What current creates the earth's magnetic field. Attractive planet. To implement the project it is necessary

Most planets in the solar system have magnetic fields to one degree or another.
A special branch of geophysics that studies the origin and nature of the Earth's magnetic field is called geomagnetism. Geomagnetism considers the problems of the emergence and evolution of the main, constant component of the geomagnetic field, the nature of the variable component (about 1% of the main field), as well as the structure of the magnetosphere - the uppermost magnetized plasma layers of the earth's atmosphere, interacting with the solar wind and protecting the Earth from penetrating cosmic radiation . An important task is to study the patterns of variations in the geomagnetic field, since they are caused by external influences associated primarily with solar activity.

This may be surprising, but today there is no single point of view on the mechanism of the emergence of the magnetic field of planets, although the magnetic hydrodynamo hypothesis, based on the recognition of the existence of a conductive liquid outer core, is almost universally accepted. Thermal convection, that is, the mixing of matter in the outer core, contributes to the formation of ring electric currents. The speed of movement of matter in the upper part of the liquid core will be somewhat lower, and in the lower layers - greater relative to the mantle in the first case and the solid core in the second. Such slow flows cause the formation of ring-shaped (toroidal) electric fields, closed in shape, that do not extend beyond the core. Due to the interaction of toroidal electric fields with convective currents, a total magnetic field of a dipole nature arises in the outer core, the axis of which approximately coincides with the axis of rotation of the Earth. To “start” such a process, an initial, at least very weak, magnetic field is required, which can be generated by the gyromagnetic effect when a rotating body is magnetized in the direction of its rotation axis.

The solar wind also plays an important role - a flow of charged particles, mainly protons and electrons, coming from the Sun. For the Earth, the solar wind is a stream of charged particles in a constant direction, and this is nothing more than an electric current.

According to the definition of the direction of the current, it is directed in the direction opposite to the movement of negatively charged particles (electrons), i.e. from Earth to Sun. Particles that form the solar wind, having mass and charge, are carried away by the upper layers of the atmosphere in the direction of the Earth's rotation. In 1958, the Earth's radiation belt was discovered. This is a huge zone in space, covering the Earth at the equator. In the radiation belt, the main charge carriers are electrons. Their density is 2–3 orders of magnitude higher than the density of other charge carriers. And thus there is an electric current caused by the directed circular motion of solar wind particles, carried away by the circular motion of the Earth, generating an electromagnetic “vortex” field.

It should be noted that the magnetic flux caused by the current of the solar wind also penetrates the flow of hot lava rotating with the Earth inside it. As a result of this interaction, an electromotive force is induced in it, under the influence of which a current flows, which also creates a magnetic field. As a result, the Earth's magnetic field is the resulting field from the interaction of the ionospheric current and the lava current.

The actual picture of the Earth's magnetic field depends not only on the configuration of the current sheet, but also on the magnetic properties of the earth's crust, as well as on the relative location of magnetic anomalies. Here we can draw an analogy with a circuit with current in the presence of a ferromagnetic core and without it. It is known that the ferromagnetic core not only changes the configuration of the magnetic field, but also significantly enhances it.

It has been reliably established that the Earth’s magnetic field responds to solar activity, however, if we associate the emergence of the planets’ magnetic field only with current layers in the liquid core interacting with the solar wind, then we can conclude that the planets of the solar system, which have the same direction of rotation, must have the same direction magnetic fields. However, for example, Jupiter refutes this statement.

It is interesting that when the solar wind interacts with the excited magnetic field of the Earth, a torque directed towards the rotation of the Earth acts on the Earth. Thus, the Earth, relative to the solar wind, behaves similarly to a self-excited DC motor. The energy source (generator) in this case is the Sun. Since both the magnetic field and the torque acting on the earth depend on the current of the Sun, and the latter on the degree of solar activity, then with increasing solar activity the torque acting on the Earth should increase and the speed of its rotation should increase.

Components of the geomagnetic field

The Earth's own magnetic field (geomagnetic field) can be divided into the following three main parts - main (internal) magnetic field of the Earth, including global anomalies, magnetic fields of local areas of outer shells, alternating (external) magnetic field of the Earth.

1. MAIN MAGNETIC FIELD OF THE EARTH (internal) , experiencing slow changes over time (secular variations) with periods from 10 to 10,000 years, concentrated in the intervals of 10–20, 60–100, 600–1200 and 8000 years. The latter is associated with a change in the dipole magnetic moment by a factor of 1.5–2.

Magnetic field lines created by a computer model of the geodynamo show how the structure of the Earth's magnetic field is simpler outside of it than inside the core (tangled tubes in the center). On the Earth's surface, most of the magnetic field lines come out from the inside (long yellow tubes) at the South Pole and enter inward (long blue tubes) near the North Pole.

Most people don't usually think about why the compass needle points north or south. But the planet's magnetic poles were not always positioned as they are today.

Mineral studies show that the Earth's magnetic field has changed its orientation from north to south and back hundreds of times over the 4-5 billion years of the planet's existence. However, nothing like this has happened over the past 780 thousand years, despite the fact that the average period of reversal of magnetic poles is 250 thousand years. In addition, the geomagnetic field has weakened by almost 10% since it was first measured in the 1930s. XIX century (i.e. almost 20 times faster than if, having lost its source of energy, it reduced its strength naturally). Is the next pole shift coming?

The source of magnetic field oscillations is hidden in the center of the Earth. Our planet, like other bodies in the Solar System, creates its magnetic field with the help of an internal generator, the operating principle of which is the same as a conventional electric one, converting the kinetic energy of its moving particles into an electromagnetic field. In an electric generator, movement occurs in the turns of a coil, and inside a planet or star - in a conducting liquid substance. A huge mass of molten iron with a volume 5 times larger than the Moon circulates in the core of the Earth, forming the so-called geodynamo.

Over the past ten years, scientists have developed new approaches to studying the operation of the geodynamo and its magnetic properties. Satellites transmit clear snapshots of the geomagnetic field on the Earth's surface, and modern computer modeling techniques and laboratory-created physical models help interpret orbital observational data. The experiments led scientists to a new explanation of how repolarization occurred in the past and how it may begin in the future.

The Earth's interior contains a molten outer core, where complex turbulent convection generates a geomagnetic field.

Geodynamo energy

What powers the geodynamo? By the 40s. of the last century, physicists recognized three necessary conditions for the formation of the planet’s magnetic field, and subsequent scientific constructions were based on these provisions. The first condition is a large volume of electrically conductive liquid mass, saturated with iron, forming the outer core of the Earth. Beneath it lies the Earth's inner core, consisting of almost pure iron, and above it is 2,900 km of solid rock, dense mantle and thin crust, forming continents and ocean floors. The pressure on the core created by the earth's crust and mantle is 2 million times higher than on the surface of the Earth. The temperature of the core is also extremely high - about 5000o Celsius, as is the temperature of the surface of the Sun.

The above-described parameters of the extreme environment predetermine the second requirement for the operation of a geodynamo: the need for an energy source to set the liquid mass in motion. Internal energy, partly of thermal and partly of chemical origin, creates expulsion conditions inside the nucleus. The core heats up more at the bottom than at the top. (High temperatures have been “walled up” inside it since the formation of the Earth.) This means that the hotter, less dense metal component of the core tends to rise. When the liquid mass reaches the upper layers, it loses some of its heat, giving it to the overlying mantle. Then the liquid iron cools, becoming denser than the surrounding mass, and sinks. The process of moving heat by raising and lowering a liquid mass is called thermal convection.

The third necessary condition for maintaining a magnetic field is the rotation of the Earth. The resulting Coriolis force deflects the movement of the rising liquid mass inside the Earth in the same way as it turns ocean currents and tropical cyclones, the movement vortices of which are visible in satellite images. At the center of the Earth, the Coriolis force twists the rising liquid mass into a corkscrew or spiral, like a loose spring.

