bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Solar Wind Proton Temperature Anisotropy at Mars' Orbital Location
Authors: Lentz C. L. , Chasapis A. , Qudsi R. A. , Halekas J. , Maruca B. A. , Andersson L. , Baker D. N. 
Published: September 2021

AbstractThe Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft can act as an intermittent upstream solar wind monitor at 1.5 AU. To inspect the evolution of solar wind turbulence in the Martian exosphere, we have gathered proton (i.e., ionized hydrogen) temperature measurements taken by the Solar Wind Ion Analyzer (SWIA) onboard the MAVEN spacecraft. Here we investigate instabilities driven by the proton temperature anisotropy at Mars during southern hemisphere fall, winter, spring, and summer seasons. We look at the relationship between the temperature anisotropy, (i.e., the ratio of the perpendicular proton temperature component to the parallel proton temperature component), and the parallel plasma beta, , to determine any constraints imposed by kinetic instabilities. Furthermore, we report on the properties of turbulence near Mars' orbital location during upstream solar wind intervals from January 2015 to December 2016 (1 Martian year). We find that the probability distributions of ()‐values become limited when deviates greatly from unity. We also find evidence of intermittency implying nonlinear, non‐homogeneous energy transfer. Additionally, spectral indices obtained from basic fittings of power spectral densities of magnetic field fluctuations demonstrate a power law decay for inertial ranges ( Hz to 0.1 Hz).
Hydrostatic Dehydration Fabrics of Antigorite at High Pressure and High Temperature: Implications for Trench Parallel Seismic Anisotropy at Convergent Plate Boundaries
Authors: Liu W. L. , Qi H. W. , Zhang J. F. , Wu X. , Li J. F. , Zhao R. , Wang Y. F. , Jin Z. M. 
Published: September 2021

AbstractAntigorite dehydration is well known as a key process at convergent boundaries for the genesis of mantle wedge partial melting and intermediate‐depth earthquakes. However, the crystallographic preferred orientations (CPOs) of prograde minerals from antigorite dehydration and their effects on the seismic anisotropy of subducting slabs remain ambiguous and controversial. Here we report antigorite dehydration experiments on a foliated serpentinized peridotite at pressures of 0.3–6 GPa and temperatures of 700–900°C. Our results show that olivine CPO evolves from a fiber‐[100] type in fine grains to a type‐C like in coarse grains. We propose that the fiber‐[100] olivine CPO is developed by topotactic growth during incipient hydrostatic dehydration, while the orthorhombic type‐C like olivine CPO is developed by anisotropic growth resulting from an anisotropic fluid flow during later dehydration. The type‐C like olivine CPO in the antigorite‐rich layers after antigorite dehydration could contribute to the trench parallel fast shear wave seismic anisotropy at convergent plate boundaries.
Rock Deformation Monitoring Using Monte Carlo Waveform Inversion
Authors: Lai Ssu‐Ting , Fuji Nobuaki , Katayama Ikuo , Bonilla Luis Fabian , Capdeville Yann 
Published: September 2021

AbstractWe estimate elastic and anelastic parameters and their evolution during laboratory rock deformation experiments, while developing a Monte Carlo waveform inversion. The transducer‐to‐transducer one‐source one‐station active seismic data of dry and water‐saturated samples are obtained from Zaima and Katayama (2018), https://doi.org/10.1029/2018JB016377. We first performed a trial‐and‐error estimate of the boundary conditions in order to suppress its influence on waveforms. The synthetic seismic data were generated using equivalent homogeneous models with different combinations of elastic and anelastic parameters with the aid of spectral element method. We compared them with the laboratory experimental data. Based on the comparisons, we obtained the time‐lapse variations of seismic velocities and attenuation of rock samples during deformation experiments, which we interpreted as crack developments. Our simultaneous estimation of elastic and anelastic parameters allowed us to detail the dynamics prior to the rock failure.
A Newly Discovered Late‐Cretaceous East Asian Flat Slab Explains Its Unique Lithospheric Structure and Tectonics
Authors: Peng Diandian , Liu Lijun , Wang Yaoyi 
Published: September 2021

