Search Results (13)

This study examines the spatiotemporal evolution of midlatitude ionospheric disturbances during the intense geomagnetic storm on 10–11 October 2024, focusing on the North American and European sectors. It utilizes multi-instrument datasets from ground-based observations, including Global Navigation Satellite System (GNSS) receivers and ionosondes, supplemented by the measurements from the Swarm, DMSP and GUVI/TIMED satellites. The results reveal significant longitudinal and latitudinal variations in regional ionospheric responses, specifically related to Storm Enhanced Density (SED) and the midlatitude trough. Key findings include: (a) During the main phase of the storm, the North American midlatitude ionosphere exhibited a pronounced longitudinal contrast: a positive SED-driven phase in the west versus a negative trough-dominated phase in the east. In the early recovery phase, the western sector transitioned to a trough-induced negative phase, while the eastern sector showed a positive phase related to auroral particle precipitation during substorms. (b) The North American SED featured a strong northwest-extending plume with a westward shift velocity of 200–300 m/s at 45°N, and a sharp density gradient of 60–65 TECU on its northeastern side, in contrast to the trough. (c) The European sector displayed a “sandwich-like” latitudinal pattern, with “positive–negative–positive” variations during the storm. (d) The European sector’s storm-time trough expanded rapidly equatorward, reaching a minimum of ~35° magnetic latitude (MLAT), while broadening latitudinally to a width of 18–20°. These density gradient structures, along with the longitudinal/latitudinal differences, highlight the dynamic processes occurring in the magnetosphere–ionosphere–thermosphere system during intense storms and contribute to the understanding of storm-response mechanisms across different sectors. Full article

Accurate methane emission estimates are essential for climate policy, yet current field methods often struggle with spatial constraints and source complexity. Ground-based mobile approaches frequently miss key plume features, introducing bias and uncertainty in emission rate estimates. This study addresses these limitations by using small unmanned aerial systems equipped with precision gas sensors to measure methane alongside co-released tracers. We tested whether arc-shaped flight paths and alternative ratio estimation methods could improve the accuracy of tracer-based emission quantification under real-world constraints. Controlled releases using ethane and nitrous oxide tracers showed that (1) arc flights provided stronger plume capture and higher correlation between methane and tracer concentrations than traditional flight paths; (2) the cumulative sum method yielded the lowest relative error (as low as 3.3%) under ideal mixing conditions; and (3) the arc flight pattern yielded the lowest relative error and uncertainty across all experimental configurations, demonstrating its robustness for quantifying methane emissions from downwind plume measurements. These findings demonstrate a practical and scalable approach to reducing uncertainty in methane quantification. The method is well-suited for challenging environments and lays the groundwork for future applications at the facility scale. Full article

In recent years, numerous satellite-based systems have been developed to monitor and study volcanic activity from space. This progress reflects the growing demand for accurate and timely monitoring to reduce volcanic risk. Observing volcanoes from a satellite perspective provides key advantages, enabling continuous data acquisition and near-real-time assessment of volcanic activity. Multispectral sensors operating across various regions of the electromagnetic spectrum can detect thermal anomalies associated with lava flows, pyroclastic flows, ash plumes, and volcanic gases. Traditional hotspot detection techniques based on fixed thresholds often miss subtle anomalies on a global scale. In contrast, advanced machine learning algorithms offer a data-driven alternative. We designed and implemented the V-STAR application (Volcanic Satellite Thermal Anomalies Recognition) on Google Earth Engine (GEE) to leverage cloud computing for processing large geospatial datasets in real time. It employs supervised machine learning, specifically Random Forests, to adapt to evolving volcanic conditions. This enhances the accuracy and responsiveness of volcanic monitoring, offering valuable insights into potential eruptive behavior. Here, we present V-STAR as a robust and accessible tool that integrates satellite data and advanced analytics. Through its intuitive interface, V-STAR provides a comprehensive visualization of key volcanic features. The resulting analyses reveal hidden patterns in thermal data, contributing to improved disaster risk reduction strategies associated with volcanic hazards. Full article

