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Abstract

Traditional ionospheric modeling is inseparable from dense Global Navigation Satellite System (GNSS) reference stations. In this study, based on definite linear variation characteristics of the ionosphere along the longitudinal and latitudinal directions, a regional ionospheric total electron content (TEC) fusion model was proposed using relatively sparse GNSS linear stations beyond 100 km. Compared with the inverse distance weighting model using two adjacent stations with 100 km distance and three surrounding stations with 30 km distance, the accuracy of the proposed model has an improvement by 39.6% and 55.6% respectively, reaching a root-mean-square error of 0.32 TECU (TEC Unit) at mid-latitudes in high solar activity year. In the low solar activity year, the accuracy of the proposed model also achieves a high accuracy of 0.24 TECU at mid-latitudes and 0.86 TECU at low-latitudes. Finally, the proposed model was verified by precise point positioning (PPP). Compared with the traditional PPP, the ionosphere model enhanced PPP can significantly shorten the convergence time from 22.1 to 10.3 min in the magnetic storm period, and from 23.2 to 8.8 min in the quiet period.

Abstract

The SMILE ground segment comprises the Chinese Academy of Sciences (CAS) ground segment and the European Space Agency (ESA) ground segment, which collaborate closely on this mission. The Ground Support System (GSS) and the Science and Application System (SAS) are two important components of the CAS ground segment. Development of these systems began in 2016, focusing on requirements for addressing the significant challenges associated with the SMILE mission. The GSS is primarily responsible for data reception, mission operations, data processing, data management, and data services. It has established an operational platform based on a “common platform + mission-specific plug-ins” model, enabling support for the SMILE mission through the development of tailored plugins. The SAS functions as a dedicated scientific research center for the SMILE mission within CAS, managing science operations, processing scientific data, and conducting scientific data analysis. Its establishment was driven by the unique requirements of the SMILE mission. Additionally, the SAS is tasked with fostering collaboration between CAS and ESA, designing effective frameworks to coordinate scientists in planning SMILE science operations. This paper provides a brief overview of the design of the GSS and SAS, as well as SMILE mission operations. We anticipate that these two systems will effectively support the SMILE mission in the future.

Abstract

NASA’s Europa Clipper mission is the first focused exploration of an ocean world, with the main goal of assessing the habitability of Jupiter’s moon Europa. After entering Jupiter orbit in 2030, the Flight System (spacecraft plus instrument payload) will collect science data while flying past Europa a planned 49 times at typical closest approach distances of 25–100 km. The mission will investigate Europa’s interior, composition, and geology, and will search for and characterize any current activity including possible plumes. The mission’s science objectives will be accomplished with a payload component of the Flight System that includes both remote sensing instruments covering the ultraviolet, visible, infrared, and thermal infrared ranges of the electromagnetic spectrum, as well as an ice-penetrating radar, and in situ instruments, that will be used to study the magnetic field, dust, gas, and plasma surrounding Europa. The spacecraft component of the Flight System is designed to permit all science instruments to operate and gather science data simultaneously. This paper will outline the driving requirements for the overall spacecraft as well as describe the resulting spacecraft design and its key characteristics, including an overview of flight system-level integration and testing.

Nature Geoscience, Published online: 05 February 2025; doi:10.1038/s41561-025-01639-x

Uptake of explainable artificial intelligence (XAI) methods in geoscience is currently limited. We argue that such methods that reveal the decision processes of AI models can foster trust in their results and facilitate the broader adoption of AI.

Abstract

Since the Voyager mission flybys in 1979, we have known the moon Io to be both volcanically active and the main source of plasma in the vast magnetosphere of Jupiter. Material lost from Io forms neutral clouds, the Io plasma torus and ultimately the extended plasma sheet. This material is supplied from Io’s upper atmosphere and atmospheric loss is likely driven by plasma-interaction effects with possible contributions from thermal escape and photochemistry-driven escape. Direct volcanic escape is negligible. The supply of material to maintain the plasma torus has been estimated from various methods at roughly one ton per second. Most of the time the magnetospheric plasma environment of Io is stable on timescales from days to months. Similarly, Io’s atmosphere was found to have a stable average density on the dayside, although it exhibits lateral (longitudinal and latitudinal) and temporal (both diurnal and seasonal) variations. There is a potential positive feedback in the Io torus supply: collisions of torus plasma with atmospheric neutrals are probably a significant loss process, which increases with torus density. The stability of the torus environment may be maintained by limiting mechanisms of either torus supply from Io or the loss from the torus by centrifugal interchange in the middle magnetosphere. Various observations suggest that occasionally (roughly 1 to 2 detections per decade) the plasma torus undergoes major transient changes over a period of several weeks, apparently overcoming possible stabilizing mechanisms. Such events (as well as more frequent minor changes) are commonly explained by some kind of change in volcanic activity that triggers a chain of reactions which modify the plasma torus state via a net change in supply of new mass. However, it remains unknown what kind of volcanic event (if any) can trigger events in torus and magnetosphere, whether Io’s atmosphere undergoes a general change before or during such events, and what processes could enable such a change in the otherwise stable torus. Alternative explanations, which are not invoking volcanic activity, have not been put forward. We review the current knowledge on Io’s volcanic activity, atmosphere, and the magnetospheric neutral and plasma environment and their roles in mass transfer from Io to the plasma torus and magnetosphere. We provide an overview of the recorded events of transient changes in the torus, address several contradictions and inconsistencies, and point out gaps in our current understanding. Lastly, we provide a list of relevant terms and their definitions.

