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The equator’s unique combination of high humidity and temperature renders optical satellite imagery highly susceptible to persistent cloud cover. In contrast, synthetic aperture radar (SAR) offers a robust alternative due to its ability to penetrate clouds with microwave imaging. This study addresses the challenges of cloud-induced data gaps and cross-sensor geometric biases by proposing an advanced optical and SAR image-matching framework specifically designed for cloud-prone equatorial regions. We use a prompt-driven visual segmentation model with automatic prompt point generation to produce cloud masks that guide cross-modal feature-matching and joint adjustment of optical and SAR data. This process results in a comprehensive digital orthophoto map (DOM) with high geometric consistency, retaining the fine spatial detail of optical data and the all-weather reliability of SAR. We validate our approach across four equatorial regions using five satellite platforms with varying spatial resolutions and revisit intervals. Even in areas with more than 50 percent cloud cover, our method maintains sub-pixel edging accuracy under manual check points and delivers comprehensive DOM products, establishing a reliable foundation for downstream environmental monitoring and ecosystem analysis.

This paper presents the analysis of the actual, predicted, and simulated technical performance of a residential 2.835 kWp retrofitted grid-connected photovoltaic (GCPV) system under the feed-in-tariff (FiT) scheme in Klang, Malaysia located in the equatorial region. The technical performance indices of the GCPV system were assessed based on the three-year energy production in 2018, 2019 and 2020. The actual and predicted technical performance were calculated using SEDA mathematical model, which the solar irradiation data was acquired from PVsyst software. Meanwhile, the simulated technical performance was obtained using PVsyst software. The results showed that the prediction using mathematical model has higher percentage difference within the range of 12.54-13.29%, compared to PVsyst simulation that was within 7.93-11.93%. This study has highlighted the factors that contributed to the technical performance underprediction of both mathematical model and PVsyst simulation, which are the estimation of losses and annual irradiation data accuracy. Lastly, the FiT gross income calculated for the three consecutive years were within the range of 3310.80 MYR and 3357.30 MYR. This FiT gross income result conveys an example of Malaysian case study, to enlighten the public, on the economic aspect of installing GCPV system under FiT scheme.

We present results of a study of post-midnight equatorial spread F (ESF) events over the Jicamarca Radio Observatory (JRO) that examined unambiguous radar measurements of event origin in the American sector. Our analysis considers variations in post-midnight ESF generation due to changing seasonal, solar, and geomagnetic conditions. We analyzed 396 nights of observations made with the 14-panel version of the Advanced Modular Incoherent Scatter Radar (AMISR-14) between July 2021 and August 2023. We leveraged the 10-beam AMISR-14 mode, which effectively measures ~ 400 km zonally of the equatorial F-region ionosphere, to identify and classify post-midnight ESF as either local (i.e., generated within the instrument field of view) or non-local (i.e., generated outside the instrument field of view). Our results for the occurrence rates of post-midnight ESF exhibit a strong seasonal dependence, with maximum values in June solstice and minimum values for equinoxes. The results also show the post-midnight ESF occurrence rates are anticorrelated to the solar flux conditions. As for geomagnetic activity, the results indicate that occurrence rates decrease considerably under geomagnetically quiet conditions. The combination of these seasonal, solar flux, and geomagnetic activity influences suggests the weakened downward plasma drifts late at night during June solstice conditions can be reversed to upward drifts by contributions from disturbance drifts. In the case of upward drifts caused by geomagnetic disturbances, the reversed upward post-midnight drifts may then contribute to conditions favoring ESF development provided that a prompt penetration or disturbance dynamo electric field with appropriate polarity, even from modest geomagnetic activity, is present. In support of this proposed post-midnight ESF generation mechanism, we also present and discuss simultaneous AMISR-14 and collocated incoherent scatter radar measurements of a June solstice 2023 event. Perhaps most importantly, our results show the occurrence rates of local and non-local post-midnight ESF as observed with AMISR-14 are nearly identical. That is, local events were observed effectively as often as non-local events, and vice versa, under all seasonal, solar, and geomagnetic conditions. Therefore, data-driven forecasting approaches relying exclusively on local (i.e., “overhead”) measurements of ionospheric/thermospheric conditions may not always be well-suited to reproducing the observed ESF phenomenology. Graphical Abstract Key Points We analyzed ~2 years of two-dimensional radar measurements to determine the climatology of post-midnight ESF generated locally (i.e., within the radar field of view) and non-locally. We found nearly the same (50/50) occurrence rates for post-midnight ESF events that developed locally and non-locally, independent of season and solar flux conditions. Collocated ESF and drift observations show the unequivocal case of a post-midnight ESF event generated under conditions of abnormal vertical plasma drifts. The observations also show that even moderate geomagnetic activity can contribute to the generation of post-midnight ESF during June solstice. The observations support the hypothesis that post-midnight ESF is more likely to occur under certain conditions of weak post-midnight drifts with contributions from disturbance electric fields.

