Hasil untuk "Geophysics. Cosmic physics"

L. Amendola, S. Appleby, D. Bacon et al.

Euclid is a European Space Agency medium-class mission selected for launch in 2019 within the Cosmic Vision 2015–2025 program. The main goal of Euclid is to understand the origin of the accelerated expansion of the universe. Euclid will explore the expansion history of the universe and the evolution of cosmic structures by measuring shapes and red-shifts of galaxies as well as the distribution of clusters of galaxies over a large fraction of the sky.Although the main driver for Euclid is the nature of dark energy, Euclid science covers a vast range of topics, from cosmology to galaxy evolution to planetary research. In this review we focus on cosmology and fundamental physics, with a strong emphasis on science beyond the current standard models. We discuss five broad topics: dark energy and modified gravity, dark matter, initial conditions, basic assumptions and questions of methodology in the data analysis.This review has been planned and carried out within Euclid’s Theory Working Group and is meant to provide a guide to the scientific themes that will underlie the activity of the group during the preparation of the Euclid mission.

R. Calderon, K. Lodha, A. Shafieloo et al.

We implement Crossing Statistics to reconstruct in a model-agnostic manner the expansion history of the universe and properties of dark energy, using DESI Data Release 1 (DR1) BAO data in combination with one of three different supernova compilations (PantheonPlus, Union3, and DES-SN5YR) and Planck CMB observations. Our results hint towards an evolving and emergent dark energy behaviour, with negligible presence of dark energy at z ≳ 1, at varying significance depending on data sets combined. In all these reconstructions, the cosmological constant lies outside the 95% confidence intervals for some redshift ranges. This dark energy behaviour, reconstructed using Crossing Statistics, is in agreement with results from the conventional w 0–w a dark energy equation of state parametrization reported in the DESI Key cosmology paper. Our results add an extensive class of model-agnostic reconstructions with acceptable fits to the data, including models where cosmic acceleration slows down at low redshifts. We also report constraints on H 0 r d from our model-agnostic analysis, independent of the pre-recombination physics.

Lu Huang, Rong-Gen Cai, Shao-Jiang Wang

Recently, a 3σ-4σ preference for dynamical dark energy has been reported by the Dark Energy Spectroscopic Instrument (DESI) collaboration, which has inspired hot debates on new physics or systematics. In this paper, we reveal that this preference is significantly biased by an external low-redshift supernova (low-z SN) sample, which was combined with the Dark Energy Survey SN program (DES-SN) in their Year-Five data release (DESY5). Using the intercept in the SN magnitude-distance relation as a diagnostic for systematics, we find not only large dispersions but also a large discrepancy in the low-z SN sample when compared with the high-z DES-SN sample within the single DESY5 compilation, in contrast to the uniform behavior found in the PantheonPlus data. Correcting for this low-z systematics with or without including the cosmic microwave background data can largely reduce the preference for dynamical DE to be less than 2σ. Therefore, the DESI preference for dynamical DE is biased by some unknown systematics in the low-z SN sample.

Seyed Hamidreza Mirpoorian, K. Jedamzik, L. Pogosian

Recent measurements of baryon acoustic oscillations (BAO) by the Dark Energy Spectroscopic Instrument (DESI) exhibit a mild-to-moderate tension with cosmic microwave background (CMB) and Type Ia supernova (SN) observations when interpreted within the ΛCDM framework. This discrepancy has been cited as evidence for dynamical dark energy (DDE). Given the profound implications of DDE for fundamental physics, we explore whether the tension can instead be resolved by modifying the physics of recombination. We find that a phenomenological model of modified recombination can effectively reconcile the BAO and CMB datasets and, unlike DDE, also predicts a higher Hubble constant H 0, thereby partially alleviating the Hubble tension. A global fit to BAO, CMB, and calibrated SN data favors modified recombination over DDE.

