Post on magnetic field. Earth's magnetic field
Let's understand together what a magnetic field is. After all, many people live in this field all their lives and do not even think about it. Time to fix it!
A magnetic field
A magnetic field is a special kind of matter. It manifests itself in the action on moving electric charges and bodies that have their own magnetic moment (permanent magnets).
Important: a magnetic field does not act on stationary charges! A magnetic field is also created by moving electric charges, or changing in time electric field, or magnetic moments of electrons in atoms. That is, any wire through which current flows also becomes a magnet!
A body that has its own magnetic field.
A magnet has poles called north and south. The designations "northern" and "southern" are given only for convenience (as "plus" and "minus" in electricity).
The magnetic field is represented by power magnetic lines . The lines of force are continuous and closed, and their direction always coincides with the direction of the field forces. If around permanent magnet scatter metal shavings, metal particles will show a clear picture of the magnetic field lines emerging from the north and entering the south pole. Graphical characteristic of the magnetic field - lines of force.
Magnetic field characteristics
The main characteristics of the magnetic field are magnetic induction, magnetic flux and magnetic permeability. But let's talk about everything in order.
Immediately, we note that all units of measurement are given in the system SI.
Magnetic induction B – vector physical quantity, which is the main power characteristic of the magnetic field. Denoted by letter B . The unit of measurement of magnetic induction - Tesla (Tl).
Magnetic induction indicates how strong a field is by determining the force with which it acts on a charge. Given power called Lorentz force.
Here q - charge, v - its speed in a magnetic field, B - induction, F is the Lorentz force with which the field acts on the charge.
F- a physical quantity equal to the product of magnetic induction by the area of the contour and the cosine between the induction vector and the normal to the plane of the contour through which the flow passes. Magnetic flux is a scalar characteristic of a magnetic field.
We can say that the magnetic flux characterizes the number of magnetic induction lines penetrating a unit area. The magnetic flux is measured in Weberach (WB).
Magnetic permeability is the coefficient that determines the magnetic properties of the medium. One of the parameters on which the magnetic induction of the field depends is the magnetic permeability.
Our planet has been a huge magnet for several billion years. The induction of the Earth's magnetic field varies depending on the coordinates. At the equator, it is about 3.1 times 10 to the minus fifth power of Tesla. In addition, there are magnetic anomalies, where the value and direction of the field differ significantly from neighboring areas. One of the largest magnetic anomalies on the planet - Kursk and Brazilian magnetic anomaly.
The origin of the Earth's magnetic field is still a mystery to scientists. It is assumed that the source of the field is the liquid metal core of the Earth. The core is moving, which means that the molten iron-nickel alloy is moving, and the movement of charged particles is the electric current that generates the magnetic field. The problem is that this theory geodynamo) does not explain how the field is kept stable.
The earth is a huge magnetic dipole. The magnetic poles do not coincide with the geographic ones, although they are in close proximity. Moreover, the Earth's magnetic poles are moving. Their displacement has been recorded since 1885. For example, over the past hundred years, the magnetic pole in the Southern Hemisphere has shifted by almost 900 kilometers and is now in the Southern Ocean. The pole of the Arctic hemisphere is moving across the Arctic Ocean towards the East Siberian magnetic anomaly, the speed of its movement (according to 2004 data) was about 60 kilometers per year. Now there is an acceleration of the movement of the poles - on average, the speed is growing by 3 kilometers per year.
What is the significance of the Earth's magnetic field for us? First of all, the Earth's magnetic field protects the planet from cosmic rays and the solar wind. Charged particles from deep space do not fall directly to the ground, but are deflected by a giant magnet and move along its lines of force. Thus, all living things are protected from harmful radiation.
During the history of the Earth, there have been several inversions(changes) of magnetic poles. Pole inversion is when they change places. The last time this phenomenon occurred about 800 thousand years ago, and there were more than 400 geomagnetic reversals in the history of the Earth. Some scientists believe that, given the observed acceleration of the movement of the magnetic poles, the next pole reversal should be expected in the next couple of thousand years.
Fortunately, no reversal of poles is expected in our century. So, you can think about the pleasant and enjoy life in the good old constant field of the Earth, having considered the main properties and characteristics of the magnetic field. And so that you can do this, there are our authors, who can be entrusted with some of the educational troubles with confidence in success! and other types of work you can order at the link.
