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In tokamaks, a leading platform for fusion energy, periodic filamentary plasma eruptions known as edge-localized modes occur in plasmas with high-energy confinement and steep pressure profiles at the plasma edge. These edge-localized modes could damage the tokamak wall but can be suppressed using small three-dimensional magnetic perturbations. Here we demonstrate that these magnetic perturbations can change the magnetic topology just inside the steep gradient region of the plasma edge. We identify signatures of a magnetic island, and their observation is linked to the suppression of edge-localized modes. We compare high-resolution measurements of perturbed magnetic surfaces with predictions from ideal magnetohydrodynamic theory where the magnetic topology is preserved. Although ideal magnetohydrodynamics adequately describes the measurements in plasmas exhibiting edge-localized modes, it proves insufficient for plasmas where these modes are suppressed. Nonlinear resistive magnetohydrodynamic modelling supports this observation. Our study experimentally confirms the predicted role of magnetic islands in inhibiting the occurrence of edge-localized modes. This will be beneficial for physics-based predictions in future fusion devices to control these modes.

Elevated and increasing NO3−${{\\text{NO}}_{3}}^{-}$concentration in groundwater affect groundwater supplies in China and elsewhere. However, how groundwater flow affects NO3−${{\\text{NO}}_{3}}^{-}$concentration in groundwater has yet to be fully understood. Herein, multi‐isotopes (15N, 11B, 18O, and 2H) and local indicators of spatial association (LISA) were used to elucidate the spatiotemporal variation, sources, and patterns of NO3−${{\\text{NO}}_{3}}^{-}$and its response to groundwater flow in Poyang Lake Basin where agriculture, industry and urban coexist. The location of NO3−${{\\text{NO}}_{3}}^{-}$hotspots identified by LISA tended to move from the middle to lower reaches of Ganfu Plain with groundwater flow, and hotspots area expanded in the upper reaches of Xin River Basin and northwest of the study area during the transition from dry season to wet season. Our results revealed that variations of regional NO3−${{\\text{NO}}_{3}}^{-}$concentration were controlled by groundwater recharge or flow mode (vertical or lateral), biogeochemical processes and sources (sewage and manure). In some areas with the single stratigraphic structure (unconfined aquifer), spatiotemporal variation of NO3−${{\\text{NO}}_{3}}^{-}$concentration was influenced by local pollution sources and vertical recharge of current precipitation (vertical flow). In some areas with binary structures (confined aquifer), groundwater was mainly recharged by lateral flow and NO3−${{\\text{NO}}_{3}}^{-}$concentration was mainly affected by mixing effect of upstream groundwater, reflecting human activities in the upper reaches rather than local human activities. In lakeside floodplain, groundwater NO3−${{\\text{NO}}_{3}}^{-}$was attenuated by the dissimilatory NO3−${{\\text{NO}}_{3}}^{-}$reduction to NH4+${{\\text{NH}}_{4}}^{+}$ . This study provides a novel insight into groundwater flow controlling on spatiotemporal distribution of NO3−${{\\text{NO}}_{3}}^{-}$concentration in the regional scale. Key Points Regional‐seasonal changes of hotspots and cool spots of nitrate concentration were identified by local indicators of spatial association Nitrate hotspots showed a seasonal shift along flow or expansion dominated by groundwater recharge mode linked with aquifer heterogeneity We developed a conceptual model of spatiotemporal variation in regional nitrate content that describes the crucial role of groundwater flow

