Earth's magnetic poles
You pick up a compass, pull the lever towards you so that the magnetic needle falls on the tip of the needle. When the arrow calms down, try to position it in a different direction. And you won't get anything. No matter how much you deviate the arrow from its original position, after it calms down, it will always point north with one end, and south with the other.
What force causes the compass needle to stubbornly return to its original position? Everyone asks himself a similar question, looking at a slightly oscillating, as if alive, magnetic needle.
From the history of discoveries
At first, people believed that such a force was the magnetic attraction of the North Star. Subsequently, it was found that the compass needle is controlled by the Earth, since our planet is a huge magnet.
But the magnetic needle is not always exactly directed along the north-south line, but has a deviation from this direction. This deviation is called magnetic declination.
Getting to know a person amazing properties terrestrial magnetism took place at the dawn of historical time. Already in ancient times, people were aware of magnetic iron ore - magnetite. But who and when determined that natural magnets are always oriented in the same way in space with respect to the geographic poles of the Earth, is not exactly known. In Chinese treatises dated to the 11th century BC. e., there are fragments that can be interpreted as evidence of the use of a compass for navigation purposes. The first known descriptions of the compass appeared in China only 23 centuries later - in the 11th century, and in Europe even later - in the 12th century. We owe the first reliable message about the magnetic compass that appeared in Europe to the English monk Alexander Neckem. Around 1187, he described a device consisting of an arrow indicating the direction, and in his compass the arrow floated, and was not suspended from a thread. Another important milestone in the history of geomagnetism is a letter written in 1269 by Pierre de Mericourt. In this message, in particular, it was said that a natural magnet has two poles and that these poles tend to be established along the geographic meridian, pointing to the earth's poles - north and south.
There is some information that already X. Columbus knew that the compass needle deviates from the geographic meridian and that this deviation is not the same in various parts Earth.
“... In September 1492, many Spaniards gathered on the embankment. Their eyes were fixed on the sea, where three ships were rocking on the waves. These ships had an unusual voyage: to cross an almost completely unknown hitherto ocean and reach fabulous India...
The ships set sail. The native Spanish coast was getting further and further away with each passing hour.
On September 13, the sailors were surprised to find that the compass needle had changed its direction, deviating to the west. The next day, the deviation was noticed again. The navigator reported to X. Columbus that the ship's compass needle had deviated by 11 degrees from its intended direction in four days.
Sitting in his cabin, Columbus thought for a long time. He could not explain this behavior of the compass needle in any way. Maybe turn back? But there, in Spain, shame awaits him, and ahead, if he discovers new lands, glory and honors await him. And Columbus decided to keep going. To reassure the sailors, he told them that it was not the compass needle that had changed its direction, but the North Star had shifted somewhat from its place. Therefore, there is nothing to worry about and the journey continues.
The sailors calmed down, and soon the ships reached the New World.
The deviation of the magnetic needle of the compass, discovered by Columbus, served as an impetus for the study of this phenomenon, since navigators needed accurate information about the magnitude of the magnetic declination in various parts of our planet. From that time on, declinations in different places on the Earth begin to be determined and, based on these data, magnetic maps are created, which show in which direction the magnetic needle of the compass deviates in a given place and by how many degrees.
In 1544, Hartmann, a pastor from Nuremberg, established that the direction to the geographical and to magnetic pole s differ, and the angle between these directions (declination) depends on the coordinates of the observation site. The next major step was taken by Robert Norman, who discovered another geo parameter. magnetic field, namely the inclination. Norman discovered that a freely suspended magnet needle not only moves in the direction of the magnetic poles, but also tilts with respect to the horizontal plane. Through this observation, Norman made a truly fundamental conclusion that the source of the force that guides the arrow is located inside the Earth, and not outside it.
In 1600, William Gilbert, the personal physician of the English Empress Elizabeth 1, on the basis of his endless experiments, to which he devoted his whole life, came to the conclusion that the Earth itself is a great magnet. XVII century marked by new discoveries in the field of geomagnetism. And the most remarkable of them can be considered the discovery of the phenomenon of "secular course". Edmund Halley, Astronomer Royal at the English Court, having made numerous repeated measurements of declination both in London and elsewhere, proved that it is subject to systematic regular changes. In the 18th - 19th centuries such outstanding encyclopedic scientists as Humboldt, Gay-Lussac, Maxwell and Gauss dealt with the problems of geomagnetism. Among the projects organized by Gauss and Humboldt was, in particular, the “Göttingen Union”, unprecedented in scale in the history of geomagnetism. Within the framework of this project, simultaneous measurements of the geomagnetic field were carried out in 50 points of the globe for 5 years (from 1836 to 1841) for 28 time intervals.