The earth is a giant magnet around which a magnetic field forms. The magnetic poles of the Earth do not coincide with the true geographic poles - north and south. The lines of force that run from one magnetic pole to another are called magnetic meridians. A certain angle is formed between the magnetic and geographic meridians (about 11.5 ° - approx .. Therefore, the magnetized compass needle accurately shows the direction of the magnetic meridians, and the direction to the north geographic pole is only approximately.
A freely suspended magnetic needle is located horizontally only on the line of the magnetic equator, which does not coincide with the geographic one. If you move north of the magnetic equator, then the northern end of the arrow will gradually drop. The angle formed by the magnetic needle and the horizontal plane is called the magnetic inclination. At the North Magnetic Pole (77° N and 102° W), a freely suspended magnetic needle will be installed vertically with the north end down, and at the South Magnetic Pole (65° S and 139° E - note .. Thus, the magnetic needle shows the direction of the magnetic field lines above the earth's surface.
It is believed that our planet itself generates a constant magnetic field. It is formed due to complex system electric currents arising from the rotation of the Earth and the movement liquid substance in its outer core. The position of the magnetic poles and the distribution of the magnetic field over the earth's surface change over time. The Earth's magnetic field extends to a height of about 100,000 km. It deflects or captures solar wind particles that are harmful to all living organisms. These charged particles form the Earth's radiation belt, and the entire region of near-Earth space in which they are located is called the magnetosphere.
The sun sends a huge stream of energy to the Earth, consisting of electromagnetic radiation (visible light, infrared and radio radiation - approx.); ultraviolet and X-rays; solar cosmic rays, which appear only during very strong flares; and the solar wind - a constant stream of plasma formed mainly by protons (hydrogen ions).
The electromagnetic radiation of the Sun comes to the Earth in 8 minutes, and the particle streams, which bring the main part of the perturbation from the Sun, move at a speed of about 1000 km/s and are delayed for two or three days. The main cause of solar wind disturbances, which significantly affect terrestrial processes, are the grandiose ejections of matter from the solar corona. When moving towards the Earth, they turn into magnetic clouds and lead to strong, sometimes extreme disturbances on the Earth. Especially strong perturbations of the Earth's magnetic field - magnetic storms - disrupt radio communications and cause intense auroras.
Aurora Borealis over Earth (viewed from space)
Magnetic anomalies
In some regions of the planet, deviations of the magnetic declination and magnetic inclination from the average values for a given territory are observed. For example, in the Kursk region, in the region of an iron ore deposit, the magnetic field strength is 5 times higher than the average for this region. The field is called so - the Kursk magnetic anomaly - note .. Sometimes such deviations are observed over vast areas. The East Siberian magnetic anomaly is characterized by a western magnetic declination, not an eastern one.
The Earth's magnetic field is a formation generated by sources within the planet. It is the object of study of the corresponding section of geophysics. Next, let's take a closer look at what the Earth's magnetic field is, how it is formed.
general information
Not far from the surface of the Earth, approximately at a distance of three of its radii, the lines of force from the magnetic field are arranged in a system of "two polar charges". Here is an area called the "plasma sphere". With distance from the surface of the planet, the influence of the flow of ionized particles from the solar corona increases. This leads to compression of the magnetosphere from the side of the Sun, and vice versa, the Earth's magnetic field is pulled out from the opposite, shadow side.
plasma sphere
A tangible effect on the surface magnetic field of the Earth is exerted by the directed movement of charged particles in upper layers atmosphere (ionosphere). The location of the latter is from a hundred kilometers and above from the surface of the planet. The Earth's magnetic field holds the plasmasphere. However, its structure strongly depends on the activity of the solar wind and its interaction with the retaining layer. and frequency magnetic storms on our planet is caused by solar flares.
Terminology
There is a concept of "magnetic axis of the Earth". This is a straight line that passes through the corresponding poles of the planet. The "magnetic equator" is the great circle of the plane perpendicular to this axis. The vector on it has a direction close to the horizontal. The average strength of the Earth's magnetic field is significantly dependent on geographical location. It is approximately equal to 0.5 Oe, that is, 40 A / m. At the magnetic equator, the same indicator is approximately 0.34 Oe, and near the poles it is close to 0.66 Oe. In some anomalies of the planet, for example, within the Kursk anomaly, the indicator is increased and amounts to 2 Oe. Field lines of the Earth's magnetosphere with a complex structure , projected onto its surface and converging at its own poles, are called "magnetic meridians".