AbstractThe existence of historical flat slabs remains debated. We evaluate past subduction since 200 Ma using global models with data assimilation. By reproducing major Mesozoic slabs whose dip angles satisfy geological constraints, the model suggests a previously unrecognized continental‐scale flat slab during the Late Cretaceous beneath East Asia, a result independent of plate reconstructions, continental lithospheric thickness, convergence rate, and seafloor age. Tests show that the pre‐Cretaceous subduction history, both along the western Pacific and Tethyan trenches, is the most important reason for the formation of this prominent flat Izanagi slab. Physically, continuing subduction increases the gravitational torque, which, through balancing the suction torque, progressively reduces dynamic pressure above the slab and decreases the slab dip angle. The flat Izanagi slab explains the observed East Asian lithospheric thinning that led to the formation of the North‐South Gravity Lineament, tectonic inversion of sedimentary basins, uplift of the Greater Xing'an‐Taihang‐Xuefeng mountains and the abrupt termination of intraplate volcanism during the Late Cretaceous.
Seismic Anisotropy and Mantle Flow Constrained by Shear Wave Splitting in Central Myanmar
Authors: Fan Enbo , He Yumei , Ai Yinshuang , Gao Stephen S. , Liu Kelly H. , Jiang Mingming , Hou Guangbing , Mon Chit Thet , Thant Myo , Sein Kyaing 
Published: September 2021

AbstractThis study represents the first campaign‐style teleseismic shear wave splitting (SWS) investigation of central Myanmar, an area that is tectonically controlled by the oblique subduction of the Indian Plate underneath the Eurasian Plate. The resulting 678 well‐defined and 247 null SWS measurements obtained from recently deployed 71 broadband seismic stations show that the Indo‐Burma Ranges (IBR) possess mostly N‐S fast orientations that are parallel to the trend of the depth contours of the subducted slab. Relative to the global average of 1.0 s, extremely large splitting times with station‐averaged values ranging from 1.28 to 2.79 s and an area‐averaged value of 2.09 ± 0.55 s are observed in the IBR. In contrast, the Central Basin (CB) and the Shan Plateau (SP) are characterized by slightly larger than normal splitting times. The fast orientations observed in the CB are mostly NE‐SW in the northern part of the study area, N‐S in the central part, and NW‐SE in the southern part. The fast orientations change from nearly N‐S along the N‐S oriented Sagaing Fault, to NW‐SE in the central and eastern portions of the SP. These observations, together with SWS measurements using local S events, crustal anisotropy measurements using P‐to‐S receiver functions, and the estimated depth of the source of anisotropy using the spatial coherency of the splitting parameters, suggest the presence of a trench‐parallel sub‐slab flow system driven by slab rollback, a trench‐perpendicular corner flow, and a trench‐parallel flow possibly entering the mantle wedge through a slab window or gap.
Seismic Velocity Structure Along and Across the Ultraslow‐Spreading Southwest Indian Ridge at 64°30′E Showcases Flipping Detachment Faults
Authors: Corbalán A. , Nedimović M. R. , Louden K. E. , Cannat M. , Grevemeyer I. , Watremez L. , Leroy S. 
Published: September 2021