At the beginning of the twentieth century, in 1909, a floating magnetic laboratory was launched - the Carnegie yacht, which belonged to the Department of Terrestrial Magnetism of the Carnegie Institution in Washington. For almost 20 years, it was used to measure the magnetic field at various points of the World Ocean, and in 1953 the Soviet non-magnetic schooner Zarya set off on its first voyage, which, in three decades of constant expeditions, passed all the oceans, leaving 350 thousand nautical miles. In 1947, the Soviet physicist Ya.I. To explain the causes of the magnetic field, Frenkel proposed the hypothesis of the earth's dynamo, which was subsequently developed and substantially supplemented by other scientists and turned into a coherent theory of the origin of the geomagnetic field. An epochal event in the history of magnetology was the explanation of the nature of ocean magnetic anomalies. The honor of this discovery belongs to two scientists - D. Matthews and F. Vine. In their only joint paper, published in 1963 in Nature under the title "Magnetic anomalies over oceanic ridges," they proposed a model that explained all the major features of oceanic magnetic anomalies with extraordinary ease and grace. This work formed the basis of all contemporary research geomagnetic field.
Magnetic poles - magnetosphere
Compared to the magnetic fields we encounter in Everyday life(speaker cores, AC magnetic pulses in household appliances, lamps, power lines, etc.), the Earth's magnetic field is a very weak field. Nevertheless, this so-called main geomagnetic field, which has a planetary nature, exists everywhere on earth. People learned to measure some of its elements even before the discovery of the magnetic field itself. So, the first maps of the magnetic declination, which brought so much trouble to the sailors of antiquity, appeared back in mid-sixteenth century.
The realization that the magnetic poles do not coincide with the geographic ones put everything in its place and made it possible to understand that declination is the angle between the north direction and the magnetic meridian along which the compass needle is set. Just as long ago, the magnitude of the inclination, the angle between the horizontal plane and the magnetic needle, has been measured.
Now the magnetic field on the surface of our planet has been studied in sufficient detail. It turned out that it is by no means constant, but constantly changing. Throughout the year, hundreds of magnetic observatories, dozens of special ships and aircraft, numerous teams of magnetologists in various parts of the globe.
It turned out that the magnetic field is subject to a variety of changes. Some of them are regular and are observed daily, in particular the so-called diurnal variations, which are characterized by cyclical fluctuations in the magnetic field strength and magnetic declination. Other variations are no less well known - short-period oscillations, the duration of which does not exceed several minutes, as well as magnetic storms, whose duration can be measured for days.
All these variations are directly related to the activity of the Sun. On “quiet magnetic days”, the interaction of the solar wind with ionospheric currents causes smooth, regular changes in the components of the magnetic field with a period close to 24 hours. The magnetic storms mentioned above are irregular sporadic perturbations of the Earth's magnetosphere. They begin at the moment when the pressure of the solar wind on the magnetosphere changes sharply and it is unable to “take away” the flow of high-energy particles from the Earth. As a result, they penetrate the ionosphere, disrupting the regular structure of near-Earth electric currents. Magnetic storms are of different intensity and duration, but, as a rule, the complete restoration of the "calm" of the geomagnetic field occurs 2-3 days after the start of the storm.
In the event that the pressure jump (density) of the solar wind is not able to “break through” the magnetosphere, then the distortions of the magnetic lines of force are local in nature and magnetic disturbances do not cover the entire globe, but only some separate region. They are very frequent "guests" in the northern regions of the globe. Auroras are also most commonly associated with these disturbances.
During the year, there are two periods of a sharp increase in magnetic activity - these are the periods of the spring and autumn solstices, that is, March and September. At this time, the number of magnetic storms increases significantly. If on average 1-2 magnetic storms occur per month, then in March and September their number increases several times, and the autumn peak of magnetic activity is more energetic - in autumn the number of magnetic storms is greater than in spring, and can reach up to 7-8 per month .
The frequency of occurrence of storms is strongly influenced by the global 11-year cycle of solar activity, which largely determines all natural processes on the earth. By the way, 2003 was - the year - the maximum solar activity.
In addition to such short-term fluctuations of the magnetic field, there are much slower, smooth changes in its parameters, with a period of several hundred years. They are connected with the processes taking place inside the earth and are called secular variations. Secular variations can be likened to the respiration of a magnetic field - at each point on the earth's surface, the direction of the magnetic field periodically changes, and the magnitude of the magnetization of the planet as a whole does not remain constant. History of regular magnetic observations is a little over 100 years old, so the information about secular variations obtained from these measurements, of course, could not be complete. For a long time it seemed that any attempts of magnetologists to look into the distant past of our planet, to find out how its magnetic field changed over time, were doomed to failure. However, Nature herself has in store for people a wonderful clue that helped solve one of the most tricky mysteries of the evolution of the earth.