We describe a mode for two-dimensional UHF (445 MHz) radar observations of F-region irregularities using the 14-panel version of the advanced modular incoherent scatter radar (AMISR-14). We also present and discuss examples of observations made by this mode. AMISR-14 is installed at the Jicamarca Radio Observatory (JRO, 11.95°S, 76.87°W, ~ 0.5° dip latitude) in Peru and, therefore, allows studies of ionospheric irregularities at the magnetic equator. The new mode takes advantage of the electronic beam-steering capability of the system to scan the equatorial F-region in the east–west direction. Therefore, it produces two-dimensional views of the spatial distribution of sub-meter field-aligned density irregularities in the magnetic equatorial plane. The scans have a temporal resolution of 20 s and allow observations over a zonal distance of approximately 400 km at main F-region heights. While the system has a lower angular and range resolution than interferometric in-beam VHF radar imaging observations available at Jicamarca, it allows a wider field-of-view than that allowed with the VHF system. Here, we describe the mode, and present and discuss examples of observations made with the system. We also discuss implications of these observations for studies of ESF at the JRO.KeypointsA new mode for two dimensional observations of F-region irregularities in the magnetic equatorial plane using AMISR-14 is described.Examples of observations are presented and illustrate the ability of the system to capture the genesis, evolution, and decay of sub-meter ESF irregularities.The benefits of the new mode are highlighted and implications of the new observations for studies and better understanding of ESF are discussed.

Background Increased use of long-lasting insecticidal nets (LLINs) over the last decade has considerably improved the control of malaria in sub-Saharan Africa. However, there is still a paucity of data on the influence of LLIN use and other factors on mosquito bionomics in different epidemiological foci. The objective of this study was to provide updated data on the evolution of vector bionomics and malaria transmission patterns in the equatorial forest region of Cameroon over the period 2000–2017, during which LLIN coverage has increased substantially. Methods The study was conducted in Olama and Nyabessan, two villages situated in the equatorial forest region. Mosquito collections from 2016–2017 were compared to those of 2000–2001. Mosquitoes were sampled using both human landing catches and indoor sprays, and were identified using morphological taxonomic keys. Specimens belonging to the An. gambiae complex were further identified using molecular tools. Insecticide resistance bioassays were undertaken on An. gambiae to assess the susceptibility levels to both permethrin and deltamethrin. Mosquitoes were screened for Plasmodium falciparum infection and blood-feeding preference using the ELISA technique. Parasitological surveys in the population were conducted to determine the prevalence of Plasmodium infection using rapid diagnostic tests. Results A change in the species composition of sampled mosquitoes was recorded between the 2000–2001 collections and those of 2016–2017. A drop in the density of the local primary vectors An. nili and An. moucheti in the forest region was recorded, whereas there was an increase in the density of An. gambiae ( s.l .), An. marshallii , An. ziemannii and An. paludis . A change in the biting behaviour from indoor to outdoor was recorded in Olama. Very few indoor resting mosquitoes were collected. A change in the night biting cycle was recorded with mosquitoes displaying a shift from night biting to late evening/early in the night. Several mosquitoes were found positive for Plasmodium infection, thus sustaining continuous transmission of malaria in both sites. Reduction of malaria transmission in Nyabessan was lower than that seen in Olama and associated with deforestation and the construction of a dam that may have enabled a more efficient vector, An. gambiae ( s.l .), to invade the area. A high level of resistance to pyrethroids (permethrin and deltamethrin) was detected for An. gambiae in both sites . High parasite prevalence was recorded in both sites, with children of 0–16 years being the most affected. In both Olama and Nyabessan, bed net usage appeared to correlate to protection against malaria infection. Conclusions The study shows important changes in the bionomics of vector populations and malaria transmission patterns in the equatorial forest region. The changes call for more concerted efforts to address challenges such as insecticide resistance, environmental modifications or behavioural changes affecting the performance of current control measures.

