Geomagnetic field: features, structure, characteristics and history of research

2024 Author: Henry Conors | [email protected]. Last modified: 2024-02-12 02:43

The geomagnetic field (GP) is generated by sources located inside the Earth, as well as in the magnetosphere and ionosphere. It protects the planet and life on it from the harmful effects of cosmic radiation. His presence was observed by everyone who held the compass and saw how one end of the arrow points to the south, and the other to the north. Thanks to the magnetosphere, great discoveries in physics were made, and so far its presence is used for marine, underwater, aviation and space navigation.

General characteristics

Our planet is a huge magnet. Its north pole is located in the "upper" part of the Earth, not far from the geographic pole, and its south pole is near the corresponding geographic pole. From these points, the magnetic lines of force that make up the magnetosphere proper extend for many thousands of kilometers into space.

Magnetic and geographic poles are fairly far apart. If you draw a clear line between the magnetic poles, you can end up with a magnetic axis with an angle of inclination of 11.3 ° to the axis of rotation. This value is not constant, and all because the magnetic poles move relative to the surface of the planet, changing their location annually.

Nature of the geomagnetic field

The magnetic shield is generated by electric currents (moving charges) that are born in the outer liquid core, located inside the Earth at a very decent depth. It's a fluid metal, and it moves. This process is called convection. The moving substance of the nucleus forms currents and, as a result, magnetic fields.

Magnetic shield reliably protects the Earth from cosmic radiation. Its main source is the solar wind - the movement of ionized particles flowing from the solar corona. The magnetosphere deflects this continuous flow, redirecting it around the Earth, so that hard radiation does not have a detrimental effect on all life on the blue planet.

If the Earth did not have a geomagnetic field, then the solar wind would deprive it of the atmosphere. According to one hypothesis, this is exactly what happened on Mars. The solar wind is far from the only threat, as the Sun also releases large amounts of matter and energy in the form of coronal ejections, accompanied by a strong stream of radioactive particles. However, even in these cases, the Earth's magnetic field protects it by deflecting these currents fromplanets.

The magnetic shield reverses its poles approximately every 250,000 years. The north magnetic pole takes the place of the north, and vice versa. Scientists have no clear explanation why this is happening.

Research history

Acquaintance of people with the amazing properties of terrestrial magnetism happened at the dawn of civilization. Already in antiquity, magnetic iron ore, magnetite, was known to mankind. However, who and when revealed that natural magnets are equally oriented in space in relation to the geographic poles of the planet is unknown. According to one version, the Chinese were already familiar with this phenomenon in 1100, but they began to use it in practice only two centuries later. In Western Europe, the magnetic compass began to be used in navigation in 1187.

Structure and characteristics

The Earth's magnetic field can be divided into:

• the main magnetic field (95%), the sources of which are located in the outer, conductive core of the planet;
• anomalous magnetic field (4%) created by rocks in the upper layer of the Earth with good magnetic susceptibility (one of the most powerful is the Kursk magnetic anomaly);
• external magnetic field (also called variable, 1%) associated with solar-terrestrial interactions.

Regular geomagnetic variations

Changes in the geomagnetic field over time under the influence of both internal and external (in relation to the surface of the planet) sources are called magnetic variations. They areare characterized by the deviation of the HP components from the average value at the place of observation. Magnetic variations have a continuous restructuring in time, and often such changes are periodic.

Regular variations that repeat daily are changes in the magnetic field associated with solar and lunar-diurnal changes in the MS intensity. Variations peak during the day and at lunar opposition.

Irregular geomagnetic variations

These changes occur as a result of the influence of the solar wind on the Earth's magnetosphere, changes within the magnetosphere itself and its interaction with the ionized upper atmosphere.

• Twenty-seven-day variations exist as a pattern to the re-growth of magnetic disturbance every 27 days, corresponding to the period of rotation of the main celestial body relative to the earthly observer. This trend is due to the existence of long-lived active regions on our home star, observed during several of its revolutions. It manifests itself in the form of a 27-day recurrence of geomagnetic disturbances and magnetic storms.
• Eleven-year variations are associated with the periodicity of the Sun's spot-forming activity. It was found that during the years of the greatest accumulation of dark areas on the solar disk, magnetic activity also reaches its maximum, however, the growth of geomagnetic activity lags behind the growth of solar activity on average by a year.
• Seasonal variations have two highs and two lows corresponding toequinoxes and solstice times.
• Secular, in contrast to the above, - of external origin, are formed as a result of the movement of matter and wave processes in the liquid electrically conductive core of the planet and are the main source of information about the electrical conductivity of the lower mantle and core, about the physical processes leading to the convection of matter, as well as the mechanism of generation of the Earth's geomagnetic field. These are the slowest variations - with periods ranging from several years to a year.