In the middle of the 19th century, the phenomenon of thermoremanent magnetization of lavas - paleomagnetism - was discovered. Gradually, step by step, scientists have established that the carriers of the ancient geomagnetic field can be rocks of various origins, both igneous and sedimentary.
It turned out that the rocks erupted during volcanic eruptions in the form of lava have an amazing ability to store information about the Earth's magnetic field. Rocks heated to a temperature of 500-700°C, as they cool, acquire magnetization, the magnitude and direction of which correspond to the Earth's magnetic field that acted on the rock during cooling. This magnetization persists for millions of years and, like a tape, brings us evidence from the remote past of the planet. By determining the age of lava formations by geological methods and "reading" the paleomagnetic information stored in them, it is possible to restore the history of the earth's magnetic field for certain.
Paleomagnetic studies have revealed irrefutable evidence of repeated reversals (pole reversals) of the geomagnetic field in past epochs. It turned out that the magnetic poles changed places more than once. Thanks to the achievements of physicists who have developed methods for determining the absolute age of rocks, paleomagnetologists have the opportunity not only to record the main events in the history of the geomagnetic field (primarily reversals), but also to determine their duration and the absolute start and end times of reversals - that is, to create a time scale ( time scale) of geomagnetic field reversals. Magnetologists call this scale magnetochronological.
The first such scale was rather "scanty" - it covered a period of only 3.5 million years and did not differ in great detail. The fact is that the lavas mostly erupted only in certain tectonomagmatic epochs, within a relatively narrow range.
time interval. Therefore, it became clear that, examining only lavas volcanic eruptions, "read" the entire history of the earth's magnetic field will fail.
The situation changed radically as soon as large-scale studies of the magnetic field of the oceans began. The very first continuous measurements along the lines crossing the Atlantic Ocean revealed sharp differences in the structure of the ocean's magnetic field compared to land. The result was truly sensational. It turned out that instead of a complex form of magnetic anomalies on land, which varies greatly from region to region, oceanic magnetic anomalies in all oceans have a regular, systematic character.
The magnetic field of the World Ocean is a parallel strip with an alternating direction of the magnetization of rocks - it alternately either coincides with the direction of the modern magnetic field (direct magnetization), or directly opposite to it (reverse magnetization). These anomalies stretch for thousands of kilometers, sometimes without any distortion. For example, in Atlantic Ocean they are traced from Iceland to Cape Horn.
Oceanic anomalies are of great intensity and huge size. But perhaps the most striking feature of these magnetic stripes is their mirror symmetry with respect to the mid-ocean ridge, that is, any positive or negative anomaly on one side of the ridge necessarily has its “twin” on the other. Moreover, the “twin” anomalies are located at the same distance from the axis of the ridge.
Magnetic prospecting geophysicists, who are accustomed to explaining magnetic field anomalies by the peculiarities of the geological structure and material composition of rocks in the study area, were at a loss: the usual, well-developed land models and schemes did not “work” as applied to the ocean. However, the explanation of this phenomenon was not long in coming - the revolution that took place in geology raised the global lithospheric plate tectonics to the pedestal of the sciences of the earth. She presented magnetologists with truly priceless gift- the ability to explore the history of the geomagnetic field throughout the existence of the oceans.
The joint efforts of paleomagnetologists and marine magnetometrists created the most detailed magnetochronological scale - the history of geomagnetic field reversals over 4 billion years. Moreover, just a cursory glance at this scale is enough to notice that the life of the Earth's magnetic field is quite stormy.
The magnetic poles of our planet change places from time to time - there is an inversion of the magnetic field. The south magnetic pole becomes the north, and vice versa. During such periods, the direction of the magnetic field turns out to be opposite to the modern one. The process of "rotation" of the poles takes at least 10 thousand years. And despite the huge achievements of magnetology and geophysics recent decades, the reasons for such transformations are still a mystery.
However, systematic detailed studies of reversals have made it possible to suggest that there may be a connection between the periodic change of flora and fauna on Earth and cyclic changes in the magnetic field. Many researchers believe that during the period of polarity reversal, the magnetic field weakens significantly or even disappears altogether, while the earth at this time remains defenseless against cosmic radiation flows, which have a tremendous impact on the planet's biosphere. The most daring hypotheses are associated with a change in the polarity of the magnetic poles even the appearance of a person.
It is too early to say how true these or other assumptions are. Undoubtedly, one thing - the very existence of life on our planet is impossible without a magnetic field that protects all living things from the destructive effects of cosmic radiation.