The Earth has an iron-rich liquid mass concentrated at its center, sufficient energy to support convection, and a Coriolis force to swirl convection currents. This factor is extremely important for maintaining the operation of the geodynamo for millions of years. But new knowledge is needed to answer the question of how the magnetic field is formed and why the poles change places from time to time.

Repolarization

Scientists have long wondered why the Earth's magnetic poles switch places from time to time. Recent studies of vortex movements of molten masses inside the Earth make it possible to understand how repolarization occurs.

A magnetic field, much more intense and more complex than the field of the core, within which magnetic oscillations are formed, was discovered at the boundary of the mantle and core. Electric currents arising in the core prevent direct measurements of its magnetic field.

It is important that most of the geomagnetic field is generated only in four broad regions at the core-mantle boundary. Although the geodynamo produces a very strong magnetic field, only 1% of its energy travels outside the core. The general configuration of the magnetic field measured at the surface is called a dipole, which most of the time is oriented along the earth's axis of rotation. As in the field of a linear magnet, the main geomagnetic flow is directed from the center of the Earth in the Southern Hemisphere and towards the center in the Northern Hemisphere. (The compass needle points to the north geographic pole, since the south magnetic pole of the dipole is nearby.) Space observations have shown that the magnetic flux has an uneven global distribution, the greatest tension can be seen on the Antarctic coast, under North America and Siberia.

Ulrich R. Christensen of the Max Planck Institute for Solar System Research in Katlenburg-Lindau, Germany, believes that these vast areas of land have existed for thousands of years and are maintained by ever-evolving convection within the core. Could similar phenomena be the cause of pole reversals? Historical geology shows that pole changes occurred in relatively short periods of time - from 4 thousand to 10 thousand years. If the geodynamo had stopped working, the dipole would have existed for another 100 thousand years. A rapid change in polarity gives reason to believe that some unstable position violates the original polarity and causes a new change of poles.

In some cases, the mysterious instability can be explained by some chaotic change in the structure of the magnetic flux, which only accidentally leads to repolarization. However, the frequency of polarity changes, which has become more and more stable over the past 120 million years, indicates the possibility of external regulation. One of the reasons for this may be a temperature difference in the lower layer of the mantle, and as a result, a change in the nature of core outpourings.

Some symptoms of repolarization were identified when analyzing maps that were made from the Magsat and Oersted satellites. Gauthier Hulot and his colleagues from the Paris Geophysical Institute noted that long-term changes in the geomagnetic field occur at the core-mantle boundary in places where the direction of the geomagnetic flow is opposite to the normal one for a given hemisphere. The largest of the so-called reverse magnetic field stretches from the southern tip of Africa west to South America. In this area, the magnetic flux is directed inward, towards the core, while most of it in the Southern Hemisphere is directed from the center.

Regions where the magnetic field is directed in the opposite direction for a given hemisphere arise when twisted and winding magnetic field lines accidentally break through beyond the Earth's core. Areas of reversed magnetic field can significantly weaken the magnetic field on the Earth's surface, called a dipole, and indicate the beginning of a reversal of the Earth's poles. They appear when rising liquid mass pushes horizontal magnetic lines upward in the molten outer core. This convective outpouring sometimes twists and extrudes the magnetic line(s). At the same time, the rotational forces of the Earth cause a helical circulation of the melt, which can tighten the loop on the extruded magnetic line (b). When the buoyancy force is strong enough to eject the loop from the core, a pair of magnetic flux patches form at the core-mantle boundary.

The most significant discovery made by comparing the latest Oersted measurements with those taken in 1980 was that new regions of magnetic reversals continue to form, for example at the core-mantle boundary beneath the east coast of North America and the Arctic. Moreover, previously identified areas have grown and moved slightly towards the poles. At the end of the 80s. XX century David Gubbins of the University of Leeds in England, studying old maps of the geomagnetic field, noted that the spread, growth and poleward shift of sections of the inverse magnetic field explains the decline in dipole strength over historical time.

According to theoretical principles about magnetic field lines, small and large vortices arising in the liquid medium of the nucleus under the influence of the Coriolis force twist the field lines into a knot. Each rotation collects more and more lines of force in the core, thus increasing the energy of the magnetic field. If the process continues unhindered, the magnetic field intensifies indefinitely. However, electrical resistance dissipates and aligns the turns of field lines enough to stop the spontaneous growth of the magnetic field and continue the reproduction of internal energy.

Areas of intense magnetic normal and reverse fields form at the core-mantle boundary, where small and large eddies interact with east-west magnetic fields, described as toroidal, that penetrate into the core. Turbulent fluid movements can twist toroidal field lines into loops called poloidal fields, which have a north-south orientation. Sometimes twisting occurs when a fluid mass is raised. If such an outpouring is powerful enough, the top of the poloidal loop is pushed out of the nucleus (see inset on the left). As a result of this ejection, two sections are formed in which the loop crosses the core-mantle boundary. On one of them, a direction of magnetic flux arises that coincides with the general direction of the dipole field in a given hemisphere; in another section the flow is directed in the opposite direction.

When rotation brings a section of the reversed magnetic field closer to the geographic pole than the section with normal flux, there is a weakening of the dipole, which is most vulnerable near its poles. This can explain the reversed magnetic field in southern Africa. With the global onset of a pole reversal, areas of reversed magnetic fields can grow throughout the region near the geographic poles.

Contour maps of the Earth's magnetic field at the core-mantle boundary, compiled from satellite measurements, show that most of the magnetic flux is directed from the center of the Earth in the Southern Hemisphere and towards the center in the Northern Hemisphere. But in some areas the opposite picture emerges. The reversed magnetic field regions grew in number and size between 1980 and 2000. If they filled the entire space at both poles, repolarization could occur.

Pole reversal models

Magnetic field maps show how, with normal polarity, most of the magnetic flux is directed from the center of the Earth (yellow) in the Southern Hemisphere and towards its center (blue) in the Northern Hemisphere (a). The onset of repolarization is marked by the appearance of several areas of reverse magnetic field (blue in the Southern Hemisphere and yellow in the Northern Hemisphere), reminiscent of the formation of its sections at the core-mantle boundary. Over approximately 3 thousand years, they reduced the strength of the dipole field, which was replaced by a weaker, but more complex transition field at the core-mantle boundary (b). Pole reversals became a frequent occurrence after 6 thousand years, when sections of the reverse magnetic field (c) began to predominate at the core-mantle boundary. By this time, a complete reversal of the poles had also manifested itself on the surface of the Earth. But only after another 3 thousand years there was a complete replacement of the dipole, including the Earth’s core (d).

What is happening to the internal magnetic field today?

Most of us know that the geographic poles constantly make complex looping movements in the direction of the Earth's daily rotation (axis precession with a period of 25,776 years). Typically, these movements occur near the imaginary axis of rotation of the Earth and do not lead to noticeable climate change. Read more about pole shift. But few people noticed that at the end of 1998 the overall component of these movements shifted. Within a month, the pole shifted towards Canada by 50 kilometers. Currently, the North Pole is “creeping” along the 120th parallel of western longitude. It can be assumed that if the current trend in pole movement continues until 2010, the north pole could shift by 3-4 thousand kilometers. The end point of the drift is the Great Bear Lakes in Canada. The South Pole will accordingly shift from the center of Antarctica to the Indian Ocean.

The shift of magnetic poles has been recorded since 1885. Over the past 100 years, the magnetic pole in the southern hemisphere has moved almost 900 km and entered the Indian Ocean. The latest data on the state of the Arctic magnetic pole (moving towards the East Siberian world magnetic anomaly through the Arctic Ocean): showed that from 1973 to 1984 its mileage was 120 km, from 1984 to 1994. – more than 150 km. It is characteristic that these data are calculated, but they were confirmed by specific measurements of the north magnetic pole. According to data at the beginning of 2002, the drift speed of the north magnetic pole increased from 10 km/year in the 70s, to 40 km/year in 2001 year.

