Feed aggregator

Tropical cyclones can have severe consequences for both the marine and terrestrial environments, as well as the organisms and communities who inhabit them. In the oceans, there can be alterations in sea surface temperature that disrupt biological processes and hospitable conditions for life, the devastation of surface algae and other primary producers, which impacts complex marine food chains, as well as damaging coral reefs. Meanwhile, on land, the heavy rainfall, strong winds and storm surges can lead to significant damage to property and infrastructure, as well as loss of lives.

On Sept. 18, 2024, NOAA shared the first images of the Western Hemisphere from its GOES-19 satellite. The satellite's Advanced Baseline Imager (ABI) instrument recently captured stunning views of Earth.

Author(s): Erwin Walter, John P. Farmer, Martin S. Weidl, Alexander Pukhov, and Frank Jenko

Charged and quasineutral beams propagating through an unmagnetized plasma are subject to numerous collisionless instabilities on the small scale of the plasma skin depth. The electrostatic two-stream instability, driven by longitudinal and transverse wakefields, dominates for dilute beams. This lead…

[Phys. Rev. E 110, 035208] Published Thu Sep 19, 2024

Lavas from hotspots—whether erupting in Hawaii, Samoa or Iceland—likely originate from a worldwide, uniform reservoir in Earth's mantle, according to an evaluation of volcanic hotspots published in Nature Geoscience.

A paper, titled "How local governments avoid floodplain development through consistent implementation of routine municipal ordinances, plans, and programs," published in Oxford Open Climate Change uncovers evidence suggesting that, contrary to expectations, most U.S. cities are not doing too badly in avoiding development in areas prone to flooding, and those that are effective appear to be applying existing tools and strategies well, rather than doing anything particularly novel.

A researcher from the University of Southampton (UK) has found evidence that the treeless, rugged, grassland landscape of the Falkland Islands was home to a lush, diverse rainforest up to 30 million years ago.

Nature Geoscience, Published online: 19 September 2024; doi:10.1038/s41561-024-01538-7

An investigation of global trace-element data suggests that the parental melts of hotspot lavas are uniform in their elemental composition, consistent with derivation from a common depleted and outgassed mantle reservoir.

Abstract

The properties of a plasma sheath are investigated numerically by using a fluid model in which a monoenergetic electron beam is taken into account. To suit the realistic environment, secondary electrons emitted from the wall surface due to collision between the electrons and the wall surface is considered. The result reveals that the effective emission coefficient depends on the emission generated by a monoenergetic electron beam when the temperature of a monoenergetic electron beam is high. The effective emission coefficient of secondary electrons changes monotonically with the increase of emission coefficient generated by beam electrons. Using the Sagdeev pseudopotential method, a modified Bohm criterion can be obtained. It is found that the ion Bohm velocity increases with increasing beam electron energy and emission coefficient generated by a monoenergetic electron beam. Moreover, when the emission coefficient generated by a monoenergetic electron beam is small, the wall potential decreases with increasing beam electron energy and concentration. When the emission coefficient generated by a monoenergetic electron beam is large, the opposite is true. It is also shown that a monoenergetic electron beam can cause an increase in the critical effective secondary electron emission coefficient, and the increase is nonmonotonic.

Abstract

Based on the two-dimensional resistive magnetohydrodynamics (MHD) model, this study explores the impact of shear flow on the resonant magnetic perturbation (RMP)-induced double tearing mode (DTM). The results indicate that the effectiveness of shear flow in suppressing the double tearing mode is primarily dependent on the flow velocity at the outer rational surface. A notable finding is that, with higher flow velocities, the double tearing mode is effectively suppressed. However, in cases of very weak flow velocities, the shear flow still exerts an influence, but with a limited suppression effect. Specifically, it can only inhibit the inner island, while the outer island continues to grow under the influence of the resonant magnetic perturbation.