Earth's external magnetic field - the magnetosphere - propagates in outer space more than 20 earth diameters and reliably protects our planet from a powerful stream of cosmic particles.
STRUCTURE OF THE MAGNETOSPHERE: solar wind, shock wave front, interplanetary magnetic field, tail of the magnetosphere, magnetopause (magnetosphere boundary), night side of the magnetopause, day side of the magnetopause, point of intersection of field lines, ionosphere, particles trapped by field lines, plasma sphere, aurora oval .
The most striking manifestation of the magnetosphere are magnetic storms - fast chaotic fluctuations of all components of the geomagnetic field. Often, magnetic storms capture the entire globe: they are recorded by all magnetic observatories in the world - from Antarctica to Svalbard, and the type of magnetograms obtained in the most remote points Earth, remarkably similar. Therefore, it is no coincidence that such magnetic storms are called global.
The amplitude of the magnetic field oscillations during a storm is hundreds or even thousands of times higher than the level of oscillations on “calm” days, but they usually increase by no more than 1–3% relative to the main (internal) magnetic field of the Earth. The external magnetic field is the field of currents flowing in the ionosphere - the outer shell of the Earth's atmosphere, located approximately at a distance of 100 to 600 km from its surface. This shell is saturated with partially ionized gas - plasma, which is permeated by the geomagnetic field. The rotation of the Earth inevitably leads to the rotation of its gaseous outer shells, which, in addition to terrestrial gravity, experience the pressure of the solar wind.
Magnetic storms
Magnetic storms have a strong impact on radio communications, on telecommunication lines and on power plants. So, during a strong magnetic storm on February 11, 1958, which engulfed the entire globe, radio communications were interrupted in many places.
The electric currents caused in the Earth by a magnetic storm were so great in Sweden that the electrical insulating material on the cables caught fire, the fuses and transformers burned out, the signaling on the railways was interrupted.
Why do magnetic storms occur?
Why do magnetic storms occur? It turns out that the Sun is to blame for this, or rather, the processes taking place on this star closest to us.
It has been established that when magnetic storms occur on the Earth, spots are observed on the Sun, exceptionally strong explosions occur.
The fact that the compass needle fluctuates is not always the fault of the Sun. There are places on the globe where the arrow is influenced by rocks.
It is known that all rocks have magnetic properties. But among them, igneous crystalline rocks are the most magnetic.
Therefore, where crystalline rocks of a certain composition lie at depth, magnetic anomalies are observed. In such places on Earth, the compass needle, instead of pointing north, may turn west, east, or even south.
The strongest magnetic anomalies occur in areas where iron ore rocks occur at depth. That's why geologists have long been searching for minerals using a compass. For example, the world's largest iron ore deposit, the Kursk Magnetic Anomaly, was discovered, as well as the Sokolovsko-Sarbai iron ore deposit in Kazakhstan.
AT recent times scientists came to the conclusion that the magnetic properties of the Earth affect not only the magnetic needle of the compass, but also living organisms.
The influence of the magnetic property of the Earth on living organisms
Those of you who breed fish in an aquarium know that they can be trained so that after you knock on the glass of the aquarium, “he” swims to a certain place where they are usually fed. Tapping can be replaced by lighting a light bulb and, as it has recently become clear, a magnet. It turns out that the fish feel its action.
Man is even more sensitive, as well as animals, to processes occurring periodically on the Sun (strong explosions, the appearance of spots). These processes, as you now know, are caused by magnetic storms.
Scientists have long noticed that the rapid activity of the Sun occurs in about 11 years. They also noticed an eleven-year period in the life of some organisms. So, for example, if you carefully examine the annual rings on the saw cut of an old tree, you will notice that the thickness of these rings is not the same. The recurrence of wider and narrower rings has a certain regularity - it reflects the eleven-year cycle of solar activity.
A huge amount of material has been collected on the frequency of mass diseases among people and animals. And again, a relationship has been established between epidemics and changes in solar activity. So, the flu “comes” during the years of maximum solar activity, and foot and mouth disease, this scourge of animal husbandry, on the contrary, during the years of low solar activity.
Very interesting data are received concerning diphtheria. It is noted that the disease gave outbreaks during the years of minimum solar activity.
During the period of the restless Sun, the growth of trees intensifies, hordes of insects - agricultural pests - multiply catastrophically or suddenly disappear.
It may seem surprising, but the number of car accidents, according to statistics, as a rule, increases - and often four times! - on the second day after ... solar flares. With the help of special instruments, it was noticed that during flares on the Sun, people's reaction to signals slows down, and, moreover, by several times compared to the days of a quiet Sun.