In addition, the strength of the earth's magnetic field drops, and very unevenly. Thus, over the past 22 years it has decreased by an average of 1.7 percent, and in some regions - for example, in the South Atlantic Ocean - by 10 percent. However, in some places on our planet the magnetic field strength, contrary to the general trend, has even increased slightly.

We emphasize that the acceleration of the movement of the poles (on average by 3 km/year per decade) and their movement along the corridors of magnetic pole inversion (more than 400 paleoinversions made it possible to identify these corridors) makes us suspect that this movement of the poles should not be seen as an excursion, and the reversal of the Earth's magnetic field.

Acceleration can bring the movement of the poles up to 200 km per year, so that the reversal will take place much faster than expected by researchers who are far from professional assessments of real polarity reversal processes.

In the history of the Earth, changes in the position of the geographic poles have occurred repeatedly, and this phenomenon is primarily associated with the glaciation of vast areas of land and dramatic changes in the climate of the entire planet. But only the last catastrophe, most likely associated with a pole shift, which occurred about 12 thousand years ago, received echoes in human history. We all know that Mammoths are extinct. But everything was much more serious.

The extinction of hundreds of animal species is beyond doubt. There are discussions about the Flood and the Death of Atlantis. But one thing is certain - the echoes of the greatest catastrophe in human memory have a real basis. And it is most likely caused by a pole shift of only 2000 km.

The model below shows the magnetic field inside the core (a bunch of field lines in the center) and the appearance of a dipole (long curved lines) 500 years (a) before the middle of the repolarization of the magnetic dipole (b) and 500 years later at the stage of its completion (c).

Magnetic field of the Earth's geological past

Over the past 150 million years, repolarization has occurred hundreds of times, as evidenced by minerals magnetized by the Earth's field during the heating of rocks. Then the rocks cooled, and the minerals retained their previous magnetic orientation.

Magnetic field reversal scales: I – for the last 5 million years; II – over the last 55 million years. Black color – normal magnetization, white color – reverse magnetization (according to W.W. Harland et al., 1985)

Magnetic field reversals are a change in the sign of the axes of a symmetrical dipole. In 1906, B. Brun, measuring the magnetic properties of Neogene, relatively young lavas in central France, discovered that their magnetization was opposite in direction to the modern geomagnetic field, that is, the North and South magnetic poles seemed to have swapped places. The presence of reversely magnetized rocks is not a consequence of some unusual conditions at the time of its formation, but the result of an inversion of the Earth's magnetic field at the moment. Reversal of the polarity of the geomagnetic field is the most important discovery in paleomagnetology, which made it possible to create the new science of magnetostratigraphy, which studies the division of rock deposits based on their direct or reverse magnetization. And the main thing here is to prove the synchronicity of these sign reversals throughout the entire globe. In this case, geologists have a very effective method for correlating sediments and events in their hands.

In the real magnetic field of the Earth, the time during which the polarity sign changes can be either short, up to a thousand years, or millions of years.
The time intervals of predominance of any one polarity are called geomagnetic epochs, and some of them are given the names of the outstanding geomagnetologists Bruness, Matuyama, Gauss and Hilbert. Within epochs, shorter intervals of one polarity or another are distinguished, called geomagnetic episodes. The most effective identification of intervals of direct and reverse polarity of the geomagnetic field was carried out for geologically young lava flows in Iceland, Ethiopia and other places. A limitation of these studies is that the lava eruption was an intermittent process, so it is possible that some magnetic episode may have been missed.

When it became possible to determine the position of the paleomagnetic poles of the time interval of interest to us using selected rocks of the same age, but taken on different continents, it turned out that the calculated averaged pole, say, for Upper Jurassic rocks (170 - 144 million years) of North America and the same the pole for the same rocks in Europe will be in different places. It looked like there were two North Poles, which cannot happen with a dipole system. In order for there to be one North Pole, the position of the continents on the surface of the Earth had to change. In our case, this meant the convergence of Europe and North America until their shelf edges coincide, that is, to the ocean depths of about 200 m. In other words, it is not the poles that are moving, but the continents.

The use of the paleomagnetic method made it possible to carry out detailed reconstructions of the opening of the relatively young Atlantic, Indian, and Arctic oceans and to understand the history of the development of the more ancient Pacific Ocean. The current arrangement of the continents is the result of the breakup of the supercontinent Pangea, which began about 200 million years ago. The linear magnetic field of the oceans makes it possible to determine the speed of plate movement, and its pattern provides the best information for geodynamic analysis.

Thanks to paleomagnetic studies, it was established that the split of Africa and Antarctica occurred 160 million years ago. The most ancient anomalies with an age of 170 million years (Middle Jurassic) were found along the edges of the Atlantic off the coast of North America and Africa. This is the time when the supercontinent began to disintegrate. The South Atlantic arose 120 - 110 million years ago, and the North Atlantic much later (80 - 65 million years ago), etc. Similar examples can be given for any of the oceans and, as if “reading” the paleomagnetic record, one can reconstruct the history of their development and the movement of lithospheric plates.

World anomalies– deviations from the equivalent dipole of up to 20% of the intensity of individual areas with characteristic dimensions of up to 10,000 km. These anomalous fields experience secular variations, resulting in changes over time over many years and centuries. Examples of anomalies: Brazilian, Canadian, Siberian, Kursk. In the course of secular variations, global anomalies shift, disintegrate and re-emerge. At low latitudes there is a westerly drift in longitude at a rate of 0.2° per year.

2. MAGNETIC FIELDS OF LOCAL AREAS outer shells with a length from several to hundreds of km. They are caused by the magnetization of rocks in the upper layer of the Earth, which make up the earth's crust and are located close to the surface. One of the most powerful is the Kursk magnetic anomaly.

3. ALTERNATING MAGNETIC FIELD OF THE EARTH (also called external) is determined by sources in the form of current systems located outside the earth's surface and in its atmosphere. The main sources of such fields and their changes are corpuscular flows of magnetized plasma coming from the Sun along with the solar wind, and forming the structure and shape of the Earth's magnetosphere.

First of all, it is clear that this structure has a “layered” shape. However, sometimes one can observe a “rupture” of the upper layers, apparently occurring under the influence of increasing solar wind. For example like here:

At the same time, the degree of “heating” depends on the speed and density of the Solar wind at such a moment; it is reflected in the color scale from yellow to violet, which actually reflects the amount of pressure on the magnetic field in this zone (top right figure).

Structure of the magnetic field of the Earth's atmosphere (Earth's external magnetic field)

The Earth's magnetic field is influenced by the flow of magnetized solar plasma. As a result of interaction with the Earth's field, the outer boundary of the near-Earth magnetic field is formed, called magnetopause. It limits the earth's magnetosphere. Due to the influence of solar corpuscular flows, the size and shape of the magnetosphere are constantly changing, and an alternating magnetic field arises, determined by external sources. Its variability owes its origin to current systems developing at various altitudes from the lower layers of the ionosphere to the magnetopause. Changes in the Earth's magnetic field over time, caused by various reasons, are called geomagnetic variations, which differ both in their duration and in their localization on the Earth and in its atmosphere.

Magnetosphere is a region of near-Earth space controlled by the Earth's magnetic field. The magnetosphere is formed as a result of the interaction of the solar wind with the plasma of the upper atmosphere and the Earth's magnetic field. The shape of the magnetosphere is a cavity and a long tail, which repeat the shape of magnetic field lines. The subsolar point is on average at a distance of 10 Earth radii, and the tail of the magnetosphere extends beyond the orbit of the Moon. The topology of the magnetosphere is determined by the areas of solar plasma invasion into the magnetosphere and the nature of current systems.

