Simulations show that the magnetic field can change 10 times faster than previously thought

A new study by the University of Leeds and the University of California at San Diego reveals that changes in the direction of Earth’s magnetic field can take place 10 times faster than previously thought.

Their study offers a new insight into the spiraling flux of iron 2,800 kilometers below the planet’s surface and how it has influenced the movement of the magnetic field for the past hundred thousand years.

Our magnetic field is generated and maintained by a convective flux of molten metal that forms the Earth’s outer core. The movement of liquid iron creates the electrical currents that feed the field, which not only helps guide navigation systems, but also protects us from harmful extraterrestrial radiation and keeps our atmosphere in place.

The magnetic field is constantly changing. Satellites now provide new means of measuring and tracking your current changes, but the field existed long before the invention of man-made recording devices. To capture the field’s evolution through geological time, scientists analyze the magnetic fields recorded by sediments, lava flows, and man-made artifacts. Accurately tracking the Earth’s central field signal is extremely difficult, and therefore the field change rates estimated by this type of analysis are still debated.

Now, Dr. Chris Davies, an associate professor at Leeds, and Professor Catherine Constable of the Scripps Institution of Oceanography, UC San Diego, California, have taken a different approach. They combined computer simulations of the field generation process with a recently released reconstruction of the time variations in Earth’s magnetic field spanning the past 100,000 years.

Their study, published in Nature’s Communications, shows that changes in the direction of the Earth’s magnetic field reached rates that are up to 10 times greater than the currently reported fastest variations of up to one degree per year.

They demonstrate that these rapid changes are associated with local weakening of the magnetic field. This means that these changes have generally occurred at times when the field has reversed polarity or during geomagnetic excursions when the dipole axis, corresponding to the field lines emerging from one magnetic pole and converging on the other, moves away of the locations of the North and South geographic poles.

The clearest example of this in their study is a sharp change in the direction of the geomagnetic field of about 2.5 degrees per year 39,000 years ago. This change was associated with locally weak field strength, in a confined space region just off the west coast of Central America, and followed the Laschamp global excursion, a brief reversal of Earth’s magnetic field approximately 41,000 years ago .

Similar events are identified in computer simulations of the field that can reveal far more detail of their physical origin than limited paleomagnetic reconstruction.

Their detailed analysis indicates that the faster directional changes are associated with the movement of reversed flow patches across the surface of the liquid core. These patches are more prevalent at lower latitudes, suggesting that future searches for rapid direction changes should focus on these areas.

Dr. Davies of the School of Earth and Environment said: “We have a very incomplete understanding of our magnetic field before 400 years ago. Since these rapid changes represent some of the most extreme behaviors of the liquid nucleus, they could provide important information”. on the behavior of the deep interior of the Earth “.

Professor Constable said: “Understanding whether computer simulations of the magnetic field accurately reflect the physical behavior of the geomagnetic field as inferred from geological records can be very difficult.

“But in this case, we have been able to show excellent agreement on both the rates of change and the general location of the most extreme events in a variety of computer simulations. A further study of the evolving dynamics in these simulations offers a strategy useful to document how such rapid changes occur and whether they are also in times of stable magnetic polarity like what we are experiencing today. ”