Global-to-Cartesian 3-D EM modeling using a nested IE approach with application to long-period responses from island geomagnetic observatories

2020 ◽  
Author(s):  
Chaojian Chen ◽  
Mikhail Kruglyakov ◽  
Alexey Kuvshinov
Keyword(s):  
Anomalous Behavior ◽  
Small Scale ◽  
Induction Effect ◽  
Modeling Framework ◽  
Long Period ◽  
Mantle Conductivity ◽  
Integral Equation Approach ◽  
Cocos Island ◽  
High Resolution Bathymetry ◽  
Coarse Grids

<p>There is a significant interest in constraining the mantle conductivity beneath oceans. One of the main sources of data that can be used to reveal the conductivity distribution in the oceanic mantle are time-varying magnetic fields measured at island geomagnetic observatories. From these data local electromagnetic (EM) responses are estimated and then inverted in terms of conductivity. The challenge here is that island responses are strongly distorted by the ocean induction effect (OIE) originating from the lateral conductivity contrasts between the conductive ocean and resistive land. OIE is generally modeled by global simulations using relatively coarse grids (down to 0.25 degree resolution) to represent the bathymetry. Insufficiently accurate accounting for the OIE may lead to the wrong interpretation of the observed responses. We study whether the small-scale bathymetry features influence the island responses. To address this question we developed a global-to-Cartesian 3-D EM modeling framework based on a nested integral equation approach, which allows to efficiently account for the effects of high-resolution bathymetry. Two geomagnetic observatories, located in Indian (Cocos Island) and Pacific (Oahu Island) Oceans, are chosen to study the OIE in long-period responses. Numerical tests demonstrate that accounting of the very local bathymetry (down to 1 km resolution) dramatically change modeling results. Remarkably, the anomalous behavior of the imaginary parts of the responses at Cocos Island, namely, the change of sign at short periods, is reproduced by using highly detailed bathymetry.</p>

Long-period variations in the magnetic field of small-scale solar structures

2016 ◽  
Vol 56 (8) ◽  
pp. 1052-1059 ◽  
Author(s):  
P. V. Strekalova ◽  
Yu. A. Nagovitsyn ◽  
A. Riehokainen ◽  
V. V. Smirnova
Keyword(s):  
Magnetic Field ◽  
Small Scale ◽  
Long Period ◽  
Period Variations ◽  
The Magnetic Field

scholarly journals UAV-DEMs for Small-Scale Flood Hazard Mapping

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1717 ◽  
Author(s):  
Antonio Annis ◽  
Fernando Nardi ◽  
Andrea Petroselli ◽  
Ciro Apollonio ◽  
Ettore Arcangeletti ◽  
...  
Keyword(s):  
High Resolution ◽  
Hydrologic Modeling ◽  
Flood Hazard ◽  
Hydraulic Modeling ◽  
Flood Frequency ◽  
Hazard Mapping ◽  
Small Scale ◽  
Ungauged Basins ◽  
Modeling Framework ◽  
Flood Simulations

Devastating floods are observed every year globally from upstream mountainous to coastal regions. Increasing flood frequency and impacts affect both major rivers and their tributaries. Nonetheless, at the small-scale, the lack of distributed topographic and hydrologic data determines tributaries to be often missing in inundation modeling and mapping studies. Advances in Unmanned Aerial Vehicle (UAV) technologies and Digital Elevation Models (DEM)-based hydrologic modeling can address this crucial knowledge gap. UAVs provide very high resolution and accurate DEMs with low surveying cost and time, as compared to DEMs obtained by Light Detection and Ranging (LiDAR), satellite, or GPS field campaigns. In this work, we selected a LiDAR DEM as a benchmark for comparing the performances of a UAV and a nation-scale high-resolution DEM (TINITALY) in representing floodplain topography for flood simulations. The different DEMs were processed to provide inputs to a hydrologic-hydraulic modeling chain, including the DEM-based EBA4SUB (Event-Based Approach for Small and Ungauged Basins) hydrologic modeling framework for design hydrograph estimation in ungauged basins; the 2D hydraulic model FLO-2D for flood wave routing and hazard mapping. The results of this research provided quantitative analyses, demonstrating the consistent performances of the UAV-derived DEM in supporting affordable distributed flood extension and depth simulations.