G. Brunetti, T. W. Jones

Radio observations prove the existence of relativistic particles and magnetic field associated with the intra-cluster-medium (ICM) through the presence of extended synchrotron emission in the form of radio halos and peripheral relics. This observational evidence has fundamental implications on the physics of the ICM. Nonthermal components in galaxy clusters are indeed unique probes of very energetic processes operating within clusters that drain gravitational and electromagnetic energy into cosmic rays (CRs) and magnetic fields. These components strongly affect the (micro-)physical properties of the ICM, including viscosity and electrical conductivities, and have also potential consequences on the evolution of clusters themselves. The nature and properties of CRs in galaxy clusters, including the origin of the observed radio emission on cluster-scales, have triggered an active theoretical debate in the last decade. Only recently we can start addressing some of the most important questions in this field, t...

Liyu ZHANG, Donghua YOU, Rong LI et al.

In recent years, multiple wells in the Sichuan Basin have produced industrial gas from the marlstone/marl-bearing limestone strata in the first member of the Middle Permian Maokou Formation (Mao 1), demonstrating promising exploration potential. Previous studies have suggested that the marlstone/marl-bearing limestone in Mao 1 exhibits self-generation and self-storage characteristics, forming low-porosity, low-permeability fracture-porosity type tight carbonate reservoirs with diverse storage spaces. Notably, diagenetic shrinkage pores and fractures formed during the transformation of sepiolite to talc contribute significantly to the storage space. To further investigate the genesis of clay minerals in Mao 1 and their significance for reservoir storage, rock samples were collected from six wells and one outcrop in the southern Sichuan Basin. A series of analyses, including microscopy, argon ion microscopy, X-ray diffraction (XRD), major and trace element analysis, strontium isotopic ratios (87Sr/86Sr), porosity tests, and nitrogen (N2) adsorption experiments, were conducted to study the characteristics of clay minerals in the marlstone/marl-bearing limestone of Mao 1. Microscopic observations and XRD results showed that the clay minerals mainly occurred as matrix minerals, irregular patches/spots, and replacements of biogenic calcareous shells. These minerals were primarily magnesian clay minerals such as talc and magnesium-rich montmorillonite, with minor amounts of sepiolite. Additionally, the marlstone/marl-bearing limestone in Mao 1 had relatively low Al2O3 contents and ΣREE concentrations, and its Y/Ho ratios and 87Sr/86Sr values resembled those of contemporaneous seawater, indicating limited terrigenous clastic input. This suggested that the magnesian clay minerals were originally authigenic clays formed during the deposition-early diagenesis period (in the sepiolite stage). The porosity/pore volume of the reservoir was positively correlated with the total clay mineral content and the magnesium-rich montmorillonite content, but no significant correlation or even a slight negative correlation was observed with the talc content. This indicated that the storage space in the marlstone reservoir was affected by the total clay content and the diagenetic evolution stage. The overall pore space increased with higher clay content. When thermal evolution was at the mature to highly mature stage and magnesium-rich montmorillonite was dominant, clay pores and fractures were developed, enhancing reservoir properties. However, excessive diagenetic evolution (over-mature thermal stage with higher talc content) was unfavorable for pore development.

F. F. Pollitz, K. A. Guns, C. E. Yoon

Abstract The Mw7.0 December 5, 2024 Offshore Cape Mendocino earthquake ruptured a ∼60 km long portion of the east‐west trending Mendocino fault zone (MFZ). In order to clarify the rupture process, we assemble three‐component seismograms from regional seismic stations, horizontal coseismic displacement vectors derived from Global Navigation Satellite System (GNSS) time series, and a Sentinel‐1 ascending interferogram. These data are interpreted with a model of slip distributed on two vertical fault planes representative of the eastern MFZ and spanning the ∼70 km length of the aftershock zone. Assuming right‐lateral strike slip, we find that the rupture initiates in the oceanic mantle at 20−30 km depth and proceeds unilaterally updip and toward the east. Early aftershocks locate adjacent to the peak slip areas, tracking the coseismic rupture propagation from oceanic mantle to shallower depth and implying a significant role of static stress transfer in driving aftershocks in an ocean plate environment.

Zhenbiao Liu, Yanxiang Yu, Liang Xiao et al.