The tail of the magnetosphere is formed by the lines of force of the Earth's magnetic field, emerging from the polar regions and extended under the influence of the solar wind to hundreds of Earth radii from the Sun to the night side of the Earth. As a result, the plasma of the solar wind and solar corpuscular flows seem to flow around the earth’s magnetosphere, giving it a peculiar tailed shape.
In the tail of the magnetosphere, at large distances from the Earth, the strength of the Earth’s magnetic field, and therefore their protective properties, are weakened, and some particles of solar plasma are able to penetrate and enter the interior of the Earth’s magnetosphere and magnetic traps of radiation belts. Penetrating into the head of the magnetosphere into the region of auroral ovals under the influence of changing pressure of the solar wind and the interplanetary field, the tail serves as a place for the formation of streams of precipitating particles, causing auroras and auroral currents. The magnetosphere is separated from interplanetary space by the magnetopause. Along the magnetopause, particles of corpuscular flows flow around the magnetosphere. The influence of the solar wind on the Earth's magnetic field is sometimes very strong. Magnetopause is the outer boundary of the Earth’s (or planet’s) magnetosphere, at which the dynamic pressure of the solar wind is balanced by the pressure of its own magnetic field. With typical solar wind parameters, the subsolar point is 9–11 Earth radii away from the center of the Earth. During periods of magnetic disturbances on Earth, the magnetopause can go beyond the geostationary orbit (6.6 Earth radii). With a weak solar wind, the subsolar point is located at a distance of 15–20 Earth radii.

Geomagnetic variations

Changes in the Earth's magnetic field over time under the influence of various factors are called geomagnetic variations. The difference between the observed magnetic field strength and its average value over any long period of time, for example, a month or a year, is called geomagnetic variation. According to observations, geomagnetic variations change continuously over time, and such changes are often periodic.

Daily variations geomagnetic fields arise regularly, mainly due to currents in the Earth's ionosphere caused by changes in the illumination of the Earth's ionosphere by the Sun during the day.

Daily geomagnetic variation for the period 03/19/2010 12:00 to 03/21/2010 00:00

The Earth's magnetic field is described by seven parameters. To measure the earth's magnetic field at any point, we must measure the direction and strength of the field. Parameters describing the direction of the magnetic field: declination (D), inclination (I). D and I are measured in degrees. The general field strength (F) is described by the horizontal component (H), the vertical component (Z) and the northern (X) and eastern (Y) components of the horizontal intensity. These components can be measured in Oersteds (1 Oersted = 1 gauss), but usually in nanoTesla (1nT x 100,000 = 1 oersted).

Irregular Variations magnetic fields arise due to the influence of the flow of solar plasma (solar wind) on the Earth’s magnetosphere, as well as changes within the magnetosphere and the interaction of the magnetosphere with the ionosphere.

The figure below shows (from left to right) images of the current magnetic field, pressure, convection currents in the ionosphere, as well as graphs of changes in the speed and density of the solar wind (V, Dens) and the values ​​of the vertical and eastern components of the Earth’s external magnetic field.

27 day variations exist as a tendency to repeat the increase in geomagnetic activity every 27 days, corresponding to the period of rotation of the Sun relative to an earthly observer. This pattern is associated with the existence of long-lived active regions on the Sun, observed during several solar revolutions. This pattern manifests itself in the form of a 27-day repeatability of magnetic activity and magnetic storms.

Seasonal variations magnetic activity are confidently identified on the basis of average monthly data on magnetic activity obtained by processing observations over several years. Their amplitude increases with increasing overall magnetic activity. It was found that seasonal variations in magnetic activity have two maxima, corresponding to the periods of the equinoxes, and two minima, corresponding to the periods of the solstices. The reason for these variations is the formation of active regions on the Sun, which are grouped in zones from 10 to 30° northern and southern heliographic latitudes. Therefore, during the periods of equinoxes, when the planes of the earth's and solar equators coincide, the Earth is most susceptible to the action of active regions on the Sun.

11 year variations. The connection between solar activity and magnetic activity is most clearly manifested when comparing long series of observations, multiples of 11 year periods of solar activity. The best known measure of solar activity is the number of sunspots. It was found that in the years of the maximum number of sunspots, magnetic activity also reaches its greatest value, but the increase in magnetic activity is somewhat delayed in relation to the increase in solar activity, so that on average this delay is one year.

Centuries-long variations – slow variations in the elements of terrestrial magnetism with periods of several years or more. Unlike diurnal, seasonal, and other variations of external origin, secular variations are associated with sources lying within the earth's core. The amplitude of secular variations reaches tens of nT/year; changes in the average annual values ​​of such elements are called the secular variation. Isolines of secular variations are concentrated around several points - centers or foci of the secular variation; in these centers the magnitude of the secular variation reaches its maximum values.

Magnetic storm - impact on the human body

The local characteristics of the magnetic field change and fluctuate, sometimes for many hours, and then restore to their previous level. This phenomenon is called a magnetic storm. Magnetic storms often begin suddenly and simultaneously across the globe.

A day after the solar flare, the shock wave of the solar wind reaches the Earth's orbit and a magnetic storm begins. Seriously ill patients clearly react from the first hours after the flare on the Sun, the rest - from the moment the storm began on Earth. What everyone has in common is a change in biorhythms during these hours. The number of cases of myocardial infarction increases the day after the outbreak (about 2 times more compared to magnetically quiet days). On the same day, a magnetospheric storm caused by the flare begins. In absolutely healthy people, the immune system is activated, there may be an increase in performance, and an improvement in mood.

Note: geomagnetic calm, lasting several days or more in a row, has a depressing effect on the body of a city dweller in many ways, like a storm - causing depression and weakened immunity. A slight “bounce” of the magnetic field within the range Kp = 0 – 3 helps to more easily withstand changes in atmospheric pressure and other weather factors.

The following gradation of Kp-index values ​​is accepted:

Kp = 0-1 – geomagnetic situation is calm (calm);

Kp = 1-2 – geomagnetic conditions from calm to slightly disturbed;

Kp = 3-4 – from slightly disturbed to disturbed;

Kp = 5 and above – weak magnetic storm (level G1);

Kp = 6 and above – average magnetic storm (level G2);

Kp = 7 and above – strong magnetic storm (level G3); accidents are possible, deterioration of health in weather-dependent people

Kp = 8 and above – a very strong magnetic storm (level G4);

Kp = 9 – extremely strong magnetic storm (level G5) – the maximum possible value.

Online observation of the state of the magnetosphere and magnetic storms here:

As a result of numerous studies conducted at the Institute of Space Research (IKI), the Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (IZMIRAN), the Medical Academy. THEM. Sechenov and the Institute of Medical and Biological Problems of the Russian Academy of Sciences, it turned out that during geomagnetic storms in patients with pathologies of the cardiovascular system, especially those who had suffered a myocardial infarction, blood pressure jumped, blood viscosity noticeably increased, the speed of its flow in the capillaries slowed down, and vascular tone changed and stress hormones were activated.

Changes also occurred in the body of some healthy people, but they mainly caused fatigue, decreased attention, headaches, dizziness and did not pose a serious danger. The astronauts’ bodies reacted somewhat more strongly to the changes: they developed arrhythmias and changed vascular tone. Experiments in orbit also showed that it is electromagnetic fields that negatively affect the human condition, and not other factors that act on Earth, but are excluded in space. In addition, another “risk group” was identified - healthy people with an overstrained adaptation system associated with exposure to additional stress (in this case, weightlessness, which also affects the cardiovascular system).

The researchers came to the conclusion that geomagnetic storms cause the same adaptive stress as a sharp change in time zones, which disrupts a person’s biological circadian rhythms. Sudden solar flares and other manifestations of solar activity dramatically change the relatively regular rhythms of the Earth's geomagnetic field, which causes animals and people to disrupt their own rhythms and generate adaptive stress.

Healthy people cope with it relatively easily, but for people with pathologies of the cardiovascular system, with an overstrained adaptation system and for newborns, it is potentially dangerous.