In some countries, including the Soviet Union, a special solar service has been organized. So, for example, magnetographs are installed on some beaches, recording fluctuations in terrestrial magnetism. When the weather on the Sun deteriorates, people without a device do not notice it! the sea still sparkles and shimmers in the sun and not a cloud in the sky. And the magnetograph reports: perturbations occur on the Sun. Doctors, having learned about this, manage to protect their patients from the sunny bad weather in time.
Conclusion
Many people ask: is the magnetic compass obsolete in our time? After all, now navigators have such precise instruments as a gyrocompass and a variety of radar devices. Yes, besides, on ships made of metal, the magnetic needle is unlikely to point in the right direction. After all, it is known that - any iron thing significantly rejects; arrow.
And yet, a small movable arrow serves people even now. On any modern ship, one or two magnetic compasses must be installed. In addition to the compass, the tumbler has a map that shows the magnitude of the magnetic declination for each point.
Knowing the magnitude of the magnetic declination and having the readings of the ship's compass, the navigator introduces an amendment into them and determines the true course of the ship. For example, in the Baltic Sea the magnetic declination is 4-6 degrees, the declination is east. This means that the compass needle is deviated from the true north-south direction by 6 degrees to the east. To determine the true course of the ship, you need to correct the compass reading by 6 degrees.
Our scientists have found a way to get rid of the deviation of the compass needle under the influence of iron objects on the ship (such a deviation is called deviation). To do this, special magnets and iron objects are placed around the compass in a certain order.
Thanks to the science of deviation, the magnetic compass has remained faithful assistant sailors and on iron ships.
In the 20th century, with the advent of aviation, it became necessary to use a magnetic compass on airplanes. In this case, the destruction of the compass deviation on aircraft is carried out in the same way as on ships.
It is interesting to note that not only man uses the power of earth's magnetism (for example, for navigation). There is some reason to believe that birds, which surprise us with their ability to find places in which they were once born and lived, also use these forces.
Not so long ago were held interesting experiences with carrier pigeons, which, as you know, are distinguished by the ability to determine their permanent location. Five pigeons were taken away from the city where they were. Released into the wild, the birds unmistakably returned back. Then a small magnet was attached to each pigeon under the wings and the experiment was repeated. It turned out that only one pigeon out of five returned home, and then after a long wandering on the way.
According to modern concepts, it was formed about 4.5 billion years ago, and from that moment our planet is surrounded by a magnetic field. Everything on Earth, including people, animals and plants, is affected by it.
The magnetic field extends up to a height 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 bounded by a spherical surface with a radius of approximately 10-15 Earth radii, and on the opposite side it is elongated like a cometary 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 with respect to the axis of rotation of the earth by 12°. It is located about 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 magnetic poles of the Earth do not coincide with the true geographic poles. At present, the coordinates of the magnetic poles are as follows: north - 77 ° N.L. 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
The lines of force that run from one magnetic pole to the other are called magnetic meridians. An angle is formed between the magnetic and geographic meridians, called magnetic declination. Every place on Earth has its own angle of declination. In the Moscow region, the declination angle is 7° to the east, and in Yakutsk, 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 geographic one. If you move north of the magnetic equator, then the northern end of the arrow will gradually drop. 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 the north end down, and at the South Magnetic Pole, its south 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, he moves 15 km per year. AT last years the speed of movement of the magnetic poles has increased dramatically. 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.
For geological history our planet, the terrestrial magnetic field has changed its polarity more than 100 times.
The magnetic field is characterized by intensity. In some places on the Earth, magnetic field lines deviate from the normal field, forming anomalies. For example, in the region of the Kursk Magnetic Anomaly (KMA), the field strength is four times higher than normal.
There are diurnal changes in the Earth's magnetic field. The reason for these changes in the Earth's magnetic field is the electric currents flowing in the atmosphere for high altitude. They are caused by solar radiation. Under the action of the solar wind, the Earth's magnetic field is distorted and acquires a "tail" in the direction from the Sun, which extends for hundreds of thousands of kilometers. The main reason for the emergence of the solar wind, as we already know, is the grandiose ejections of matter from the corona of the Sun. 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. Some magnetic storms begin unexpectedly and almost simultaneously throughout the Earth, while others develop gradually. They can last for hours or even days. Often magnetic storms occur 1-2 days after solar flare due to the passage of the Earth 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 a latitude of 66-67° (in the aurora zone) and occur simultaneously with the 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. Above 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 day side penetrates into the magnetosphere, and then into the upper atmosphere. Particles from the tail of the magnetosphere rush here during magnetic storms, reaching the boundaries upper atmosphere at high latitudes in 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 due to sources located in the depths of the Earth. They can be roughly divided into two groups. Most of them are associated with processes in the earth's core, where, as a result of continuous and regular movements of the electrically conductive substance, a system of electric currents is created. The other is related to the fact that rocks earth's crust, being magnetized by the main electric field(field of the nucleus), create their own magnetic field, which is added to the magnetic field of the nucleus.