提出了一种改进的拟合椭圆算法用于测量等震线长短轴，即将等震线测量的模式和直接测量算法的概念以约束的形式加入拟合椭圆算法，并使用最小二乘法求解椭圆系数，在与传统等震线测量方法保持一致的基础上，减少了直接测量方法的主观不确定性。在此基础上讨论了拟合椭圆算法的适用性和鲁棒性，将等震线长短轴的测量结果与前人的结果进行了对比。结果表明：拟合椭圆算法的适用性较好，可用于等震线的拟合；拟合椭圆算法的鲁棒性较好，计算结果较为稳定；对于未闭合且形状复杂的等震线，计算结果相对离散，要单独验证结果是否合理；利用拟合椭圆算法得到的等震线长短轴结果与前人的结果较为一致，可用于建立烈度衰减关系。

Penelope Godwin, Penelope Godwin, Siyuan Tian et al.

Woody vegetation restoration projects are an important feature of landscape function in Indonesian karst savannas. Understanding the relationship between available moisture and vegetation condition can assist with the planning and implementation of revegetation efforts. Working at vegetation restoration sites in East Nusa Tenggara, Indonesia, we applied a windowed cross-correlation method to mean values of NDVI to examine the lag between moisture input and NDVI response for both rainfall and soil moisture between 1999 and 2018. To test for increasing or decreasing trends in NDVI and rainfall time series, we undertook Mann–Kendall trend analyses. We identified increasing trends in Landsat 7 NDVI at two of four restoration sites, with annual increases in NDVI of 2.7 and 3.74 × 10−4 respectively. We found that rainfall dependent sites had significant Pearson’s correlations with NDVI ranging from 0.52 to 0.71, while NDVI was not correlated with rainfall at shallow groundwater sites. There was a clear negative effect of the very dry period on all sites, and this was less pronounced at shallow groundwater sites. Wet years resulted in a positive response to NDVI across all sites, while the response was lower in very wet years with annual rainfall above 1,200 mm. We found that between 2 and 4 months of antecedent rainfall gave the highest correlation with NDVI, while for soil moisture the closest relationship was found with no lag and 1 month lag. Through this study, we demonstrated the applicability of using NDVI, rainfall, and soil moisture trend analyses to identify groundwater-dependent vegetation patches and monitor the effectiveness of vegetation restoration.

M. W. Dunlop, M. W. Dunlop, H.-S. Fu et al.

We review the range of applications and use of multi spacecraft techniques, applicable to close formation arrays of spacecraft, focusing on spatial gradient based methods, and the curlometer in particular. The curlometer was originally applied to Cluster multi-spacecraft magnetic field data, but later was updated for different environments and measurement constraints such as the NASA MMS mission, small-scale formation of 4 spacecraft; the 3 spacecraft configurations of the NASA THEMIS mision, and derived 2-4 point measurements from the ESA Swarm mission. In general, spatial gradient based methods are adaptable to a range of multi-point and multi-scale arrays. We also review the range of other techniques based on the computation of magnetic field gradients and magnetic field topology in general, including: magnetic rotation analysis and various least squares approaches. We review Taylor expansion methodology (FOTE), in particular, which has also been applied to both Cluster and MMS constellations, as well as interpretation of simulations. Four-point estimates of magnetic gradients are limited by uncertainties in spacecraft separations and the magnetic field, as well as the presence of non-linear gradients and temporal evolution. Nevertheless, the techniques can be reliable in many magnetospheric regions where time stationarity is largely applicable, or when properties of the morphology can be assumed (for example, the expected orientation of underlying large-scale structure). Many magnetospheric regions have been investigated directly (illustrated here by the magnetopause, ring current and field-aligned currents at high and low altitudes), and options for variable numbers of spacecraft have been considered. The comparative use of plasma measurements and possible new methodology for arrays of spacecraft greater than four are also considered briefly.

Kai Huang, Quanming Lu, Yi‐Hsin Liu et al.