[...]new assessments of rain fade and rain fade mitigation were required for the HTS system before it is fully implemented [3]-[5]. [...]these initial studies on rain fade and rain fade mitigation were conducted in the northern latitude countries which has lower rainfall rate than the equatorial region. Rain attenuation is obtained from the knowledge of specific attenuation integrated over an effective path length from the ground terminal to the rain height [17]. [...]a rain prediction model consists of two parts which are the specific attenuation and the path length of the rain. Direct measurement of specific attenuation is more accurate but difficult to obtain because the correlation of rainfall rate and satellite signal loss due to rain fade has to be obtained simultaneously. [...]investigating specific attenuation for Ku-band atmospheric attenuation using direct measurement is critical and may improve the prediction of rain attenuation in the equatorial region since a new high throughput satellite system requires a small margin of error. [...]this article aims to produce and evaluate specific attenuation for a Ku-band frequency in the equatorial region based on direct measurement of Ku-band beacon and rainfall rate and then obtain specific attenuation coefficients by correlations using a semi-empirical method.

Using NASA's Global‐scale Observations of the Limb and Disk (GOLD) imager, we report nightside ionospheric changes during the G5 super geomagnetic storm of 10 and 11 May 2024. Specifically, the nightside southern crest of the Equatorial Ionization Anomaly (EIA) was observed to merge with the aurora near the southern tip of South America. During the storm, the EIA southern crest was seen moving poleward as fast as 450 m/s. Furthermore, the aurora extended to mid‐latitudes reaching the southern tips of Africa and South America. The poleward shift of the equatorial ionospheric structure and equatorward motion of the aurora means there was no mid‐latitude ionosphere in this region. These observations offer unique insights into the ionospheric response to extreme geomagnetic disturbances, highlighting the complex interplay between solar activity and Earth's upper atmosphere. Plain Language Summary On Earth's nightside during the super geomagnetic storm that occurred on 10 May 2024, NASA's GOLD imager saw something new: a part of Earth's ionosphere, the southern peak of what typically appears as a double‐peaked structure in the ionospheric density at equatorial and low latitudes, merged with the aurora near the southern tip of South America. This has never been reported before. Additionally, the boundary of the aurora expanded further equatorward than usual. These observations of what happened in the Earth's ionosphere during this super storm are reported for the first time in this study. Key Points EIA crests between ∼70° and 35°W moved poleward, with northern and southern crest reaching ∼38°N and ∼35°S Mlat in the American sector Southern EIA crest moved poleward with a speed of ∼450 m/s near ∼55°W Glon during strong IMF Bz and d(Dst)/dt First observation of the merging of an EIA crest with the aurora indicating no mid‐latitude ionosphere