The nature of occurrence. Assumptions and conjectures
Not so long ago, the assumption about the connection between the emergence of the Earth's magnetosphere and the current flow in a liquid metal core, located at a distance of a quarter or a third of the radius of our planet, gained the right to exist. Scientists have an assumption about the so-called "telluric currents" flowing near earth's crust. It should be said that over time there is a transformation of the formation. The Earth's magnetic field has changed many times over the past one hundred and eighty years. This is fixed in the oceanic crust, and this is evidenced by studies of remanent magnetization. By comparing the sections on both sides of the ocean ridges, the time of divergence of these sections is determined.
Earth's magnetic pole shift
The location of these parts of the planet is not constant. The fact of their displacements has been recorded since the end of the nineteenth century. In the Southern Hemisphere, the magnetic pole has shifted by 900 km during this time and ended up in the Indian Ocean. Similar processes are taking place in the northern part. Here the pole is shifting towards the magnetic anomaly at Eastern Siberia. From 1973 to 1994, the distance that the section moved here was 270 km. These pre-calculated data were later confirmed by measurements. According to the latest data, the speed of the magnetic pole of the Northern Hemisphere has increased significantly. It has grown from 10 km/year in the seventies of the last century to 60 km/year at the beginning of this century. At the same time, the strength of the earth's magnetic field decreases unevenly. So, over the past 22 years, it has decreased by 1.7% in some places, and somewhere by 10%, although there are also areas where, on the contrary, it has increased. The acceleration in the displacement of the magnetic poles (by approximately 3 km per year) gives reason to assume that their movement observed today is not an excursion, this is another inversion.
This is indirectly confirmed by the increase in the so-called "polar gaps" in the south and north of the magnetosphere. The ionized material of the solar corona and space rapidly penetrates into the resulting extensions. From this, everything is collected in the polar regions of the Earth. large quantity energy, which in itself is fraught with additional heating of the polar ice caps.
Coordinates
In the science that studies cosmic rays, use the coordinates of the geomagnetic field, named after the scientist McIlvine. He was the first to suggest using them, since they are based on modified variants of the activity of charged elements in a magnetic field. Two coordinates (L, B) are used for a point. They characterize the magnetic shell (the McIlwain parameter) and the field induction L. The latter is a parameter equal to the ratio of the average distance of the sphere from the center of the planet to its radius.
"Magnetic inclination"
Several thousand years ago, the Chinese made an amazing discovery. They found that magnetized objects can be placed in a certain direction. And in the middle of the sixteenth century, Georg Cartmann, a German scientist, made another discovery in this area. This is how the concept of "magnetic inclination" appeared. This name means the angle of deviation of the arrow up or down from the horizontal plane under the influence of the planet's magnetosphere.
From the history of research
In the region of the northern magnetic equator, which is different from the geographic one, the northern end goes down, and in the south, on the contrary, it goes up. In 1600, the English physician William Gilbert first made assumptions about the presence of the Earth's magnetic field, causing a certain behavior of pre-magnetized objects. In his book, he described an experiment with a ball equipped with an iron arrow. As a result of research, he came to the conclusion that the Earth is a large magnet. The experiments were also carried out by the English astronomer Henry Gellibrant. As a result of his observations, he came to the conclusion that the Earth's magnetic field is subject to slow changes.
José de Acosta described the possibility of using a compass. He also established the difference between the Magnetic and North Poles, and in his famous history(1590) substantiated the theory of lines without magnetic deflection. Christopher Columbus also made a significant contribution to the study of the issue under consideration. He owns the discovery of the inconsistency of the magnetic declination. Transformations are made dependent on changes in geographic coordinates. Magnetic declination is the angle of deviation of the arrow from the North-South direction. In connection with the discovery of Columbus, research intensified. Information about what the Earth's magnetic field is was extremely necessary for navigators. M. V. Lomonosov also worked on this problem. For the study of terrestrial magnetism, he recommended conducting systematic observations using permanent points (like observatories) for this. It was also very important, according to Lomonosov, to carry out this at sea. This idea of the great scientist was realized in Russia sixty years later. The discovery of the Magnetic Pole in the Canadian archipelago belongs to the English polar explorer John Ross (1831). And in 1841, he also discovered the other pole of the planet, but already in Antarctica. The hypothesis about the origin of the Earth's magnetic field was put forward by Carl Gauss. He soon proved that most of it is fed from a source inside the planet, but the cause of its slight deviations is in the external environment.
In 1905, Einstein named the cause of terrestrial magnetism as one of the five main mysteries of contemporary physics.
