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The navigation and radio communication systems experience significant disruptions due to post‐sunset equatorial ionospheric irregularities. There is ongoing debate regarding the impact of meridional/trans‐equatorial wind speed on these irregularities, though it is widely agreed that the Pre‐Reversal Enhancement (PRE) plasma vertical drift velocity plays a key role in their occurrence. In this study, it is examined how F‐layer meridional neutral winds affect the post‐sunset equatorial ionospheric irregularities using GOCE satellite data in the years 2012–2013 employing statistical analysis. The Rate of Total Electron content (TEC) Index (ROTI) is commonly used to monitor ionospheric irregularities. The finding reveals a strong correlation between ROTI values and the differences in meridional wind speeds at the north and south equatorial ionization anomaly (EIA) crests. Observations show that smaller speed differences (less than ∼5 m/s) between the north and south EIA crests support the formation of post‐sunset ionospheric irregularities, while larger speed differences (more than 5 m/s) do not support irregularity formation.

The relation between the occurrence of ionospheric irregularities and the spatial gradient of total electron content (TEC) derived from two closely located stations (ASAB: 4.34∘ N, 114.39∘ E and DEBK: 3.71∘ N, 109.34∘ E, geomagnetic), located within the equatorial region, over Ethiopia, during the postsunset hours was investigated. In this study, the Global Positioning System (GPS)-derived TEC during the year 2014 obtained from the two stations were employed to investigate the relationship between the gradient of TEC and occurrence of ionospheric irregularities. The spatial gradient of TEC (ΔTEC∕Δlong) and its standard deviation over 15 min, σ(ΔTEC∕Δlong), were used in this study. The rate of change of TEC-derived indices (ROTI, ROTIave) were also utilized. Our results revealed that most of the maximum enhancement and reduction values in ΔTEC∕Δlong are noticeable during the time period between 19:00 and 24:00 LT. In some cases, the peak values in the spatial gradient of TEC are also observed during daytime and postmidnight hours. The intensity level of σ(ΔTEC∕Δlong) observed after postsunset show similar trends with ROTIave, and was stronger (weaker) during equinoctial (solstice) months. The observed enhancement of σ(ΔTEC∕Δlong) in the equinoctial season shows an equinoctial asymmetry where the March equinox was greater than the September equinox. During the postsunset period, the relation between the spatial gradient of TEC obtained from two closely located Global Navigation Satellite System (GNSS) receivers and the equatorial electric field (EEF) was observed. The variation in the gradient of TEC and ROTIave observed during the evening time period show similar trends with EEF with a delay of about 1–2 h between them. The relationship between σ(ΔTEC∕Δlong) and ROTIave correlate linearly with correlation coefficient of C=0.7975 and C=0.7915 over ASAB and DEBK, respectively. The majority of the maximum enhancement and reduction in the spatial gradient of TEC observed during the evening time period may be associated with ionospheric irregularities or equatorial plasma bubbles. In addition to latitudinal gradients, the longitudinal gradient of TEC has contributed significantly to the TEC fluctuations.

In this paper, for the first time, simultaneous atmospheric temperature perturbation profiles obtained from the TIMED/SABER satellite and equatorial ion density and vertical plasma drift velocity observations with and without ESF activity obtained from the C/NOFS satellite are used to investigate the effect of gravity waves (GW) on ESF. The horizontal and vertical wavelengths of ionospheric oscillations and GWs are estimated by applying wavelet analysis techniques. In addition, vertically propagating GWs that dissipate energy in the ionosphere-thermosphere system are investigated using the spectral analysis technique. We find that the vertical wavelength of GW, corresponding to dominant wavelet power, ranges from 12 to 31 km regardless of the conditions of the ionosphere; however, GWs with vertical wavelengths between about 1 to 13 km are found every day, saturated between 90 and 110 km at different longitudinal sectors. Filtering out vertical wavelengths above 13 km from temperature perturbations, ranges of zonal wavelengths of GW (i.e., from about 290 to 950 km) are found corresponding to irregular and non-irregular ionosphere. Similarly, corresponding to dominant oscillations, the zonal wavelength of ion density perturbations is found within 16 to 1520 km. Moreover, we find an excellent agreement among the median zonal wavelengths of GW for the cases of irregular and non-irregular ionosphere and ion density perturbations that are 518, 495, and 491 km, respectively. The results imply that seed perturbations due to GW with a vertical wavelength from about 1 to 13 km evolve to ion density irregularity and may be amplified due to post-sunset vertical upward drift velocity.

