Earth's Magnetic Field Can Change Direction 10 times Faster than Thought

Earth's magnetic field appears to be able to change direction around 10 times faster than was previously thought, scientists have discovered. By recreating the last 100,000 years of the field's activity, researchers were able to show how it has changed over time. Findings showed sharp changes in direction tend to take place when the field is weakened locally, during periods of reversal.

The magnetic field is generated by the planet's liquid core, with the swirling motions of iron creating a field that extends out into space. It provides a barrier protecting Earth from harmful radiation from the sun, as well as helping to maintain our atmosphere by deflecting the solar wind—a stream of charged particles coming from the sun.

Movements of the liquid core mean the magnetic field is constantly changing. At times, it gets much weaker and the magnetic north and south poles flip. These periods are associated with increased radiation and have been linked with extinctions. Because changes take place over extremely long periods of time, understanding how, when and why it happens is challenging.

In a study published in Nature Communications, Christopher Davies, from the School of Earth and Environment at the U.K.'s University of Leeds, and Catherine Constable from the Scripps Institution of Oceanography, U.C. San Diego, have now looked at how quickly directional changes can take place.

Davies and Constable combined computer simulations of the geodynamo together with a recently published reconstruction of how it has changed over the last 100,000 years. This allowed them to show the speed of directional changes and events taking place with the magnetic field at these times.

Previous research had suggested rapid directional changes amounted to around one degree per year. However, the latest study suggests maximum rates of change can reach up to 10 degrees per year, which is "almost 100 times faster than current changes."

"The fastest changes that we have found generally occur in places and times when the field is unusually weak," Davies told Newsweek. Magnetic field reversals tend to take place when the field is weaker, potentially indicating a link between the two. "It is possible that the field is generally weak during reversals and so we might expect rapid changes in the field direction during reversals, but...this has not yet been investigated."

One extreme event saw the field direction change 2.5 degrees per year 39,000 years ago. This roughly coincides with a period when the magnetic field almost reversed. Known as the Laschamp event, the field weakened to around five percent what it is today and the magnetic north and south poles went on an excursion.

Findings also showed rapid directional changes tend to take place at lower latitudes, where the magnetic field is weaker generally. They said future research looking at rapid directional changes should focus on the lower latitudes. "Further study of the evolving dynamics in these simulations offers a useful strategy for documenting how such rapid changes occur and whether they are also found during times of stable magnetic polarity like what we are experiencing today," Constable said in a statement.

Davies said they plan to continue researching these shifts in the magnetic field: "Exploring the links between rapid directional changes and polarity reversals is certainly an interesting avenue," he said. "Also, we have only looked at the very fastest changes, but there is a whole spectrum of rates of change that may provide further insight into the dynamics of Earth's liquid core."

earth magnetic field
Representation of Earth's magnetic field. Researchers have found directional changes can take place ten times faster than previously thought. iStock