Information on geomagnetic field intensity in the past is essential for understanding the behavior and mechanism of the geodynamo. A fundamental unresolved problem of relative paleointensity (RPI) estimations ...

Abstract

Trends in the deep-ocean M \(_2\) barotropic tide, deduced from nearly three decades of satellite altimetry and recently presented by Opel et al. (Commun Earth Environ 5:261, https://doi.org/10.1038/s43247-024-01432-5, 2024), are here updated with a slightly longer time series and with a focus on potential systematic errors. Tidal changes are very small, of order 0.2 mm/year or less, with a tendency for decreasing amplitudes, which is evidently a response to the ocean’s increasing stratification and an increasing energy loss to baroclinic motion. A variety of systematic errors in the satellite altimeter system potentially corrupt these small trend estimates. The Dynamic Atmosphere Correction (DAC), derived from an ocean model and used for de-aliasing, introduces a spurious trend (exceeding 0.1 mm/year in places) caused by changes in ECMWF atmospheric tides. Both operational and reanalysis atmospheric tides have spurious trends over the altimeter era. Tidally coherent errors in satellite orbits, including from use of inconsistent tidal geocenter models, are more difficult to bound, although differences between two sets of satellite ephemerides are found to reach 0.1 mm/year for M \(_2\) . Orbit errors are more deleterious for some other constituents, including the annual cycle. Tidal leakage in the “mesoscale correction,” needed here to suppress non-tidal ocean variability, is a known potential problem, and if the leakage changes over time, it impacts ocean-tide trend estimation. Tests show the error is likely small in the open ocean ( \(<0.04\)  mm/year) but large in some marginal seas ( \(>0.2\)  mm/year). Potential contamination from other altimeter corrections (e.g., ionospheric path delay) is likely negligible for M \(_2\) but can be difficult to bound.

Abstract

Global navigation satellite system (GNSS) Doppler measurements are immune to cycle slips, providing a robust way to detect ionospheric irregularities. This study presents a novel approach to detect equatorial plasma bubble (EPB) using a support vector machine (SVM) algorithm based on the GNSS Doppler measurements. The input of the detector is the Doppler index (DI), which is extracted from the dual-frequency differential Doppler observations. Data from HKWS station located in Hong Kong during 2022 are employed to train the SVM model and validate its performance. The results show the trained SVM model achieves 96.7% validation accuracy of EPB detection. To assess the general capability of the model, EPB events throughout the entire year of 2023 are investigated at both the HKWS station and the HYDE station. The results show the performance of EPB detection by the SVM model using DI is comparable to that of by visually inspecting the total electron content time series based on GNSS carrier-phase measurements. In addition, the characteristics of EPB occurrence are also consistent to previous studies, suggesting the detection results are reliable.

Abstract

Chondritic meteorites (chondrites) contain evidence for the interaction of liquid water with the interiors of small bodies early in Solar System history. Here we review the processes, products and timings of the low-temperature aqueous alteration reactions in CR, CM, CI and ungrouped carbonaceous chondrites, the asteroids Ryugu and Bennu, and hydrated dark clasts in different types of meteorites. We first consider the nature of chondritic lithologies and the insights that they provide into alteration conditions, subdivided by the mineralogy and petrology of hydrated chondrites, the mineralogy of hydrated dark clasts, the effects of alteration on presolar grains, and the evolution of organic matter. We then describe the properties of the aqueous fluids and how they reacted with accreted material as revealed by physicochemical modelling and hydrothermal experiments, the analysis of fluid inclusions in aqueously formed minerals, and isotope tracers. Lastly, we outline the chronology of aqueous alteration reactions as determined using the 53Mn-53Cr and 129I-129Xe systems.

Abstract

It is often accepted that the magnetic field structure of coronal mass ejections (CMEs) is accurately represented by the highly twisted circular cross-section magnetic flux rope model, which is the basis of all most commonly used sketches and representations of CMEs. This paradigm has been developed based on studies in the 1970s and 1980s, and it was the inspiration for a series of fitting models developed in the 1990s and 2000s to provide 3-D visualizations and representations for data obtained by remote sensing and in situ measurements. There has been a wealth of measurements since this paradigm was first developed, in particular numerous multi-point measurements and remote heliospheric observations of CMEs in addition to more physical models and numerical simulations. Taken together, they have demonstrated that such a paradigm, although it provides an explanation for certain CME signatures, is inadequate to represent the complexity of the magnetic field structure in numerous other cases. This manuscript reviews 40 years of continuous observations and ongoing research efforts since the proposal of the highly twisted circular cross-section flux rope model, and presents a more elaborate and realistic representation that better reflects the true complexity of the magnetic ejecta within CMEs.

