Hasil untuk "Geophysics. Cosmic physics"

Tianhao Chen, Xiaoyong Zhuge, Hui Yu et al.

The radius of maximum wind (RMW) is a critical parameter for characterizing the tropical cyclone (TC) inner core structure, wind field distribution, and potential hazard extent. While spaceborne cross-polarized synthetic aperture radar (SAR) enables high-precision wind field measurements, its high operational cost and low temporal resolution restrict widespread application. To address this challenge, this study develops an RMW retrieval algorithm leveraging geostationary satellite infrared imagery, with SAR-derived wind products serving as ground truth. Focusing on TCs over Western North Pacific during 2016–2024, a dataset comprising 110 eyed and 121 noneye TC samples was curated from quality-controlled SAR observations. The proposed algorithm extends the eye-radius-based RMW estimation method, which was originally designed for clear-eyed TC, to unclear-eyed scenarios. Simultaneously, it introduces a novel proxy based on the radius of strongest convection for retrieving RMW in noneye TCs. Rigorous evaluation through independent validation, cross-validation, and comparative analysis confirms that the algorithm achieves superior accuracy relative to the Joint Typhoon Warning Center best-track records. Ablation experiments and sensitivity tests examining satellite data sources, temporal asynchrony, eyewall replacement cycles, and center positioning accuracy, further substantiate the robustness and stability of the proposed algorithm. This work establishes an operationally feasible and scalable framework for high-accuracy, high-frequency monitoring of TC inner core dynamics, with direct implications for advancing forecasting and hazard assessment capabilities.

Wangtun Yang, Yang Zhang, Heng Zhang et al.

This article presents an integrated approach for superpixel segmentation (SPS) and classification, leveraging a deep learning (DL) method tailored to high-resolution remote sensing imagery (RSI). The main contributions of this method include designing a SPS approach based on a convolution-based network architecture that directly predicts superpixels on a regular grid, while adding a classification branch that leverages SPS to classify individual superpixels. The proposed method introduces a dynamic adaptive quantization framework and bit mapping modules, enabling the model to flexibly adapt to various bit-width configurations. End-to-end training integrates SPS and classification tasks within the same deep neural network. Comprehensive experiments utilized RSI datasets across three typical scenes: urban, suburban, and agricultural-pastoral areas. Quantitative and qualitative results confirm the superiority for both SPS and semantic segmentation tasks, showing strong potential for scene understanding and land cover classification. Ablation studies further confirm the efficiency and necessity of various components in the model design. This work provides new ideas and technical support for achieving high-precision, fine-grained interpretation of remote sensing scenes.

C. Guervilly, E. Dormy

Abstract Convection is the main heat transport mechanism in the Earth's liquid core and is thought to power the dynamo that generates the geomagnetic field. Core convection is strongly constrained by rotation while being turbulent. Given the difficulty in modeling these conditions, some key properties of core convection are still debated, including the dominant energy‐carrying lengthscale. Different regimes of rapidly rotating, unmagnetized, turbulent convection exist depending on the importance of viscous and inertial forces in the dynamics, and hence different theoretical predictions for the dominant flow lengthscale have been proposed. Here we study the transition from viscously dominated to inertia‐dominated regimes using numerical simulations in spherical and planar geometries. We find that the cross‐over occurs when the inertial lengthscale approximately equals the viscous lengthscale. This suggests that core convection in the absence of magnetic fields is dominated by the inertial scale, which is hundred times larger than the viscous scale.

M. B. Dhanya, Chemukula Mathin Yadav, Smitha V. Thampi et al.

Abstract The Moon encountered an extreme space weather event (NOAA G5 class) on 10 May 2024, caused by a series of coronal mass ejections (CMEs). Chandra's Atmospheric Composition Explorer‐2 (CHACE‐2), a neutral gas mass spectrometer on board Chandrayaan‐2 orbiter, made in situ observations of the lunar exosphere during this period. Observations show an increase in total pressure around the arrival time of the CME impact on the Moon. The corresponding total number densities derived from these observations show an enhancement in the total number densities by more than an order of magnitude. The increase in lunar exospheric number densities by a factor >10, due to the solar wind ion sputter process, is consistent with earlier theoretical modeling. This is the first observational confirmation of the enhancement in lunar exospheric densities during a CME impact.

