One of the key skills of any HF DX hunter is the ability to assess conditions at any given time. Excellent transmission conditions, when many stations from all over the world are heard on the bands, can change so that the bands become empty and only a few stations make their way through the noise and crackle of the air. In order to understand what and why is happening on the radio, as well as to evaluate its capabilities at a given time, three main indices are used: solar flux, A p and K p . A good practical understanding of what these values are and what their meaning is is an undeniable advantage even for a radio amateur with the best and most modern set of communications equipment.
Earth's atmosphere
The ionosphere can be thought of as something multi-layered. The boundaries of the layers are quite arbitrary and are determined by areas with a sharp change in the ionization level (Fig. 1). The ionosphere has a direct impact on the nature of the propagation of radio waves, because depending on the degree of ionization of its individual layers, radio waves can be refracted, that is, the trajectory of their propagation ceases to be rectilinear. Quite often the degree of ionization is high enough that radio waves are reflected from highly ionized layers and return to Earth (Fig. 2).
The conditions for the passage of radio waves on the HF bands are constantly changing depending on changes in the ionization levels of the ionosphere. Solar radiation, reaching the upper layers of the earth's atmosphere, ionizes gas molecules, generating positive ions and free electrons. This entire system is in dynamic equilibrium due to the process of recombination, the reverse of ionization; when positively charged ions and free electrons interact with each other, they again form gas molecules. The higher the degree of ionization (the more free electrons), the better the ionosphere reflects radio waves. In addition, the higher the level of ionization, the higher the frequencies at which good transmission conditions can be provided. The level of ionization of the atmosphere depends on many factors, including the time of day, time of year, and the most important factor - the cycle solar activity. It is reliably known that the intensity of solar radiation depends on the number of spots on the Sun. Accordingly, the maximum radiation received from the Sun is achieved during periods of maximum solar activity. In addition, during these periods geomagnetic activity also increases due to the increased intensity of the flow of ionized particles from the Sun. Usually this flow is quite stable, but due to solar flares it can increase significantly. The particles reach near-Earth space and interact with the Earth's magnetic field, causing disturbances and generating magnetic storms. In addition, these particles can cause ionospheric storms, during which short-wave radio communications become difficult and sometimes even impossible.
Solar radiation flux
A quantity known as solar radiation flux is the main indicator of solar activity and determines the amount of radiation the Earth receives from the Sun. It is measured in solar flux units (SFU) and is determined by the level of radio noise emitted at 2800 MHz (10.7 cm). The Penticton Radio Astronomy Observatory in British Columbia, Canada, publishes this value daily. The solar radiation flux has a direct impact on the degree of ionization and, consequently, the electron concentration in the F 2 region of the ionosphere. As a result, it gives a very good idea of the possibility of establishing long-distance radio communications.
The magnitude of the solar flux can vary within 50 - 300 units. Small values indicate that the maximum usable frequency (MUF) will be low and the overall radio wave conditions will be poor, especially on the high frequency bands. (Fig. 2) On the contrary, large solar flux values indicate sufficient ionization, which allows long-distance communications to be established at higher frequencies. However, it should be remembered that it takes several days in a row with high solar flux values for the passage conditions to significantly improve. Typically, during periods of high solar activity, the solar flux exceeds 200 with short-term bursts up to 300.
Geomagnetic activity
There are two indices that are used to determine the level of geomagnetic activity - A and K. They show the magnitude of magnetic and ionospheric disturbances. The K index shows the magnitude of geomagnetic activity. Every day, every 3 hours, starting from 00:00 UTC, the maximum deviations of the index value relative to the values for a quiet day at the selected observatory are determined, and the largest value is selected. Based on these data, the value of the K index is calculated. The K index is a quasi-logarithmic value, so it cannot be averaged to obtain a long-term historical painting state of the Earth's magnetic field. To solve this problem, there is an index A, which represents the daily average. It is calculated quite simply - each measurement of the K index, made, as mentioned above, with a 3-hour interval, according to Table 1
is converted to an equivalent index. The values of this index obtained during the day are averaged and the result is the value of the A index, which on normal days does not exceed 100, and during very serious geomagnetic storms can reach 200 or even more. The values of the A index may differ at different observatories, since disturbances in the Earth's magnetic field can be local in nature. To avoid discrepancies, the A indices obtained at different observatories are averaged and the resulting global index A p is obtained. In the same way, the value of the K p index is obtained - the average value of all K indices obtained at various observatories around the globe. Its values between 0 and 1 characterize a quiet geomagnetic environment, and this may indicate the presence of good transmission conditions in the short-wave ranges, provided that the intensity of the solar radiation flux is sufficiently high. Values between 2 and 4 indicate a moderate or even active geomagnetic environment, which is likely to negatively affect radio wave conditions. Further on the scale of values: 5 indicates a minor storm, 6 indicates a strong storm, and 7 - 9 indicates a very strong storm, as a result of which there will most likely be no passage on the HF. Despite the fact that geomagnetic and ionospheric storms are interrelated, it is worth noting again that they are different. A geomagnetic storm is a disturbance in the Earth's magnetic field, and an ionospheric storm is a disturbance in the ionosphere.
Interpretation of index values
The simplest way to use index values is to enter them as input into a radio wave propagation forecast program. This will allow you to get a more or less reliable forecast. In their calculations, these programs take into account additional factors, such as signal propagation paths, because the influence of magnetic storms will be different for different paths.
