative recombination of O\({}_{2}\)\({}^{+}\) at altitudes of \(\sim\)250 km. However, the instrumentations that can provide thermospheric wind information remain scarce in a number of regions including in Africa, and especially in the southern hemisphere. As a result, data-driven modelling approaches such as the horizontal wind model, HWM [20; 21; 22] can be challenged to accurately specify thermospheric winds [4; 13; 23] and additional measurements are needed. This review focuses on reports of FPI measurements of the thermospheric neutral winds across the African region. In Africa, few FPI measurements of the thermospheric neutral winds were reported. Five installations of FPI were reported across the region, as indicated in Table 1 and in Figure 1. The red line in Figure 1 represents the geomagnetic equator. In the next section, we present summaries/highlights of research reports on FPI measurements of thermospheric neutral winds across the region. Sections 3 and 4 review the meridional and zonal wind magnitudes and directions, respectively. Section 5 reviews comparisons of the FPI measurements with the HWM predictions.