It is impossible to predict the response. It all depends on many factors: on the person’s condition, on the nature of the storm, on the frequency spectrum of electromagnetic oscillations, etc. It is not yet known how changes in the geomagnetic field affect the biochemical and biophysical processes occurring in the body: what the receivers of geomagnetic signals-receptors are, whether a person reacts to exposure to electromagnetic radiation with the entire body, individual organs, or even individual cells. Currently, in order to study the influence of solar activity on people, a heliobiology laboratory is being opened at the Institute of Space Research.

9. N.V. Koronovsky. MAGNETIC FIELD OF THE GEOLOGICAL PAST OF THE EARTH // Moscow State University. M.V. Lomonosov. Soros Educational Journal, N5, 1996, p. 56-63

In recent days, a large amount of news about the Earth's magnetic field has appeared on scientific information sites. For example, news that it has been changing significantly recently, or that the magnetic field contributes to the leakage of oxygen from the earth’s atmosphere, or even that cows in pastures are oriented along the lines of the magnetic field. What is a magnetic field and how important is all this news?

The Earth's magnetic field is the area around our planet where magnetic forces operate. The question of the origin of the magnetic field has not yet been completely resolved. However, most researchers agree that the presence of the Earth's magnetic field is at least partly due to its core. The earth's core consists of a solid interior and a liquid exterior. The rotation of the Earth creates constant currents in the liquid core. As the reader may remember from physics lessons, the movement of electric charges results in the appearance of a magnetic field around them.

One of the most common theories explaining the nature of the field, the theory of the dynamo effect, assumes that convective or turbulent movements of a conducting fluid in the core contribute to self-excitation and maintenance of the field in a stationary state.

The earth can be considered as a magnetic dipole. Its south pole is located at the geographic North Pole, and its north pole, respectively, is at the South Pole. In fact, the geographic and magnetic poles of the Earth do not coincide not only in “direction”. The magnetic field axis is tilted relative to the Earth's rotation axis by 11.6 degrees. Since the difference is not very significant, we can use a compass. Its arrow points precisely to the Earth's South Magnetic Pole and almost exactly to the North Geographic Pole. If the compass had been invented 720 thousand years ago, it would have pointed to both the geographic and magnetic north poles. But more on that below.

The magnetic field protects the inhabitants of the Earth and artificial satellites from the harmful effects of cosmic particles. Such particles include, for example, ionized (charged) solar wind particles. The magnetic field changes the trajectory of their movement, directing the particles along the field lines. The necessity of a magnetic field for the existence of life narrows the range of potentially habitable planets (if we proceed from the assumption that hypothetically possible life forms are similar to earthly inhabitants).

Scientists do not rule out that some terrestrial planets do not have a metallic core and, accordingly, lack a magnetic field. Until now, planets made of solid rock, like Earth, were thought to contain three main layers: a solid crust, a viscous mantle, and a solid or molten iron core. In a recent paper, scientists from the Massachusetts Institute of Technology proposed the formation of "rocky" planets without a core. If the theoretical calculations of the researchers are confirmed by observations, then to calculate the probability of meeting humanoids in the Universe, or at least something resembling illustrations from a biology textbook, it will be necessary to rewrite them.

Earthlings may also lose their magnetic protection. True, geophysicists cannot yet say exactly when this will happen. The fact is that the Earth's magnetic poles are not constant. Periodically they change places. Not long ago, researchers found that the Earth “remembers” the reversal of the poles. Analysis of such “memories” showed that over the past 160 million years, magnetic north and south have changed places about 100 times. The last time this event occurred was about 720 thousand years ago.

The change of poles is accompanied by a change in the configuration of the magnetic field. During the “transition period,” significantly more cosmic particles that are dangerous to living organisms penetrate to Earth. One of the hypotheses explaining the disappearance of dinosaurs states that the giant reptiles became extinct precisely during the next pole change.

In addition to the “traces” of planned activities to change the poles, researchers noticed dangerous shifts in the Earth’s magnetic field. An analysis of data on his condition over several years showed that in recent months, things began to happen to him. Scientists have not recorded such sharp “movements” of the field for a very long time. The area of ​​concern to researchers is located in the South Atlantic Ocean. The "thickness" of the magnetic field in this area does not exceed a third of the "normal" one. Researchers have long noticed this “hole” in the Earth’s magnetic field. Data collected over 150 years show that the field here has weakened by ten percent over this period.

At the moment, it is difficult to say what threat this poses to humanity. One of the consequences of weakening the field strength may be an increase (albeit insignificant) in the oxygen content in the earth's atmosphere. The connection between the Earth's magnetic field and this gas was established using the Cluster satellite system, a project of the European Space Agency. Scientists have found that the magnetic field accelerates oxygen ions and “throws” them into outer space.

Despite the fact that the magnetic field cannot be seen, the inhabitants of the Earth feel it well. Migratory birds, for example, find their way, focusing on it. There are several hypotheses explaining how exactly they sense the field. One of the latest suggests that birds perceive a magnetic field. Special proteins - cryptochromes - in the eyes of migratory birds are able to change their position under the influence of a magnetic field. The authors of the theory believe that cryptochromes can act as a compass.

In addition to birds, sea turtles use the Earth's magnetic field instead of GPS. And, as an analysis of satellite photographs presented as part of the Google Earth project showed, cows. After studying photographs of 8,510 cows in 308 areas of the world, scientists concluded that these animals preferentially (or from south to north). Moreover, the “reference points” for cows are not geographical, but rather the magnetic poles of the Earth. The mechanism by which cows perceive the magnetic field and the reasons for this particular reaction to it remain unclear.

In addition to the listed remarkable properties, the magnetic field contributes. They arise as a result of sudden changes in the field that occur in remote regions of the field.

The magnetic field was not ignored by supporters of one of the “conspiracy theories” - the theory of a lunar hoax. As mentioned above, the magnetic field protects us from cosmic particles. The "collected" particles accumulate in certain parts of the field - the so-called Van Alen radiation belts. Skeptics who do not believe in the reality of the moon landings believe that astronauts would have received a lethal dose of radiation during their flight through the radiation belts.

The Earth's magnetic field is an amazing consequence of the laws of physics, a protective shield, a landmark and the creator of auroras. If it weren't for it, life on Earth might have looked completely different. In general, if there were no magnetic field, it would have to be invented.

According to modern ideas, it was formed approximately 4.5 billion years ago, and from that moment our planet has been surrounded by a magnetic field. Everything on Earth, including people, animals and plants, is affected by it.

The magnetic field extends to an altitude of about 100,000 km (Fig. 1). 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 magnetosphere(Fig. 2). On the side of the Earth illuminated by the Sun, the magnetosphere is limited by a spherical surface with a radius of approximately 10-15 Earth radii, and on the opposite side it is extended like a comet's tail over a distance of up to several thousand Earth radii, forming a geomagnetic tail. The magnetosphere is separated from the interplanetary field by a transition region.

Earth's magnetic poles

The axis of the earth's magnet is inclined relative to the earth's rotation axis by 12°. It is located approximately 400 km away from the center of the Earth. The points at which this axis intersects the surface of the planet are magnetic poles. The Earth's magnetic poles do not coincide with the true geographic poles. Currently, the coordinates of the magnetic poles are as follows: north - 77° north latitude. and 102°W; southern - (65° S and 139° E).

Rice. 1. The structure of the Earth’s magnetic field

Rice. 2. Structure of the magnetosphere

Lines of force running from one magnetic pole to another are called magnetic meridians. An angle is formed between the magnetic and geographic meridians, called magnetic declination. Every place on Earth has its own declination angle. In the Moscow region the declination angle is 7° to the east, and in Yakutsk it is about 17° to the west. This means that the northern end of the compass needle in Moscow deviates by T to the right of the geographic meridian passing through Moscow, and in Yakutsk - by 17° to the left of the corresponding meridian.