Hybrid Rocket Engines (HREs) combine the advantages of solid and liquid propellants, offering thrust control, simplicity, safety, and cost efficiency. Part of the research on this rocket architecture focuses on optimising combustion chamber design to enhance performance, a process traditionally reliant on time-consuming experimental adjustments to chamber lengths. In this study, two configurations of HREs were designed and tested. The tests aimed to study the impact of post-chamber lengths on rocket engine performance by experimental firings on a laid-back test engine. This study focused on designing, manufacturing, and testing a laid-back hybrid engine with two chamber configurations. The engine features a small combustion chamber, an L-shaped mount, a spark ignition, and nitrogen purging. Data acquisition includes thermocouples, pressure transducers, and a load cell for thrust measurement. Our experimental findings provide insights into thrust, temperature gradients, pressure, and plume characteristics. A non-linear regression model derived from the experimental data established an empirical relationship between performance and chamber lengths, offering a foundation for further combustion flow studies. The post-chamber length positively impacted the engine thrust performance by 2.7%. Conversely, the pre-chamber length negatively impacted the performance by 1.3%. Further data collection could assist in refining the empirical relation and identifying key threshold values. Full article

Safe and reliable lunar landings are crucial for future exploration of the Moon. The regolith ejected by a lander’s rocket exhaust plume represents a significant obstacle in achieving this goal. It prevents spacecraft from reliably utilizing their navigation sensors to monitor their trajectory and spot emerging surface hazards as they near the surface. As part of NASA’s 2024 Human Lander Challenge (HuLC), the team at the University of Michigan developed an innovative concept to help mitigate this issue. We developed and implemented a machine learning (ML)-based sensor fusion system, ARC-LIGHT, that integrates sensor data from the cameras, lidars, or radars that landers already carry but disable during the final landing phase. Using these data streams, ARC-LIGHT will remove erroneous signals and recover a useful detection of the surface features to then be used by the spacecraft to correct its descent profile. It also offers a layer of redundancy for other key sensors, like inertial measurement units. The feasibility of this technology was validated through development of a prototype algorithm, which was trained on data from a purpose-built testbed that simulates imaging through a dusty environment. Based on these findings, a development timeline, risk analysis, and budget for ARC-LIGHT to be deployed on a lunar landing was created. Full article

The plasma bulk velocity is one of the key parameters describing the behavior of a plasma jet and is relevant for applications such as plasma spraying or electric propulsion. Therefore, different measurement techniques to determine the velocity were developed in the past. This paper presents a novel, non-invasive method for spatially resolved velocity measurements. The method is based on tracking of characteristic features in tomographic reconstructions of the plasma plume. A high-speed image recording system combined with tomographic acquisition is therefore the backbone of this method. The proposed setup captures the object under study from six different directions at a frame rate up to one million frames per second, providing high spatial and temporal resolution. The tomographic reconstructions are then calculated using the ART algorithm to track features in the plasma fluctuations, from which the bulk velocity is determined. The setup was tested with a DC plasma torch operated at reduced pressures in the range of tens of millibars. For the analyzed parameters, the axial velocity reached a maximum of 1061 m/s at a distance of three centimeters from the plasma torch exit and decreased to 919 m/s further downstream at a distance of seven centimeters, which is in good accordance with previous work. Therefore, the proposed diagnostic method can serve as a non-invasive alternative to velocity measurements, providing additional information in the form of a 3D model of the plasma bulk. Full article

