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How does Earth’s liquid outer core generate the geomagnetic field?
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Ionosphere and magnetosphere
The layers of Earth's atmosphere, with a yellow line showing the air temperature at various heights.
Earth’s geomagnetic field is generated by the geomagnetic dynamo, a process occurring within the planet's electrically conducting liquid outer core. This mechanism relies on the interaction between fluid motion, rotation, and magnetic fields.12
The Dynamo Mechanism
The core consists of liquid iron, which is an excellent electrical conductor. As this fluid moves, it carries existing magnetic field lines with it. The motion of this conducting material across the magnetic field generates an electric current, which in turn produces a secondary magnetic field. This secondary field reinforces the original, creating a self-sustaining system.12
Driving Forces
- Convection: The fluid motion is primarily driven by thermal convection. As the inner core slowly freezes, it releases energy that heats the surrounding liquid, causing hot, buoyant fluid to rise toward cooler regions.1
- Coriolis Force: Because Earth rotates, the Coriolis force acts on the rising fluid, introducing twists and helical motions. These twists are essential for distorting the magnetic field lines into the complex, self-sustaining patterns that maintain the geomagnetic field.13