A freely suspended magnetic needle is located horizontally only on the line of the magnetic equator, which does not coincide with the geographical one. If you move north of the magnetic equator, the northern end of the needle will gradually descend. The angle formed by a magnetic needle and a horizontal plane is called magnetic inclination. At the North and South magnetic poles, the magnetic inclination is greatest. It is equal to 90°. At the North Magnetic Pole, a freely suspended magnetic needle will be installed vertically with its northern end down, and at the South Magnetic Pole its southern end will go down. Thus, the magnetic needle shows the direction of the magnetic field lines above the earth's surface.

Over time, the position of the magnetic poles relative to the earth's surface changes.

The magnetic pole was discovered by explorer James C. Ross in 1831, hundreds of kilometers from its current location. On average, it moves 15 km in one year. In recent years, the speed of movement of the magnetic poles has increased sharply. For example, the North Magnetic Pole is currently moving at a speed of about 40 km per year.

The reversal of the Earth's magnetic poles is called magnetic field inversion.

Throughout the geological history of our planet, the Earth's magnetic field has changed its polarity more than 100 times.

The magnetic field is characterized by intensity. In some places on Earth, magnetic field lines deviate from the normal field, forming anomalies. For example, in the area of ​​the Kursk Magnetic Anomaly (KMA), the field strength is four times higher than normal.

There are daily variations in the Earth's magnetic field. The reason for these changes in the Earth's magnetic field is electric currents flowing in the atmosphere at high altitudes. They are caused by solar radiation. Under the influence of the solar wind, the Earth's magnetic field is distorted and acquires a “trail” in the direction from the Sun, which extends for hundreds of thousands of kilometers. The main cause of the solar wind, as we already know, is the enormous ejections of matter from the solar corona. As they move towards the Earth, they turn into magnetic clouds and lead to strong, sometimes extreme disturbances on the Earth. Particularly strong disturbances of the Earth's magnetic field - magnetic storms. Some magnetic storms begin suddenly and almost simultaneously across the entire Earth, while others develop gradually. They can last for several hours or even days. Magnetic storms often occur 1-2 days after a solar flare due to the Earth passing through a stream of particles ejected by the Sun. Based on the delay time, the speed of such a corpuscular flow is estimated at several million km/h.

During strong magnetic storms, the normal operation of the telegraph, telephone and radio is disrupted.

Magnetic storms are often observed at latitude 66-67° (in the aurora zone) and occur simultaneously with auroras.

The structure of the Earth's magnetic field varies depending on the latitude of the area. The permeability of the magnetic field increases towards the poles. Over the polar regions, the magnetic field lines are more or less perpendicular to the earth's surface and have a funnel-shaped configuration. Through them, part of the solar wind from the dayside penetrates into the magnetosphere and then into the upper atmosphere. During magnetic storms, particles from the tail of the magnetosphere rush here, reaching the boundaries of the upper atmosphere in the high latitudes of the Northern and Southern Hemispheres. It is these charged particles that cause the auroras here.

So, magnetic storms and daily changes in the magnetic field are explained, as we have already found out, by solar radiation. But what is the main reason that creates the permanent magnetism of the Earth? Theoretically, it was possible to prove that 99% of the Earth’s magnetic field is caused by sources hidden inside the planet. The main magnetic field is caused by sources located in the depths of the Earth. They can be roughly divided into two groups. The main part of them is associated with processes in the earth's core, where, due to continuous and regular movements of electrically conductive matter, a system of electric currents is created. The other is due to the fact that the rocks of the earth’s crust, when magnetized by the main electric field (the field of the core), create their own magnetic field, which is summed with the magnetic field of the core.

In addition to the magnetic field around the Earth, there are other fields: a) gravitational; b) electric; c) thermal.

Gravitational field The earth is called the gravity field. It is directed along a plumb line perpendicular to the surface of the geoid. If the Earth had the shape of an ellipsoid of revolution and masses were evenly distributed in it, then it would have a normal gravitational field. The difference between the intensity of the real gravitational field and the theoretical one is a gravity anomaly. Different material composition and density of rocks cause these anomalies. But other reasons are also possible. They can be explained by the following process - the equilibrium of the solid and relatively light earth's crust on the heavier upper mantle, where the pressure of the overlying layers is equalized. These currents cause tectonic deformations, the movement of lithospheric plates and thereby create the macrorelief of the Earth. Gravity holds the atmosphere, hydrosphere, people, animals on Earth. Gravity must be taken into account when studying processes in the geographic envelope. The term " geotropism" are the growth movements of plant organs, which, under the influence of the force of gravity, always ensure the vertical direction of growth of the primary root perpendicular to the surface of the Earth. Gravity biology uses plants as experimental subjects.

If gravity is not taken into account, it is impossible to calculate the initial data for launching rockets and spacecraft, to carry out gravimetric exploration of ore deposits, and, finally, the further development of astronomy, physics and other sciences is impossible.

The question has always arisen, how does a compass work? And today we will talk about such a thing as the EARTH’S MAGNETIC FIELD. And since, unfortunately, the editor is limited in time, and we want to give something interesting, we will tell you about “terrestrial magnetism” using several different sources.

So:

The Earth's magnetic field has long remained a mystery, because there are no stone magnets, right? But once you discover that there is a colossal amount of iron inside the Earth, everything seems to fall into place. Iron does not form a “permanent” magnet like those attached to plastic piglets and bear cubs, which we, without knowing why, buy to attach to the refrigerator. The bowels of the earth are more like a dynamo. By the way, this is called a geomagnetic dynamo. As we already mentioned, the iron in the Earth's core is mostly in a molten state, with the exception of a solid, dense "ball" at the very center. The liquid part still continues to heat up. Previously, this phenomenon was explained by the fact that radioactive elements, being denser than everything else in the chemical composition of the planet, sank into the very center, being locked there, and the heat was provided by the radioactive energy emitted by them. Modern theory offers a completely different explanation: the liquid part of the core heats up, as the solid part cools down. Molten iron in contact with the solid core itself gradually solidifies, and heat is released. That heat has to go somewhere, it can't just disappear like a breath of warm air - there are thousands of miles of solid rock all around. Heat is transferred to the molten core layer, heating it.

You may be surprised by the fact that the part that comes into contact with the solid core can cool and solidify and, at the same time, heat up during this solidification process. The explanation is simple: hot molten iron rises as it heats up. Remember the hot air balloon. When you heat air, it rises. This happens because when air is heated, it expands, becomes less dense, and less dense substances float above denser ones. The balloon holds air in a huge silk bag, often brightly colored and emblazoned with the logos of banks or real estate agencies, and rises with the air. Hot iron is not painted with anything, but rises in the same way as hot air, moving away from the solid core. It slowly floats up, cooling, and then, when it gets too cold, or rather relatively cold, begins to sink into the depths again. As a result, the earth's core is in continuous motion, heating up inside and cooling outside. It cannot rise all at once, that is, some areas of the core float, while others sink again. This type of circulating heat transfer is called convection.

According to physicists, if certain three conditions are met, moving liquids can create a magnetic field. First, the liquid must conduct electric current, and iron does this very well. Secondly, at least a small magnetic field must initially be present, and there are good reasons to believe that our Earth, then still very young, had a certain amount of personal magnetism. Thirdly, something must rotate this fluid, distorting the original magnetic field, and for the Earth such rotation occurs due to the Coriolis force, similar to the centrifugal force, but acting weaker and resulting from the rotation of the Earth around its axis. Roughly speaking, rotation distorts the initially weak magnetic field, twisting it like spaghetti on a fork. The magnetism then rises to the top, caught by the floating masses of the iron core. As a result of all this rotation, the magnetic field becomes much stronger.