In addition to the magnetic field around the Earth, there are other fields: a) gravitational; b) electrical; c) thermal.
Gravity 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 an ellipsoid of revolution and the masses were evenly distributed in it, then it would have a normal gravitational field. The difference between the tension of the real gravitational field and theoretical - gravity anomaly. Different material composition, density of rocks cause these anomalies. But other reasons are also possible. They can be explained by the following process - the balance 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 Earth's macrorelief. Gravity keeps the atmosphere, hydrosphere, people, animals on Earth. The force of gravity must be taken into account when studying processes in a geographic envelope. The term " geotropism” called the growth movements of plant organs, which, under the influence of the force of gravity, always provide a vertical direction of growth of the primary root perpendicular to the surface of the Earth. Gravitational biology uses plants as experimental objects.
If gravity is not taken into account, it is impossible to calculate the initial data for launching rockets and spaceships, make gravimetric exploration of ore minerals and, finally, the further development of astronomy, physics and other sciences is impossible.
A MAGNETIC FIELD. ELECTROMAGNETS. PERMANENT MAGNETS. EARTH'S MAGNETIC FIELD
Option 1
I (1) When electric charges are at rest, then around them is found ...
1. electric field.
2. magnetic field.
3. electric and magnetic fields.
II (1) How are iron filings arranged in a direct current magnetic field?
1. Messy.
2. In straight lines along the conductor.
3. Along closed curves, covering the conductor.
III (1) What metals are strongly attracted by a magnet? 1. Cast iron. 2. Nickel. 3. Cobalt. 4. Steel.
IV (1) When one of the poles of a permanent magnet was brought to the magnetic needle, the south pole of the needle was repelled. Which pole was raised?
1. North. 2. Southern.
V (1) -Steel magnet is broken in half. Will the ends be magnetic? BUT and AT at the place of the magnet break (Fig. 180)?
1. Ends A and B will not have magnetic properties.
2. End BUT AT- southern.
3. End AT becomes the north magnetic pole, and BUT - southern.
VI (1) Steel pins are brought to the magnetic poles of the same name. How will the pins be located if they are released (Fig. 181)?
1. Will hang vertically. 2. The heads will be attracted to each other. 3. The heads will push off each other.
VII (1) As directed magnetic lines between the poles of an arcuate magnet (Fig. 182)?
1. From A to B. 2. From B to BUT.
VIII (1) Is the magnetic spectrum formed by the same or opposite poles (Fig. 183)?
1. Same name. 2. Different names.
IX (1) What are the magnetic poles shown in figure 184?
1. BUT- northern, AT- southern.
2. A - south, AT- northern.
3. L - northern, AT- northern.
4. L - southern, AT- southern.
X (1) The north magnetic pole is located at ... the geographic pole, and the south is located at ...
1. southern ... northern. 2. northern ... southern.
I (1) A metal rod was attached to the current source using wires (Fig. 185). What fields are formed around the rod when a current appears in it?
1. Only one electric field.
2. Only one magnetic field.
3. Electric and magnetic fields.
II (1) What are the magnetic lines of the magnetic field of the current?
1. Closed curves enclosing a conductor.
2. Curves located near the conductor.
3. Circles.
III (1) Which of the following substances is weakly attracted by a magnet?
1. Paper. 2. Steel. 3. Nickel. 4. Cast iron.
IV (1) Opposite magnetic poles ..., and like-...
1. attract ... repel.
2. repel... attract.
V (1) With a razor blade (end BUT)"touched the north magnetic pole of the magnet. Will the ends of the blade then have magnetic properties (Fig. 186)?
1. They won't.
2. End BUT becomes the north magnetic pole, and AT - southern.
3. End AT becomes the north magnetic pole, and BUT - southern.
VI (1) A magnet suspended from a thread is set in a north-south direction. Which pole of the magnet will turn to the north magnetic pole of the Earth?
1. North. 2. South.
VII (1) How are the magnetic lines directed between the poles of the magnet shown in figure 187?
1. From A to V. 2. From AT to BUT.
VIII (1) The north and south poles of a magnetic needle are attracted to the end of the steel rod. Is the rod magnetized?
1. Magnetized, otherwise the arrow would not be attracted.
2. Definitely impossible to say.
3. The rod is not magnetized. Only one pole would be attracted to a magnetized rod.
IX (1) A magnetic needle is located at the magnetic poles
(Fig. 188). Which of these poles is north and which is south?