Nature Geoscience, Published online: 03 February 2025; doi:10.1038/s41561-024-01636-6

Greenland-wide observations of crevasse volume and distribution suggest substantial increases in crevassing between 2016 and 2021 at marine-terminating sectors with accelerating ice flow.

We conduct a series of numerical experiments of thermal convection of compressible fluids with temperature-dependent viscosity, in order to study how the adiabatic compression and model geometries affect the m...

Many studies have estimated crustal deformation from observed geodetic data. So far, because most studies have applied a smoothness constraint, which includes the assumption of local uniformity of a strain-rat...

The Kenyan rift system is prone to deformation due to various geological processes and human activities, such as overexploitation of groundwater and exploitation of geothermal energy. Crustal deformation monit...

Abstract

Integrated Water Vapor (IWV) is crucial in environmental research, offering insights into atmospheric dynamics. Direct IWV measurement is challenging, necessitating alternative estimation technologies. Existing methods including Global Navigation Satellite System (GNSS), radiosondes, water vapor radiometers (WVR), satellite remote sensing, and numerical weather models (NWM), have specific limitations. GNSS and WVR provide high precision and temporal resolution (e.g., 5 min) but are limited to specific locations. Radiosondes, while accurate, have sparse spatial distribution and low temporal resolution (e.g., twice daily). Satellite remote sensing offers broad spatial resolution but lower temporal resolution (hours to days) and reduced accuracy under cloudy conditions and due to satellite tracks. NWMs provide global hourly products but their accuracy depends on meteorological data and model precision.

This study introduces a regional IWV predictive model using Machine Learning to address these challenges. Utilizing IWV data from GNSS stations, the study develops a predictive model based on least squares support vector machine, which autonomously determines optimal parameters to enhance performance. The model enables accurate IWV estimation at any location within a region, using inputs such as latitude, longitude, altitude, and temperature, achieving an average root mean square error of 0.95 mm. The model’s performance varies across seasons and terrains, showing adaptability to diverse conditions. The model’s reliability is validated by comparing its predictions with the conventional ERA5 IWV method, showing a 61% improvement rate. This refined IWV estimation model is applied for regional climate analysis, demonstrating its practical utility in environmental research, specifically for the Upper Rhine Graben Region.

Nature Geoscience, Published online: 30 January 2025; doi:10.1038/s41561-024-01628-6

Waves breaking on sandy beaches globally contribute a similar amount of dissolved silicon to oceans as that from rivers, according to a global analysis informed by experiments performed on a simulated quartz sand beach.

The precise position and geometry of a fault and the recognition of contemporary active strands are pivotal elements for formulating regulations for earthquake fault zones and fault setbacks. The western front...

Abstract—The editing problem in clustering (deletion and addition of edges and/or vertices in an initial graph for building a cluster structure), including various options of the problem (edge cluster editing, vertex cluster editing, etc.) is studied. A literature survey on the problems (problem types and solving approaches) is presented. The cluster edge editing problem is in focus. Several mathematical optimization models for the problem are described: (i) the basic edge editing problem with minimization of the general number of added edges and the number of deleted edges, (ii) the option of the above-mentioned problem with weights of all vertex pairs (including the bi-criteria problem case), and (iii) a multi-criteria problem with vector weights of the vertex pairs. In addition, some other editing problems are briefly described: (a) the edge deletion editing problem, (b) edge editing problem with several vertex types, and (c) vertex deletion editing problem. The problems discussed are illustrated by numerical examples. Some future research directions are pointed out.

Abstract—An estimation problem distributionally robust with respect to random noise is considered for a signal with the bounded second-order derivative on a finite number of observations. The objective functional is the probability that the L2-norm of the estimation error will exceed a pre-specified threshold. Its worst-case value on the set of all signals with the bounded second-order derivative and arbitrary distributions of the noise vector with fixed mean and covariance is to be minimized over the finite-dimensional class of spline estimators. The optimization problem is solved using the methods of convex programming by representing the objective functional in terms of the mean square bound following Markov’s inequality and the tight bound in the form of the multivariate Selberg inequality. A numerical experiment is carried out to compare the obtained solutions to the problem of restoration of the trajectory of a target with bounded acceleration.

Abstract—Problems of image smoothing and segmentation are among the most important directions of processing and analysis of video information, which have much in common in their formulation, final goals, and solution methods. The similarities and differences of the problems are shown on the base of the image model using the analysis and comparison of known smoothing and segmentation algorithms.