Article
Geochemistry & Geophysics
M. Istas, N. Gillet, C. C. Finlay, M. D. Hammer, L. Huder
Summary: In this study, the pygeodyn data assimilation tool is used to analyze ground and satellite-based geomagnetic data sets. The dynamics of the Earth's outer core on interannual to decadal timescales is investigated, and new findings on the operation of quasi-geostrophic Magneto-Coriolis waves are reported. An improved ensemble Kalman filter algorithm is introduced, which takes into account cross-correlations between variables, resulting in better stability and reduced computational cost. The updated scheme also allows for the use of observations in different forms, enabling global constraints on core dynamics even at short periods.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Magnus D. Hammer, Christopher C. Finlay, Nils Olsen
Summary: In this study, local time-series of the magnetic field gradient tensor elements at satellite altitude were derived using a Geomagnetic Virtual Observatory (GVO) approach. The derived gradient element time-series allow for global investigations of spatio-temporal variations in the gradient tensor elements. Evidence for a regional increase event in 2017 was found based on the first time derivative of the gradient tensor elements.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Geochemistry & Geophysics
G. Ropp, V Lesur
Summary: A series of models of the Earth magnetic field and core surface flow have been estimated from 1999 to 2022 using magnetic satellite and ground observatory data. The models show characteristics similar to previous models, but with higher time resolution. Principal component analysis reveals that the largest flow variations occur at high latitudes and under the western part of the Pacific Ocean. Filtering out longer flow variation periods leads to a filtered azimuthal flow with approximately 7-year periodicities propagating westward. These patterns are mainly present at mid- and equatorial latitudes and are compatible with perturbations in the main flow caused by small columnar flows intersecting the core-mantle boundary.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Materials Science, Multidisciplinary
Anil K. Bastola, Mokarram Hossain
Summary: Magnetoactive soft materials (MSMs) are emerging as a promising class of smart materials with applications in artificial muscles, soft robotics, drug delivery, surgery, and metamaterials. They offer advantages such as remote actuation, high strain and strain rate, self-sensing, and fast response, making them ideal for shape morphing, dynamic locomotion, and reconfigurable structures. This review article provides a comprehensive overview of MSMs and discusses future perspectives for developing multifunctional magnetoactive devices.
MATERIALS & DESIGN
(2021)
Article
Geochemistry & Geophysics
Wolfgang Szwillus, Eldar Baykiev, Yixiati Dilixiati, Joerg Ebbing
Summary: Estimating the depth to magnetic bottom (DTB) is a challenging problem in potential field inversion. Spectral methods, the most popular approach, have been questioned for their reliability. This study proposes a Bayesian approach to estimate susceptibility and DTB from magnetic data using a two-step inversion procedure. The uncertainties due to unknown hyperparameters are rigorously propagated, and pointwise constraints based on heat flow measurements can be easily included. Synthetic tests and application to real data demonstrate the accuracy and applicability of the new algorithm.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Geochemistry & Geophysics
Nils Olsen
Summary: The sensitivity of magnetic measurements taken by satellites in elliptical orbits to the lithospheric magnetic field is studied. The variances of the lithospheric Gauss coefficients for different satellite orbital constellations are compared and analytical expressions for the variances are presented. It is found that low-altitude magnetic data collected by satellites in low-perigee elliptical orbits enable improved global lithospheric field modelling at spatial wavelengths beyond what is currently possible with data from satellites in circular orbits.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Artem Gorbunov, Stephen Fraser, Prince Cuffey, Emmanuel Lansana, Henry Deen, Tim Archer
Summary: In 2019, a nationwide airborne geophysical survey was conducted in Sierra Leone to provide a national geoscientific benchmark and attract foreign investment. Self-organizing maps and neural network products were used to challenge subjective interpretation workflows and enhance geological understanding.
GEOPHYSICAL PROSPECTING
(2023)
Article
Multidisciplinary Sciences
Chengying Liu, Junsheng Nie, Zaijun Li, Qingqing Qiao, Jordan T. Abell, Fei Wang, Wenjiao Xiao
Summary: This study examines environmental records based on magnetic parameters from the Tengger Desert in China over the past 3 million years. It reveals wet-dry cycles with a dominant frequency of 405 kiloyears, with drier intervals corresponding to eccentricity minima, consistent with previous reconstructions of East Asian summer and North African summer monsoon precipitation variability.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2021)
Article
Materials Science, Multidisciplinary
Chennakesava Kadapa, Mokarram Hossain
Summary: This paper investigates the magnetization mechanisms, response behaviors, and simulation framework of magneto-active polymers (MAPs), as well as explores the characteristics and behaviors of MAPs under different conditions.
