A 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 one end of the arrow pointing south and the other pointing north. Thanks to the magnetosphere, great discoveries were made in physics, and still 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 the south pole is next to the corresponding geographic pole. From these points for many thousands of kilometers into space extend the magnetic lines of force that make up the magnetosphere itself.
Magnetic and geographic poles are quite far from each other. If you draw a clear line between the magnetic poles, you can finally get 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.
The nature of the geomagnetic field
The magnetic screen is generated by electric currents (moving charges), which are born in an external liquid core located inside the Earth at a very decent depth. It is a flowing metal, and it moves. This process is called convection. The moving matter of the nucleus forms currents and, as a result, magnetic fields.
The magnetic screen reliably protects the Earth from cosmic radiation. Its main source is the solar wind - the movement of ionized particles flowing out of the solar corona. The magnetosphere deflects this continuous stream, redirecting it around the Earth, due to which hard radiation does not have a detrimental effect on all living things of the blue planet.
If the Earth did not have a geomagnetic field, then the solar wind would deprive its atmosphere. According to one hypothesis, this is exactly what happened on Mars. The solar wind is far from the only threat, since the Sun also releases a large amount of matter and energy in the form of coronal emissions, accompanied by a strong stream of radioactive particles. However, even in these cases, the Earth's magnetic field protects it, deflecting these currents from the planet.
A magnetic screen changes its poles approximately once every 250, 000 years. The magnetic north pole takes the place of the north, and vice versa. Scientists do not have a clear explanation of why this is happening.
Research history
Acquaintance of people with the amazing properties of terrestrial magnetism occurred at the dawn of civilization. Already in antiquity, mankind was known for magnetic iron ore - magnetite. However, who and when revealed that natural magnets are equally oriented in space with respect to the geographical poles of the planet is unknown. According to one version, the Chinese were familiar with this phenomenon as early as 1100, however, 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
Earth's magnetic field can be divided into:
- the main magnetic field (95%), the sources of which are in the outer, conducting electric current core of the planet;
- an 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 alternating, 1%) associated with solar-terrestrial interactions.
Regular geomagnetic variations
Changes in the geomagnetic field in time under the influence of both internal and external (with respect to the surface of the planet) sources are called magnetic variations. They are characterized by a deviation of the GP components from the average value at the observation site. Magnetic variations have a continuous adjustment in time, and often such changes are periodic in nature.
Regular variations that are repeated daily are changes in the magnetic field associated with solar and lunar diurnal changes in the intensity of the GP. Variations reach a maximum during the day and during the lunar confrontation.
Irregular geomagnetic variations
These changes arise 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 of re-growth of magnetic perturbation every 27 days, corresponding to the period of rotation of the main celestial body relative to the earth observer. This trend is due to the existence of active long-lived regions on our native star, observed over several of its revolutions. It manifests itself in the form of a 27-day repeatability of geomagnetic disturbances and magnetic storms.
- Eleven-year variations are associated with the periodicity of the sun's spot-forming activity. It was revealed that during the years of the largest concentration of dark areas on the solar disk, magnetic activity also reaches its maximum, however, the growth of geomagnetic activity lags behind the average solar growth by an average of one year.
- Seasonal variations have two maximums and two minimums corresponding to the periods of the equinoxes and the solstice time.
- Centuries-old, in contrast to the above, of external origin, are formed as a result of the movement of matter and wave processes in the planet’s liquid conductive core and are the main source of information about the electrical conductivity of the lower mantle and core, about the physical processes leading to convection of matter, as well as about the mechanism Earth geomagnetic field generation. These are the slowest variations - with periods from several years to a year.
The influence of the magnetic field on the living world
Despite the fact that the magnetic screen 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 (cryptochroms) that are able to change their position under the influence of a geomagnetic field. The authors of this hypothesis are sure that cryptochromes can play the role of a compass. However, not only birds, but also sea turtles use a magnetic screen as a GPS navigator.
Human exposure to the magnetic screen
The influence of the geomagnetic field on a person is fundamentally different from any other, whether it is radiation or a dangerous current, since it affects the human body completely.
Scientists believe that the geomagnetic field operates in the ultra-low frequency range, as a result of which it meets the basic physiological rhythms: respiratory, cardiac and brain. A person may not feel anything, but the body still reacts to it with functional changes in the nervous, cardiovascular systems and brain activity. For many years, psychiatrists have been tracking the relationship between bursts of intensity of the geomagnetic field and exacerbation of mental illnesses, often leading to suicide.
"Indexing" of geomagnetic activity
Perturbations of the magnetic field associated with changes in the magnetosphere-ionosphere 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 on the basis of magnetic screen measurements taken daily at three-hour intervals, starting at 00:00 UTC (Coordinated Universal Time). The highest indices of magnetic disturbance are compared with the values of the geomagnetic field of a calm day for a particular scientific institution, while the maximum values from the observed deviations are taken into account.
Based on the obtained data, the index K is calculated. Due to the fact that it is a quasi-logarithmic quantity (i.e., it increases by unity with an increase in perturbation by about 2 times), it cannot be averaged to obtain a long-term historical picture of the state of the planet's geomagnetic field. For this, there is an index A, which is a daily average value. It is determined quite simply - each dimension of the index K is converted to an equivalent index. The values of K obtained throughout the day are averaged, thanks to which it is possible to obtain an index A, the value of which on ordinary days does not exceed the threshold of 100, and during the period of severe magnetic storms can exceed 200.
Since the perturbations of the geomagnetic field at different points on the planet are not the same, the values of the index A from different scientific sources can vary 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 r appears. The same with 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 the optimal conditions for passage in the short-wave ranges are preserved. Of course, subject to a fairly intense flow of solar radiation. A 2-point geomagnetic field 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, which seriously interfere with the mentioned range, and in case of a strong storm (8-9 points), the passage of short waves is impossible.
| Ar | To r | Description |
| 0 | 0 | Calm |
| 2 | 1 | |
| 3 | ||
| 4 | ||
| 7 | 2 | Weakly indignant |
| fifteen | 3 | |
| 27 | 4 | Outraged |
| 48 | 5 | Magnetic storm |
| 80 | 6 | |
| 132 | 7 | Great magnetic storm |
| 208 | eight | |
| 400 | nine |
The effect of magnetic storms on human health
Negative effects of magnetic storms affect 50-70% of the world's population. At the same time, the onset of a stress reaction in some people is observed 1-2 days before magnetic disturbance, when flashes are observed in the sun. For others, at the peak or some time after excessive geomagnetic activity.
Meto-dependent people, as well as those who suffer from chronic diseases, need to track information about the geomagnetic field for a week, so that with the possible approach of magnetic storms, physical and emotional stress, as well as any actions and events that can lead to stress, can be excluded.