Abstract A three‐dimensional particle‐in‐cell simulation is performed to study secondary reconnection between two interlinked flux tubes produced by neighboring guide field reconnection x‐lines. The reconnecting magnetic fields of this secondary reconnection is enhanced toward the diffusion region, agree well with that in observations. The magnetic field pileup is attributed to the upstream magnetic tension force, that smashes the flux tubes into each other. We propose that the primary reconnection x‐line length is a key parameter to determine the formation of interlinked flux tubes and secondary reconnection therein. Interlinked flux tubes will form only if the x‐line is short; when the x‐line is long enough, the regular flux ropes are formed instead. The critical x‐line length to form interlinked flux tubes is determined by the distance between two neighbor x‐lines and the magnetic shear angle of the primary reconnection. The results provide a novel scenario of secondary reconnection generation during three‐dimensional reconnection.

A. Tello Fallau, A. Tello Fallau, C. Goetz et al.

<p>The plasma environment of comet 67P provides a unique laboratory to study plasma phenomena in the interplanetary medium. There, waves are generated which help the plasma relax back to stability through wave–particle interactions, transferring energy from the wave to the particles and vice versa. In this study, we focus on mirror-mode-like structures (low-frequency, transverse, compressional and quasi-linearly polarised waves). They are present virtually everywhere in the solar system as long as there is a large temperature anisotropy and a high plasma beta. Previous studies have reported the existence of mirror modes at 67P, but no further systematic investigation has so far been done. This study aims to characterise the occurrence of mirror modes in this environment and identify possible generation mechanisms through well-studied previous methods. Specifically, we make use of the magnetic-field-only method, implementing a <span class="inline-formula"><i>B</i></span>–<span class="inline-formula"><i>n</i></span> anti-correlation and a new peak/dip identification method. We investigate the magnetic field measured by Rosetta from November 2014 to February 2016 and find 565 mirror mode signatures. Mirror modes were mostly found as single events, with only one mirror-mode-like train in our dataset. Also, the occurrence rate was compared with respect to the gas production rates, cometocentric distance and magnetic field strength, leading to a non-conclusive relation between these quantities. The lack of mirror mode wave trains may mean that mirror modes somehow diffuse and/or are overshadowed by the large-scale turbulence in the inner coma. The detected mirror modes are likely highly evolved as they were probably generated upstream of the observation point and have traversed a highly complex and turbulent plasma to reach their detection point. The plasma environment of comets behaves differently compared to planets and other objects in the solar system. Thus, knowing how mirror modes behave at comets could lead us to a more unified model for mirror modes in space plasmas.</p>

Yikun Li, Xiaojun Li, Jiaxin Song et al.

Change vector analysis (CVA) and post-classification change detection (PCC) have been the most widely used change detection methods. However, CVA requires sound radiometric correction to achieve optimal performance, and PCC is susceptible to accumulated classification errors. Although change vector analysis in the posterior probability space (CVAPS) was developed to resolve the limitations of PCC and CVA, the uncertainty of remote sensing imagery limits the performance of CVAPS owing to three major problems: 1) mixed pixels; 2) identical ground cover type with different spectra; and 3) different ground cover types with the same spectrum. To address this problem, this article proposes the FCM-CSBN-CVAPS approach under the CVAPS framework. The proposed approach decomposes the mixed pixels into multiple signal classes using the fuzzy C means (FCM) algorithm. Although the mixed pixel problem is less severe in the high-resolution image, the change detection performance is still enhanced because, as a soft clustering algorithm, FCM is less susceptible to cumulative clustering error. Then, a context-sensitive Bayesian network (CSBN) is constructed to establish multiple-to-multiple stochastic linkages between signal pairs and ground cover types by incorporating spatial information to resolve problems 2) and 3) discussed above. Finally, change detection is performed using CVAPS in the posterior probability space. The effectiveness of the proposed approach is evaluated on three bitemporal remote sensing datasets with different spatial sizes and resolutions. The experimental results confirm the effectiveness of FCM-CSBN-CVAPS in addressing the uncertainty problems of change detection and its superiority over other relevant change detection techniques.

Binghai Gao, Yi He, Xueye Chen et al.