Hannah I. Sinigaglio, Janusz Murakowski, Dennis W. Prather

For many years, microwave radiometers (MWRs) have contributed to the accuracy of atmospheric models, which are used for weather forecasting and climate-change monitoring. In this work, a new MWR architecture is proposed that utilizes the advantages of photonics to measure a wide swath of microwave spectrum from 50 to 70 GHz. An optical-fiber-based arrayed waveguide grating is used to optically process the spectral content from a V-band radio front end. The result is a radiometer that measures the microwave spectrum near the 60 GHz oxygen absorption peak. The instrument described in this work is shown to produce brightness temperature spectra that fit with expected trends for given weather conditions and has a noise equivalent delta temperature of 0.68 K for an integration time of 8.8 s. The microwave-photonic approach to radiometry offers the capability to measure wider spectral bands than accessible using conventional means, and to probe currently unobserved frequencies, within a reasonable form-factor. Further development of the approach outlined in this work will lead to a space-worthy MWR for improved spectral coverage of atmospheric measurements.

Changzhi Xu, Shaolin Liu, Dinghui Yang et al.

为了充分发挥谱元法和有限差分法各自在数值模拟复杂介质中地震波传播的优点，同时避免各自缺点，本文提出了模拟地震波传播的谱元-有限差分（SEM-FDM）混合方法。该混合方法在起伏地形附近采用谱元法计算地表附近的地震波传播；在远离起伏地形的区域之下，采用有限差分法计算地震波传播；之后通过构建数据交换区实现两种方法的耦合。结果表明，本文提出的谱元-有限差分混合方法能有效地模拟任意非均匀介质中的地震波传播，具有刻画复杂地形的能力，能处理自由地表边界条件，且能适应模型内的速度间断面。通过模型试算，并与谱元法进行对比，验证了该混合方法用于地震波模拟的有效性和高精度性。

R. Benbrik, M. Boukidi, M. Ech-chaouy et al.

In this work, we present a comprehensive review of the most up-to-date exclusion limits on Vector-Like Quarks (VLQs) derived from ATLAS and CMS data at the Large Hadron Collider (LHC). Our analysis encompasses both pair and single production modes, systematically comparing results from the two collaborations to identify and employ the most stringent bounds at each mass point. We evaluate the excluded parameter space for VLQs under singlet, doublet, and triplet representations. For top-like VLQs (T), the exclusion limits rule out masses up to 1.49 TeV in singlet scenarios, while single production constrains the mixing parameter κ to values below 0.26 at mT ~ 1.5 TeV and up to 0.42 for mT ~ 2 TeV. For bottom-like VLQs (B), the strongest exclusion limits from pair production exclude masses up to 1.52 TeV in doublet configurations, with single production constraining κ values between 0.2 and 0.7 depending on the mass. For exotic VLQs, such as X and Y, pair production excludes masses up to 1.46 TeV and 1.7 TeV, respectively. The constraints on κ from these analyses become increasingly restrictive at higher masses, reflecting the enhanced sensitivity of single production channels in this regime. For X, κ is constrained below 0.16 for masses between 0.8 and 1.6 TeV and further tightens to κ < 0.2 as the mass approaches 1.8 TeV. Similarly, for Y, κ values are constrained below 0.26 around mY ~ 1.7 TeV, with exclusions gradually relaxing at higher masses. These exclusion regions, derived from the most stringent LHC search results, offer a unified and up-to-date perspective on VLQ phenomenology. The results were computed using VLQBounds, a new Python-based tool specifically developed for this purpose.

Yan Li, Wei Hu, Qiang Xu et al.

