Geophysicists at the University of Leeds Yon Mound and Phil Livermore believe that in a couple of thousand years there will be an inversion of the Earth's magnetic field. British scientists presented their findings in a column of The Conversation. "Lenta.ru" provides the main theses of the authors and explains why geophysicists are most likely right.
The magnetic field protects the Earth from dangerous cosmic radiation by deflecting charged particles away from the planet. However, this force field is not permanent. In the entire history of the planet, there have been at least several hundred magnetic field reversals, when the north and south magnetic poles were swapped.
In the process of polarity reversal, the planet's magnetic field takes on a complex shape and weakens. During this period, its value can drop to ten percent of the original value and at the same time not two poles are formed, but several, including, for example, at the equator. On average, magnetic field reversals occur once every million years, but the interval between reversals is not constant.
In addition to geomagnetic reversals, incomplete reversals occurred in the history of the Earth, when the magnetic poles moved to low latitudes, up to the intersection of the equator, and then returned. The last time a geomagnetic reversal, the so-called Brunes-Matuyama phenomenon, occurred about 780 thousand years ago. A temporary reversal - the Lashamp event - happened 41 thousand years ago and lasted less than a thousand years, during which the direction of the planet's magnetic field actually changed for about 250 years.
Earth from orbit
Photo: Stuart Rankin / Flickr
Changes in the magnetic field during inversion weaken the planet's protection from cosmic radiation and increase the level of radiation on Earth. If the geomagnetic reversal happened today, it would dramatically increase the risks to the operation of near-Earth satellites, aviation and ground-based electrical infrastructure. Geomagnetic storms that occur with a sharp increase in solar activity give scientists the opportunity to assess the threats that the planet may face when its magnetic field is abruptly weakened.
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In 2003, a solar storm caused power outages in Sweden and necessitated changes to air travel routes to avoid temporary network disruptions and reduce radiation risks to satellites and ground infrastructure. But this storm is considered insignificant in comparison with the Carrington event - the geomagnetic storm of 1859, when auroras occurred even in the vicinity of the Caribbean islands.
Meanwhile, the specific impact that a major storm could have on today's electronic infrastructure is still unclear. We can certainly say that the economic damage from power outages, heating systems, air conditioning, geo-location and the Internet will be very significant: only by rough estimates, it is estimated at at least $ 40 billion per day.
The direct impact that the inversion of the magnetic field will produce on living beings and people is also difficult to predict: modern man in the entire history of his existence has not encountered such an event. There are studies that try to link geomagnetic reversals and volcanic activity to mass extinctions. However, Mound and Livermore note, there is no noticeable activation of volcanism, so most likely humanity will have to deal exclusively with electromagnetic effects.
Earth's magnetic field 500 years before the reversal (according to supercomputer modeling)
Image: GA Glatzmaier
Earth's magnetic field immediately after the reversal (according to supercomputer modeling)
Image: GA Glatzmaier
Earth's magnetic field after 500 years of reversal (according to supercomputer modeling)
Image: GA Glatzmaier
It is known that many species of animals have some form of magnetoreception, which allows them to sense changes in the Earth's magnetic field. Animals use this feature to navigate during long migrations. It is not yet clear what effect the geomagnetic reversal will have on such species. It is only known that the ancient people managed to successfully survive the Lashamp event, and life on the planet over the entire history of its existence has faced complete reversals of the geomagnetic field hundreds of times.
Two circumstances - the age of the Brunhes-Matuyama phenomenon and the observed weakening of the Earth's geomagnetic field by about five percent per century - suggest cautiously that an inversion may occur within the next two thousand years. It is difficult to name more exact dates. The planet's magnetic field is generated by a liquid iron-stone core that obeys the same laws of physics as the hydrosphere and atmosphere.
Meanwhile, humanity has learned to predict weather changes only a few days ahead. In the case of the core located at a depth of about three thousand kilometers from the Earth's surface, the situation is much more complicated - primarily due to the extremely scarce information about the structure and processes taking place in the interior of the planet. Scientists have at their disposal approximate information on the composition and structure of the nucleus, as well as a global network of ground-based geophysical observatories and orbiting satellites that can measure changes in the geomagnetic field and thus track the movement of the Earth's core.
Not much is really known about the planet's core. For example, only recently have Japanese scientists, in laboratory experiments simulating the conditions inside the Earth, reliably established that its third major component is silicon: it accounts for about five percent of the mass of the Earth's core. Other shares are in iron (85 percent) and nickel (10 percent). As usual in such cases, the supporters of the alternative hypothesis of the third element remained, who believe that it is not silicon, but oxygen.
Color map of Mercury
Photo: NASA Goddard Space Flight Center / Flickr
Little scientists know about the structure of the planet's mantle. Only three years ago it became reliably known that in the transitional layer between the upper and lower mantle, at a depth of 410-660 kilometers, there are vast reserves of water. Subsequently, these data were repeatedly confirmed. Further analysis showed that water can also be contained in the underlying layers, at a depth of about a thousand kilometers. But even in this case, it is not known whether it is dispersed within the entire layer or occupies only certain local areas.
Climbing higher, scientists are faced with another problem - the nature and origin of tectonics of lithospheric plates. Strictly speaking, the Earth is considered the only planet in the solar system where there is tectonics, but no one still knows when and why it arose. Answering these questions would allow us to track the past and future of the continents - in particular, the current stage of the Wilson cycle. Scientists presented the preliminary data once again at a specialized conference held in 2016.
The nature of the planet's magnetic field is the biggest geophysical problem. It is reliably known that in addition to Mercury, the Earth and four gas giants, Ganymede, the largest satellite of Jupiter, also has a magnetosphere, but how the planet supports its own magnetosphere is very little known. At the disposal of scientists so far there is practically the only theory of geodynamo. According to this theory, in the bowels of the planet is a metal core with a solid center and a liquid shell. Due to the decay of radioactive elements, heat is released, leading to the formation of convective flows of a conductive fluid. These currents generate the planet's magnetic field.
Although the theory of geodynamo is practically uncontested, it causes great difficulties. According to classical magnetohydrodynamics, the dynamo effect should decay, and the planet's core should cool down and harden. There is still no exact understanding of the mechanisms due to which the Earth maintains the dynamo self-generation effect together with the observed features of the magnetic field, primarily geomagnetic anomalies, migration, and pole reversal.
The recent discovery of an iron jet inside the Earth's core, as noted by Mound and Livermore, testifies to the growing possibilities of science in studying the dynamics of processes occurring in the interior of the planet. The jet was formed in the liquid outer core of the Earth in the area located below the North Pole. The width of the object is currently 420 kilometers. The jet has reached such dimensions since 2000, every year increasing in width up to 40 kilometers.
Geophysicists believe that the iron jet they discovered is one of the objects that create the Earth's magnetic field. In combination with numerical methods and laboratory experiments, this and other discoveries, according to experts, should greatly accelerate progress in this area of geophysics. It is possible, Mound and Livermore point out, that scientists will soon be able to predict the behavior of the Earth's core.
Yuri Sukhov