Journal
GEOPHYSICAL RESEARCH LETTERS
Volume 48, Issue 4, Pages -Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1029/2020GL090803
Keywords
core dynamics; Magneto‐ Coriolis modes; MHD modes; secular variations
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Funding
- Labex OSUG@2020 [ANR10 LABX56]
- European Space Agency [4000127193/19/NL/IA]
- CNES (Centre National d'Etudes Spatiales, France)
- SNF [200021_185088]
- Swiss National Science Foundation (SNF) [200021_185088] Funding Source: Swiss National Science Foundation (SNF)
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The study proposes a hybrid QG model to explain the fast changes in Earth's magnetic field, identifying modes with periods of a few years at parameters relevant to the Earth's core. It demonstrates a concentration of energy in the equatorial region for a simple poloidal magnetic field considered here. The high frequency and energy concentration near the equator make these modes a plausible mechanism for explaining similar features observed in recent geomagnetic field observations.
Fast changes of Earth's magnetic field could be explained by inviscid and diffusion-less quasi-geostrophic (QG) Magneto-Coriolis modes. We present a hybrid QG model with columnar flows and three-dimensional magnetic fields and find modes with periods of a few years at parameters relevant to Earth's core. For the simple poloidal magnetic field that we consider here they show a localization of kinetic and magnetic energy in the equatorial region. This concentration of energy near the equator and the high frequency make them a plausible mechanism to explain similar features observed in recent geomagnetic field observations. Our model potentially opens a way to probe the otherwise inaccessible magnetic field structure in the Earth's outer core.
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