The strength of the Earth's magnetic field changes sharply every ten years due to the existence of special turbulent waves inside the planet's core, "shaking up" its matter when it reaches the border with the mantle. French and Danish geologists write about this in the journal Nature Geoscience.
The core of our planet, according to scientists today, consists of two layers - a solid metal core in the center, and a layer of liquid iron and nickel surrounding it. This metallic "liquid" does not stand still, but constantly moves, like water in a boiling kettle, and this movement generates a magnetic field that protects life on Earth from cosmic rays, solar flares and other dangerous cosmic phenomena.
Today, no one knows how this movement occurs, since it is virtually impossible to look into the Earth's core using seismic devices, which is why scientists have to study its secrets using mathematical models and laboratory experiments to reproduce the conditions in the core using super-powerful presses and anvils.
Scientists recently discovered that the Earth's core is extremely heterogeneous in structure, which led them to suspect that there are not two, but three layers inside it. Two more groups of geologists have discovered unusual "bubbles" of iron, which rise from the core to the mantle, and also found traces of the existence of a kind of "jet streams" of iron inside it.
Julien Obert from the Institute of Physics of the Earth in Paris (France) and his colleague Christopher Finlay from the Technical University of Denmark in Lyngby studied another strange feature of the Earth's core, discovered at the end of the last century.
Until that time, scientists believed that the planet's magnetic field is weakening or strengthening at a rather slow pace, almost imperceptible to our instruments. In 1978, the situation changed dramatically when the first accurate geomagnetic instruments recorded that the rate of these changes increased by several orders of magnitude. After about a year, this “spurt” stopped and the magnetic field returned to normal, but something similar was repeated in the next decade.
In total, over the past half century, scientists have recorded ten such events, the nature of which, as well as their effect on field strength and pole migration, is still a matter of controversy among geologists.
Finlay and Aubert found an explanation for their appearance by examining data recorded during the last three geomagnetic tugs in 2007, 2011 and 2014, and analyzing the findings of their recent attempts to explain how the Earth's poles are inverted.
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Then scientists suggested that periodic temporary or permanent changes of the planet's poles were associated with the existence of special vibrations inside it, the so-called "dynamo waves". They move from the equator to the poles and rebuild the magnetic structure of the nucleus at regular intervals.
Something similar, as noted by geophysicists, occurs at the time of the appearance of "geomagnetic jerks". They manifest themselves most strongly in the vicinity of the planet's equator, where zones appear in which the strength of the magnetic field increases or decreases especially strongly. This prompted them to think that such anomalies could generate some kind of deep waves inside the core, associated with the fact that the Earth rotates on its axis.
Guided by this idea, scientists created a very detailed computer model of its matter, with the help of which they calculated how such oscillations would arise and move. To carry out these calculations, Aubert and Finlay needed a powerful supercomputer and 4 million hours of computer time, but these costs paid off.
It turned out that geomagnetic jerks appeared in such a system by themselves due to the fact that the waves that appeared in the central regions of the core gradually slowed down and intensified as they approached its border with the mantle. When they reached this zone, these vibrations in a special way "stirred up" his matter, which led to a sharp increase or decrease in the magnetic field.
Scientists hope that the results of their calculations and a computer model will help pinpoint the role that geomagnetic jerks play in the evolution of the Earth's magnetic field and in the reversal of its poles.