MECHANICS OF MATERIALS
(2022)
Review
Computer Science, Information Systems
Reda Bakri, Gautier Corgne, Xavier Margueron
Summary: High-frequency and high-power density converters are important for various applications. Planar magnetic components are being increasingly used in power electronic converters due to their advantages, and thermal modeling plays a crucial role in enhancing their performance. This paper presents a literature review and multicriteria comparison of studies on the thermal modeling of planar magnetics, and addresses key points and issues to guide designers.
Article
Geochemistry & Geophysics
Gordon R. J. Cooper
Summary: Source-distance methods can be used to locate the position and depth of potential field sources. By improving the existing analytic signal amplitude-based methods, they can be more flexible in the orders of analytic signal amplitude that they use. This not only enhances their robustness against noise and interference, but also allows the reliability of the results to be assessed by repeating the methods using different orders.
GEOPHYSICAL PROSPECTING
(2023)
Article
Geochemistry & Geophysics
William Morris, Hernan Ugalde, Moritz Kirsch, Richard Gloaguen, Malte Ibs-von Seht, Bernhard Siemon, Uwe Meyer
Summary: This research examines magnetic data and applies various methods to locate anomalous anthropogenic signals. The probable origin of each specific pattern can be differentiated using a 2D shape index and increased flight height. Verification of anthropogenic anomalies is achieved by comparing anomalous solution grids with GIS-based reference data.
GEOPHYSICAL PROSPECTING
(2022)
Review
Nanoscience & Nanotechnology
Shinji Isogami, Yukiko K. Takahashi
Summary: Light elements such as B, C, and N play a crucial role in various functional materials and have attracted considerable attention in recent years. In this article, the evolution and utilization of light elements are reviewed, and their representative applications and characteristics are highlighted. Additionally, the effect of B and C on magnetic structures is discussed, and future strategies for practical material development are proposed.
ADVANCED ELECTRONIC MATERIALS
(2023)
Article
Engineering, Electrical & Electronic
Michael D'Antonio, Shiladri Chakraborty, Alireza Khaligh
Summary: This article introduces a novel planar-based transformer design with controllable leakage inductance, utilizing semi-interleaved windings and a leakage flux core leg with a horizontal air gap. Through detailed reluctance modeling and a genetic algorithm-based optimization, it is shown that the proposed transformer design outperforms other integrated magnetic structures in terms of efficiency, footprint area, and parasitic capacitance. Fabricated designs based on the optimization analysis show theoretical efficiency drops of 1.19% and 0.83%, demonstrating improvements in electrical and thermal performance for microinverter applications.
IEEE TRANSACTIONS ON POWER ELECTRONICS
(2021)
Article
Engineering, Electrical & Electronic
Blaz Jelenc
Summary: The article discusses two methods of generating a uniform magnetic field in an arbitrary 2-D polygonal region - using electrical surface currents with locally constant current densities and using permanently magnetized materials with locally constant magnetizations.
IEEE TRANSACTIONS ON MAGNETICS
(2021)
Article
Geochemistry & Geophysics
T. Leveque, C. Fallet, M. Mandea, R. Biancale, J. M. Lemoine, S. Tardivel, S. Delavault, A. Piquereau, S. Bourgogne, F. Pereira Dos Santos, B. Battelier, Ph. Bouyer
Summary: The French National Center for Space Studies conducted an evaluation study called GRICE to explore the impact of cold atom technologies on space geodesy missions and end users of geodetic data. They proposed a mission scenario for gravity field mapping based on a long baseline gradiometer and conducted simulations to assess the performance of the mission.
