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Abstract

Lunar polar region has become the focus of future explorations due to the possible ice reservoir in the permanently shadowed craters. However, the space environment near the polar crater is quite complicated, and a plasma mini-wake can be caused by the topographic obstruction. So far, three-dimensional (3D) numerical simulations of the mini-wake around a crater far larger than the Debye length are still limited. Here we present a 3D electrostatic hybrid particle-in-cell model to study the plasma mini-wake of a polar crater on scale of about 1 km. It is found that the mini-wake can begin upstream from the crater with a cone angle of about 8.8°. There is a plasma void with extra electrons near the leeward crater wall, where the electric potential can be as low as −60 V. A part of solar wind ions can be diverted into the crater, and the ratio of the diverted flux is about 4% on the crater bottom and about 18% on the windward crater wall, which provide an important source for the surface sputtering. Further studies show that the mini-wake can change with the solar wind parameters and the crater shapes. Our results are helpful to assess the space environment and the water loss rate of a polar crater, and have general implications in studying the plasma mini-wake caused by a crater on the other airless bodies.

Abstract

The influence of northern polar vortex in the stratosphere (SPV) in December-January on Asia's surface air temperature (SAT) in February has been examined using reanalysis data sets and a barotropic model. An out-of-phase interannual linkage between the SPV in December-January and SAT in February during 1979–2022 has been observed, that is, a strong (weak) SPV corresponds to a cooling (warming) over Asia. Approximately 25% of the SAT over Asia in February can be explained by the SPV in December-January. This relationship between the SPV and SAT is independent of the Arctic Oscillation. The influence of the SPV on SAT over Asia cannot be solely explained by radiative processes, but is instead related to circulation anomalies in the troposphere. A stronger SPV tends to result in negative geopotential height anomalies with cyclonic circulation over Asia. The SPV-related geopotential height over Asia is accompanied by a weakened teleconnection pattern between the North Atlantic and Asia, with three centers from the northeastern Atlantic-eastern Europe-Asia, and fewer stationary waves propagated from North Atlantic into Asia. These anomalous circulation patterns and anomalous northerly wind over Central Asia in February are beneficial to the colder air transportation from the higher latitudes to Asia, facilitating a surface cooling over Asia. Our results shed light on the interannual linkage between SPV and SAT over Asia, suggesting that the SPV in December-January could be considered as a new predicator of SAT in February over Asia.

Abstract

Water-soluble organic carbon (WSOC) deposited in ambient snowpack play key roles in regional carbon cycle and surface energy budget, but the impacts of photo-induced processes on its optical and chemical properties are poorly understood yet. In this study, melted samples of the seasonal snow collected from northern Xinjiang, northwestern China, were exposed to ultraviolet (UV) radiation to investigate the photolytic transformations of WSOC. Molecular characteristics and chemical composition of WSOC and its brown carbon (BrC) constituents were investigated using high-performance liquid chromatography interfaced with a photodiode array detector and a high-resolution mass spectrometer. Upon illumination, formation of nitrogen- and sulfur-containing species with high molecular weight was observed in snow samples influenced by soil- and plant-derived organics. In contrast, the representative sample collected from remote region showed the lowest molecular diversity and photolytic reactivity among all samples, in which no identified BrC chromophores decomposed upon illumination. Approximately 65% of chromophores in urban samples endured UV irradiation. However, most of BrC composed of phenolic/lignin-derived compounds and flavonoids disappeared in the illuminated samples containing WSOC from soil- and plant-related sources. Effects of the photochemical degradation of WSOC on the potential modulation of snow albedo were estimated. Apparent half-lives of WSOC estimated as albedo reduction in 300–400 nm indicated 0.1–0.4 atmospheric equivalent days, which are shorter than typical photolysis half-lives of ambient biomass smoke aerosol. This study provides new insights into the roles of WSOC in snow photochemistry and snow surface energy balance.