scholarly journals FEATURES OF EXCITATION AND AZIMUTHAL AND MERIDIONAL PROPAGATION OF LONG-PERIOD Pi3 OSCILLATIONS OF THE GEOMAGNETIC FIELD ON DECEMBER 8, 2017

2020 ◽  
Vol 6 (3) ◽  
pp. 56-72
Author(s):  
Aleksey Moiseev ◽  
Sergei Starodubtsev ◽  
Vladimir Mishin
Keyword(s):  
Geomagnetic Field ◽  
Large Scale ◽  
Current System ◽  
Dynamic Pressure ◽  
Small Scale ◽  
Frequency Range ◽  
Latitude Range ◽  
Magnetospheric Convection ◽  
Long Period ◽  
Geomagnetic Observations

We study the Pi3 pulsations (with a period T=15–30 min) that were recorded on December 8, 2017 at ground stations in the midnight sector of the magnetosphere at the latitude range of DP2 current system convective electrojets. We have found that Pi3 are especially pronounced in the pre-midnight sector with amplitude of up to 300 nT and duration of up to 2.5 hrs. The pulsation amplitude rapidly decreased with decreasing latitude from F′=72° to F′=63°. The event was recorded during the steady magnetospheric convection. In the southward Bz component of the interplanetary magnetic field, irregular oscillations were detected in the Pi3 frequency range. They correspond to slow magnetosonic waves occurring without noticeable variations in the dynamic pressure Pd. Ground-based geomagnetic observations have shown azimuthal propagation of pulsations with a 0.6–10.6 km/s velocity east and west of the midnight meridian. An analysis of the dynamics of pulsations along the meridian has revealed their propagation to the equator at a velocity 0.75–7.87 km/s. In the projection onto the magnetosphere, the velocities are close in magnitude to the observed propagation velocities of substorm injected electrons. In the dawn-side magnetosphere during ground-observed Pi3 pulsations, compression mode oscillations were recorded. We conclude that propagation of geomagnetic field oscillations in this event depends on the dynamics of particle injections under the action of a large-scale electric field of magnetospheric convection, which causes the plasma to move to Earth due to reconnection in the magnetotail. Small-scale oscillations in the magnetosphere were secondary, excited by the solar wind oscillations penetrating into the magnetosphere.

scholarly journals Abundances of Classical Cepheids and Evidence for Secondary Star-Formation

1987 ◽  
Vol 115 ◽  
pp. 545-547
Author(s):  
Sunetra Giridhar
Keyword(s):  
Galactic Plane ◽  
Equations Of Motion ◽  
Density Wave ◽  
Spiral Waves ◽  
Small Scale ◽  
Stellar Orbits ◽  
Secondary Star ◽  
Long Period ◽  
Runge Kutta Method ◽  
Classical Cepheids

In addition to the well-known radial abundance gradient in the disc of our Galaxy, there are indications of small-scale variations (Talent and Dufour 1979, Giridhar 1983). We have compiled spectroscopic abundances for long period Cepheids and to eliminate the effect of differences in ages, derived their places of formation by calculating their galactic orbits backwards in time. The stellar orbits were calculated considering the axisymmetric gravitational potential as well as the spiral potential due to the density wave. The parameters related to spiral waves are taken from Yuan (1969). The equations of motion in the (ζ, η, ξ) system were numerically integrated using the Runge-Kutta method and birthsites were transformed to (ζ, η) in the reference frame of the spiral pattern. The details of the computations are described by Giridhar (1985). In addition to the accepted value of 13.5 km s−1 kpc−1 for pattern velocity, birthsites were also calculated for ωp = 11.5 and 15.5 km s−1 kpc−1. Figure 1 shows the birthsites in the galactic plane for the three values of the pattern velocity. The Cepheids in the figure can be identified through the serial number in Table I which contains our compilation of Fe/H and derived birthsites. It is obvious from the figure that the systematic shifts in birthsites for different pattern velocities are not large enough to affect the assignment of birthsites to different arms.

scholarly journals Dynamically borrowing strength from another study through shrinkage estimation

2019 ◽  
Vol 29 (1) ◽  
pp. 293-308 ◽  
Author(s):  
Christian Röver ◽  
Tim Friede
Keyword(s):  
Controlled Trial ◽  
Meta Analysis ◽  
Randomized Study ◽  
Random Effect ◽  
Model Specification ◽  
Small Scale ◽  
Sources Of Information ◽  
Recent Trial ◽  
Modeling Framework ◽  
Clinical Registry