Coastal aquifers are commonly layered, and thus, a clear understanding of groundwater flow and salt transport in layered coastal aquifers is important for managing fresh groundwater. However, the influence of leakage between adjacent aquifers on flow and transport processes remains largely unknown where the influence of tides is considered. This study used laboratory experiments and numerical simulation to examine the processes of flow and transport within a tidal aquifer‐aquitard system (i.e., an unconfined aquifer underlain by a semi‐confined aquifer, with an intervening thin aquitard). The laboratory‐scale observations of the current study are the first observations of offshore fresh groundwater within a semi‐confined coastal aquifer. The numerical and laboratory results are in close agreement, revealing that upward leakage from the semi‐confined aquifer into the saltwater wedge of the overlying unconfined aquifer caused buoyant instabilities to form. The development of freshwater fingers created complex saltwater‐freshwater mixing, leading to mixed saltwater influx‐efflux patterns across the sloping aquifer‐ocean interface. Compared with non‐tidal conditions, tidal forces reduced the net upward leakage from the semi‐confined aquifer to the overlying unconfined aquifer. This increased the horizontal flow toward the sea, which in turn reduced the extent of the saltwater wedge in the semi‐confined aquifer. The higher rates of both fresh and saline submarine groundwater discharge (SGD), caused by tides, led to lower groundwater ages in the semi‐confined aquifer. These findings have important implications for unveiling the complex characteristics of seawater intrusion, SGD and geochemical hotspots within layered coastal aquifers. Plain Language Summary Coastal aquifers contain complex and dynamic hydrological and geochemical processes, which profoundly influence the global water cycle and chemical mass balance. Many coastal aquifers exhibit layerd structures in the form of high‐permeability aquifers alternating with thin aquitards. Inter‐aquifer leakage is a common issue in layered coastal aquifers, but few studies explore its impact on the mixing zone of saltwater wedges. The effects of tides on groundwater dynamics and the seawater extent in layered aquifers also remain poorly known. This study used laboratory experiments and numerical modeling to explore the effects of inter‐aquifer leakage and tides on flow and salinity dynamics within layered aquifer systems. We found that the upward leakage extended the mixing zones from the edges of the saltwater wedge to its interior within unconfined aquifers, leading to mixed saltwater influx‐efflux patterns across the aquifer‐ocean interface. The introduction of tides restricted the seawater extent in semi‐confined aquifers. This is a primary consequence of the tide‐induced increase in the horizontal freshwater flow toward the sea through the semi‐confined aquifer, in addition to the increases in the density‐driven seawater recirculation caused by tides. These findings highlight the important role of inter‐aquifer leakage and tides in layered coastal aquifers. Key Points Leakage from semi‐confined aquifers caused mixed‐convective flow within the saltwater wedge of overlying unconfined aquifers Tidal fluctuations reduced the net upward freshwater leakage, and consequently the extent of seawater, in semi‐confined coastal aquifers Tides increased both fresh and saline submarine groundwater discharge in semi‐confined aquifers, reducing groundwater ages

Volcanic aquifers have become valuable resources for providing water to approximately 2.5 million people in the Yogyakarta-Sleman Groundwater Basin, Indonesia. Nevertheless, hydrogeochemical characteristics at the basin scale remain poorly understood due to the complexity of multilayered aquifer systems. This study collected sixty-six groundwater samples during the rainy and dry seasons for physicochemical analysis and geochemical modeling to reveal the hydrogeochemical characteristics and evolution in the Yogyakarta-Sleman Groundwater Basin. The results showed that groundwater in the unconfined and confined aquifers exhibited different hydrogeochemical signatures. The Ca–Mg–HCO 3 facies dominated groundwater from the unconfined aquifer. The groundwater facies evolved into a mixed Ca–Mg–Cl type along the flow direction towards the discharge zone. Meanwhile, groundwater from the confined aquifer showed mixed Ca–Na–HCO 3 , Na–HCO 3 , and Na–Cl–SO 4 facies. The presence of Mg in the confined aquifer was replaced by Na, which was absorbed in the aquifer medium, thus showing the ion exchange process. The main geochemical processes can be inferred from the Gibbs diagram, where most groundwater samples show an intensive water–rock interaction process mainly influenced by the weathering of silicate minerals. Additionally, only groundwater samples from the confined aquifer were saturated with certain minerals (aragonite, calcite, and dolomite), confirming that the groundwater followed the regional flow system until it had sufficient time to reach equilibrium and saturation conditions. This study successfully explained the hydrogeochemical characteristics and evolution of a multilayer volcanic aquifer system that can serve as a basis for groundwater basin conservation.