Abstract Understanding the motion of particles in very dense granular flows is crucial for comprehending the dynamics of many geological phenomena, and advancing our knowledge of granular material physics. We conduct transparent ring shear experiments to directly observe the granular motion under relatively high‐pressure conditions, and find that the granular velocity non‐linearly decays, forming an approximately 7‐particle‐diameter‐thick localized shear band. A fitting curve underlying non‐local physics can be used to well predict velocity profile geometries that are almost independent of normal stress and shear velocity. Moreover, experimental results show monotonically decreasing granular kinetic temperature, which may be caused by energy dissipation due to more inelastic contacts under high confining pressures. The variation of granular temperature will significantly influence the local yield stress and rheological properties, which may lead to inhomogeneous fluidity of the material and thus to shear localization in very dense granular flows.

Taimoor Ashraf, Jazeela Aslam, Muhammad Sajid Mehmood et al.

Abstract The built environment is associated with higher air and surface temperatures in urban areas compared to rural counterparts. This study focuses on the Sheikhupura district in Punjab, Pakistan, where rapid urbanization and deforestation have significantly impacted land surface temperature (LST) from 2000 to 2020. Utilizing Geographic Information Systems (GIS) and Remote Sensing (RS) techniques, four Landsat images from the United States Geological Survey (USGS) were analyzed to assess spatiotemporal variations in LULC and LST. The single infrared channel approach was employed to calculate LST, and LULC maps were created using supervised classification for the years 2000, 2010, and 2020. The results indicate a substantial increase in built-up areas from 66.9708 square kilometers in 2000 to 259.8147 square kilometers in 2020, accompanied by a significant reduction in vegetation and agricultural land. Correspondingly, the maximum LST rose from 28.9354 °C in 2000 to 31.5173 °C in 2020, highlighting the urban heat island effect. Zonal statistics revealed a decrease in mean high temperatures from 24.45 to 20.3 °C over the same period, suggesting variability in temperature distribution due to changes in land cover types. These findings underscore the need for sustainable urban planning to mitigate the adverse effects of urbanization on local climates. Future work should focus on developing strategies to increase green spaces and reforestation efforts to counteract rising temperatures. Additionally, further research is recommended to explore the long-term impacts of these changes on local biodiversity and ecosystem services, providing a holistic approach to urban sustainability.

KM3NeT Collaboration S. Aiello, A. Albert, S. A. Garre et al.

The KM3NeT neutrino telescope is currently being deployed at two different sites in the Mediterranean Sea. First searches for astrophysical neutrinos have been performed using data taken with the partial detector configuration already in operation. The paper presents the results of two independent searches for neutrinos from compact binary mergers detected during the third observing run of the LIGO and Virgo gravitational wave interferometers. The first search looks for a global increase in the detector counting rates that could be associated with inverse beta decay events generated by MeV-scale electron anti-neutrinos. The second one focuses on upgoing track-like events mainly induced by muon (anti-)neutrinos in the GeV–TeV energy range. Both searches yield no significant excess for the sources in the gravitational wave catalogs. For each source, upper limits on the neutrino flux and on the total energy emitted in neutrinos in the respective energy ranges have been set. Stacking analyses of binary black hole mergers and neutron star-black hole mergers have also been performed to constrain the characteristic neutrino emission from these categories.

Yufei Zhou, Chao Shen, Yong Ji

Abstract Shock ripples and shock–discontinuity interactions (SDIs) have long been proposed to explain the frequent occurrence of high‐speed jets (HSJs) in the magnetosheath; however, there is no direct observational evidence for either of them occurring near a shock. Herein, we report a large‐scale, long‐duration undulated quasi‐perpendicular shock surface that is capable of generating HSJs. Based on the curvatures estimated for the shock undulation and for a nearby hot flow anomaly (HFA), we suggest that the shock ripple mechanism and the SDI mechanism combine to generate HSJs, that is, during an SDI, shock undulations and an upstream HFA form simultaneously, and the solar wind between them is deflected by the undulation into jets. The HSJs, discontinuity, and HFA are then convected downstream. An HSJ consistent with our mechanism in another event is presented.