AbstractWe present two ∼150‐km‐long orthogonal 2D P‐wave tomographic velocity models across and along the ridge axis of the ultraslow‐spreading Southwest Indian Ridge at 64°30′E. Here, detachment faults largely accommodate seafloor accretion by mantle exhumation. The velocity models are constructed by inverting first arrival traveltimes recorded by 32 ocean bottom seismometers placed on the two profiles. The velocities increase rapidly with depth, from 3 to 3.5 km/s at the seafloor to 7 km/s at depths ranging from 1.5 to 6 km below the seafloor. The vertical gradient decreases for velocities >7 km/s. We suggest that changes in velocity with depth are related to changes in the degree of serpentinization and interpret the lithosphere to be composed of highly fractured and fully serpentinized peridotites at the top with a gradual downward decrease in serpentinization and pore space to unaltered peridotites. One active and five abandoned detachment faults are identified on the ridge‐perpendicular profile. The active axial detachment fault (D1) shows the sharpest lateral change (horizontal gradient of ∼1 s–1) and highest vertical gradient (∼2 s–1) in the velocities. In the western section of the ridge‐parallel profile, the lithosphere transitions from non‐volcanic to volcanic over a distance of ∼10 km. The depth extent of serpentinization on the ridge‐perpendicular profile ranges from ∼2 to 5 km, with the deepest penetration at the D1 hanging wall. On the ridge‐parallel profile, this depth (∼2.5–4 km) varies less as the profile crosses the D1 hanging wall at ∼5–9 km south of the ridge axis.
Iron Sulfides and Anomalous Electrical Resistivity in Cratonic Environments
Authors: Saxena S. , Pommier A. , Tauber M. J. 
Published: September 2021

AbstractThe interpretation of low‐resistivity anomalies in the lithospheric mantle of several cratonic regions has invoked hydrogen, or connected networks of graphite with iron‐rich silicates, and/or metal sulfides. Electrical laboratory measurements are a powerful approach for exploring these alternatives. We report electrical measurements of two xenoliths (pyroxenite and dunite) from Tanzania; two metal sulfides (FeS and Fe‐S‐Ni); and several mixtures of metal sulfides (3.4–18.2 vol.%) with xenolith. A multi‐anvil press was employed to maintain a 2 GPa pressure and temperatures up to 1,627 K. The addition of 3.4 vol.% FeS to the pyroxenite or dunite matrix has little effect on bulk resistivity, particularly for T > 800 K. However, the resistivity drops dramatically–by factors of up to 1,000, depending on temperature–upon addition of 6.5 vol.% FeS in the dunite. Addition of 18.2% FeS causes a further decrease of the same magnitude relative to the 6.5% sample. Scanning electron microscope images do not reveal the formation of a connected FeS network as part of the decreased resistivity. Possible explanations for the apparently conflicting results include connections of the sulfide that are not imaged in the back‐scattered images, either because of limited resolution, or perhaps the inherent limitations of the 2‐D perspective. The complete data set (xenoliths, metal sulfides, and mixtures) was modeled with a modified version of Archie's law, and we find satisfactory agreement over a truncated temperature range. We conclude that the low‐resistivity anomalies in Tanzania, Kaapvaal, and Gawler cratons can be explained by the presence of a few vol.% of solid sulfide.
Cyclostationary EOF Modes of Antarctic Sea Ice and Their Application in Prediction
Authors: Pei Yuhua 
Published: September 2021

AbstractThis study examines the modes of sea ice concentration (SIC) in the Southern Ocean from a new perspective using the cyclostationary empirical orthogonal function (CSEOF) method, which decomposes a space‐time field into a combination of modulating variability on phase‐locked annual cycles. The first CSEOF mode of SIC (72.55% of total variance) represents the normal annual cycle modulated by a low‐frequency oscillation. The second mode of SIC (3.39%) represents the trend pattern, which reveals that the SIC increases in most regions of the Southern Ocean except for those adjacent to the Antarctic Peninsula, wherein the decreasing SIC trend is evident in austral warm seasons. This trend mode also explains that the sea ice in the Weddell Sea is increasing in austral summer and decreasing in austral winter. The Principal Component (PC) of this model is negatively corrected with the Southern Annular Mode index with a correlation coefficient of about −0.5. The third mode of SIC (2.48%) represents a wavenumber‐2 Antarctic Circumpolar Wave mode that is linked to ENSO. As the CSEOF method decomposes the space‐time SIC field into low‐frequency modulations of phase‐locked annual cycles, it can be used for SIC prediction, by taking the spatial modes as the basis functions and predicting their PCs from the autoregressive models. However, this CSEOF‐based SIC prediction model exhibits unsatisfactory forecast skills, even with optimized model parameters. Therefore, it is still necessary to study more SIC prediction models and evaluate their forecast skills in the future.
An Extension of the Guided Wave M‐Component Model Taking Into Account the Presence of a Tall Strike Object
Authors: Li Quanxin , Rachidi Farhad , Rubinstein Marcos , Wang Jianguo , Azadifar Mohammad , Cai Li , Wang Junlin , Zhou Mi , Fan Yadong 
Published: September 2021

