The meaning of magnetic inclination in the modern explanatory dictionary, BSE. The Earth's magnetic field and its determinants: magnetic inclination Game of the subjunctive mood

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Subjunctive Game

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In 1544, the German scientist Georg Hartmann discovered magnetic inclination. Magnetic inclination is the angle by which the needle, under the influence of the Earth's magnetic field, deviates from the horizontal plane down or up. In the hemisphere north of the magnetic equator (which does not coincide with the geographic equator), the northern end of the arrow deviates downward, in the southern - vice versa. At the magnetic equator itself, the magnetic field lines are parallel to the Earth's surface.
The first assumption about the presence of the Earth's magnetic field, which causes such behavior of magnetized objects, was made by the English physician and natural philosopher William Gilbert in 1600 in his book “On the Magnet,” in which he described an experiment with a ball of magnetic ore and a small iron arrow. Gilbert came to the conclusion that the Earth is a large magnet. Observations by the English astronomer Henry Gellibrand showed that the geomagnetic field is not constant, but changes slowly.
José de Acosta (one of the Founders of Geophysics, according to Humboldt) in his History (1590) first appeared the theory of four lines without magnetic declination (he described the use of a compass, the angle of deviation, the differences between the Magnetic and North Pole; although the deviations were already known in the 15th century, he described the fluctuation of deviations from one point to another; he identified places with zero deviation: for example, in the Azores).
The angle by which the magnetic needle deviates from the north-south direction is called magnetic declination. Christopher Columbus discovered that magnetic declination does not remain constant, but changes with changes in geographic coordinates. Columbus's discovery gave impetus to a new study of the Earth's magnetic field: information about it was needed by sailors. In 1759, the Russian scientist M.V. Lomonosov, in his report “Discourse on the Great Accuracy of the Sea Route,” gave valuable advice to increase the accuracy of compass readings. To study terrestrial magnetism, M.V. Lomonosov recommended organizing a network of permanent points (observatories) in which to carry out systematic magnetic observations; Such observations must be carried out widely at sea. Lomonosov's idea of ​​organizing magnetic observatories was realized only 60 years later in Russia.
In 1831, the English polar explorer John Ross discovered the magnetic pole in the Canadian archipelago - the region where the magnetic needle occupies a vertical position, that is, the inclination is 90°. In 1841, James Ross (nephew of John Ross) reached the other magnetic pole of the Earth, located in Antarctica.
Carl Gauss put forward a theory about the origin of the Earth's magnetic field and in 1839 proved that the main part of it comes out of the Earth, and the reason for small, short deviations in its values ​​must be sought in the external environment.
(Wikipedia)

A compass is a device, the invention of which allowed man to learn to find the location of the planet's poles, thus orienting himself in the area. The blue end of its arrow shows where north is located, and the red end indicates the south direction.

However, when determining cardinal directions using this method, in some cases you can make a mistake. After all, the geographic north and south of the planet do not exactly coincide with the magnetic ones, and it is the location of the latter that is indicated by the compass needle. To be precise in this matter, scientists have introduced a number of concepts, which include magnetic declination and magnetic inclination. They help to detect measurement errors, as well as determine the distance from the poles. In addition, these determinants make it possible to record changes in the field itself that occur over time.

What is the earth's magnetic field?

Our planet can be imagined as a magnet of enormous size. The compass needle is also something like that, only in a miniature version. That is why its ends always point to the magnetic poles of the Earth, taking a position along its magnetic lines.

But what is the source and nature of such a grandiose phenomenon on a planetary scale? People began to be interested in this several centuries ago. At first, versions were put forward that the cause of magnetism was hidden in the earth's core. They thought so until they discovered clear evidence of the influence of solar activity on this natural phenomenon. And then scientists suggested that the source of the earth's magnetism is not in the core.