Also in 1905, the French geophysicist Bernard Brunhes measured the magnetism of Pleistocene lava deposits in the southern department of Cantal. The magnetization vector of these rocks was almost 180 degrees with the planetary magnetic field vector (his compatriot P. David obtained similar results even a year earlier). Brunhes concluded that three-quarters of a million years ago, during an outpouring of lava, the direction of the geomagnetic field lines was opposite to the modern one. So the effect of inversion (reversal of polarity) of the Earth's magnetic field was discovered. In the second half of the 1920s, Brunhes' conclusions were confirmed by P. L. Mercanton and Monotori Matuyama, but these ideas were recognized only by the middle of the century.
We now know that the geomagnetic field has existed for at least 3.5 billion years, and during this time the magnetic poles exchanged places thousands of times (Brunhes and Matuyama studied the last reversal, which now bears their names). Sometimes the geomagnetic field retains its orientation for tens of millions of years, and sometimes for no more than five hundred centuries. The reversal process itself usually takes several millennia, and after its completion, the field strength, as a rule, does not return to its previous value, but changes by several percent.
The mechanism of geomagnetic reversal is not quite clear even today, and even a hundred years ago it did not allow a reasonable explanation at all. Therefore, the discoveries of Brunhes and David only reinforced Einstein's assessment - indeed, terrestrial magnetism was extremely mysterious and incomprehensible. But by that time it had been studied for over three hundred years, and in the 19th century such stars of European science as great traveler Alexander von Humboldt, brilliant mathematician Carl Friedrich Gauss and brilliant experimental physicist Wilhelm Weber. So Einstein really looked at the root.
How many magnetic poles do you think our planet has? Almost everyone will say that two are in the Arctic and Antarctic. In fact, the answer depends on the definition of the concept of a pole. The geographic poles are considered to be the points of intersection of the earth's axis with the surface of the planet. Since the Earth rotates as a rigid body, there are only two such points and nothing else can be invented. But with magnetic poles, the situation is much more complicated. For example, a pole can be considered a small area (ideally again a point) where the magnetic lines of force are perpendicular to the earth's surface. However, any magnetometer registers not only the planetary magnetic field, but also the fields of local rocks, electric currents of the ionosphere, solar wind particles, and other additional sources of magnetism (and their average share is not so small, on the order of a few percent). The more accurate the device, the better it does this - and therefore it becomes more and more difficult to isolate the true geomagnetic field (it is called the main one), the source of which is located in the depths of the earth. Therefore, the pole coordinates determined by direct measurement are not stable even for a short period of time.
You can act differently and establish the position of the pole on the basis of certain models of terrestrial magnetism. In the first approximation, our planet can be considered a geocentric magnetic dipole, the axis of which passes through its center. At present, the angle between it and the earth's axis is 10 degrees (a few decades ago it was more than 11 degrees). With more accurate modeling, it turns out that the dipole axis is shifted relative to the center of the Earth in the direction of the northwestern part Pacific Ocean at about 540 km (this is an eccentric dipole). There are other definitions as well.
But that is not all. The terrestrial magnetic field does not really have dipole symmetry and therefore has multiple poles, and in huge numbers. If we consider the Earth as a magnetic quadrupole, a quadrupole, we will have to introduce two more poles - in Malaysia and in the southern part Atlantic Ocean. The octupole model specifies the eight poles, and so on. The most advanced modern models of terrestrial magnetism operate with as many as 168 poles. It should be noted that only the dipole component of the geomagnetic field temporarily disappears during the inversion, while the others change much more weakly.
The poles are reversed
Many people know that the generally accepted names for the poles are exactly the opposite. There is a pole in the Arctic, to which the north end of the magnetic needle points, - therefore, it should be considered south (poles of the same name repel, opposite ones attract!). Likewise, the north magnetic pole is based at high latitudes in the southern hemisphere. However, traditionally we name the poles according to geography. Physicists have long agreed that the lines of force come out of the north pole of any magnet and enter the south. It follows from this that the lines of terrestrial magnetism leave the south geomagnetic pole and are drawn to the north. This is the convention, and it is not worth breaking it (it's time to recall the sad experience of Panikovsky!).
The magnetic pole, no matter how you define it, does not stand still. The north pole of the geocentric dipole in 2000 had coordinates of 79.5 N and 71.6 W, and in 2010 - 80.0 N and 72.0 W. The true North Pole (the one that physical measurements reveal) has shifted since 2000 from 81.0 N and 109.7 W to 85.2 N and 127.1 W. For almost the entire 20th century, he did not exceed 10 km per year, but after 1980 he suddenly began to move much faster. In the early 1990s, its speed exceeded 15 km per year and continues to grow.