Prognostic assumed-probability-density-function (distribution density function) approach: further generalization and demonstrations
Jun-Ichi Yano
Nonlin. Processes Geophys., 31, 359–380, https://doi.org/10.5194/npg-31-359-2024, 2024
A methodology for directly predicting the time evolution of the assumed parameters for the distribution densities based on the Liouville equation, as proposed earlier, is extended to multidimensional cases and to cases in which the systems are constrained by integrals over a part of the variable range. The extended methodology is tested against a convective energy-cycle system as well as the Lorenz strange attractor.

Abstract

To investigate continental dynamics underneath the south-central Tibetan plateau, which composes the Himalayan, Lhasa, and Qiangtang blocks, we have conducted comprehensive examinations of seismic azimuthal anisotropy in the crust using receiver functions (RFs) and crustal and mantle anisotropy using teleseismic shear wave splitting (SWS) analysis. In the Qiangtang block, the observed predominantly E-W fast orientations from RF and SWS analyses with similar magnitude are interpreted as resulting from eastward crustal flow with minor contributions from the mantle. In the Lhasa block, the crustal anisotropy is approximately N-S oriented, which is parallel to the strike of rift basins and southward crustal flow. Anisotropy revealed by SWS demonstrates a rotation from E-W in the north to NE-SW in the south, which can be interpreted as reflecting mantle flow field induced by the northward movement of the subducting Indian plate. The addition of PKS and SKKS measurements and extension of epicentral distance range to 171.8° for SWS analysis revealed dominantly strong E-W oriented anisotropy in most parts of the Himalayan block, where most previous studies reported pervasively null measurements. The absence of azimuthal anisotropy is observed in two regions in the Himalayan block which is attributable to mantle upwelling through a previously identified slab window. A two-layered anisotropy structure with different fast orientations for the upper and lower layers can be constrained in the southern Qiangtang and the vicinity of the Main Boundary Thrust.

Author(s): E. Castro-Ávila, Paolo Malgaretti, Jens Harting, and J. D. Muñoz

We employ a lattice Boltzmann method to compute the acoustic radiation force produced by standing waves on a compressible object for the density matched case. Instead of simulating the fluid mechanics equations directly, the proposed method uses a lattice Boltzmann model that reproduces the wave equ…

[Phys. Rev. E 110, 025304] Published Tue Aug 13, 2024

Abstract

The Netherlands-China Low-Frequency Explorer (NCLE) (Boonstra et al., 2017, https://www.ursi.org/proceedings/procGA17/papers/Paper_J19-2(1603).pdf; Chen et al., 2020, https://ui.adsabs.harvard.edu/abs/2020AAS…23610203C/abstract) is a radio instrument for astrophysical studies in the low-frequency range (80 kHz–80 MHz). As a technology demonstrator, NCLE shall inform the design of future radio receivers that aim at low-frequency radio astronomy. NCLE can make observations at very high spectral resolution (<1 kHz) and generate radio sky maps at an angular resolution of ≈1.5 radians. NCLE uses three monopole antennas, each 5 m long, and three identical analog signal chains to process the signal from each antenna. A single digital receiver samples the signal and calculates the auto-correlated and cross-correlated spectra. The instrument's analog and digital signal chains are extensively configurable. They can be fine-tuned to produce broadband spectra covering the instrument's complete operating frequency range or sub-bands. NCLE was developed within a veryshort timescale of 2 years, and currently, it is on board Queqiao, the relay spacecraft of the Chang'e- 4 mission, in a halo orbit around the Earth-Moon L2 point. This paper outlines the science cases, instrument architecture with focus on the signal chain, and discusses the laboratory measurements during the pre-launch phase.

Abstract

The unusual stripe-like scattered echoes were observed by the Hainan Coherent Scatter Phased Array Radar (HCOPAR) in the nigh of 9 Sep. 2017. There were parallel stripes with the interval of ∼33 min appearing from 12:57 to 17:50 UT. While the emergence of the scattered echoes, the Hainan Digisonde has observed the Spread-F, and the Total Electron Content (TEC) maps recorded by the Global Navigation Satellite System (GNSS) in China show that there was no Equatorial Plasma Bubble (EPB), but the Medium-Scale Traveling Ionospheric Disturbance (MSTID) traveled southwestward. The spatial and temporal distributions of the stripe-like echoes and the MSTID show great consistency, indicating that the F-region Field-Aligned Irregularities were generated in the wave peaks and troughs of the MSTID. The MSTID has decayed greatly while reaching the HCOPAR, and the echo pattern is determined by the wave features of the MSTID.

