Articles | Volume 14, issue 12
https://doi.org/10.5194/se-14-1267-2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/se-14-1267-2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Earth's core variability from magnetic and gravity field observations
Anita Thea Saraswati
CORRESPONDING AUTHOR
Littoral, Environnement et Sociétés, La Rochelle Université and CNRS (UMR7266), La Rochelle, France
Centre National d’Etudes Spatiales, 2 Place Maurice Quentin, 75039, Paris, France
Olivier de Viron
Littoral, Environnement et Sociétés, La Rochelle Université and CNRS (UMR7266), La Rochelle, France
Mioara Mandea
Centre National d’Etudes Spatiales, 2 Place Maurice Quentin, 75039, Paris, France
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Anny Cazenave, Julia Pfeffer, Mioara Mandea, and Veronique Dehant
Earth Syst. Dynam., 14, 733–735, https://doi.org/10.5194/esd-14-733-2023, https://doi.org/10.5194/esd-14-733-2023, 2023
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While a 6-year oscillation has been reported for some time in the motions of the fluid outer core of the Earth, in the magnetic field and in the Earth rotation, novel results indicate that the climate system also oscillates at this 6-year frequency. This strongly suggests the existence of coupling mechanisms affecting the Earth system as a whole, from the deep Earth interior to the surface fluid envelopes.
Damien Delforge, Olivier de Viron, Marnik Vanclooster, Michel Van Camp, and Arnaud Watlet
Hydrol. Earth Syst. Sci., 26, 2181–2199, https://doi.org/10.5194/hess-26-2181-2022, https://doi.org/10.5194/hess-26-2181-2022, 2022
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Causal inference methods (CIMs) aim at identifying causal links from temporal dependencies found in time-series data. Using both synthetic data and real-time series from a karst system, we study and discuss the potential of four CIMs to reveal hydrological connections between variables in hydrological systems. Despite the ever-present risk of spurious hydrological connections, our results highlight that the nonlinear and multivariate CIM has a substantially lower false-positive rate.
Olivier de Viron, Michel Van Camp, Alexia Grabkowiak, and Ana M. G. Ferreira
Solid Earth, 12, 1601–1634, https://doi.org/10.5194/se-12-1601-2021, https://doi.org/10.5194/se-12-1601-2021, 2021
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As the travel time of seismic waves depends on the Earth's interior properties, seismic tomography uses it to infer the distribution of velocity anomalies, similarly to what is done in medical tomography. We propose analysing the outputs of those models using varimax principal component analysis, which results in a compressed objective representation of the model, helping analysis and comparison.
Mioara Mandea and Eduard Petrovský
Hist. Geo Space. Sci., 10, 163–172, https://doi.org/10.5194/hgss-10-163-2019, https://doi.org/10.5194/hgss-10-163-2019, 2019
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Throughout the International Union of Geodesy and Geophysics' (IUGG's) centennial anniversary, the International Association of Geomagnetism and Aeronomy is holding a series of activities to underline the ground-breaking facts in the area of geomagnetism and aeronomy. Over 100 years, the history of this research is rich, and here we present a short tour through some of the IAGA's major achievements, starting with the scientific landscape before IAGA, through its foundation until the present day.
Roman Sidorov, Anatoly Soloviev, Alexei Gvishiani, Viktor Getmanov, Mioara Mandea, Anatoly Petrukhin, and Igor Yashin
Ann. Geophys. Discuss., https://doi.org/10.5194/angeo-2018-111, https://doi.org/10.5194/angeo-2018-111, 2018
Manuscript not accepted for further review
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Decidated to the combined analysis of space weather data (geomagnetic activity, cosmic ray secondaries and ionospheric data) obtained during the September 2017 solar flares and geomagnetic storms, this study is an attempt to construct a technique for circumterrestrial physical data analysis in order to analyze various space weather effects and obtain new mutually supportive information during major space weather events on different phases of geomagnetic storm evolution.
Venera Dobrica, Crisan Demetrescu, and Mioara Mandea
Solid Earth, 9, 491–503, https://doi.org/10.5194/se-9-491-2018, https://doi.org/10.5194/se-9-491-2018, 2018
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By analyzing frequency constituents of declination secular variation at inter-decadal and sub-centennial timescales from geomagnetic observatories with data longer than 1 century and several historical data sets, we suggest that the geomagnetic jerk concept should be considered as a more general notion, namely the evolution of the secular variation as a result of the superposition of two (or more) constituents describing the effects of processes in the Earth’s core at two (or more) timescales.
