Jerks in the acceleration of the Earth's protective magnetic field are triggered by rising blobs of molten material within the planet's core, a new model suggests.
Occurring around every 6 to 12 years, jerks have been identified by scientists as early back at 1901, but the exact nature of their origins had been a mystery.
Researchers modelled the physical conditions within the Earth's core using a supercomputer and found that rising blobs create powerful waves in the core.
These waves change the flow of liquid that induces the planet's magnetic field, triggering the jerks as a result.
The revelation comes as scientists have been forced to publish an update on the planet's magnetic north pole a year early.
It has been wildly shifting towards Russia, at around 34 miles (55km) a year, although researchers on the current study haven't officially linked the two.
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Researchers modelled the conditions within the Earth's core using a supercomputer and found that rising blobs create powerful waves (depicted in red and blue) in the core. These waves change the flow of liquid that induces the planet's magnetic field (orange), triggering jerks
The Earth's geomagnetic field shields our planet from the ravages of the solar wind and cosmic rays that would otherwise strip away the vital upper atmosphere.
On occasion, however, the geomagnetic field is known to suddenly jerk — temporarily changing acceleration.
Records of magnetic jerks date back as far as 1901, with a new jerk typically recorded around every 10 years.
Jerks can vary in strength across the globe, and may only impact certain regions.
For example, a jerk recorded in 1949 was clearly observed in Tucson, North America, but could not be detect in Europe.
Furthermore, when occurring worldwide, jerks can act at different times on different regions, and often appear earlier in the northern than the southern hemisphere.
Unlike other geomagnetic phenomena like the northern and southern lights — which occur from charged particles in the solar wind colliding with our atmosphere — the jerks are thought to originate within the core of the Earth.
The magnetic field itself is generated in the outer core as a result of the movement of liquid iron in convection currents that carry heat away from the inner core.
However, the exact root cause of the jerks has been subject to much debate.
Prominent hypotheses put forward to explain the phenomenon include changes in the liquid flow in the Earth's outer core, twisting movements in the solid inner core, or strong earthquakes.
Direct observations of the Earth's are inherently impossible.
So instead, geophysicists Julien Aubert of the University of Paris and Christopher Finlay of the Technical University of Denmark have painstakingly recreated the conditions inside the outer core in a model that tracks how the core evolves.
The researchers found that the supercomputer model could simulate geomagnetic jerks that acted just like real-life jerks recorded in