One of the latest scientific hypotheses, trying to unravel the mystery of what the Earth’s magnetic field is, says the following. Water from the oceans, which occupy a vast territory of the blue planet, evaporates in large quantities under the influence of the energy of the Sun and is electrified, receiving a positive charge. In this case, the earth's surface itself becomes negatively charged. All this provokes the movement of ion flows. This is where the planets themselves appear.

Geographical and magnetic axes

It is not at all difficult to understand what the geographic axis of the Earth is. A planetary ball rotates around it, where certain points remain motionless. In order to understand where the axis is, you need to connect the poles with an imaginary line. But the Earth-magnet or, to put it scientifically, the geomagnetic sphere, also has similar points. If you draw a straight line connecting the north magnetic pole and the south, it will be the magnetic axis of the planet.

Similarly, the Earth magnet has an equator. This is a circle located in a plane that is perpendicular to a straight line called the axis. Magnetic meridians are determined in a manner similar to what has just been stated. These are arcs that bend vertically around the geomagnetic sphere.

Magnetic declination

It is clear that magnetic and geographic meridians, like axes, cannot coincide completely, but only approximately. The angle between them at a certain point on the earth's surface is usually called magnetic declination. It should be noted that for each specific area this indicator, when determined, will be different. And its magnitude helps determine the error between the true direction and compass readings.

Since the direction of the magnetic poles does not coincide with the geographic ones, this error, it turns out, must be taken into account in navigation calculations. This difference can be very important for sailors, pilots and military personnel. On many geographical maps, for convenience, the magnitude of the magnetic declination is indicated in advance.

It is interesting that from the point of view of physics, the true and magnetic poles not only do not coincide, but also seem to be turned upside down, that is, the south corresponds to the magnetic north, and vice versa.

The compass needle is designed to determine the location of the magnetic poles at any point on the Earth. What will happen to the readings of this device directly at the North and South Poles? If the compass is designed in a classical way, then the needle will no longer move freely on the central needle along the body, but will press against it or, on the contrary, deviate. At the northern geographic pole it will pirouette 90° downward, while at the southern pole it will shoot vertically upward with its northern end. The opposite tip of the arrow, that is, the southern one, will behave exactly the opposite.

These metamorphoses do not occur suddenly at one moment when moving towards the poles. It should be noted that the compass needle deviates almost constantly at a certain angle in the vertical direction under the influence of the magnetic field: in the northern hemisphere - downwards, and in the southern hemisphere, respectively, upwards with its northern end. This angle is called magnetic inclination.

A similar phenomenon has been known for a long time and was discovered by the Chinese back in the 11th century. But in Europe it was described much later, in the 16th century. And this was done by an astronomer and engineer from Germany Georg Hartmann.

Measurement methods

The fact that the magnetic inclination changes in a certain way depending on the geographical location and the coordinates that describe it was proven by Christopher Columbus. As you approach the equator, the angle decreases. It becomes equal to zero at the equatorial line itself. However, at the time of this great traveler, they had not yet learned to accurately determine the value of this quantity. The first instruments, called inclinators, which made it possible to determine the angle of inclination of the Earth's magnetic field, were invented only more than half a century after the death of Columbus.

The first such design was proposed by the Englishman Robert Norman in 1576. But she turned out to be not entirely accurate in her testimony. Later, more advanced and sensitive inclinators were invented.

Magnetic inclination, corner I between the geomagnetic field strength vector T and a horizontal plane at the considered point on the earth’s surface (see. Terrestrial magnetism ).n. m is measured from the horizontal plane up or down; N.m. is positive when the vector T directed downward from the horizontal plane, which is the case in the Northern Hemisphere, and negative when T directed upward - in the Southern Hemisphere. Nm varies on the earth's surface from 0° to ± 90°. Curves connecting points on the earth's surface with the same values ​​of N.M. are called isoclines . Isocline I= 0 is called the magnetic equator; point where I= 90°, - the north magnetic pole of the Earth; point where I= - 90°, - south magnetic pole (see. Earth's magnetic poles ). N. m. measured inclinators .

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