Construction activities of accelerated urbanization in Shenzhen have increased the landslide risk area, which has intensified the potential threat to human and natural environment. However, the risk of landslides in Shenzhen is poorly evaluated. In this article, a landslide risk evaluation (LRE) model is constructed using landslide susceptibility map (LSM) and landslide vulnerability. In the experiment, a stacking ensemble learning (SEL) model is constructed based on convolutional neural network (CNN), multilayer perceptron, gated recurrent unit (GRU), and support vector machine regression to generate LSM by using topography, geology, human engineering activities, time-series precipitation, and time-series normalized difference vegetation index. Road network, building distribution density and annual average precipitation data are used to evaluate landslide vulnerability based on entropy weight method. In this article, multiple statistical indicators are used to evaluate the performance of the LSM model, and Interferometric Synthetic Aperture Radar (InSAR) deformation data are utilized to verify the LRE results in Shenzhen. The results show that the SEL method has more refined results for LSM, with a best overall evaluation accuracy, especially in the receiver operating characteristic curve, where the accuracy is improved by nearly 8&#x0025;. In LRE of Shenzhen, very high, high, moderate, low, and very low risk areas account for 0.283&#x0025;, 0.451&#x0025;, 0.859&#x0025;, 36.890&#x0025;, and 61.517&#x0025;, respectively. In most of very high-risk area, InSAR deformation results show a clear concentrated deformation trend with a large deformation rate. Research results can provide technical and data support for landslide disaster prevention in Shenzhen.

A. Franceschini, G. Rodighiero

In addition to its relevant astrophysical and cosmological significance, the Extragalactic Background Light (EBL) is a fundamental source of opacity for cosmic high energy photons, as well as a limitation for the propagation of high-energy particles in the Universe. We review our previously published determinations of the EBL photon density in the Universe and its evolution with cosmic time, in the light of recent surveys of IR sources at long wavelengths. We exploit deep survey observations by the Herschel Space Observatory and the Spitzer telescope, matched to optical and near-IR photometric and spectroscopic data, to re-estimate number counts and luminosity functions longwards of a few microns, and the contribution of resolved sources to the EBL. These new data indicate slightly lower photon densities in the mid- and far-infrared and sub-millimeter compared to previous determinations. This implies slightly lower cosmic opacity for photon-photon interactions. The new data do not modify previously published EBL modeling in the UV-optical and near-IR up to several microns, while reducing the photon density at longer wavelengths. This improved model of the EBL alleviates some tension that had emerged in the interpretation of the highest-energy TeV observations of local \textit{blazar}s, reducing the case for new physics beyond the standard model (like violations of the Lorenz Invariance, LIV, at the highest particle energies), or for exotic astrophysics, that had sometimes been called for to explain it. Applications of this improved EBL model on current data are considered, as well as perspectives for future instrumentation, the Cherenkov Telescope Array (CTA) in particular.

D. Indumathi

The India-based Neutrino Observatory (INO) is a proposed underground facility located in India that will primarily house the magnetised Iron CALorimeter (ICAL) detector to study atmospheric neutrinos produced by interactions of cosmic rays with Earth’s atmosphere. The physics goal is to to make precision measurements of the neutrino mixing and oscillation parameters through such a study. We present here the results from detailed simulations studies, as well as a status report on the project. In particular, we highlight the sensitivity of ICAL to the open issue of the neutrino mass ordering, which can be determined independent of the CP phase at ICAL.

N.‐P. Finger, M. K. Kaban, M. Tesauro et al.

Abstract Recently, the continually increasing availability of seismic data has allowed high‐resolution imaging of lithospheric structure beneath the African cratons. In this study, S‐wave seismic tomography is combined with high resolution satellite gravity data in an integrated approach to investigate the structure of the cratonic lithosphere of Africa. A new model for the Moho depth and data on the crustal density structure is employed along with global dynamic models to calculate residual topography and mantle gravity residuals. Corrections for thermal effects of an initially juvenile mantle are estimated based on S‐wave tomography and mineral physics. Joint inversion of the residuals yields necessary compositional adjustments that allow to recalculate the thermal effects. After several iterations, we obtain a consistent model of upper mantle temperature, thermal and compositional density variations, and Mg# as a measure of depletion, as well as an improved crustal density model. Our results show that thick and cold depleted lithosphere underlies West African, northern to central eastern Congo, and Zimbabwe Cratons. However, for most of these regions, the areal extent of their depleted lithosphere differs from the respective exposed Archean shields. Meanwhile, the lithosphere of Uganda, Tanzania, most of eastern and southern Congo, and the Kaapvaal Craton is thinner, warmer, and shows little or no depletion. Furthermore, the results allow to infer that the lithosphere of the exposed Archean shields of Congo and West African cratons was depleted before the single blocks were merged into their respective cratons.