Meta-analytic methods may be used to combine evidence from different sources of information. Quite commonly, the normal–normal hierarchical model (NNHM) including a random-effect to account for between-study heterogeneity is utilized for such analyses. The same modeling framework may also be used to not only derive a combined estimate, but also to borrow strength for a particular study from another by deriving a shrinkage estimate. For instance, a small-scale randomized controlled trial could be supported by a non-randomized study, e.g. a clinical registry. This would be particularly attractive in the context of rare diseases. We demonstrate that a meta-analysis still makes sense in this extreme case, effectively based on a synthesis of only two studies, as illustrated using a recent trial and a clinical registry in Creutzfeld-Jakob disease. Derivation of a shrinkage estimate within a Bayesian random-effects meta-analysis may substantially improve a given estimate even based on only a single additional estimate while accounting for potential effect heterogeneity between the studies. Alternatively, inference may equivalently be motivated via a model specification that does not require a common overall mean parameter but considers the treatment effect in one study, and the difference in effects between the studies. The proposed approach is quite generally applicable to combine different types of evidence originating, e.g. from meta-analyses or individual studies. An application of this more general setup is provided in immunosuppression following liver transplantation in children.

scholarly journals From climatological to small-scale applications: simulating water isotopologues with ICON-ART-Iso (version 2.3)

2018 ◽  
Vol 11 (12) ◽  
pp. 5113-5133 ◽  
Author(s):  
Johannes Eckstein ◽  
Roland Ruhnke ◽  
Stephan Pfahl ◽  
Emanuel Christner ◽  
Christopher Diekmann ◽  
...  
Keyword(s):  
Water Cycle ◽  
Global Network ◽  
Small Scale ◽  
Modeling Framework ◽  
Flexible Tool ◽  
Daily Cycles ◽  
Tropopause Region ◽  
High Flexibility ◽  
Water Isotopologues ◽  
Δd And Δ18o

Abstract. We present the new isotope-enabled model ICON-ART-Iso. The physics package of the global ICOsahedral Nonhydrostatic (ICON) modeling framework has been extended to simulate passive moisture tracers and the stable isotopologues HDO and H218O. The extension builds on the infrastructure provided by ICON-ART, which allows for high flexibility with respect to the number of related water tracers that are simulated. The physics of isotopologue fractionation follow the model COSMOiso. We first present a detailed description of the physics of fractionation that have been implemented in the model. The model is then evaluated on a range of temporal scales by comparing with measurements of precipitation and vapor. A multi-annual simulation is compared to observations of the isotopologues in precipitation taken from the station network GNIP (Global Network for Isotopes in Precipitation). ICON-ART-Iso is able to simulate the main features of the seasonal cycles in δD and δ18O as observed at the GNIP stations. In a comparison with IASI satellite retrievals, the seasonal and daily cycles in the isotopologue content of vapor are examined for different regions in the free troposphere. On a small spatial and temporal scale, ICON-ART-Iso is used to simulate the period of two flights of the IAGOS-CARIBIC aircraft in September 2010, which sampled air in the tropopause region influenced by Hurricane Igor. The general features of this sample as well as those of all tropical data available from IAGOS-CARIBIC are captured by the model. The study demonstrates that ICON-ART-Iso is a flexible tool to analyze the water cycle of ICON. It is capable of simulating tagged water as well as the isotopologues HDO and H218O.

A multiscale method for wave propagation in 3D heterogeneous poroelastic media

Geophysics ◽  
2019 ◽  
Vol 84 (4) ◽  
pp. T237-T257
Author(s):  
Wensheng Zhang ◽  
Hui Zheng
Keyword(s):  
Wave Propagation ◽  
Computational Cost ◽  
Mesh Size ◽  
Multiscale Method ◽  
Small Scale ◽  
Physical Parameters ◽  
Local Problem ◽  
Wave Simulation ◽  
Poroelastic Media ◽  
Coarse Grids