Predicting the key plume evolution features of groundwater contamination are crucial for assessing uncertainty in contamination control and remediation, while implementing detailed complex numerical models for a large number of scenario simulations is time-consuming and sometimes even impossible. This work develops surrogate models with an effective and practicable pathway for predicting the key plume evolution features, such as the distance of maximum plume spreading, of groundwater contamination with natural attenuation. The representative various scenarios of the input parameter combinations were effectively generated by the orthogonal experiment method and the corresponding numerical simulations were performed by the reliable Groundwater Modeling System. The PSO-SVM surrogate models were first developed, and the accuracy was gradually enhanced from 0.5 to 0.9 under a multi-objective condition by effectively increasing the sample data size from 54 sets to 78 sets and decreasing the input variables from 25 of all the considered parameters to a smaller number of the key controlling factors. The statistical surrogate models were also constructed with the fitting degree all above 0.85. The achieved findings provide effective generic surrogate models along with a scientific basis and investigation approach reference for the environmental risk management and remediation of groundwater contamination, particularly with limited data. Full article

The utilization of geological formations, distinguished by natural porosity and permeability and protected by low-permeability caprock, has emerged as an effective strategy for carbon dioxide (CO₂) storage. This method significantly contributes to mitigating anthropogenic greenhouse gas emissions and addressing the challenges of climate change. Recent research has unveiled the potential of CO₂ to enhance geothermal heat energy extraction in geothermal reservoirs by acting as a subsurface heat exchange fluid. This review paper explores the viability of CO₂ in augmenting geothermal heat energy extraction, comparing it to conventional water-based geothermal systems. Special emphasis is placed on CO₂ plume geothermal (CPG) systems, characterized by rapid deployment and long-term utilization of geothermal energy resources. With the overarching objective of establishing net-zero energy communities, the analysis of such systems offers a comprehensive understanding of their features, providing a fresh perspective on extracted energy within the context of energy supply in integrated, sustainable energy in built systems. Notably, these systems demonstrate efficacy in meeting the power requirements of an energy community, spanning both distinct heating and electricity needs. However, the key challenge lies in selecting suitable locations. This scientific review aims to comprehend the characteristics of CPG under specific temperature and pressure conditions while optimizing subsurface permeability. This insight is pivotal for identifying future locations for CPG operations with the intent of powering small energy communities. Full article

This study focuses on the numerical analysis of a challenging issue involving the regulation of the human body’s microenvironment through personalized ventilation. We intended to first concentrate on the main flow, namely, the personalized ventilation jet, before connecting the many interacting components that are impacting this microenvironment (human body plume, personalized ventilation jet, and the human body itself as a solid obstacle). Using the laminar model and the large eddy simulation (LES) model, the flow field of a cross-shaped jet with very low Reynolds numbers is examined numerically. The related results are compared to data from laser doppler velocimetry (LDV) and particle image velocimetry (PIV) for a reference jet design. The major goal of this study is to evaluate the advantages and disadvantages of the CFD approach for simulating the key features of the cross-shaped orifice jet flow. It was discovered that the laminar model overestimated the global jet volumetric flow rate and the flow expansion. LES looks more suitable for the numerical prediction of such dynamic integral quantities. In light of the computational constraints, it quite accurately mimics the mean flow behavior in the first ten equivalent diameters from the orifice, where the mesh grid was extremely finely tuned. From the perspective of the intended application, the streamwise velocity distributions, streamwise velocity decay, and volumetric flow rate anticipated by the LES model are rather well reproduced. Full article