Yes, in a sense, you can say that the Earth behaves as if it has a huge magnet inside it, but in reality everything is much more complicated. To make the picture a little more specific, let us recall that there are at least seven other factors that determine the presence of a magnetic field on the Earth. Thus, some components of the earth's crust can be permanent magnets. Like a compass needle pointing north, they gradually lined up with the stronger geomagnetic dynamo, further strengthening it. In the upper layers of the atmosphere there is a layer of charged ionized gas. Before satellites were invented, the ionosphere played a critical role in radio communications: radio waves bounced off charged gas rather than escaping into space. The ionosphere is in motion, and moving electricity creates a magnetic field. At an altitude of about 15,000 miles (24,000 km) flows a ring current—a layer of low-density ionized particles that forms a huge torus. This slightly weakens the strength of the Earth's magnetic field.

The next two factors are the so-called magnetopause and magnetic tail, which arose under the influence of the solar wind on the Earth’s magnetosphere. The solar wind is a constant stream of particles emitted by the hyperactive Sun. The magnetopause is the head wave of the Earth’s magnetic field, moving against the solar wind, and the magnetic tail is the trace of this wave from the opposite side of the planet, where the Earth’s own magnetic field “leaks” outward, moreover, being destroyed under the influence of the solar wind. In addition, the solar wind causes a kind of thrust along the Earth's orbit, creating an additional distortion of the magnetic field lines, known as the field-aligned current in the magnetosphere. And finally, there are auroral flows. The Northern Lights, or aurora borealis, are delightful, mysterious sheets of pale light shimmering in the northern polar sky. A similar performance, aurora australis, can be observed near the South Pole. Auroras are created by two bands of electrical current flowing from the magnetopause into the magnetic tail. This, in turn, creates new magnetic fields and two electric currents - western and eastern.

So, you say, the Earth is just a big magnet? Well, yes, and the ocean is a bowl of water.

Magnetic materials found in ancient rocks indicate that from time to time the Earth's magnetic field changes its polarity, the north magnetic pole becomes south and vice versa. This happens approximately once every half a million years, although a strict pattern has not been observed. No one knows exactly why this happens, but mathematical models show that the Earth's magnetic field can be oriented equally likely in both directions, with neither direction being stable. Any position sooner or later loses stability and passes the baton to the opposite one. Transitions occur quickly, over about 5 thousand years, while the periods between them are a hundred times longer.

Most planets have magnetic fields, and this fact is even more difficult to explain than the earth’s field. We still have a lot to learn about planetary magnetism.

Alfred Wegener

One of the most impressive properties of our planet was discovered in 1912, but was not taken into account until the 60s. The most convincing evidence in its favor was precisely the change of magnetic poles. The point is that the earth's continents do not stand still, but slowly drift along the surface of the planet. According to a German scientist Alfred Wegener, who was the first to publish his theory, the current separate continents used to be one supercontinent, which he called Pangea(i.e. "The whole earth"). It existed about 300 million years ago.

Surely Wegener was not the first to think of this. His idea was, at least in part, influenced by the striking similarity between the coastlines of Africa and South America. This is especially noticeable on the map. Naturally, Wegener relied on other data. He was not a geologist, but a meteorologist, a specialist in ancient climates, and he was surprised that in regions with a cold climate rocks were found that clearly arose in regions with a warm one, and vice versa. For example, in the Sahara you can still find the remains of ancient glaciers, which are 420 million years old, and in Antarctica you can find fossilized ferns. In those days, anyone would have told him that the climate had simply changed. However, Wegener was convinced that the climate remained almost the same, with the exception of the Ice Age, and that the continents themselves changed, that is, moved. He assumed that they separated as a result of convection in the Earth's mantle, but he was not sure.

This idea was considered crazy, especially since it was not proposed by a geologist, and besides, Wegener ignored all the facts that did not fit into his theory. And the fact that the similarity between Africa and South America is not so ideal, and that continental drift could not be explained. Convection clearly has nothing to do with it, since it is too weak. Great A'Tuin(suspects that A'Tuin is a girl) may carry the whole world on his back, but he is just a fiction, and in the real world, it seems, such forces are simply unthinkable.

We did not use the word “unthinkable” by chance. Many brilliant and respected scientists often repeat the same mistake. They confuse the expression “I don’t understand how this can be” with “It’s completely impossible.” One of these, ashamed as it may be to admit, one of us two, was a mathematician, and an excellent one, but when his calculations showed that the earth’s mantle cannot move continents, it did not even occur to him that the theories on which the calculations were based were wrong. His name was Sir Harold Jeffreys, and his problem was that he clearly lacked a flight of fancy, because not only the outlines of the continents on both sides of the Atlantic coincided. From the point of view of geology and paleontology, everything also converged. Take, for example, the fossilized remains of a beast named mesosaur, who lived 270 million years ago in both South America and Africa. It is unlikely that the mesosaur swam across the Atlantic Ocean; rather, it simply lived on Pangea, having managed to settle across both continents when they were not yet separated.

However, in the 60s of the twentieth century, Wegener’s idea was recognized, and his theory of “continental drift” was established in science. At a meeting of leading geologists, a young man named Edward Ballard, who closely resembled Ponder Toups, and two of his colleagues demonstrated the capabilities of a then new device called a computer. They tasked the machine to find the best match not only between Africa and South America, but also North America and Europe, taking into account possible but small changes. Instead of taking the current contours of the coastline, which was not a very bright idea to begin with, allowing opponents of the drift theory to argue that the continents did not coincide, the young scientists used a contour corresponding to a depth of 3,200 feet (1,000 m) below sea level, since, according to in their opinion, it was less subject to erosion. The contours fit well and the geology was so great. And although people at the conference still did not come to a consensus, the theory of continental drift finally received some recognition.

Today we have much more evidence and a clear understanding of the drift mechanism. In the central part of the Atlantic Ocean, halfway between South America and Africa, one of the mid-ocean ridges stretches from south to north (these, by the way, exist in all other oceans). Volcanic materials rise from the depths along the entire ridge and then spread along its slopes. And this has been happening for 200 million years. You can even send a submarine and just watch the process. Of course, a lifetime would not be enough to notice this, but America is moving away from Africa at a rate of 3/4 inch (2 cm) per year. Our nails grow at approximately the same speed, however, modern equipment is capable of recording these changes.

The clearest evidence of continental drift comes from the Earth's magnetic field: rocks on both sides of the ridges have a curious pattern of magnetic stripes that change polarity from north to south and back again, with the pattern on both slopes being symmetrical. This means that the strips froze in the magnetic field as they cooled. When the earth's dynamo changed its polarity from time to time, the rocks of the ridge became magnetized in its field. Then, after the magnetized rocks were separated, identical patterns appeared on opposite sides of the ridge.

The surface of the Earth is not a solid sphere. Both the continents and the ocean floor float on huge, particularly hard plates that can move apart when magma seeps between them. (And most often this happens due to convection in the mantle. Jeffreys simply did not know everything that we know about the movement of the mantle.) There are about a dozen plates, ranging in width from six hundred (1000 km) to six thousand (10,000 km) miles, and they turn around all the time. Where their boundaries touch, rub and slide, earthquakes and volcanic eruptions constantly occur. Especially in the Pacific Fire Belt, which stretches along the entire perimeter of the Pacific Ocean and includes the west coast of Chile, Central America, the United States and beyond the Japanese islands and New Zealand. They are all on the edge of one giant slab. Where the plates collide, mountains arise: one plate ends up under the other and lifts it, crushing and crushing its edge. India is not at all part of the Asian continent, it simply crashed into it, creating the world's highest mountains - the Himalayas. It accelerated so much that it still continues its movement, and the Himalayas are growing.

(c) Discworld Science, Terry Pratchett, Jack Cohen, Ian Stewart(In general, read this book; you won’t find a better guide in an entertaining form (but before that, familiarize yourself, in principle, with Pratchett’s “Discworld” series in bibliographical NOT AS POPULAR order)).

Video of the Magnetic Field from Roscosmos:

How does a compass work?