Olga Maltseva, Artem Kharakhashyan, Tatyana Nikitenko

Despite the continuous improvement of the widely used empirical model international reference ionosphere (IRI), the recently appeared new models must be tested worldwide. Testing along the meridians has the advantage of dealing with the latitudinal dependent parameters. This paper uses new models of parameters foF2 (critical frequency), TEC (total electron content), and τ (equivalent slab thickness of the ionosphere), which are of great importance for evaluating the effects of space weather. IRI-Plas, NNT2F2, and NTSM models were tested using data from 6 ionosondes located along the meridian 110° E in March 2012. It is shown that the IRI-Plas model provides the closest values to experiment with respect to τ, while the NTSM model provides a rather limited reflection of the latitude dependence. Analyses of foF2(NNT2F2) have shown that, the NNT2F2 model provides good conformity with experimental values in this area, but it is very dependent on the TEC processing method. The latitudinal dependences of foF2 obtained with TEC and polynomial dependence τ(Appr) showed the presence of positive deviations from medians not only during disturbances but also quiet periods, longitudinally at the meridian.

Alexandra G. Konings, Nataniel M. Holtzman, Krishna Rao et al.

Abstract Microwave radiometry can be used to measure vegetation water content through vegetation optical depth (VOD). VOD can vary due to changes in water stress alone, but also scales with aboveground biomass. Several studies have therefore interpreted VOD temporal anomalies as linearly proportional to biomass anomalies, neglecting the influence of water stress. Here, we explicitly test this assumption using a new annual‐resolution data set of biomass derived from optical, radar, and lidar remote sensing. Both L‐band and X‐band VOD datasets are tested. Although VOD and biomass variations are highly correlated in space, their temporal anomalies are almost uncorrelated. At regional scale, it is as common for VOD anomalies to be more correlated to root‐zone soil moisture anomalies (a proxy for water stress) than to biomass anomalies as for the opposite to occur. Care should therefore be taken when deriving biomass anomalies from VOD, especially in the absence of any large‐scale biomass disturbances.

D. M. Coffey, L. A. Munk, D. E. Ibarra et al.

Abstract Despite current and projected future reliance on lithium (Li) as a resource, deficiencies remain in genesis models of closed‐basin Li brines. Subsurface geochemical interactions between water and bulk solid phases from lacustrine sediments, are shown here to be the most important process for brine genesis and sustainability of the Clayton Valley, NV brine deposit. A new subsurface basin model was developed and used to select Li‐bearing solids to test the release mechanisms for Li. Ash (20–350 ppm Li) and bulk sediments (1,000–1,700 ppm Li) samples across depths in the basin represent the majority of the subsurface Li‐bearing materials. Temperature dependent (25°C–95°C) batch reaction experiments using low‐salinity groundwater from the basin indicate a positive relationship between the amount of Li released and temperature. Four‐step sequential extractions on a subset of bulk sediments indicate most Li is released from water and weak acid‐soluble portions with approximately 30% of the total Li contained in the sediments released overall. We conceptualize that Li is released from these samples via three mechanisms: (a) release of adsorbed Li; (b) cation exchange of Li and Mg and; (c) possible minor release from the silicate structure at elevated temperatures. Based on these results and the abundance of Li‐bearing sediments in the subsurface we estimate the mean Li mass in the basin materials to be between 24.4 and 58.0 Mt which provides a continuous supply from water‐rock interactions. This is now the largest known accumulation of Li in a basin‐fill continental setting on a global scale.

