We Now Know Why Earth's Magnetic Field Has A Colossal Twitch Every Few Years

Visualization of the interior of Earth's core, as represented by a computer simulation model (view of the equatorial plane and a spherical surface near the inner core, seen from the North Pole). Magnetic field lines (in orange) are stretched by turbulent convection (in blue and red). © Aubert et al./IPGP/CNRS Photo library

Earth’s magnetic field is not as stable and certain as a compass might suggest. Every now and again, a sudden jerk rumbles through the magnetic field, twitching the planet's magnetic field lines. After first being described in 1978, scientists finally believe they know what causes these mysterious geomagnetic jerks: sudden spurts of hot liquid metal sloshing around in Earth’s core.

Our planet might look like it’s all rock and water, but deep beneath our feet, there is a swirling sea of liquid metal. This is why Earth has a magnetic field. Researchers already know that movement within the core, in the form of “slow” convection movement, can cause changes in the magnetic field over the course of centuries. They now believe the smaller but sharper geomagnetic jerks that occur every 10 years or so might be the result of "rapid" hydromagnetic waves in the core.

Reporting in the journal Nature Geoscience, scientists from the Institut de Physique du Globe de Paris and the Technical University of Denmark used supercomputers to model Earth’s core and reproduce the succession of events that lead to geomagnetic jerks.

Their computer modeling showed that the jerks, occurring approximately every 10 years, can be traced back to "a sudden buoyancy release" – a rapid gush of convection that rushes towards the core's surface – that occurred 25 years previously. As reported by Newsweek, the intermittent jerks in Earth's core could possibly be a factor in recent observations that seem to suggest the magnetic north pole is shifting across the globe in an unpredictable fashion.

"[Geomagnetic jerks] represent a major obstacle to the prediction of geomagnetic field behavior for years to decades ahead," reads the new study. "The ability to numerically reproduce jerks offers a new way to probe the physical properties of Earth’s deep interior."

The magnetic field is surprisingly important to life on Earth, so understanding its intricacies and oddities is also of great importance. First of all, we (and many other species) use it for navigation. We obviously use the magnetic field when we look at a compass, but more high-tech methods of navigation, such as smartphones and satellites, also rely on the magnetic field lines.

Beyond this, it also plays a fundamental role in protecting the Earth from charged particles in solar wind and cosmic rays, which would otherwise strip away the ozone layer that protects the Earth from harmful ultraviolet radiation.

Despite its importance, the magnetic field still holds many mysteries. One of the most intriguing is the possibility of Earth’s magnetic field decaying significantly, collapsing, and flipping polarity – north would flip to south and south to north. According to geological records, Earth is actually overdue a flip. The last time a complete reversal happened was 781,000 years ago, although there was a temporary flip some 41,000 years ago when the poles reversed for 250 years before switching back to the way they are today.

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