SummarySalt diapirs dominate the structure in many sedimentary basins and control the preservation and migration of hydrocarbon. The formation of salt diapirs generally falls into two endmember models: active (up-building) and passive (down-building) diapirism. In the active model, salt diapirs rise from salt buoyancy to pierce through the sedimentary overburden, whereas in the passive model, salt diapirs result from differential loading of sediments during deposition. These endmember models are mostly conceptual or kinematic, the mechanics of active and passive diapirism, and their relative roles and interactions in the formation of salt diapirs, remain uncertain. Here, we use two-dimensional high-resolution numerical models to investigate the primary factors and critical conditions for active and passive diapirism. Our results indicate that it is improper to use driving mechanisms to classify salt diapirs, because the buoyancy-driven active salt diapirism involves differential loading, while the passive diapirism requires salt buoyancy. The rise of salt diapirs is more sensitive to the effective viscosity of the overburden than to the salt viscosity. Stiff overburdens could prevent the rise of salt diapirs, but they could be pierced by salt diapirs if plastic yield of the overburden is allowed. During deposition, the coupled salt-sediment deformation, driven by both salt buoyancy and differential loading of sediments, can lead to various diapiric salt structures and minibasins. Regional tectonic stress generally promotes salt diapirism by enhancing strain weakening of salts and overburdens. We suggest that the classification of active and passive salt diapirism is an oversimplification in most cases. We propose a general model of the formation of salt diapirs that usually begins with dome initiation driven by salt buoyancy, followed by syndepositional down-building controlled by sedimentation and differential loading, and ends with canopy formation when sedimentation stops.

New research from a team at Los Alamos National Laboratory is improving landslide prediction capabilities, making simulations faster and more accurate, which in turn will improve safety for communities that are at risk of their infrastructure being washed away.

A new study that explores ancient temperatures and rainfall patterns in the tropical Andes of South America has revealed how 16,000 years of climate history in this part of the world was driven by carbon dioxide levels and ocean currents from global climate events.

As Earth warms, the Arctic Ocean's ability to absorb carbon dioxide from the atmosphere is waning due to melting permafrost and worsening coastal erosion, according to new research.

Publication date: 15 September 2024

Source: Earth and Planetary Science Letters, Volume 642

Author(s):

Publication date: 15 September 2024

Source: Earth and Planetary Science Letters, Volume 642

Author(s): Sierra N. Ferguson, Alyssa R. Rhoden, Michelle R. Kirchoff

Publication date: 15 September 2024

Source: Earth and Planetary Science Letters, Volume 642

Author(s): Gui-Mei Lu, Yi-Gang Xu, Wei Wang, Christopher J. Spencer, Nick M.W. Roberts, Kent C. Condie

Publication date: 15 September 2024

Source: Earth and Planetary Science Letters, Volume 642

Author(s): Tony Alfredo Stabile, Elshafey Raafat Fat-Helbary, Vincenzo Serlenga, Serena Panebianco, Pietro Tizzani, Raffaele Castaldo, Luciano Telesca, Ezzat Mohamed El-Amin, Ahmed Hamed

Publication date: 15 September 2024

Source: Earth and Planetary Science Letters, Volume 642

Author(s): He Zhao, Ying Cui, Lei Zhang, Zhong-Qiang Chen, Thomas J. Algeo, Yongsheng Liu, Zhaochu Hu, Jun Sun

Publication date: 15 September 2024

Source: Earth and Planetary Science Letters, Volume 642

Author(s): Minmin Fu, Alexey V. Fedorov

Publication date: 15 September 2024

Source: Earth and Planetary Science Letters, Volume 642

Author(s): Chuanjin Liu, Lingyun Ji, Liangyu Zhu, Caijun Xu, Jiangtao Qiu