A. Kounine

The Alpha Magnetic Spectrometer (AMS) is a 15-nation project on the International Space Station (ISS). Following a 16-year period of construction and testing and a precursor flight on the Space Shuttle in 1998, AMS was installed on the ISS on May 19, 2011. AMS is a precision particle physics magnetic spectrometer. Since its installation on the ISS, it has collected more than 140 billion cosmic rays. Precision measurements by AMS of the fluxes of cosmic ray positrons, electrons, antiprotons, protons and light nuclei as well as their ratios show several unexpected and intriguing features. The new AMS results on the positron flux reveal a new source of high energy positrons. Surprisingly, in this rigidity range the spectral indices of cosmic ray nuclei experience progressive hardening over the rigidity interval of few hundred GV. AMS continues studies of complex antimatter candidates with stringent detector verification and collection of additional data.

V. Okorokov

The top quark, the heaviest quark and, indeed, the heaviest elementary particle known today, constitutes a novel probe of the long-lived medium in quark-gluon phase which, as expected, can be produced even in light nuclei collisions at ultra-high energies. Some distinctive features are considered for particle production in the top sector in ultra-high energy domain. The antitop-top pair production is studied within the quantum chromodynamics and effective field theory approach used for calculations of total partonic cross sections. Predictions for all observables are computed at NNLO in quantum chromodynamics and at LO in effective field theory. These quantitative results can be important for both the future collider experiments at center-of-mass energy frontier and the improvement of the phenomenological models for development of the cosmic ray cascades in ultra-high energy domain. Thus the study allows the better understanding of heavy particle production and emphasizes the exciting interrelation between the high-energy physics on accelerators and ultra-high energy cosmic ray measurements.

V. Petkov, A. Fazliakhmetov, A. Gangapshev et al.

A current status of the project of a large volume scintillation telescope at the Baksan neutrino observatory is presented. The main research activities of the BLVST are low- energy neutrino physics, astrophysics and geophysics. To detect geoneutrinos, large-scale new- generation scintillator detectors located at large depths in the regions with a low background level from nuclear reactors are required. The Baksan Neutrino Observatory is geographically located in one of these places. Recently resumed R&D activities are aimed at the creation of new-generation telescope with a target mass of 10 kt at a depth of 4800 m.w.e. A small scale prototype is already under construction.

Ruiguang Wang, Chang-gen Yang, Haoqi Lu et al.

The Jiangmen Underground Neutrino Observatory (JUNO) is a 20 kton liquid scintillator detectorwith primary physics goal of neutrino mass hierarchy determination and precise measurement ofthe neutrino oscillation parameters, as well as the measurement of solar neutrinos, geo-neutrinos,supernova neutrinos and the diffuse supernova neutrinos. The detector will be built in a 700m deep underground laboratory. A multi-veto system will be built for cosmic muon detectionand background reduction. The central detector will be submerged in the ultra pure water poolinstrumented with about 2000 MCP-PMTs (20 inches) to serve as an active water Cherenkovdetector for muon tagging. Both the pool walls and the central detector external surface willbe coated with Tyvek reflector to increase the light collection efficiency. The muon detectionefficiency will be > 95% for water Cherenkov detector. With this veto system, the cosmic muoninduced fast neutron background can be reduced to the level of ~0.1 /day

Siva Prasad Kodukula

Vacuum energy density has been defined and mass formation from ‘space-time’ has been viewed in a different perspective. This explanation for vacuum energy is based on ‘space-time’ and conversion of space in to time keeping ‘space-time density’ as constant. Equations for ‘space-time’ and mutual conversion of space and time have been derived. As a result, new concept of mass creation has been explained. By postulating that space time density of universe is constant, low and high values of cosmological constants has been shown as the exchange of energy between space, time and energy. The concept has been used to explain dark energy concept of the universe. It concluded a result that velocity of light is changing with the apparent expansion of the universe. The derived equation is possible for experimental verification. Obviously it is a contradiction to Big bang model. So the derived equation with the help of quantum concepts explained the 2.7o K cosmic micro wave background radiation. Finally it proposed a relation between diameter of hydrogen atom and Hubble’s constant with another postulate that gives importance to the existence of positive and negative charges below atomic level that describe the basic facts of quantum physics.

N. A. Bezrukova, A. Chernokulsky