Rapid geomagnetic changes inferred from Earth observations and numerical simulations
Christopher J Davies1, Catherine G Constable2
1School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK. c.davies@leeds.ac.uk.
Nature Communications
|July 8, 2020
Summary
Earth's magnetic field can change direction extremely rapidly, up to ~10° per year, especially when the field strength decreases. These findings from geodynamo simulations and paleomagnetic data suggest these rapid changes originate from core surface flux movement.
Area of Science:
- Geophysics
- Earth Science
- Dynamo Theory
Background:
- Earth's magnetic field direction exhibits extreme variations, offering insights into geodynamo processes.
- Previous paleomagnetic studies reported controversial rapid directional changes (up to 1°/yr), with unknown physical origins in the Earth's core.
Purpose of the Study:
- To investigate the physical processes behind extreme directional changes in Earth's magnetic field.
- To compare geodynamo simulation results with observational paleomagnetic field models.
Main Methods:
- Analysis of a suite of geodynamo simulations.
- Comparison with a recent observational field model covering the past 100,000 years.
- Utilized a simple analogue model to understand flux movement dynamics.
Main Results:
- Excellent agreement was found between simulation and observational data for extreme directional change amplitudes and latitude ranges.
- Maximum rates of directional change reached approximately 10°/yr, significantly faster than current changes.
- These rapid changes predominantly occurred during periods of decreasing magnetic field strength.
Conclusions:
- Extreme magnetic field directional changes are compatible with the physics of the geodynamo process.
- The movement of reversed flux across the core surface is strongly associated with these rapid variations.
- Future research on rapid directional changes should prioritize investigations in low-latitude regions.
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