Seamounts are features generated by hot spots and associated intraplate volcanic activity. The geochemical characteristics of igneous rocks constituting seamounts provide evidence of important details of dynamic processes in the Earth, such as mantle magma source areas, and are key to understanding how mantle plume processes control the formation and evolution of seamounts and their resulting geochemical characteristics. The Pacific Ocean contains a large number of hitherto unstudied seamounts, whose ages and geochemical characteristics remain poorly known. This study presents the geochemical characteristics of six basalt samples from five seamounts in the Western Pacific and the ⁴⁰Ar/⁹Ar ages of three samples are determined. The new analysis yielded ⁴⁰Ar/³⁹Ar ages for seamounts samples MP3D21, MP5D11, and MP5D15A of 95.43 ± 0.33, 62.4 ± 0.26, and 99.03 ± 0.4 Ma, respectively. The geochemical profiles of seamounts samples MP3D04, MP3D21, MP5D11, MP5D15A, MPID201, and MPID202 are consistent with alkaline basalts, as evidence by alkali-rich, silicon-poor compositions along with high titanium concentrations. The primitive mantle normalized rare-earth elements and trace elements spider pattern are similar to those of ocean island basalts. The Ta/Hf and Nb/Zr ratios and La/Zr-Nb/Zr discriminant diagrams indicate that the six seamounts formed from magma that originated in the deep mantle. Full article

Regional climate change is one of the key factors that should be taken into account when planning the development of the coastal tourism, including investments and construction of tourism-related infrastructure. A case study for the Black Sea coast of Russia shows a series of potential negative hydrological, meteorological, and biological factors that accompany regional warming of the Black Sea Region, that can impede the development of coastal tourism and devalue billions of dollars in investments by the State, private companies, and individuals. We discuss such natural phenomena as air and sea warming, extreme weather events, coastal upwelling, heavy rains, river plumes, wind and waves, tornado, rip currents, sea-level rise, algal bloom, introduced species, and other features characteristic for the region that seriously impact coastal tourism today, and may intensify in the nearest future. Sporadic occurrence of extreme weather events, unpleasant and sometimes dangerous sea and atmosphere phenomena during the summer tourist season, and from year to year can be of critical psychological importance when choosing your next vacation and tourism destination. The research does not include anthropogenic factors, geopolitical, and socio-economic processes, and the COVID-19 pandemic that play an important role in the sustainable development of coastal tourism as well. Full article

Although emissions have a direct impact on air pollution, meteorological processes may influence inmission concentration, with the only way to control air pollution being through the rates emitted. This paper presents the close relationship between air pollution and meteorology following the scales of atmospheric motion. In macroscale, this review focuses on the synoptic pattern, since certain weather types are related to pollution episodes, with the determination of these weather types being the key point of these studies. The contrasting contribution of cold fronts is also presented, whilst mathematical models are seen to increase the analysis possibilities of pollution transport. In mesoscale, land–sea and mountain–valley breezes may reinforce certain pollution episodes, and recirculation processes are sometimes favoured by orographic features. The urban heat island is also considered, since the formation of mesovortices determines the entry of pollutants into the city. At the microscale, the influence of the boundary layer height and its evolution are evaluated; in particular, the contribution of the low-level jet to pollutant transport and dispersion. Local meteorological variables have a major influence on calculations with the Gaussian plume model, whilst some eddies are features exclusive to urban environments. Finally, the impact of air pollution on meteorology is briefly commented on. Full article

Investigation into geological storage of CO₂ is underway at Hontomín (Spain). The storage reservoir is a deep saline aquifer formed by naturally fractured carbonates with low matrix permeability. Understanding the processes that are involved in CO₂ migration within these formations is key to ensure safe operation and reliable plume prediction. A geological model encompassing the whole storage complex was established based upon newly-drilled and legacy wells. The matrix characteristics were mainly obtained from the newly drilled wells with a complete suite of log acquisitions, laboratory works and hydraulic tests. The model major improvement is the integration of the natural fractures. Following a methodology that was developed for naturally fractured hydrocarbon reservoirs, the advanced characterization workflow identified the main sets of fractures and their main characteristics, such as apertures, orientations, and dips. Two main sets of fracture are identified based upon their mean orientation: North-South and East-West with different fracture density for each the facies. The flow capacity of the fracture sets are calibrated on interpreted injection tests by matching their permeability and aperture at the Discrete Fracture Network scale and are subsequently upscaled to the geological model scale. A key new feature of the model is estimated permeability anisotropy induced by the fracture sets. Full article