The influence of the magnetic field on the living world

Despite the fact that the magnetic shield cannot be seen, the inhabitants of the planet feel it perfectly. For example, migratory birds build their route, focusing on it. Scientists put forward several hypotheses regarding this phenomenon. One of them suggests that birds perceive it visually. In the eyes of migratory birds there are special proteins (cryptochromes) that are able to change their position under the influence of the geomagnetic field. The authors of this hypothesis are sure that cryptochromes can act as a compass. However, not only birds, but also sea turtles use the magnetic screen as a GPS navigator.

The impact of a magnetic screen on a person

The effect of the geomagnetic field on a person is fundamentally different from any other, be it radiation or a dangerous current, since it affects the human body completely.

Scientists believe that the geomagnetic field operates in an ultra-low frequency range, as a result of which it meets the mainphysiological rhythms: respiratory, cardiac and cerebral. A person may not feel anything, but the body still reacts to it with functional changes in the nervous, cardiovascular systems and brain activity. Psychiatrists have been tracking the relationship between bursts of geomagnetic field intensity and exacerbation of mental illnesses for many years, often leading to suicide.

"Indexing" geomagnetic activity

Magnetic field disturbances associated with changes in the magnetospheric-ionospheric current system are called geomagnetic activity (GA). To determine its level, two indices are used - A and K. The latter shows the value of GA. It is calculated from magnetic shield measurements taken every day at three-hour intervals, starting at 00:00 UTC (Universal Time Coordinated). The highest values of the magnetic disturbance are compared with the values of the geomagnetic field of a quiet day for a certain scientific institution, while the maximum values of the observed deviations are taken into account.

Based on the obtained data, the K index is calculated. Due to the fact that it is a quasi-logarithmic value (that is, it increases by one with an increase in disturbance by about 2 times), it cannot be averaged in order to obtain a long-term historical picture of the state of the geomagnetic fields of the planet. To do this, there is an index A, which is a daily average. It is determined quite simply - each dimension of the index K is converted intoequivalent index. The K values obtained throughout the day are averaged, thanks to which it is possible to obtain the A index, the value of which on ordinary days does not exceed the threshold of 100, and during the most serious magnetic storms it can exceed 200.

Since the disturbances of the geomagnetic field in different parts of the planet are manifested differently, the values of the A index from different scientific sources can differ markedly. In order to avoid such a run-up, the indices A obtained by the observatories are reduced to the average and the global index A_p appears. The same is true for the index K_p, which is a fractional value in the range 0-9. Its value from 0 to 1 indicates that the geomagnetic field is normal, which means that optimal conditions for passing in the short-wave bands are preserved. Of course, subject to a fairly intense flow of solar radiation. A geomagnetic field of 2 points is characterized as a moderate magnetic disturbance, which slightly complicates the passage of decimeter waves. Values from 5 to 7 indicate the presence of geomagnetic storms that create serious interference with the mentioned range, and with a strong storm (8-9 points) make the passage of short waves impossible.

Geomagnetic field activity in points

Ar	Kr	Description
0	0	Calm
2	1
3
4
7	2	Weakly indignant
15	3
27	4	Indignant
48	5	Magnetic storm
80	6
132	7	Great magnetic storm
208	8
400	9

The impact of magnetic storms on human he alth

50-70% of the world's population is affected by magnetic storms. At the same time, the onset of a stress reaction in some people is noted 1-2 days before a magnetic disturbance, when solar flares are observed. For others, at the very peak or some time after excessive geomagnetic activity.

Methodically addicted people, as well as those who suffer from chronic diseases, need to track information about the geomagnetic field for a week, in order to exclude physical and emotional stress, as well as any actions and events that can lead to stress, if magnetic storms are approaching.

Magnetic field deficiency syndrome

The weakening of the geomagnetic field in the premises (hypogeomagnetic field) occurs due to the design features of various buildings, wall materials, as well as magnetized structures. When you are in a room with a weakened GP, blood circulation is disturbed, the supply of oxygen and nutrients to tissues and organs. The weakening of the magnetic shield also affects the nervous, cardiovascular, endocrine, respiratory, skeletal and muscular systems.

Japanese doctor Nakagawa "called"this phenomenon is called “human magnetic field deficiency syndrome”. In its significance, this concept may well compete with the deficiency of vitamins and minerals.

The main symptoms indicating the presence of this syndrome are:

• fatigue;
• decrease in performance;
• insomnia;
• headache and joint pain;
• hypo- and hypertension;
• malfunctions in the digestive system;
• disorders in the cardiovascular system.