The annular solar eclipse of 21 June 2020, provided a valuable opportunity to examine the ionospheric response to celestial events. This study analyzes variations in Vertical Total electron content (VTEC) over the equatorial region using data from the UQRG Global Ionospheric Map (GIM), ground‐based GPS‐TEC measurements, and equatorial electrojet (EEJ) strength from magnetometers near the eclipse path. Significant VTEC reductions were observed during the eclipse. The early decline began in East Africa and South Asia during the morning hours, while in the Western Pacific region, the reduction occurred in the late afternoon, coinciding with the onset of the eclipse. Around local noon, a delayed decrease was detected at stations located in Southeast and East Asia. 22%–53% VTEC reduction was recorded during the eclipse's main phase, with effects persisting from 35 min to over 8 hr post‐eclipse. Post‐eclipse variations in dusk sector suggest local electrodynamical effects. The study found no significant impact on EEJ strength between 130°$130{}^{\\circ}$ E to 144°$144{}^{\\circ}$ E, and no substantial counter equatorial electrojet was detected. Conducted during the monsoon season and the longest day of the year, observed VTEC reductions likely result from eclipse‐induced pressure changes and cooling effects. GIM visualizations showed that dVTEC% decreased by up to ∼${\\sim} $ 40% globally. The findings indicate that VTEC decreases are not strongly correlated with obscuration percentage, highlighting complexity of ionospheric responses. This study enhances understanding of eclipse‐driven ionospheric variability, emphasizing the role of photoionization, recombination, geographic location, and local time, with implications for space weather forecasting and ionospheric modeling. Plain Language Summary Solar eclipses provide a rare opportunity to study the effects of the Sun's temporary blockage on Earth's ionosphere. The ionosphere is a charged layer of the upper atmosphere that plays a crucial role in communication and navigation. This study examined how the Total Electron Content (TEC) in the ionosphere changed during the 21 June 2020 annular solar eclipse over the equatorial region. By analyzing data from satellite‐based Global Ionospheric Maps (GIMs), dual‐frequency Global Navigation Satellite System receivers, and ground magnetometers, we observed that TEC levels decreased significantly by 22%–53% during the eclipse, with effects lasting from 35 min to over 8 hr after the event. However, the changes were not directly linked to the amount of sunlight blocked, suggesting that other factors, such as atmospheric cooling and pressure shifts, influenced the ionospheric response. Interestingly, the eclipse showed no noticeable effect on the equatorial electrojet (EEJ) in the sector between 130°^{\\circ}$ E and 144°^{\\circ}$ . This indicates that, unlike findings from some previous studies, the EEJ response was regionally dependent and not significantly perturbed in this longitude sector. These findings highlight the complex ways in which solar eclipses influence our atmosphere, improving our understanding of space weather and helping refine models used for GPS accuracy and radio signal predictions. Key Points Distinct spatiotemporal Total Electron Content responses occurred during the 21 June 2020 eclipse across equatorial regions A 22%–53% Vertical Total Electron Content reduction is observed at various stations during the solar eclipse Post eclipse spatial gradients varied near dusk sector but equatorial electrojet strength showed no significant change

The Upper Blue Nile region in Ethiopia, frequently affected by drought conditions and much of its water flows from highland regions to territorial countries. Hence to characterize, monitor and forecast drought, an advanced drought index which considers the combination of different climatic conditions in this region is required. The main objective of this article is to develop new drought indices by considering with and without climate signal contribution which is precious in decision making of policy makers and scientific community. In order to estimate the quality and performance of the developed indices we implemented statistical methods of RMSE, MAE and bias with the existing index of SPI across different time scales. Infact we developed two drought indices by considering SST into the meteorological variables (MVDIstS) and without considering SST (MVDIst0). Both drought indices show drought severity, larger duration than that of SPI.

Measurements of equatorial thermospheric winds, temperatures, and 630 nm relative intensities were obtained using an imaging Fabry–Perot interferometer (FPI), which was recently deployed at Bahir Dar University in Ethiopia (11.6° N, 37.4° E, 3.7° N magnetic). The results obtained in this study cover 6 months (53 nights of useable data) between November 2015 and April 2016. The monthly-averaged values, which include local winter and equinox seasons, show the magnitude of the maximum monthly-averaged zonal wind is typically within the range of 70 to 90 ms−1 and is eastward between 19:00 and 21:00 LT. Compared to prior studies of the equatorial thermospheric wind for this local time period, the magnitude is considerably weaker as compared to the maximum zonal wind speed observed in the Peruvian sector but comparable to Brazilian FPI results. During the early evening, the meridional wind speeds are 30 to 50 ms−1 poleward during the winter months and 10 to 25 ms−1 equatorward in the equinox months. The direction of the poleward wind during the winter months is believed to be mainly caused by the existence of the interhemispheric wind flow from the summer to winter hemispheres. An equatorial wind surge is observed later in the evening and is shifted to later local times during the winter months and to earlier local times during the equinox months. Significant night-to-night variations are also observed in the maximum speed of both zonal and meridional winds. The temperature observations show the midnight temperature maximum (MTM) to be generally present between 00:30 and 02:00 LT. The amplitude of the MTM was  ∼  110 K in January 2016 with values smaller than this in the other months. The local time difference between the appearance of the MTM and a pre-midnight equatorial wind was generally 60 to 180 min. A meridional wind reversal was also observed after the appearance of the MTM (after 02:00 LT). Climatological models, HWM14 and MSIS-00, were compared to the observations and the HWM14 model generally predicted the zonal wind observations well with the exception of higher model values by 25 ms−1 in the winter months. The HWM14 model meridional wind showed generally good agreement with the observations. Finally, the MSIS-00 model overestimated the temperature by 50 to 75 K during the early evening hours of local winter months. Otherwise, the agreement was generally good, although, in line with prior studies, the model failed to reproduce the MTM peak for any of the 6 months compared with the FPI data.