SummaryCurrently, gravimetric forward modelling of mass density structures with arbitrary geometries and density distributions typically involves subdividing the mass body into individual geometric elements (such as rectangular prisms), calculating their gravitational contributions that are then summed up to obtain the gravitational attraction of the whole body. To achieve a more accurate approximation of the true geometric shape and density distribution, this rectangular prism model requires fine dividing, which significantly increases computational load and reduces numerical efficiency. To address this issue, we propose the algorithm for gravimetric forward modeling of arbitrary geometric shapes and density distributions in spectral domain that significantly improves numerical efficiency while preserves computational accuracy. The novelty of our proposed algorithm lies in dividing the masses into multiple layers of equal thickness in the vertical direction, providing constant upper and lower bounds. This allows to extended Parker's formulas and apply the Fast Fourier Transform (FFT) to increase numerical efficiency. The algorithm is tested using synthetic models and then used to compute gravitational effects of topography and sediments using real data from Tibet. Results show high accuracy and numerical efficiency than rectangular prism approach.

SummaryWe propose a frequency-domain finite-element (FDFE) method to model the 2D P-SV waves propagating in porous media. This specific finite element method (FEM) is based on the framework of variational principles, which differ from previously widely used FEMs that rely on the weak formulations of the governing equations. By applying the calculus of variations, we establish the equivalence between solving the stress-strain relations, equations of motion and boundary conditions that govern the propagation of P-SV waves, and determining the extremum or stationarity of a properly defined functional. The structured rectangular element is utilized to partition the entire computational region. We validate the FDFE method by conducting a comparison with an analytically-based method for models of a horizontal planar contact of two poroelastic half-spaces, and a poroelastic half-space with a free surface. The excellent agreements between the analytically-based solutions and the FDFE solutions indicate the effectiveness of the FDFE method in modeling the poroelastic waves. Modeling results manifest that both propagative and diffusive natures of the Biot slow P-wave can be effectively modeled. The proposed FDFE method simulates wave fields in the frequency domain, allowing for easily incorporation of frequency-dependent parameters and enabling parallel computational capabilities at each frequency point (sample). We further employ the developed FDFE method to model two simplified poroelastic reservoirs, one with gas-saturated sandstone and the other with oil-saturated sandstone. The results suggest that changing the fluid phase of the sandstone reservoir from gas to oil can substantially impact the recorded solid and relative fluid-solid displacements. The modeling suggests that the proposed FDFE algorithm is a useful tool for studying the propagation of poroelastic waves.

Summer 2024 was officially the Northern Hemisphere's hottest on record. In the United States, fierce heat waves seemed to hit somewhere almost every day.

Recent satellite data reveal that the Konya Basin in the Central Anatolian Plateau of Türkiye is continually being reshaped over millions of years, according to a new analysis led by Earth scientists at the University of Toronto.

A team of researchers from the CNRS and the Paris Institute of Planetary Physics has developed an innovative imaging method that can probe the bowels of a volcano with unparalleled resolution and depth. This new method is based on the deployment of a network of geophones that capture not only the powerful shaking of earthquakes, but also the seismic noise caused by wind, the ocean, and human activity.

Publication date: Available online 14 September 2024

Source: Advances in Space Research

Author(s): Yu Zhang, Xiong Xie, Zongyu Wu, Tao Sheng, Yong Zhao

Publication date: Available online 14 September 2024

Source: Advances in Space Research

Author(s): Fengyu Xia, Shanshi Zhou, Dezhong Chen, YueLing Cao, NaNa Jiang, Weijing Qu, Xiaogong Hu

Publication date: Available online 13 September 2024

Source: Advances in Space Research

Author(s): Wentao He, Huayi Li, Shi Qiu, Ming Liu, Xinyu Wang

Publication date: Available online 13 September 2024

Source: Advances in Space Research

Author(s): Homayoon Alimoradi, Habib Rahimi, Mohsen Ovaisi Moaakhar

Publication date: Available online 12 September 2024

Source: Advances in Space Research

Author(s): Chukwuebuka J. Ugwu, Jibrin A. Alhassan, Ogbonnaya Okike, Firew M. Menteso, Ngozi M. Ugwu, Augustine E. Chukwude, Evaristus U. Iyida, Innocent O. Eya, Romanus E. Ugwoke, Dominic C. Obiegbuna, Finbar C. Odo, Orji P. Orji

The average longest periods of drought could be ten days longer by the end of the century than previously predicted by climate models, according to research published in Nature. The findings suggest that the hazards droughts pose to societies and ecosystems in the coming decades may be greater than expected.