Large, confined aquifer systems play a vital role in sustaining human settlements and industries in many regions. Understanding the sustainability of these water resources requires the evaluation of groundwater storage change. Direct in‐situ observation of groundwater storage is limited by the distribution and availability of groundwater level and aquifer storativity data. Here, we use and compare two auxiliary methods, applied at basin and sub‐basin scales, to assess groundwater storage changes in the Great Artesian Basin (GAB), one of the World's largest confined aquifer systems. The first, the groundwater budget, derives storage change as the residual of fluxes in and out of the GAB, assuming they are all accounted for and accurately estimated. The second uses time‐variable gravity data from GRACE satellites to estimate temporal changes in groundwater mass, assuming that all other components of the terrestrial water mass change detected by GRACE are correctly subtracted. Despite the depletion observed during the 20th century, groundwater storage is mostly stable during 2002–2022. An increase in storage is detected in the Surat sub‐basin, a major recharge area. This increase is attributed to an over‐representation of large recharge events during the study period and/or storage recovery following rehabilitation of free‐flowing bores. The approach consisting in disaggregating GRACE data assumes that water storage changes in confined aquifers is dominated by changes in the GAB, and as such, it may overestimate the increase in the GAB by incorrectly attributing the increase occurring in overlying aquifers to the GAB. In contrast, the recharge estimates used in the groundwater budgets do not account for flood recharge and might underestimate storage increase in the GAB. Plain Language Summary Monitoring groundwater storage in large, confined aquifers is often impossible as it requires large groundwater level and lithological data sets that are often unavailable. However, monitoring is crucial for assessing and managing the sustainability of this resource and manage it appropriately. This study uses and compares two auxiliary methods, applied at basin and sub‐basin scales, to assess groundwater storage changes in the Great Artesian Basin (GAB), one of the World's largest confined aquifer systems. The groundwater budget approach estimates water storage changes by adding up the amounts of groundwater that goes in and out of the aquifer system. The satellite gravimetry approach uses the temporal changes of Earth's gravity field to infer changes in groundwater mass. Both methods agree that, despite the depletion observed during the 20th century, groundwater storage in the GAB was mostly stable during 2002–2022. An increase in groundwater storage is detected near major recharge areas. It is attributed to an over‐representation of large recharge events during the study period and/or groundwater storage recovery following capping of free‐flowing bores. Key Points GRACE and groundwater budgets agree that water storage in the Great Artesian Basin was stable for the period 2002–2022 Increased storage in the Surat sub‐basin is attributed to bore rehabilitation and/or increased recharge during the study period Within the Surat sub‐basin, increased storage may be overestimated by GRACE and/or underestimated by the groundwater budgets

In the Beijing Plain, land subsidence is one of the most prominent geological problems, which is affected by multiple factors. Groundwater exploitation, thickness of the Quaternary deposit and urban development and construction are important factors affecting the formation and development of land subsidence. Here we choose groundwater level change, thickness of the Quaternary deposit and index-based built-up index (IBI) as influencing factors, and we use the influence factors to predict the subsidence amount in the Beijing Plain. The Sentinel-1 radar images and the persistent scatters interferometry (PSI) were adopted to obtain the information of land subsidence. By using Google Earth Engine platform and Landsat8 optical images, IBI was extracted. Groundwater level change and thickness of the Quaternary deposit were obtained from hydrogeological data. Machine learning algorithms Linear Regression and Principal Component Analysis (PCA) were used to investigate the relationship between land subsidence and influencing factors. Based on the results obtained by Linear Regression and PCA, a suitable machine learning algorithm was selected to predict the subsidence amount in the Beijing Plain in 2018 through influencing factors. In this study, we found that the maximum subsidence rate in the Beijing Plain had reached 115.96 mm/y from 2016 to 2018. The land subsidence was serious in eastern Chaoyang and northwestern Tongzhou. In addition, the area where thickness of the Quaternary deposit reached 150–200 m was prone to more serious land subsidence in the Beijing Plain. In groundwater exploitation, the second confined aquifer had the greatest impact on land subsidence. Through Linear Regression and PCA, we found that the relationship between land subsidence and influencing factors was nonlinear. XGBoost was feasible to predict subsidence amount. The prediction accuracy of XGBoost on the subsidence amount reached 0.9431, and the mean square error was controlled at 15.97. By using XGBoost to predict the subsidence amount, our research provides a new idea for land subsidence prediction.