Who hasn't seen a compass? A small thing that looks like a clock with one hand. You twist it and turn it, but the arrow stubbornly turns in one direction. The compass needle is a magnet that rotates freely on the needle. The principle of operation of a magnetic compass is based on the attraction and repulsion of two magnets. Opposite poles of magnets attract, like poles repel. Our planet is also such a magnet. Its strength is small, it is not enough to manifest itself on a heavy magnet. However, a light compass needle, balanced on a needle, also rotates under the influence of a small magnetic field.

sports compass

So that the compass needle does not dangle, but clearly shows the direction regardless of shaking, it must be quite strongly magnetized. In sports compasses, the bulb with the arrow is filled with liquid. Non-aggressive for plastic and metal parts, does not freeze at winter temperatures. The air bubble left in the flask serves as a level indicator to orient the compass in the horizontal plane.

The lead in the study of the Earth's magnetic field belongs to the English scientist William Gilbert. In his book “On the Magnet, Magnetic Bodies and the Great Magnet - the Earth,” published in 1600, he presented the Earth in the form of a giant permanent magnet, the axis of which does not coincide with the axis of rotation of the Earth. The angle between the axis of rotation and the magnetic axis is called magnetic declination.

As a result of this discrepancy, it is not entirely true to say that the compass needle always points north. It points to a point located at a distance of 2100 km from the north pole, on Somerset Island (its coordinates are 75 °, 6 N, 101 ° W - data for 1965). The Earth's magnetic poles are slowly drifting. In addition to such an error in the direction of the arrow (we will call it systematic), we must also not forget about other reasons for the compass not working correctly:

• Metal objects or magnets located near the compass deflect its needle
• Electronic devices that are sources of electromagnetic fields
• Mineral deposits – metal ores
• Magnetic storms that occur during years of strong solar activity distort the Earth's magnetic field.

Now, try to answer the questions for the smart ones:

In the meantime, I’ll give you some interesting facts about the Earth’s magnetic field.

It turns out that it weakens by about 0.5% every 10 years. According to various estimates, it will disappear in 1-2 thousand years. It is assumed that at this moment a polarity reversal between the magnet and the Earth will occur. After which the field will begin to increase again, but the north and south magnetic poles will change places. It is believed that this has happened to our planet a huge number of times.

It turns out that migratory birds also navigate “by compass,” or more precisely, the Earth’s magnetic field serves as a guide for them. Recently, scientists have learned that birds have a small magnetic “compass” in the eye area - a tiny tissue field in which magnetite crystals are located, which have the ability to magnetize in a magnetic field.

You can make a simple compass yourself. To do this, leave the sewing needle next to the magnet for several days. After this, the needle will be magnetized. After moistening it with fat or oil, carefully lower the needle onto the surface of the water poured into the cup. The fat will not let it sink, and the needle will turn from north to south (or vice versa:).

Are you impressed? Now you can check your answers to the questions:

• Where do you think the compass needle will point if you are between the north geographic pole and the north magnetic pole?
  - The northern end of the arrow will point... to the south, and the southern end - to the north!
• Where does the arrow point when the compass is near the magnetic pole?
  - it turns out that an arrow suspended on a thread in the area of ​​the magnetic pole tends to turn around... down, along the magnetic lines of the Earth!
• If, guided by a compass, you walk strictly to the northeast for a very long time, then where will you end up?
  – you will come to the north magnetic pole! Try to trace your path on the globe, it turns out to be a very interesting route.

and this is what the sea compass on Columbus's ship might have looked like

We hope you enjoyed this material. If yes, then we will make more of these different ones!

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A team of scientists led by Simon Anzellini made a new discovery. During some experiments, they established new qualities of the solid part of the earth's core

Scientists have found that the iron core of the earth is heated to 6 thousand degrees Celsius, and this information is a thousand degrees higher than previously thought. And this fact now allows us to understand the nature of the magnetic field of our planet.

Simon Ancellin, a member of the French Commissariat for Atomic Energy in Grenoble, and his colleagues were able to calculate the temperature of the Earth's iron core by observing the behavior of iron under ultra-high pressure.

A group of scientists used their own method to determine the properties of iron. A piece of iron was placed inside a diamond anvil and compressed under a pressure of 2.2 million atmospheres, and then heated by a laser beam to 4.5 thousand degrees Celsius.

The experiment was carried out to obtain data that will help scientists determine the temperature of the solid part of the earth's core, in which the pressure reaches 3.3 million atmospheres. To the surprise of scientists, the temperature in the core reached 6-6.5 thousand degrees Celsius, which exceeds earlier ideas by a thousand degrees. As scientists say, the new discovery fits well into the general understanding of scientists about the nature and structure of the planet. And it allows us to explain the cause of the Earth’s magnetic field.

Source of the Earth's magnetic field

Until the 17th century, this work was the main work on geomagnetism. From the 17th to the 20th centuries, many studies and observations began to take place, which led scientists to new conclusions and properties. At this time, the work of such scientists as Halley Halley, Alexander von Humboldt, Joseph Gay-Lussac, James Maxwell, Carl Gauss is celebrated.

The formation of the theory of electromagnetism by Maxwell in the 70s of the 19th century is quite significant. From his equations it turns out that the magnetic field is formed by electric current. Consequently, this leads to the equivalence of closed elementary currents and magnetic dipoles, the moment of which is also called the magnetic moment of the current. When added, these quantities form, say, the magnetic field of a cylindrical magnet, which is approximately equal to the field of a solenoid of the same length and the same cross-section.

But at the moment, there was no clear idea of ​​where the Earth's magnetic field comes from. Modern scientific works on the nature of geomagnetism indicate the following: “Now, turning to the “big magnet,” the matter at first glance is not so difficult: to find in the middle of the planet current systems of the required configuration and forces that form a field on the surface of the Earth, the structure of which we have studied well. When we head into the Earth, then, having passed through the crust, upper mantle and lower mantle, we will reach a huge liquid core, the existence of which was determined in the mid-20th century by Harold Jeffreys of the University of Cambridge.The actual liquid state of a large part of the core provides the conclusion of the mechanism for generating the geomagnetic field. The point is that the Earth's permanent magnetic field is formed by electric currents that appear when a conducting fluid moves in the core.Another theory on this issue has not yet been invented.

When we go further and try to understand the essence of the processes of generating the Earth’s geomagnetic field, then it’s time to use the dynamo mechanism for this purpose. In short, we will assume that the formation of a magnetic field in the outer liquid core of the Earth is carried out in the same way as in a self-excited dynamo, where a coil of wires rotates in an external magnetic field. Consequently, due to electromagnetic induction, an electric current arises in the coil and forms its own magnetic field. It increases the external magnetic field, and the current in the coil also increases.

Naturally, the liquid core of the planet is not a dynamo. But when thermal convection appears in a liquid conductor, a certain system of flows of electrically conductive liquid is formed, which is consonant with the movement of the conductor. It would not be gross violence against nature to assume the existence of certain seed magnetic fields in the nucleus. Consequently, if a liquid conductor, during its relative motion, crosses the lines of force of these fields, then an electric current is formed in it, creating a magnetic field, which increases the external seed field, and this, in turn, increases the electric current and so on, like the song about the pope and his dog, who carelessly ate a piece of meat. The process will continue until a stationary magnetic field is established, when various dynamic processes balance each other."

The earth's magnetic field is the energy of the future

Russian scientist Candidate of Physical and Mathematical Sciences Evgeny Timofeev, an employee of RSC Energia, has been working on this problem for many years. He has already managed to create a prototype of such a generator that would generate energy from the Earth's magnetic field. The generator works like this: when the device is set in motion, a sensitive voltmeter registers the occurrence of electromotive force in the circuit. The inventor clarifies that the method of operation of the device is based on the intersection of the Earth's magnetic field with a solenoid, some part of the winding of which is protected by a magnetic shield.

As the scientist states, in terms of practical use of the energy of sunlight, humanity is already much further ahead than the use of the Earth's magnetic field. In some aspects we are at the same level Tesla was at 75 years ago.