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Satellite magnetic data reveal interannual waves in Earth’s core

The Earth’s magnetic field displays variations on a broad range of time scales, from years to hundreds of millions of years. The last two decades of global and continuous satellite geomagnetic field monitoring have considerably enriched the knowledge on the rapid physical processes taking place in t...

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Autores principales: Gillet, Nicolas, Gerick, Felix, Jault, Dominique, Schwaiger, Tobias, Aubert, Julien, Istas, Mathieu
Formato: Online Artículo Texto
Lenguaje:English
Publicado: National Academy of Sciences 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9060525/
https://www.ncbi.nlm.nih.gov/pubmed/35312364
http://dx.doi.org/10.1073/pnas.2115258119
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author Gillet, Nicolas
Gerick, Felix
Jault, Dominique
Schwaiger, Tobias
Aubert, Julien
Istas, Mathieu
author_facet Gillet, Nicolas
Gerick, Felix
Jault, Dominique
Schwaiger, Tobias
Aubert, Julien
Istas, Mathieu
author_sort Gillet, Nicolas
collection PubMed
description The Earth’s magnetic field displays variations on a broad range of time scales, from years to hundreds of millions of years. The last two decades of global and continuous satellite geomagnetic field monitoring have considerably enriched the knowledge on the rapid physical processes taking place in the Earth’s outer core. Identification of axisymmetric torsional Alfvén waves with subdecadal periods from observatory and satellite data has given access to an averaged intensity of the magnetic field in the Earth’s core interior. A significant part of the rapid signal, however, resides in nonaxisymmetric motions. Their origin has remained elusive, as previous studies of magnetohydrodynamic waves in the Earth’s core mainly focused on their possible signature on centennial time scales. Here, we identify nonaxisymmetric wavelike patterns in the equatorial region of the core surface from the observed geomagnetic variations. These wavelike features have large spatial scales, interannual periods in the vicinity of 7 y, amplitudes reaching 3 km/y, and coherent westward drift at phase speeds of about 1,500 km/y. We interpret and model these flows as the signature of Magneto–Coriolis (MC) eigenmodes. Their identification offers a way to probe the cylindrical radial component of the magnetic field inside Earth’s core. It follows from our work that there is no need for a stratified layer at the top of the core to account for the rapid geomagnetic field changes.
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spelling pubmed-90605252022-09-21 Satellite magnetic data reveal interannual waves in Earth’s core Gillet, Nicolas Gerick, Felix Jault, Dominique Schwaiger, Tobias Aubert, Julien Istas, Mathieu Proc Natl Acad Sci U S A Physical Sciences The Earth’s magnetic field displays variations on a broad range of time scales, from years to hundreds of millions of years. The last two decades of global and continuous satellite geomagnetic field monitoring have considerably enriched the knowledge on the rapid physical processes taking place in the Earth’s outer core. Identification of axisymmetric torsional Alfvén waves with subdecadal periods from observatory and satellite data has given access to an averaged intensity of the magnetic field in the Earth’s core interior. A significant part of the rapid signal, however, resides in nonaxisymmetric motions. Their origin has remained elusive, as previous studies of magnetohydrodynamic waves in the Earth’s core mainly focused on their possible signature on centennial time scales. Here, we identify nonaxisymmetric wavelike patterns in the equatorial region of the core surface from the observed geomagnetic variations. These wavelike features have large spatial scales, interannual periods in the vicinity of 7 y, amplitudes reaching 3 km/y, and coherent westward drift at phase speeds of about 1,500 km/y. We interpret and model these flows as the signature of Magneto–Coriolis (MC) eigenmodes. Their identification offers a way to probe the cylindrical radial component of the magnetic field inside Earth’s core. It follows from our work that there is no need for a stratified layer at the top of the core to account for the rapid geomagnetic field changes. National Academy of Sciences 2022-03-21 2022-03-29 /pmc/articles/PMC9060525/ /pubmed/35312364 http://dx.doi.org/10.1073/pnas.2115258119 Text en Copyright © 2022 the Author(s). Published by PNAS. https://creativecommons.org/licenses/by-nc-nd/4.0/This article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND) (https://creativecommons.org/licenses/by-nc-nd/4.0/) .
spellingShingle Physical Sciences
Gillet, Nicolas
Gerick, Felix
Jault, Dominique
Schwaiger, Tobias
Aubert, Julien
Istas, Mathieu
Satellite magnetic data reveal interannual waves in Earth’s core
title Satellite magnetic data reveal interannual waves in Earth’s core
title_full Satellite magnetic data reveal interannual waves in Earth’s core
title_fullStr Satellite magnetic data reveal interannual waves in Earth’s core
title_full_unstemmed Satellite magnetic data reveal interannual waves in Earth’s core
title_short Satellite magnetic data reveal interannual waves in Earth’s core
title_sort satellite magnetic data reveal interannual waves in earth’s core
topic Physical Sciences
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9060525/
https://www.ncbi.nlm.nih.gov/pubmed/35312364
http://dx.doi.org/10.1073/pnas.2115258119
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