Jointed exoskeletons permit rapid appendage-driven locomotion but retain the soft-bodied, shape-changing ability to explore confined environments. We challenged cockroaches with horizontal crevices smaller than a quarter of their standing body height. Cockroaches rapidly traversed crevices in 300–800 ms by compressing their body 40–60%. High-speed videography revealed crevice negotiation to be a complex, discontinuous maneuver. After traversing horizontal crevices to enter a vertically confined space, cockroaches crawled at velocities approaching 60 cm·s−1, despite body compression and postural changes. Running velocity, stride length, and stride period only decreased at the smallest crevice height (4 mm), whereas slipping and the probability of zigzag paths increased. To explain confined-space running performance limits, we altered ceiling and ground friction. Increased ceiling friction decreased velocity by decreasing stride length and increasing slipping. Increased ground friction resulted in velocity and stride length attaining a maximum at intermediate friction levels. These data support a model of an unexplored mode of locomotion—“body-friction legged crawling” with body drag, friction-dominated leg thrust, but no media flow as in air, water, or sand. To define the limits of body compression in confined spaces, we conducted dynamic compressive cycle tests on living animals. Exoskeletal strength allowed cockroaches to withstand forces 300 times body weight when traversing the smallest crevices and up to nearly 900 times body weight without injury. Cockroach exoskeletons provided biological inspiration for the manufacture of an origami-style, soft, legged robot that can locomote rapidly in both open and confined spaces.

Traditional methods for simulating high-energy explosions in confined spaces, such as those based on the JWL equation, often fail to accurately capture the interaction between blast waves and combustion. To address this, we propose an enhanced Pressure Bubble Method (PBM) that dynamically integrates combustion energy release. Numerical simulations of a TNT explosion in a confined tank were conducted using FLUENT. The results demonstrate that the modified model significantly improves prediction accuracy for overpressure distribution and blast wave propagation compared to experimental data. The key novelty lies in the combustion-energy-integrated PBM, which provides a more precise and efficient simulation tool for confined explosions, especially when detailed explosive parameters are unavailable.

Groundwater storage (GWS) in confined aquifer systems is often influenced by climate variability and anthropogenic activities, and it is vital to quantify their contributions for the purpose of groundwater management and surface water allocation plans. In this study, we characterize the spatiotemporal evolution of the GWS in confined aquifer systems across Hengshui, North China Plain, and investigate its relationships with changing climate conditions and human activities through the integration of InSAR-derived surface displacements with hydraulic head observations and precipitation data, during 2004–2010 and 2016–2020. Our results indicate that the GWS in confined aquifer systems decreased markedly by 4.59 ± 0.35 km3 with an accelerating trend during the study period. The GWS variations show a strong correlation with precipitation during irrigation periods (March to July), and hence, the climate and anthropogenic-driven GWS variations can be separated from each other with a linear model. We find that the GWS depletion caused by climate variability and anthropogenic activities were −0.31 ± 0.10 km3 and −4.28 ± 0.40 km3, respectively, during the study period. The mean contribution of anthropogenic activities to the GWS variations was −71.9%, implying that the GWS variations in confined aquifer systems were primarily anthropogenic driven. It is also found that the well observations alone poorly characterize the spatiotemporal evolution of the GWS due to their limited spatial density, and the integrated InSAR/well approach appears to be promising for overcoming this challenge.

Existing groundwater flow models for leaky aquifer systems rarely consider the consolidation effects of aquitards. Neglecting these effects can significantly impact the accuracy of groundwater flow simulations within such systems. To address this issue, this paper develops a model that describes unsteady flow within a leaky aquifer system incorporating nonlinear consolidation. The flow in both unconfined and confined aquifers is radial one‐dimensional Darcian flow, whereas the flow in the aquitard is vertical one‐dimensional non‐Darcian flow, considering nonlinear consolidation. The finite difference method is used to solve the model, and the difference between the results obtained with and without considering consolidation effects is examined. The findings indicate that the groundwater head in the confined aquifer, when considering the effects of consolidation, is higher than that in the confined aquifer without consolidation effects. Initially, this difference in confined groundwater head increases rapidly with time, and then progressively decreases. The magnitude of this difference is positively correlated with the aquitard's compressibility index and permeability index, as well as with the pumping rate. Conversely, it is negatively correlated with the aquitard's threshold hydraulic gradient and initial void ratio, the confined aquifer's hydraulic conductivity and specific storage, and the unconfined aquifer's hydraulic conductivity and specific yield. During the early period of pumping, the difference is positively correlated with the aquitard's initial vertical hydraulic conductivity; however, this correlation reverses in the late period of pumping. Finally, a case study is employed to validate the effectiveness of the developed model. Key Points We develop a model that describes low‐velocity non‐Darcian flow with nonlinear consolidation in a leaky aquifer system Characteristics of aquitard consolidation influenced by nonlinear consolidation and low‐velocity non‐Darcian flow are investigated The influences of various factors on the differences in results, with and without considering consolidation effects, are analyzed