1. BUT - northern, AT - southern.
2. A - south, AT- northern.
3. A- northern, AT- northern.
4. A - south, AT- southern.
X (1) All steel and iron objects become magnetized in the earth's magnetic field. What magnetic poles does the steel casing of the furnace have in the upper and lower parts in the northern hemisphere of the Earth (Fig. 189)?
1. Top-north, "bottom-south.
2. Above - south, below - north.
3. Above and below - the south poles.
4. Above and below - the north poles.
Option3
I (1) When electric charges move, then around them there is (ut) ...
1. electric field.
2. magnetic field.
3. electric and magnetic fields.
II (1) How can the magnetic field of a coil be increased?
1. Make a coil of a larger diameter.
2. Insert an iron core inside the coil.
3. Increase the current in the coil.
III (1) Which of the following substances is not attracted by a magnet at all?
1. Glass. 2. Steel. 3. Nickel. 4. Cast iron.
IV (1) The middle of the magnet AB does not attract iron filings (Fig. 190). The magnet is broken into two parts along the line AB, Will the ends of AB at the place where the magnet breaks attract iron filings?
1. They will, but very weakly.
2. They won't.
3. There will be, since a magnet with a south and north poles is formed.
V (1) Two pins are brought to the magnetic pole. How will the pins be located if they are released (Fig. 191)?
1. Will hang vertically.
2. They will be attracted to each other.
3. Push off each other
VI (1) How are the magnetic lines directed between the poles of the magnet shown in figure 192.
1 From A to AT. 2 From B to A.
VII (1) What magnetic poles form the spectrum shown in Figure 193.
1. Same name 2 Different name
VIII (1) Figure 194 shows an arcuate magnet and its magnetic field. Which pole is north and which is south?
1. A - northern, AT- southern.
2. BUT- south, AT- northern.
3. L - northern, AT - northern.
4. L - southern, AT- southern.
IX (1) If a steel rod is placed along the meridian of the Earth and given several blows with a hammer, it will become magnetized. What magnetic pole forms at the north end?
1. North. 2. Southern.
Option 4
I (1) When a metal rod was attached to one of the poles of a current source (Fig. 195), then a ... field formed around it.
1. electric
2. magnetic
3 electric and magnetic
II (1) When the current in the coil changes, does the magnetic field change?
1. The magnetic field does not change.
2. With an increase in the current strength, the effect of the magnetic field increases.
3. With an increase in the current strength, the effect of the magnetic field weakens.
III (1) Which of the following substances are well attracted by a magnet?
1 Wood. 2. Steel. 3. Nickel. 4 Cast iron
IV (1) Brought to the iron rod magnet north pole. What pole is formed at the opposite end of the rod?
1. 
Northern. 2. Southern.
(1) The steel magnet was broken into three pieces (Fig. 196). Will ends A and B be magnetic?
1. They won't.
2. End BUT has a north magnetic pole, AT- southern.
3. End AT has a north magnetic pole.
BUT- southern.
VI (1) The end of the penknife blade is brought to the south pole of the magnetic needle. This pole is attracted to the knife Was the knife magnetized?
 |
The knife was magnetized.
The end of the knife had a north magnetic pole
2 Can't say for sure.
3 The knife is magnetized, the south magnetic pole is brought.
VII (1) In what direction will the northern end of the magnetic needle turn if it is introduced into the magnetic field shown in Figure 197?
1. From BUT cat AT to L.
VIII (I) What magnetic poles form the spectrum shown in Figure 198, like or unlike?
1 of the same name. 2. Different names. 3. A pair of north poles. 4. A pair of south poles.
IX (1) Figure 199 shows a bar magnet AB and its magnetic field. Which pole is north and which is south?
1. BUT - northern. AT- southern.
2. BUT- south, AT - northern.
X (1) Which pole of a magnetic needle will be attracted to the top of a school steel tripod in the northern hemisphere of the Earth. Which pole will be attracted from below (Fig. 200)?
1. North will be attracted from above, south from below.
2. From above, the south will be attracted, from below - the north.
3. The south pole of the magnetic needle will be attracted from above and below.
4. The north pole of the magnetic needle will be attracted from above and below.
Polar riddles
“Less than a century ago, the South Pole of the Earth was a mysterious and inaccessible land. Superhuman efforts were required to get there, overcoming scurvy and wind, loss of orientation and fantastic cold. It remained intact and mysterious until Roald Amundsen and Robert Scott reached it in 1911 and 1912. About a hundred years later, the same thing happens on the Sun.
The Sun's south pole remains Terra Incognita - barely visible from Earth, and most research ships are in regions close to the star's equator. It was only recently that the joint European-American probe Ulysses flew around the Pole for the first time. It reached its maximum heliographic latitude - 80° - about a month ago.