Jian-Fu Zhang, Jian-Fu Zhang, Ru-Yue Wang

It is well known that magnetohydrodynamic (MHD) turbulence is ubiquitous in astrophysical environments. The correct understanding of the fundamental properties of MHD turbulence is a pre-requisite for revealing many key astrophysical processes. The development of observation-based measurement techniques has significantly promoted MHD turbulence theory and its implications in astrophysics. After describing the modern understanding of MHD turbulence based on theoretical analysis and direct numerical simulations, we review recent developments related to synchrotron fluctuation techniques. Specifically, we comment on the validation of synchrotron fluctuation techniques and the measurement performance of several properties of magnetic turbulence based on data cubes from MHD turbulence simulations and observations. Furthermore, we propose to strengthen the studies of the magnetization and 3D magnetic field structure’s measurements of interstellar turbulence. At the same time, we also discuss the prospects of new techniques for measuring magnetic field properties and understanding astrophysical processes, using a large number of data cubes from the Low-Frequency Array (LOFAR) and the Square Kilometre Array (SKA).

Telescope Array Collaboration R.U. Abbasi, M. Abe, T. Abu-Zayyad et al.

The Telescope Array (TA) observatory utilizes fluorescence detectors and surface detectors (SDs) to observe air showers produced by ultra high energy cosmic rays in Earth’s atmosphere. Cosmic-ray events observed in this way are termed hybrid data. The depth of air shower maximum is related to the mass of the primary particle that generates the shower. This paper reports on shower maxima data collected over 8.5 yr using the Black Rock Mesa and Long Ridge fluorescence detectors in conjunction with the array of SDs. We compare the means and standard deviations of the observed X max distributions with Monte Carlo X max distributions of unmixed protons, helium, nitrogen, and iron, all generated using the QGSJet II-04 hadronic model. We also perform an unbinned maximum likelihood test of the observed data, which is subjected to variable systematic shifting of the data X max distributions to allow us to test the full distributions, and compare them to the Monte Carlo to see which elements are not compatible with the observed data. For all energy bins, QGSJet II-04 protons are found to be compatible with TA hybrid data at the 95% confidence level after some systematic X max shifting of the data. Three other QGSJet II-04 elements are found to be compatible using the same test procedure in an energy range limited to the highest energies where data statistics are sparse.

Nicholas Westing, Kevin C. Gross, Brett J. Borghetti et al.

A multimodal generative modeling approach combined with permutation-invariant set attention is investigated in this article to support long-wave infrared (LWIR) in-scene atmospheric compensation. The generative model can produce realistic atmospheric state vectors (T, H₂O, O₃) and their corresponding transmittance, upwelling radiance, and downwelling radiance (TUD) vectors by sampling a low-dimensional space. Variational loss, LWIR radiative transfer loss, and atmospheric state loss constrain the low-dimensional space, resulting in lower reconstruction error compared to standard mean-squared error approaches. A permutation-invariant network predicts the generative model low-dimensional components from in-scene data, allowing for simultaneous estimates of the atmospheric state and TUD vector. Forward modeling the predicted atmospheric state vector results in a second atmospheric compensation estimate. Results are reported for collected LWIR data and compared against fast line-of-sight atmospheric analysis of hypercubes-infrared (FLAASHIR), demonstrating commensurate performance when applied to a target detection scenario. Additionally, an approximate eight times reduction in detection time is realized using this neural network-based algorithm compared to FLAASH-IR. Accelerating the target detection pipeline while providing multiple atmospheric estimates is necessary for many real world, time sensitive tasks.