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.
SummaryThe uniaxial compressive strength ${\sigma }_{c}$ of rocks is a key material property in a wide range of applications. Models for ${\sigma }_{c}$ typically either require numerical solutions, restricting their wide utility, or are empirical and therefore confined to a specific case. Here, we study the theoretical pore-emanated crack model and provide an analytical emulator function that matches the 2D and 3D solutions to a high degree of accuracy over all porosities, $\phi $. A key input to both the full solution and to our emulator functions is the pore radius, assumed in the model to be circular or spherical, in a porous rock. In most porous lithologies, including sandstone, the notion of a pore radius is poorly defined since they are built from compacted or lithified grains. And so here we explore statistical methods to find a characteristic pore length scale, ${l}_2$, from an initial particle radius; this method is provided as an easy-to-use supplementary tool. We advocate for the use of our 3D function ${\sigma }_{c} \approx 1.57{K}_{Ic}/( {\phi }^{0.43}\sqrt {\pi }{l}_{2} )$ where ${K}_{Ic}$ is the fracture toughness of the solid matrix. A compilation of ${K}_{Ic}$ values for minerals and rocks allows us to explore the effect of this parameter and to make recommendations for appropriate values in the model. We compare our simple emulator function for ${\sigma }_{c}$ with existing datasets across a wide range of sandstones to demonstrate the utility of this law for applied cases. We find that our function performs particularly well for relatively low porosity sandstones ($\phi \mathbin{\lower.3ex\hbox{$\buildrel<\over {\smash{\scriptstyle \sim}\vphantom{_x}}$}} 0.15$) representative of mature basin systems from a diagenetic point of view; we discuss alternative models that are more appropriate for higher porosity sandstones.
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.
An accumulation of weak to moderate earthquakes has been recorded around the Greek island of Santorini since 24 January. The seismic activity is concentrated in the area between the islands of Santorini and Amorgos, with a center around 25 km northeast of Santorini.
As pandemic lockdowns forced humans into isolation, Earth's vegetation was thriving. The year 2020 was the greenest in modern satellite records from 2001 to 2020, according to a recent study published in Remote Sensing of Environment. Consistent growth in northern and temperate regions, combined with a brief period of tropical growth, primarily led to this remarkably verdant period.
Publication date: Available online 23 January 2025
Source: Advances in Space Research
Author(s): Nikita V. Belyakov, Svetlana Illarionova
The great ice streams of the Antarctic and Greenland are like frozen rivers, carrying ice from the massive inland ice sheets to the sea—and a change in their dynamics will contribute significantly to sea-level rise.
The amount of carbon dioxide (CO2) released by microbial decomposition of soil organic carbon on a global scale is approximately five times greater than the amount of anthropogenic CO2 emissions. Thus, it is essential to clarify the impact of climate change on soil CO2 release dynamics.
Polluted runoff is still smothering the Great Barrier Reef, our first national assessment of water quality trends in Australian rivers has revealed. The problem on the reef is getting worse, not better, despite efforts to improve farming practices and billions of dollars committed by governments to water-quality improvements.
Author(s): J. Gonzalez and J. Sheil
Already some years ago, Langdon [Phys. Rev. Lett. 44, 575 (1980)] proposed that inverse bremsstrahlung absorption in plasmas drives free electrons into non-Maxwellian distributions. Radiation-hydrodynamic simulations of plasma-based light sources, however, often (implicitly) assume Maxwellian-distri…
[Phys. Rev. E 111, L023201] Published Thu Feb 06, 2025
SummaryThe Makran Subduction Zone is a distinctive segment within the Alpine-Himalayan system, where one of the final remnants of the once-expansive Neo-Tethys Ocean is being subducted beneath the Eurasian Plate. Limited seismic data has left several questions unanswered about the structure of the subducting oceanic lithosphere, the transition from the wide and thick Makran accretionary prism to the Zagros Collision Zone, variations in sedimentary cover thickness along and perpendicular to the accretionary prism, and fluctuations in the thickness of sedimentary cover within the fore-arc Jaz Murian Depression (JMD). In this study, we utilize ambient-noise and earthquake surface wave tomography within a period range of 5–50 s to construct a high-resolution 3D shear-wave velocity model down to a depth of 60 km for the Iranian Makran and northern Oman. Using a new dataset from 65 seismic stations located in southeastern Iran and northern Oman, our analysis reveals a sharp velocity contrast within the oceanic lithosphere of the Gulf of Oman, just north of Muscat, with abnormally low-velocity oceanic lithosphere extending westward from this contrast, revealing subduction of a segmented oceanic lithosphere beneath the Makran. Our study finds no lithospheric-scale seismic velocity contrast along the ZMP fault, as usually thought as a transition boundary between the Zagros and Makran. Our velocity model shows that the wide accretionary prism of western Makran consists of two zones: a southern low-velocity zone associated with younger sediments and a northern high-velocity zone corresponding to older sediments. A considerable thinning of the sedimentary cover is observed east of longitude 59° E within the coastal Makran tectono-stratigraphic unit, aligning with the structural trend of the Pan-African Semail Gap Fault observed both onshore and offshore Oman. Additionally, a thick sedimentary basin is located beneath the eastern section of the JMD, with the thickness decreasing towards the west.
AbstractIn this paper we examine the dynamic pressure torque acting on a bumpy core-mantle boundary (CMB) at diurnal timescale in a frame tied to the planet. This torque possibly contributes to the CMB coupling constants determined from nutation observations and could affect the interpretation of these constants in terms of different CMB coupling mechanisms. We revisit the work of Wu and Wahr (1997) who have used seismic estimates for the topography at the CMB and computed the associated pressure torque effect on nutations. These authors showed that some topography wavelengths can lead to amplifications in nutations. For example, they found that the effects on the retrograde annual nutation can be at the milliarcsecond level for a degree-5 spherical harmonics of the topography. While Wu and Wahr (1997) only go up to degree 6 in their development in spherical harmonics and use a numerical technique, we go up to degree 20 and employ an analytical approach to solve the equations and to further study the Earth’s nutations. The approach is similar to the one we used for the effects of the pressure torque on the tidal variations of the length of day (LOD) (a companion paper, Puica et al., 2023). Unlike the numerical approach, this has the advantage of highlighting the mathematical dependencies between the different spherical harmonics involved in the development of the topographic torque and to highlight the frequency dependence of the results and thereby the possible resonances with inertial waves. By doing so, we can isolate and estimate the magnitude of the influence of each topographic coefficient on nutation. We show that only the core flattening may have an important role on nutation and that the other large wavelengths of the topography have a very small contribution, less than that obtained by Wu and Wahr (1997).
In a new paper published in Nature Geoscience, experts from Fraunhofer Heinrich-Hertz-Institut (HHI) advocate for the use of explainable artificial intelligence (XAI) methods in geoscience.
A new climate modeling study published in the journal Science Advances by researchers from the IBS Center for Climate Physics (ICCP) at Pusan National University in South Korea presents a new scenario of how climate and life on our planet would change in response to a potential future strike of a medium-sized (~500 m) asteroid.
Reducing sulfur in the air may inadvertently increase natural emissions of methane from wetlands such as peatlands and swamps, a new study has found.
Land topography is usually formed gradually over long periods of time, but sometimes a single event can dramatically change things. On New Year's Day in 2024, a devastating earthquake in the Noto Peninsula upended the region.
Africa is often synonymous with its drylands that cover two-thirds of the continent. Relief is brought through rainfall during the monsoon season, which is vital to help replenish water reserves for communities and wildlife alike. Now, the West Africa monsoon season runs from June through to September, while those in the east occur during March to May and October to December.
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.