Ionospheric irregularities are a common phenomenon in the low-latitude ionosphere. They can be seen in situ as depletions of plasma density, radar plasma plumes, or ionogram spread F by ionosondes. In this paper, we compared simultaneous observations of plasma plumes by the Jicamarca Unattended Long-term Investigations of the Ionosphere and Atmosphere (JULIA) radar, ionogram spread F generated from ionosonde observations installed at the Jicamarca Radio Observatory (JRO), and irregularities observed in situ by Swarm in order to determine whether Swarm in situ observations can be used as indicators of the presence of plasma plumes and spread F on the ground. The study covered the years from 2014 to 2018, as this was the period for which JULIA, Swarm, and ionosonde data sets were available. Overall, the results showed that Swarm's in situ density fluctuations on magnetic flux tubes passing over (or near) the JRO may be used as indicators of plasma plumes and spread F over (or near) the observatory. For Swarm and the ground-based observations, a classification procedure was conducted based on the presence or absence of ionospheric irregularities. There was a strong consensus between ground-based observations of ionospheric irregularities and Swarm's depth of disturbance of electron density for most passes. Cases, where ionospheric irregularities were observed on the ground with no apparent variation in the in situ electron density or vice versa, suggest that irregularities may either be localized horizontally or restricted to particular height intervals. The results also showed that the Swarm and ground-based observations of ionospheric irregularities had similar local time statistical trends with the highest occurrence obtained between 20:00 and 22:00 LT. Moreover, similar seasonal patterns of the occurrence of in situ and ground-based ionospheric irregularities were observed with the highest percentage occurrence at the December solstice and the equinoxes and low occurrence at the June solstice. The observed seasonal pattern was explained in terms of the pre-reversal enhancement (PRE) of the vertical plasma drift. Initial findings from this research indicate that fluctuations in the in situ density observed meridionally along magnetic field lines passing through the JRO can be used as an indication of the existence of well-developed plasma plumes.

This study uses multiple ground and satellite‐based measurements to investigate the extreme ionospheric response to the Mother's Day storm on May 10–11, 2024. Prompt penetration electric field caused a significant enhancement in the ionospheric vertical drift (∼${\\sim} $95 m/s) and the equatorial electrojet strength (∼${\\sim} $  275 nT) over Jicamarca. These extreme eastward electric field perturbations, along with the large meridional wind, significantly altered the F‐region plasma fountain at different local times. The afternoon equatorial ionization anomaly (EIA) not only sustained for an exceptionally long duration (∼${\\sim} $12 hr) but also expanded spatially over time. The separation between the two peaks of EIA crests exceeded ∼48°${\\sim} 48{}^{\\circ}$and ∼70°${\\sim} 70{}^{\\circ}$in the morning and evening sectors, respectively. This study shows, for the first time, that unusually strong EIA can not only develop at different local times but can also sustain for long duration under favorable conditions, which has implications for space weather applications. Plain Language Summary The Earth's upper atmosphere is significantly influenced by space weather events, particularly geomagnetic storms. In this study, we investigate the impact of an intense geomagnetic storm that occurred on 10–11 May 2024 (popularly known as Mother's Day storm) on the equatorial and low‐latitude ionosphere. Using datasets from various ground and satellites‐based (SWARM, and GOLD satellites, Global GNSS receivers, Incoherent Scatter Radar (ISR), Fabry‐ Perot interferometers (FPI), and magnetometer) measurements, we show the impact of extreme prompt penetration of electric field on the development of plasma fountain during the storm. We observe a significant increase in electron density and TEC during the main phase of the storm. Our findings highlight the role of extreme space weather disturbances on the generation of EIA at different local times and the impact of the plasma distribution on the globe. We also observe different types of electric field perturbations on low latitude ionosphere during this severe geomagnetic storm. Key Points The plasma fountain during the Mother's Day storm was unusually strong across different local time sectors The combined effects of a strong penetration electric field and meridional wind sustained the plasma fountains for an extended period The EIA crest over the Jicamarca sector merged with the expanded auroral region