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Geomagnetic spikes on the core-mantle boundary
Christopher Davies1,2, Catherine Constable2
1School of Earth &Environment, University of Leeds, Leeds LS2 9JT, UK.
Nature Communications
|May 31, 2017
Summary
Earth's magnetic field experienced extreme fluctuations around 1000 BC in the Levant. This study links these spikes to intense core-mantle boundary (CMB) flux patches, offering new insights into geomagnetic field dynamics.
Area of Science:
- Geophysics
- Earth Science
- Paleomagnetism
Background:
- Earth's magnetic field intensity showed extreme variations in the Levant around 1000 BC.
- A direct link between this regional intensity spike and the global geodynamo has been lacking.
Purpose of the Study:
- To investigate the origin and spatial extent of the 1000 BC Levantine magnetic field spike.
- To determine if the spike originated from the core-mantle boundary (CMB) and its geometric constraints.
Main Methods:
- Geodynamic modeling incorporating energetic and geometric constraints.
- Analysis of paleomagnetic data, considering age uncertainties.
Main Results:
- The Levantine spike, if from the CMB, must span over 60° longitude.
- Models suggest CMB spikes are 8-22° wide, reaching intensities around 100 mT.
- Some low-intensity data are inconsistent with the spike's geometric extent, possibly predating it.
Conclusions:
- The Levantine spike likely originated from an intense, localized CMB flux patch.
- This patch may have grown and migrated, influencing the global dipole field.
- Geomagnetic spike decay is likely governed by diffusive processes and Ohmic heating.
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