Professor Publishes New Theory Concerning the Earth’s Magnetic Field

June 15, 2009

It’s one of the oldest mysteries of science: Where does the Earth’s magnetic field come from? Research from Northwestern University offers a new take on an old problem.

Throughout history, scientists have offered different answers. First: from the Heavens. Then: the Earth is a big permanent magnet. Finally: the Earth’s core. For the past half-century, scientists have believed that the flow of fluid in the Earth’s core creates both the magnetic field itself and its variation with time. Even though there is no way to prove this — one cannot observe or measure the flow of the fluid at the core — it has become the leading theory in the field.

But Gregory Ryskin, associate professor of chemical and biological engineering at the McCormick School of Engineering and Applied Science at Northwestern University, now offers a different theory: the electricity-conducting oceans that cover more than two-thirds of the Earth are responsible for causing the slow (“secular”) changes in the magnetic field. His research was recently published by Britain’s Institute of Physics’s New Journal of Physics.

The controversial theory stems from Ryskin’s dissatisfaction with the prevailing theory that the fluid core — which is about 7,000 kilometers across around a solid core with a 1,200-kilometer radius — flows in swirls, conducting electricity and creating the magnetic field. The theory seemed plausible enough, but that wasn’t enough for Ryskin.

“In principle, it’s possible,” he says. “But I wanted to check to see whether it was possible that the ocean flow is inducing changes in the magnetic field.”

Using theories of electromagnetism and fluid dynamics, Ryskin looked at the way the Earth’s magnetic field shifts and changes — a phenomenon called secular variation. He found, among other things, that there was a connection between sharp changes in the rate of the ocean’s circulation and geomagnetic jerks, which are sharp changes in the magnetic field’s secular variation.

The Earth’s magnetic field has a more important job than just guiding compasses: it extends thousands of miles into space and protects the world from harmful radiation.

The calculations took several years to complete, and though the research is sure to be controversial, Ryskin is confident in his results.

“I have not proven it beyond doubt — it will require more work by others,” he says. “But there is a good probability that this is where it comes from.”

Read an article on the research in The Times of London.

- Emily Ayshford