Earth’s magnetic field is created by the motion of molten iron in our planet’s outer core but its detailed changes continue to elude scientists. We know the poles move, the field strength ebbs and flows, and Earth can even reverse its polarity, but many unknowns still surround these processes.
A new series of simulations, reported in a study published in Nature Communication, shows that Earth's magnetic field can shift up to 10 times faster than what it is currently believed. In particular, these rapid changes might take place when the field is at its weakest, like during a pole reversal or an excursion, where the pole position changes dramatically but only for a few thousand years, before going back.
The simulations cover the last 100,000 years and tried to reproduce geological findings related to ancient reversals or excursions. They found the changes in field direction occurred in speeds up to 10 times faster than the fastest currently reported variations of up to 1 degree a year. The models found the cause of these changes in the surface of the core, 2,800 kilometers (1,740 miles) below the surface.
“We have very incomplete knowledge of our magnetic field prior to 400 years ago. Since these rapid changes represent some of the more extreme behavior of the liquid core they could give important information about the behavior of Earth's deep interior,” co-author Dr Chris Davies from the University of Leeds said in a statement.
The evolution of the magnetic field can leave an imprint on certain rocks. Scientists have been using these geological records to track the changes to the magnetic fields over eons, and they believe that evidence of this fast and dramatic reversal could be common in lower latitudes rocks.
“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 challenging,” co-author Professor Catherine Constable said.
“But in this case, we have been able to show excellent agreement in both the rates of change and general location of the most extreme events across a range of computer simulations. 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.”