A new multiscale method for wave simulation in 3D heterogeneous poroelastic media is developed. Wave propagation in inhomogeneous media involves many different scales of media. The physical parameters in the real media usually vary greatly within a very small scale. For the direct numerical methods for wave simulation, a refined grid is required in mesh generation to maintain the match between the mesh size and the material variations in the spatial scale. This greatly increases the computational cost and computer memory requirements. The multiscale method can overcome this difficulty due to the scale difference. The basic idea of our multiscale method is to construct computational schemes on two sets of meshes, i.e., coarse grids and fine grids. The finite-volume method is applied on the coarse grids, whereas the multiscale basis functions are computed with the finite-element method by solving a local problem on the fine grids. Moreover, the local problem only needs to be solved once before time stepping. This allows us to use a coarse grid while still capturing the information of the physical property variations in the small scale. Therefore, it has better accuracy than the single-scale method when they use the same coarse grids. The theoretical method and the dispersion analysis are investigated. Numerical computations with the perfectly matched layer boundary conditions are completed for 3D inhomogeneous poroelastic models with randomly distributed small scatterers. The results indicate that our multiscale method can effectively simulate wave propagation in 3D heterogeneous poroelastic media with a significant reduction in computation cost.

scholarly journals Long quasi-periodic oscillations of the faculae and pores

2019 ◽  
Vol 627 ◽  
pp. A10 ◽  
Author(s):  
A. Riehokainen ◽  
P. Strekalova ◽  
A. Solov’ev ◽  
V. Smirnova ◽  
I. Zhivanovich ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Stable Phase ◽  
Small Scale ◽  
Solar Photosphere ◽  
Periodic Oscillations ◽  
Magnetic Structures ◽  
Long Period ◽  
Continuum Intensity ◽  
Structurally Stable ◽  
The Continuum

Aims. The main goal of this work is to analyze the structural and temporal evolution of small-scale magnetic structures (SSMSs) observed in the solar atmosphere, such as solitary faculae and pores, and reveal long quasi-periodic oscillations of these structures. Methods. The statistical method of regression analysis and the wavelet transform were used to obtain the periods of oscillations and dependences between the parameters of magnetic structures and periods of oscillations. Results. Long-period oscillations with periods in the interval of 18−260 min are found for the structurally stable phase of SSMSs at the level of the solar photosphere. These long-period oscillations were interpreted as natural oscillations of the structurally stable long-lived magnetic structures around their equilibrium position. These oscillations, which are of similar nature, are observed in the chromospheric bright formations associated with photospheric SSMSs. Dependences between the magnetic field and the continuum intensity of the facula elements were found. It is shown that the continuum intensity of a SSMS decreases when its magnetic field increases.

scholarly journals A Novel Method for Analyzing Highly Renewable and Sector-Coupled Subnational Energy Systems—Case Study of Schleswig-Holstein

2021 ◽  
Vol 13 (7) ◽  
pp. 3852
Author(s):  
Md. Nasimul Islam Maruf
Keyword(s):  
Energy Demand ◽  
Power Plants ◽  
Energy Systems ◽  
Energy Transition ◽  
Energy Modeling ◽  
Offshore Wind ◽  
Small Scale ◽  
Modeling Framework ◽  
Ground Source Heat Pumps

The energy transition requires an integration of different energy carriers, including electricity, heat, and transport sectors. Energy modeling methods and tools are essential to provide a clear insight into the energy transition. However, the methodologies often overlook the details of small-scale energy systems. The study states an innovative approach to facilitate subnational energy systems with 100% renewable penetration and sectoral integration. An optimization model, the “Open Sector-coupled Energy Model for Subnational Energy Systems” (OSeEM–SN), was developed under the Open Energy Modeling Framework (Oemof). The model is validated using the case study of Schleswig-Holstein. The study assumes three scenarios representing 25%, 50%, and 100% of the total available biomass potentials. OSeEM–SN reaches feasible solutions without additional offshore wind investment, indicating that it can be reserved for supplying other states’ energy demand. The annual investment cost varies between 1.02 and 1.44 bn €/year for the three scenarios. The electricity generation decreases by 17%, indicating that, with high biomass-based combined heat and power plants, the curtailment from other renewable plants can be decreased. Ground source heat pumps dominate the heat mix; however, their installation decreases by 28% as the biomass penetrates fully into the energy mix. The validation confirms OSeEM–SN as a beneficial tool to examine different scenarios for subnational energy systems.

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