Sébastien B. Lambert, Steven L. Marcus, and Olivier de Viron
Earth Syst. Dynam., 8, 1009–1017, https://doi.org/10.5194/esd-8-1009-2017, https://doi.org/10.5194/esd-8-1009-2017, 2017
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We explain how the extreme 2015–2016 El Niño event lengthened the day by 0.8 ms. The 2015–2016 event was an El Niño event of a different type compared to previous extreme events; thus, we expected different mechanisms of coupling with the solid Earth. We showed that the atmospheric torque on the American topography, usually acting alone during classical El Niños, was, in 2015–2016, augmented by a friction torque over the Pacific Ocean and inherent to the different nature of this particular event.
Mioara Mandea and Jean-Louis Le Mouël
Hist. Geo Space. Sci., 7, 73–77, https://doi.org/10.5194/hgss-7-73-2016, https://doi.org/10.5194/hgss-7-73-2016, 2016
Monika Korte and Mioara Mandea
Solid Earth, 7, 751–768, https://doi.org/10.5194/se-7-751-2016, https://doi.org/10.5194/se-7-751-2016, 2016
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We investigated characteristics of magnetic anomalies over southern Africa (South Africa, Namibia, and Botswana) and Germany on different scales and also compared them to gravity gradient anomalies. Such anomalies provide information relevant to understanding geological and tectonic structures. Our results indicate a better agreement between anomalies caused by shallow and deeper structures in the southern African area than in the German area.
G. Verbanac, M. Mandea, M. Bandić, and S. Subašić
Solid Earth, 6, 775–781, https://doi.org/10.5194/se-6-775-2015, https://doi.org/10.5194/se-6-775-2015, 2015
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This study of crustal monthly biases' temporal evolution at 42 geomagnetic observatories over 9 years of the CHAMP satellite mission reveals
short-period variations and long-term trends in the bias time series, signature of the induced magnetic fields, annual trends in most bias series, distinct oscillatory pattern over the whole time span, and semi-annual variations in all components. Swarm mission data and analysis of these findings will allow a better understanding of crustal bias evolution.
A. Khokhlov, J. L. Le Mouël, and M. Mandea
Geosci. Instrum. Method. Data Syst., 2, 1–9, https://doi.org/10.5194/gi-2-1-2013, https://doi.org/10.5194/gi-2-1-2013, 2013
Related subject area
Subject area: Core and mantle structure and dynamics | Editorial team: Geodesy, gravity, and geomagnetism | Discipline: Geodynamics
Magma ascent mechanisms in the transition regime from solitary porosity waves to diapirism
Pragmatic solvers for 3D Stokes and elasticity problems with heterogeneous coefficients: evaluating modern incomplete LDLT preconditioners
GHOST: Geoscientific Hollow Sphere Tessellation
Janik Dohmen and Harro Schmeling
Solid Earth, 12, 1549–1561, https://doi.org/10.5194/se-12-1549-2021, https://doi.org/10.5194/se-12-1549-2021, 2021
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In partially molten regions within the Earth, the melt is able to move separately from the surrounding rocks. This allows for the emergence of so-called solitary porosity waves, driven by compaction and decompaction due to the melt with higher buoyancy. Our numerical models can predict whether a partially molten region will ascend dominated by solitary waves or diapirism. Even in diapiris-dominated regions, solitary waves will build up and ascend as a swarm when the ascend time is long enough.
Patrick Sanan, Dave A. May, Matthias Bollhöfer, and Olaf Schenk
Solid Earth, 11, 2031–2045, https://doi.org/10.5194/se-11-2031-2020, https://doi.org/10.5194/se-11-2031-2020, 2020
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Mantle and lithospheric dynamics, elasticity, subsurface flow, and other fields involve solving indefinite linear systems. Tools include direct solvers (robust, easy to use, expensive) and advanced iterative solvers (complex, problem-sensitive). We show that a third option, ILDL preconditioners, requires less memory than direct solvers but is easy to use, as applied to 3D problems with parameter jumps. With included software, we hope to allow researchers to solve previously infeasible problems.
Cedric Thieulot
Solid Earth, 9, 1169–1177, https://doi.org/10.5194/se-9-1169-2018, https://doi.org/10.5194/se-9-1169-2018, 2018
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I present the GHOST (Geoscientific Hollow Sphere Tessellation) software which allows for the fast generation of computational meshes in hollow sphere geometries counting up to a hundred million cells. Each mesh is composed of concentric spherical shells made of quadrilaterals or triangles. I focus here on three commonly used meshes used in the geodynamics/geophysics community and further benchmark the gravity and gravitational potential procedures in the simple case of a constant density.
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Short summary
To understand core dynamics, insight from several possible observables is needed. By applying several separation methods, we show spatiotemporal variabilities in the magnetic and gravity fields related to the core dynamics. A 7-year oscillation is found in all conducted analyses. The results in the magnetic field reflect the core processes and the variabilities in the gravity field exhibit new findings that might be an interesting input to build an enhanced model of the Earth’s core.
To understand core dynamics, insight from several possible observables is needed. By applying...