AbstractWe present in this paper an extension of the guided‐wave M‐component model of Rakov et al. considering the presence of a vertically elevated strike object. The tall object is represented as a lossless, uniform transmission line. Expressions for the current distribution along the channel and along the strike object are derived. Simulation results for the electric field at close (100 m), intermediate (15 km), and far (100 km) distance ranges are presented, considering fast and slow M‐component currents. The results show that, for very tall structures and fast M‐component waves, the presence of a tall strike object can result in a sharp peak superimposed on the M‐component electric field at intermediate and far distance ranges (e.g., 15 and 100 km). At close distances, the electric field of a fast M‐component is characterized by an initial negative excursion followed by a polarity change. It is shown that the presence of the tower results in a decrease of the negative initial excursion of the field. For slow M‐component waveforms or for moderately tall structures, the presence of the tall strike object can be disregarded in the M‐component field calculations. A discussion on the influence of the M‐wave channel height and velocity on the electric fields for fast M‐component currents is also presented. The study suggests a noticeable effect of the M‐wave velocity on the electric fields at all distance ranges. The variations of the wave velocity and channel length affect the time of appearance of the superimposed sharp peak on the electric fields. However, the sharp peak magnitude, which is due to the presence of the tower, is independent of the channel length and wave velocity. It is determined by the injected current and the reflection coefficients from the ground and tower top.
Recognition of Inter‐Cloud Versus Intra‐Cloud Controls on Droplet Dispersion With Applications to Microphysics Parameterization
Authors: Hu Arthur Z. , Igel Adele L. , Chuang Patrick Y. , Witte Mikael K. 
Published: September 2021

AbstractAerosols in the atmosphere can have a large impact on weather and climate. One of its lesser‐known impacts is the aerosol‐dispersion effect, which refers to the feedback between the aerosol (or cloud droplet) concentration and the relative dispersion of the droplet size distribution. This study attempts to reconcile the inconsistent sign of the correlation between aerosol number and droplet dispersion found in past studies by distinguishing local correlation from cloud‐mean correlation. We find that while the cloud‐mean correlation between aerosol concentration and droplet size relative dispersion is largely nonexistent, in‐cloud regions with high relative dispersion are typically associated with low local droplet concentration. Even stronger correlation is found with respect to the local activation fraction (the ratio of droplet concentration to total droplet and aerosol concentration). Based on this local correlation, we propose a new equation to diagnose the shape parameter in marine stratocumulus clouds for double moment bulk schemes in cloud‐resolving or large‐eddy simulations. This new equation is more physically realistic than many existing ones that are based on the weak cloud‐mean correlation.
Cloud‐Radiation Interactions and Their Contributions to Convective Self‐Aggregation
Authors: Pope Kieran N. , Holloway Christopher E. , Jones Todd R. , Stein Thorwald H. M. 
Published: September 2021

AbstractThis study investigates the direct radiative‐convective processes that drive and maintain aggregation within convection‐permitting elongated channel (and smaller square) simulations of the UK Met Office Unified Model. Our simulations are configured using three fixed sea surface temperatures (SSTs) following the Radiative‐Convective Equilibrium Model Intercomparison Project (RCEMIP) protocol. By defining cloud types based on the profile of condensed water, we study the importance of radiative interactions with each cloud type to aggregation. We eliminate the SST dependence of the vertically integrated frozen moist static energy (FMSE) variance budget framework by normalizing FMSE between hypothetical upper and lower limits based on SST. The elongated channel simulations reach similar degrees of aggregation across SSTs, despite shortwave and longwave interactions with FMSE contributing less to aggregation as SST increases. High‐cloud longwave interactions are the main drivers and maintainers of aggregation. Their influence decreases with SST as high clouds become less abundant. This SST dependence is consistent with changes in grid spacing and the critical humidity threshold for condensation (RHcrit). However, the domain‐mean longwave‐FMSE feedback would likely decrease as grid spacing and RHcrit are reduced by lowering the condensed water path and cloud top height of high‐cloud, and altering the distribution of different cloud types. Shortwave interactions with water vapor are key maintainers of aggregation and are dependent on SST and the degree of aggregation itself. The analysis method used provides a new framework to compare the effects of radiative‐convective processes on self‐aggregation across different SSTs and model configurations to help improve our understanding of self‐aggregation.
Development and Validation of Precipitation Enhanced Densities for the Empirical Canadian High Arctic Ionospheric Model
Authors: Watson C. , Themens D. R. , Jayachandran P. T. 
Published: September 2021