JOURNAL OF GEODESY
(2021)
Article
Geosciences, Multidisciplinary
P. Alken, E. Thebault, C. D. Beggan, H. Amit, J. Aubert, J. Baerenzung, T. N. Bondar, W. J. Brown, S. Califf, A. Chambodut, A. Chulliat, G. A. Cox, C. C. Finlay, A. Fournier, N. Gillet, A. Grayver, M. D. Hammer, M. Holschneider, L. Huder, G. Hulot, T. Jager, C. Kloss, M. Korte, W. Kuang, A. Kuvshinov, B. Langlais, J. -M. Leger, V. Lesur, P. W. Livermore, F. J. Lowes, S. Macmillan, W. Magnes, M. Mandea, S. Marsal, J. Matzka, M. C. Metman, T. Minami, A. Morschhauser, J. E. Mound, M. Nair, S. Nakano, N. Olsen, F. J. Pavon-Carrasco, V. G. Petrov, G. Ropp, M. Rother, T. J. Sabaka, S. Sanchez, D. Saturnino, N. R. Schnepf, X. Shen, C. Stolle, A. Tangborn, L. Toffner-Clausen, H. Toh, J. M. Torta, J. Varner, F. Vervelidou, P. Vigneron, I. Wardinski, J. Wicht, A. Woods, Y. Yang, Z. Zeren, B. Zhou
Summary: The IAGA V-MOD working group adopted the thirteenth generation of the IGRF in December 2019, which includes definitive main field models for epoch 2015.0 and 2020.0, as well as predictive linear secular variations for 2020.0 to 2025.0. This update provides equations, spherical harmonic coefficients, and maps for magnetic parameters and their predicted changes from 2020.0 to 2025.0.
EARTH PLANETS AND SPACE
(2021)
Article
Geosciences, Multidisciplinary
Alexandre Fournier, Julien Aubert, Vincent Lesur, Guillaume Ropp
Summary: This paper presents a candidate secular variation model for the 13th generation of the International Geomagnetic Reference Field, based on an ensemble of 100 numerical models integrated between 2019.0 and 2025.0. By adjusting 100 different initial conditions extracted from a dynamo simulation to account for the geomagnetic field estimate for 2019.0, the model provides insights into the geomagnetic secular variation up to epoch 2025.0.
EARTH PLANETS AND SPACE
(2021)
Article
Geosciences, Multidisciplinary
P. Alken, E. Thebault, C. D. Beggan, J. Aubert, J. Baerenzung, W. J. Brown, S. Califf, A. Chulliat, G. A. Cox, C. C. Finlay, A. Fournier, N. Gillet, M. D. Hammer, M. Holschneider, G. Hulot, M. Korte, V. Lesur, P. W. Livermore, F. J. Lowes, S. Macmillan, M. Nair, N. Olsen, G. Ropp, M. Rother, N. R. Schnepf, C. Stolle, H. Toh, F. Vervelidou, P. Vigneron, I. Wardinski
Summary: The 13th revision of the International Geomagnetic Reference Field (IGRF) was released in December 2019, comprising two new main field models and a model of predicted secular variation. These models were produced from candidates submitted by fifteen international teams. The evaluation process, final product derivation approach, and retrospective analysis of the IGRF-12 SV candidates are documented in this study, suggesting potential benefits of combining core modeling with satellite observations for forecasting secular variation.
EARTH PLANETS AND SPACE
(2021)
Review
Astronomy & Astrophysics
D. Heyner, H. -U. Auster, K. -H. Fornacon, C. Carr, I. Richter, J. Z. D. Mieth, P. Kolhey, W. Exner, U. Motschmann, W. Baumjohann, A. Matsuoka, W. Magnes, G. Berghofer, D. Fischer, F. Plaschke, R. Nakamura, Y. Narita, M. Delva, M. Volwerk, A. Balogh, M. Dougherty, T. Horbury, B. Langlais, M. Mandea, A. Masters, J. S. Oliveira, B. Sanchez-Cano, J. A. Slavin, S. Vennerstrom, J. Vogt, J. Wicht, K. -H. Glassmeier
Summary: The paper introduces the MPO-MAG magnetometer instrument on-board the Mercury Planetary Orbiter, including its design, calibration, and scientific goals. The instrument will map the planetary magnetic field at Mercury to determine the dynamo generated field and constrain the secular variation. Studying induced magnetic fields and field-aligned currents will help to constrain the interior structure, while also studying dynamical phenomena at the Hermean magnetopause and magnetospheric cusps. During the cruise to Mercury, MPO-MAG will also contribute to studies of solar wind turbulence and transient phenomena.