As he told Popular Mechanics former leader Geomagnetic Laboratory of the Canadian Geological Survey Lawrence Newitt, now the true pole is migrating to the northwest, moving 50 km annually. If the vector of its movement does not change for several decades, then by the middle of the 21st century it will be in Siberia. According to the reconstruction carried out a few years ago by the same Newitt, in the XVII and XVIII centuries the north magnetic pole mainly shifted to the southeast and only around 1860 turned to the northwest. The true south magnetic pole has been moving in the same direction for the last 300 years, and its average annual displacement does not exceed 10–15 km.
Where does the Earth's magnetic field come from? One of the possible explanations is simply striking. The Earth has an internal solid iron-nickel core, the radius of which is 1220 km. Since these metals are ferromagnetic, why not assume that the inner core has a static magnetization, which ensures the existence of the geomagnetic field? The multipolarity of terrestrial magnetism can be attributed to the asymmetry of the distribution of magnetic domains inside the core. The migration of the poles and the reversal of the geomagnetic field is more difficult to explain, but perhaps one can try.
However, nothing comes of it. All ferromagnets remain ferromagnets (that is, they retain spontaneous magnetization) only below a certain temperature - the Curie point. For iron, it is 768°C (for nickel, much lower), and the temperature of the Earth's inner core is much higher than 5000 degrees. Therefore, we have to part with the hypothesis of static geomagnetism. However, it is possible that in space there are cooled planets with ferromagnetic cores.
Let's consider another possibility. Our planet also has a liquid outer core approximately 2300 km thick. It consists of a melt of iron and nickel with an admixture of lighter elements (sulfur, carbon, oxygen, and possibly radioactive potassium - no one knows for sure). The temperature of the lower part of the outer core almost coincides with the temperature of the inner core, and in the upper zone at the boundary with the mantle it drops to 4400°C. Therefore, it is quite natural to assume that due to the rotation of the Earth, circular currents are formed there, which may be the cause of the emergence of terrestrial magnetism.
convective dynamo
“In order to explain the emergence of a poloidal field, it is necessary to take into account the vertical flows of matter in the nucleus. They are formed due to convection: a heated iron-nickel melt emerges from the lower part of the core towards the mantle. These jets are twisted by the Coriolis force like air currents cyclones. Updrafts rotate clockwise in the Northern Hemisphere and counter-clockwise in the Southern Hemisphere, explains University of California professor Gary Glatzmayer. - When approaching the mantle, the substance of the core cools down and begins a reverse movement in depth. The magnetic fields of the updrafts and downdrafts cancel each other out, and therefore the field is not established vertically. But in the upper part of the convection jet, where it forms a loop and moves horizontally for a short time, the situation is different. In the Northern Hemisphere, field lines that faced west before the convection ascent turn 90 degrees clockwise and orient themselves to the north. In the Southern Hemisphere, they turn counterclockwise from the east and also head north. As a result, a magnetic field is generated in both hemispheres, pointing from south to north. Although this is by no means the only possible explanation for the occurrence of the poloidal field, it is considered the most probable.
It was this scheme that geophysicists discussed about 80 years ago. They believed that the flows of the conducting fluid of the outer core, due to their kinetic energy generate electric currents spanning the earth's axis. These currents generate a magnetic field predominantly of the dipole type, the lines of force of which on the Earth's surface are elongated along the meridians (such a field is called poloidal). This mechanism is associated with the operation of a dynamo, hence its name.
The described scheme is beautiful and illustrative, but, unfortunately, it is erroneous. It is based on the assumption that the motion of matter in the outer core is symmetrical about the earth's axis. However, in 1933, the English mathematician Thomas Cowling proved a theorem according to which no axisymmetric flows can ensure the existence of a long-term geomagnetic field. Even if it appears, its age will be short, tens of thousands of times less than the age of our planet. We need a more complex model.
“We don't know exactly when terrestrial magnetism arose, but it could have happened shortly after the formation of the mantle and outer core,” says David Stevenson, one of the leading experts in planetary magnetism, professor at the California Institute of Technology. - To turn on the geodynamo, an external seed field is required, and not necessarily a powerful one. This role, for example, could be assumed by the magnetic field of the Sun or the fields of currents generated in the core due to the thermoelectric effect. Ultimately, this is not too important, there were enough sources of magnetism. In the presence of such a field and the circular motion of the flow of conductive fluid, the launch of an intraplanetary dynamo became simply inevitable.”