Previously, "Ulysses" twice appeared above the solar poles - in 1994-1995 and 2000-2001. Even these brief flybys have shown that the poles of the Sun are very interesting and unusual regions. Let's list some "oddities".
The south pole of the sun is the magnetic north pole - from the point of view of the magnetic field, the star is standing on its head. By the way, the same non-standard situation exists on Earth: the north magnetic pole is located in the geographic South . In general, the magnetic fields of the Earth and the Sun, for all their unusualness, have much in common. Their poles are constantly moving, from time to time making a complete "revolution", in which the North and South magnetic poles change places. On the Sun, this reversal occurs every 11 years, in accordance with the sunspot cycle. On Earth, the "magnetic revolution" is rare and happens about once every 300 thousand years, and the cycles associated with this are still unknown. (03/13/2007, 10:03).
Ulysses: 15 years in orbit
Earth's south magnetic pole is actually the north pole of a magnet
"From a physical point of viewEarth's south magnetic pole is actually the north pole of the magnet that our planet represents. North Pole magnet - this is the pole from which the lines of force of the magnetic field come out.But to avoid confusion, this pole is called the south pole, since it is close to South Pole Earth."
Magnetic poles
“The earth's magnetic field looks like the globe is a magnet with an axis pointing approximately north to south.In the northern hemisphere all magnetic lines of force converge at a point lying at 70 ° 50 's. latitude and 96° west. longitude.This point is called the south magnetic pole. Earth. AT southern hemisphere the point of convergence of the lines of force lies at 70 ° 10 'S. latitude and 150°45' east. longitude;it is called the earth's north magnetic pole . It should be noted that the points of convergence of the earth's magnetic field lines lie not on the Earth's surface itself, but under it. The magnetic poles of the Earth, as we see, do not coincide with its geographical poles. Earth's magnetic axis, i.e. a straight line passing through both magnetic poles of the earth does not pass through its center and thus is not the earth's diameter.
Earth's magnetic field
« Earth's magnetic field similar to the field of a uniform magnetized sphere with a magnetic axis tilted 11.5° to the Earth's axis of rotation. Southernmagnetic pole Earth, to which the north end of the compass needle is attracted, does not coincide with the north geographic pole, and is located at a point with coordinates approximately 76° north latitude and 101° west longitude.Earth's north magnetic pole is located in Antarctica . The magnetic field strength at the poles is 0.63 Oe, at the equator - 0.31 Oe.
The Earth has two north poles (geographic and magnetic), both of which are in the Arctic region.
Geographic North Pole
The most extreme north point on the Earth's surface is the geographic North Pole, also known as True North. It is located at 90º north latitude but does not have a specific line of longitude because all meridians converge at the poles. The axis of the Earth connects the north and, and is a conditional line around which our planet rotates.
The geographic North Pole is located about 725 km (450 miles) north of Greenland, in the middle of the Arctic Ocean, which is 4,087 meters deep at this point. Most of the time, sea ice covers the North Pole, but recently water has been seen around the exact location of the pole.
All points are south! If you are standing at the North Pole, all points are located to the south of you (east and west do not matter at the North Pole). While the full revolution of the Earth occurs in 24 hours, the planet's rotation speed decreases as it moves away from, where it is about 1670 km per hour, and at the North Pole, there is practically no rotation.
The lines of longitude (meridians) that define our time zones are so close to the North Pole that time zones don't make sense here. Thus, the Arctic region uses the UTC (Coordinated Universal Time) standard to determine local time.
Due to tilt earth's axis The North Pole experiences six months of round-the-clock daylight from March 21 to September 21 and six months of darkness from September 21 to March 21.
Magnetic North Pole
Located approximately 400 km (250 miles) south of the true North Pole, and as of 2017 lies within 86.5°N and 172.6°W.
This place is not fixed and is constantly moving, even on a daily basis. The magnetic North Pole of the Earth is the center of the planet's magnetic field and the point to which conventional magnetic compasses point. The compass is also subject to magnetic declination, which is the result of changes in the Earth's magnetic field.
Due to the constant shifts of the magnetic N Pole and the planet's magnetic field, when using a magnetic compass for navigation, it is necessary to understand the difference between magnetic north and true north.
The magnetic pole was first determined in 1831, hundreds of kilometers from its present location. The Canadian National Geomagnetic Program monitors the movement of the magnetic North Pole.
The magnetic North Pole is constantly moving. Every day there is an elliptical movement of the magnetic pole about 80 km from its central point. On average, it moves about 55-60 km every year.
Who first reached the North Pole?