SPACE SCIENCE REVIEWS
(2021)
Article
Geochemistry & Geophysics
Mathieu Dumberry, Mioara Mandea
Summary: Fluid motion in the Earth's liquid outer core leads to internal mass redistribution and global gravity variations. Core processes contribute significantly less to gravity variations and ground deformations compared to dynamic processes in the fluid layers at the Earth's surface, making it challenging to extract the core signal.
SURVEYS IN GEOPHYSICS
(2022)
Article
Geochemistry & Geophysics
V Lesur, N. Gillet, M. D. Hammer, M. Mandea
Summary: This paragraph discusses the evidence of fast variations in the Earth's core field observed in magnetic observatory and satellite records. It explains how these variations are identified at the Earth's surface and characterized by satellite data. The paragraph also mentions the extraction of their properties at the core mantle boundary through localized and global modeling processes, with emphasis on their time scales. Finally, it lists the possible types of waves in the liquid outer core that may cause these observed fast variations.
SURVEYS IN GEOPHYSICS
(2022)
Article
Geosciences, Multidisciplinary
Alexandre Fournier, Julien Aubert, Vincent Lesur, Erwan Thebault
Summary: Each IGRF model includes a secular variation component describing the evolution of the main magnetic field for the next 5 years, with each Gauss coefficient assumed to undergo independent linear evolution. Physics-based forecasts for candidate SV models have increased, driven by satellite data spanning over two decades and progress in numerical modeling of Earth's core dynamics. Rapid geomagnetic variations identified in satellite data can impact the quality of IGRF predictions, necessitating frameworks that incorporate short-term geomagnetic processes.
EARTH PLANETS AND SPACE
(2021)
Article
Geochemistry & Geophysics
I Wardinski, H. Amit, B. Langlais, E. Thebault
Summary: By utilizing MESSENGER probe data, the study infers the internal structure of Mercury's core and suggests that the inner core size ranges from 500 to 660 km, with a corresponding stratified layer thickness of 880 to 500 km. The research provides new insights into the core structure of a planet based on magnetic field observations.
JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
(2021)
Editorial Material
Geochemistry & Geophysics
Veronique Dehant, Mioara Mandea, Anny Cazenave, Lorena Moreira
SURVEYS IN GEOPHYSICS
(2022)
Article
Geochemistry & Geophysics
G. Ropp, V Lesur
Summary: A series of models of the Earth magnetic field and core surface flow have been estimated from 1999 to 2022 using magnetic satellite and ground observatory data. The models show characteristics similar to previous models, but with higher time resolution. Principal component analysis reveals that the largest flow variations occur at high latitudes and under the western part of the Pacific Ocean. Filtering out longer flow variation periods leads to a filtered azimuthal flow with approximately 7-year periodicities propagating westward. These patterns are mainly present at mid- and equatorial latitudes and are compatible with perturbations in the main flow caused by small columnar flows intersecting the core-mantle boundary.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
T. Schwaiger, D. Jault, N. Gillet, N. Schaeffer, M. Mandea
Summary: Inference of fluid motion below the core-mantle boundary from geomagnetic observations is a highly non-unique inverse problem. A new method is proposed that provides a unique local estimate of the velocity field by assuming quasi-geostrophic flow and neglecting magnetic diffusion. The method overcomes the underdetermination by inverting the flow at each point of a spherical grid representing the core surface and mitigates the unreliable reconstruction of small-scale flows by smoothing the velocity field using Gaussian process regression.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Arnaud Pollet, David Coulot, Richard Biancale, Felix Perosanz, Sylvain Loyer, Jean-Charles Marty, Susanne Glaser, Vladimir Schott-Guilmault, Jean-Michel Lemoine, Flavien Mercier, Samuel Nahmani, Mioara Mandea
Summary: The geoscience community set a goal of 1 mm accuracy and 0.1 mm/yr stability for the terrestrial reference frame (TRF) realization in 2009. However, the last International Terrestrial Reference Frame has not yet reached this target. To achieve this goal, the use of multi-technique satellites as space-ties has been studied since 2011 and proposals have been made in response to different space agency calls.
JOURNAL OF GEODESY
(2023)