Space weather science has been a growing field in Africa since 2007. This growth in infrastructure and human capital development has been accompanied by the deployment of ground-based observing infrastructure, most of which was donated by foreign institutions or installed and operated by foreign establishments. However, some of this equipment is no longer operational due to several factors, which are examined in this paper. It was observed that there are considerable gaps in ground-based space-weather-observing infrastructure in many African countries, a situation that hampers the data acquisition necessary for space weather research, hence limiting possible development of space weather products and services that could help address socio-economic challenges. This paper presents the current status of space weather science in Africa from the point of view of some key leaders in this field, focusing on infrastructure, situation, human capital development, and the research landscape.

This study presents harmonic analysis of precipitation observations within the Lake Tana Basin for the periods of 1985–2015. The livelihood of several millions of people within the basin and outside the basin is governed by the precipitation conditions within this basin. Large spatial and temporal variabilities of precipitation can increase the incidence of extreme events such as floods and droughts. It is important to identify the characteristics of these variations, and this study aims at investigating the characteristics of the seasonal and annual cycles of precipitation within the Lake Tana Basin using harmonic analysis. Precipitation data of 31 years from four weather stations were used in the analysis. We then applied harmonic analysis to calculate the amplitude, phase shift, and variance of observation. Detailed characteristics of the first five harmonics are presented and discussed. We found the amplitude of the first harmonic to be 173.42, 177.93, 127.77, and 188.78 mm for Debre Tabor, Bahir Dar, Gondar, and Dangila, respectively. This shows that Dangila areas got more rainfall during this fundamental period than others increasing from Gondar to Dangila direction. Also, the variance in the first harmonic is smaller than the variances of other harmonics, and this means that the large variations of the precipitation originate from higher harmonics (short time periods). This shows that precipitation variations are governed mainly by monthly, seasonal, and semiannual variations. The analysis has shown that maximum precipitation for all stations occurred in July and August.

Drought is an extreme event that causes great economic and environmental damage. The main objective of this study is to evaluate sensitivity, characterization and propagation of drought in the Upper Blue Nile. Drought indices: standardized precipitation index (SPI) and the recently developed standardized reconnaissance drought index (RDIst) are applied for five weather stations from 1980 to 2015 to evaluate RDIst applicability in the Upper Blue Nile. From our analysis both SPI and RDIst applied for 3-, 6-, 12 month of time scales follow the same trend, but in some time steps the RDIst varies with smaller amplitude than SPI. The severity and longer duration of drought compared with others periods of meteorological drought is found in the years 1984, 2002, 2009, 2015 including five weather stations and entire Upper Blue Nile. For drought relationships the correlation analysis is made across the time scales to evaluate the relationship between meteorological drought (SPI), soil moisture drought (SMI), and hydrological drought (SRI). We found that the correlation between three indices (SPI, SMI and SRI) at different time scales the 24-month time scale is dominant and are given by 0.82, 0.63 and 0.56.

Equatorial longitudinal ionospheric variations are influenced by various physical processes, including the east–west directed electric field (equatorial electrojet, EEJ). However, the specific impact of EEJ variability on the total electron content (TEC) variations in different longitudinal sectors has not been thoroughly explored. Therefore, this study focuses on investigating the longitudinal changes in the EEJ and how they affect the daily patterns of the equatorial ionization anomaly (EIA) on geomagnetic calm time from 2011 to 2013. EEJ was estimated using pairs of magnetometer observations across eight sectors globally, while Global Positioning System (GPS) TEC data were collected from three stations at the southern/northern crests and trough locations within the longitudinal sector. The study presents seasonal variations in EIA TEC during different seasons alongside longitudinal variations of EEJ in both the southern/northern hemispheres. Statistical analysis reveals that the southern/northern equatorial ionospheric anomaly (EIA) crests exhibit positive correlations with the peaks of EEJ in all regions, indicating that the variations in EIA strength align with those of EEJ. The seasonal mean EEJ and EIA crests are most pronounced during equinox seasonal months over the Southeast Asian, Peruvian, and Philippine regions in the investigation period. In these regions, the correlation coefficients for the TEC near the northern crests are relatively higher than those for the southern crests, while the southern crest shows slightly higher values across the Pacific, Indian, Brazilian, and West African regions. Notably, the correlation between an integrated EEJ and the strength of EIA is stronger than that with the day maximum EEJ. The study also presents the seasonal characteristics of EEJ and EIA, with counter electrojets (CEJ) occurrences occurring more observable in Brazil and Africa. However, in most equinoctial seasons, the highest TEC peak close to the EIA crest is observed in these sectors. Research Highlights The northern/southern TEC of EIA crests exhibit variations that correlate with the variations in EEJ. TEC of EIA strength variations align with those in EEJ during different seasons. The correlation coefficients between EIA and EEJ exhibit high values across all sectors during the moderate year of 2011.