Geology & Geophysics Research Spotlight

From Magnetic Field Data, the Flow of Earth’s Core

How can researchers understand what happens at the center of the Earth when it can’t be measured directly?

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The velocity field and its associated intensity uncertainties at the level of the Earth’s core mantle boundary below Africa for the beginning of 2005. Credit: Baerenzung
The velocity field and its associated intensity uncertainties at the level of the Earth’s core mantle boundary below Africa for the beginning of 2005. Credit: Baerenzung

The outer core of the Earth is made of liquid metal, and its flow both affects and is affected by our planet’s core magnetic field. It is impossible to directly measure the outer core of the Earth, the outer boundary of which is about 2900 kilometers below our feet. However, the turbulence of the core’s liquid is so complex—including large-scale features and small-scale features—that it cannot be modeled as a simulation.

In a recent study, Baerenzung et al. developed a method to determine the flow of the core at the core-mantle boundary, using satellite-­collected information on the outer magnetic field. The authors focused on the large-scale behavior of the core, devising an equation to filter magnetic field data to leave out features smaller than 500 kilometers. Then they created an algorithm to figure out what behavior in the core would most likely result in a hypothetical set of magnetic field data.

After testing the process on made-up data, they created a snapshot of the speed and direction of flow of the outer core at the beginning of 2005, as well as the associated uncertainty. The map included several expected features, like the way that the liquid metal spirals on a planetary scale. (Journal of Geophysical Research: Solid Earth, doi:10.1002/​2013JB010358, 2014)

—Shannon Palus, Writer

 

Citation: Palus, S. (2014), From magnetic field data, the flow of Earth’s core, Eos Trans. AGU, 95(48), 452, doi:10.1002/2014EO480008

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