AbstractThe Empirical Canadian High Artic Ionospheric Model (E‐CHAIM) provides the four‐dimensional ionosphere electron density at northern high latitudes (>50° geomagnetic latitude). Despite its emergence as the most reliable model for high‐latitude ionosphere density, there remain significant deficiencies in E‐CHAIM's representation of the lower ionosphere (below ∼200 km) due to a sparsity of reliable measurements at these altitudes, particularly during energetic particle precipitation events. To address this deficiency, we have developed a precipitation component for E‐CHAIM to be driven by satellite‐based far‐ultraviolet (FUV) imager data. Satellite observations of FUV emissions may be used to infer the characteristics of energetic particle precipitation and subsequently calculate the precipitation‐enhanced ionization rates and ionosphere densities. In order to demonstrate the improvement of E‐CHAIM's ionosphere density representation with the addition of a precipitation component, this paper presents comparisons of E‐CHAIM precipitation‐enhanced densities with ionosphere density measurements of three auroral region incoherent scatter radars (ISRs) and one polar cap ISR. Calculations for 29,038 satellite imager and ISR conjunctions during the years 2005–2019 revealed that the root‐mean‐square difference between E‐CHAIM and ISR measurements decreased by up to 2.9 × 1010 ele/m3 (altitude dependent) after inclusion of the precipitation component at auroral sites, and by 2.6 × 109 ele/m3 in the polar cap. Improvements were most substantial in the winter season and during active auroral conditions. The sensitivity of precipitation‐enhanced densities to uncertainties inherent to the calculation method was also examined, with the bulk of the errors due to uncertainties in FUV imager data and choice of distribution function for precipitation energy spectra.
An Adjoint Sensitivity Model for Radionuclide Transport in Heterogeneous Discrete Fractured Porous Formation in Steady‐State Regime
Authors: Hayek Mohamed , RamaRao Banda S. , Lavenue Marsh 
Published: September 2021

AbstractThe development of the adjoint state method for the system of partial differential equations (PDEs) describing radionuclide transport in heterogeneous discrete fractured porous media in steady‐state regime is presented in this study for both continuous and discrete adjoint approaches. The continuous adjoint approach has its own advantage in the sense that the adjoint system can be derived in terms of PDEs which can be solved analytically for specific performance measures. These PDEs can then be used to obtain a physical interpretation of the adjoint state functions. The discrete adjoint approach permits a simpler mathematical treatment based on the use of the same matrix (or its transpose) of the linear system of the discretized transport equations referring to from hereon as the forward problem. Analytical solutions for both the forward problem and its associated adjoint problem have been derived for radionuclide transport in layered formations including a fracture using an analytical inversion of tridiagonal matrices. A set of 14 formulas of sensitivity coefficients with respect to pertinent system parameters has been derived and presented in integral forms. Analytical results have been compared with numerical results and have shown excellent agreements. The discrete adjoint approach has been coupled with the differential sensitivity analysis method and applied to a real field case involving the performance assessment of a site currently being considered for underground nuclear storage in northern Switzerland, Zürich Nordost. The results show that when a fracture is present in the vicinity of waste repository, the state parameter controlling flow through the fracture, referred to herein as fracture transmissivity, is among the important parameters which should be considered in sensitivity analysis studies.