Magnetic protection
Monitoring of terrestrial magnetism is carried out using an extensive network of geomagnetic observatories, the creation of which began in the 1830s.
For the same purposes, ship, aviation and space instruments are used (for example, the scalar and vector magnetometers of the Danish Oersted satellite, which have been operating since 1999).
The geomagnetic field strength varies from approximately 20,000 nanotesla off the coast of Brazil to 65,000 nanotesla near the south magnetic pole. Since 1800, its dipole component has decreased by almost 13% (and by 20% since the middle of the 16th century), while its quadrupole component has slightly increased. Paleomagnetic studies show that for several millennia before the beginning of our era, the intensity of the geomagnetic field stubbornly climbed up, and then began to decline. Nevertheless, the current planetary dipole moment is significantly higher than its average value over the past hundred and fifty million years (in 2010, paleomagnetic measurements were published indicating that 3.5 billion years ago, the Earth's magnetic field was twice as weak as the current one). This means that the whole story human societies from the emergence of the first states to our time fell on the local maximum of the earth's magnetic field. It is interesting to think about whether this influenced the progress of civilization. Such an assumption ceases to seem fantastic, given that the magnetic field protects the biosphere from cosmic radiation.
And here is another circumstance that is worth noting. In the youth and even adolescence of our planet, all the substance of its core was in the liquid phase. The solid inner core formed relatively recently, perhaps as little as a billion years ago. When this happened, the convection currents became more ordered, resulting in a more stable operation of the geodynamo. Because of this, the geomagnetic field has gained in magnitude and stability. It can be assumed that this circumstance favorably affected the evolution of living organisms. In particular, the increase in geomagnetism has improved the protection of the biosphere from cosmic radiation and thus facilitated the emergence of life from the ocean to land.
Here is the generally accepted explanation for such a launch. Let, for simplicity, the seed field be almost parallel to the Earth's rotation axis (in fact, it is sufficient if it has a nonzero component in this direction, which is almost inevitable). The speed of rotation of the substance of the outer core decreases as the depth decreases, and due to its high electrical conductivity, the magnetic field lines move with it - as physicists say, the field is "frozen" into the medium. Therefore, the lines of force of the seed field will bend, moving forward at greater depths and lagging behind at shallower ones. Eventually they will stretch and deform so much that they will give rise to a toroidal field, circular magnetic loops that wrap around the earth's axis and point in opposite directions in the northern and southern hemispheres. This mechanism is called the w-effect.
According to Professor Stevenson, it is very important to understand that the toroidal field of the outer core arose due to the poloidal seed field and, in turn, gave rise to a new poloidal field observed at the earth's surface: "Both types of planetary geodynamo fields are interconnected and cannot exist without each other" .
15 years ago, Gary Glatzmyer, along with Paul Roberts, published a very beautiful computer model geomagnetic field: “In principle, to explain geomagnetism, there has long been an adequate mathematical apparatus - the equations of magnetohydrodynamics plus equations describing the force of gravity and heat flows inside the earth's core. Models based on these equations are very complex in their original form, but they can be simplified and adapted for computer calculations. That is exactly what Roberts and I did. A supercomputer run made it possible to construct a self-consistent description of the long-term evolution of the velocity, temperature, and pressure of the matter flows in the outer core and the evolution of magnetic fields associated with them. We also found that if we play the simulation over time intervals of the order of tens and hundreds of thousands of years, then geomagnetic field reversals inevitably occur. So in this respect, our model does a pretty good job of conveying the magnetic history of the planet. However, there is a problem that has not yet been resolved. The parameters of the substance of the outer core, which are included in such models, are still too far from real conditions. For example, we had to accept that its viscosity is very high, otherwise the resources of the most powerful supercomputers will not be enough. In fact, this is not so, there is every reason to believe that it almost coincides with the viscosity of water. Our current models are powerless to take into account the turbulence, which undoubtedly takes place. But computers are gaining momentum every year, and in ten years there will be much more realistic simulations.
“The work of the geodynamo is inevitably associated with chaotic changes in the flows of the iron-nickel melt, which turn into fluctuations in magnetic fields,” adds Professor Stevenson. - Inversions of the earth's magnetism are simply the strongest possible fluctuations. Since they are stochastic in nature, they can hardly be predicted in advance - in any case, we cannot.”