In the absence of a program, you can make a good estimate forecast yourself. Obviously, high solar flux index values are good. Generally speaking, the stronger the flow, the better the conditions will be on the high-frequency HF bands, including the 6 m band. However, the flow values from previous days should also be taken into account. Maintaining large values for several days will ensure a higher degree of ionization of the F2 layer of the ionosphere. Typically, values greater than 150 will guarantee good HF transmission. High levels of geomagnetic activity also have an unfavorable side effect, significantly reducing the MUF. The higher the level of geomagnetic activity according to the Ap and Kp indices, the lower the MUF. The actual MUF values depend not only on the strength of the magnetic storm, but also on its duration.
Conclusion
Constantly monitor changes in solar and geomagnetic activity indices. This data is available on the sites www.eham.net, www.qrz.com, www.arrl.org and many others, and can also be obtained through the terminal when connecting to DX clusters. Good passage on HF is possible during periods when the solar flux exceeds 150 for several days, and the K p index at the same time remains below 2. When these conditions are met, check the bands - there is probably some good DX working there already!
Based on Understanding Solar Indices By Ian Poole, G3YWX
The geomagnetic field (GF) is generated by sources located in the magnetosphere and ionosphere. It protects the planet and life on it from the harmful influences. Its presence was observed by everyone who held a 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 have been made, and its presence is still 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 located near the corresponding geographic pole. From these points, power lines extend many thousands of kilometers into space. magnetic lines, making up the magnetosphere itself.
The magnetic and geographic poles are quite distant from each other. If you draw a clear line between the magnetic poles, you can end up with a magnetic axis with an inclination angle 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 every year.
Nature of the geomagnetic field
The magnetic screen is generated by electric currents (moving charges), which are born in the outer liquid core, located inside the Earth at a very decent depth. It is a fluid metal and it moves. This process is called convection. The moving matter of the nucleus forms currents and, as a consequence, magnetic fields.
The magnetic shield reliably protects the Earth from its main source - the solar wind - the movement of ionized particles flowing from the Magnetosphere deflects this continuous flow, redirecting it around the Earth, due to which hard radiation does not have a detrimental effect on all living things on the blue planet.
If the Earth did not have a geomagnetic field, the solar wind would strip it of 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 large amounts of matter and energy in the form of coronal ejections, accompanied by a strong flow of radioactive particles. However, even in these cases, the Earth's magnetic field protects it by deflecting these currents away from the planet.
The magnetic shield changes its poles approximately every 250,000 years. The north magnetic pole takes the place of the north one, and vice versa. Scientists have no clear explanation why this happens.
History of the study
People's acquaintance with the amazing properties of earthly magnetism occurred at the dawn of civilization. Already in ancient times, humanity was aware of magnetic iron ore- magnetite. However, who and when discovered 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 familiar with this phenomenon already 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, electrically conductive core of the planet;
- anomalous magnetic field (4%) created 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 over time under the influence of both internal and external (relative to the surface of the planet) sources are called magnetic variations. They are characterized by the deviation of the GP components from the average value at the observation site. Magnetic variations have a continuous rearrangement in time, and such changes are often periodic in nature.
Regular variations that repeat daily are changes in the magnetic field associated with solar- and lunar-diurnal changes in the MS strength. Variations reach a maximum during the day and at lunar opposition.
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 layer of the atmosphere.
- Twenty-seven-day variations exist as a pattern of repeated growth of magnetic disturbance every 27 days, corresponding to the rotation period of the main heavenly 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 repeatability of geomagnetic disturbance and
- Eleven-year variations are associated with the periodicity of sunspot activity of the Sun. It was revealed that during the years of the greatest accumulation of dark areas on the solar disk, magnetic activity also reaches its maximum, but the growth of geomagnetic activity lags behind the growth of solar activity on average by a year.
- Seasonal variations have two maxima and two minima, corresponding to the periods of the equinoxes and the time of the solstice.
- Secular, in contrast to the above, are 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 convection of matter, as well as about the mechanism 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 screen cannot be seen, the inhabitants of the planet feel it perfectly. For example, migratory birds build their route based 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 confident that cryptochromes can act as a compass. However, not only birds, but also sea turtles use a magnetic shield as a GPS navigator.
Impact of a magnetic shield on a person
The influence of the geomagnetic field on a person is fundamentally different from any other, be it radiation or 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 responds to 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. Psychiatrists have been monitoring the relationship between surges in the intensity of the geomagnetic field and exacerbation of mental illnesses, often leading to suicide, for many years.
"Indexing" of 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 daily at three-hour intervals, starting at 00:00 UTC (Coordinated Universal Time). The highest values of magnetic disturbance are compared with the values of the geomagnetic field on a quiet day for a particular scientific institution, and the maximum values of the observed deviations are taken into account.
Based on the data obtained, the K index is calculated. Due to the fact that it is a quasi-logarithmic value (i.e., it increases by one as the disturbance increases by approximately 2 times), it cannot be averaged in order to obtain a long-term historical picture of the state of the planet’s geomagnetic field. For this purpose there is an index A, which represents the daily average value. It is determined quite simply - each dimension of the K index is converted into an equivalent 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 periods of severe magnetic storms can exceed 200.
Since disturbances in the geomagnetic field manifest themselves differently in different parts of the planet, the values of the A index from different scientific sources can vary noticeably. In order to avoid such a run-up, the A indices obtained by the observatories are reduced to the average and a global index A p appears. The same is true with the K p index, 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 transmission in the shortwave ranges remain. Of course, provided there is a fairly intense flux of solar radiation. A geomagnetic field of 2 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 in the case of a strong storm (8-9 points) they make the passage of short waves impossible.
The influence of magnetic storms on human health
50-70% of the world's population are exposed to the negative effects of magnetic storms. At the same time, the onset of the stress reaction in some people is noted 1-2 days before the magnetic disturbance, when flares in the sun are observed. For others, at the very peak or some time after excessive geomagnetic activity.
Meth-dependent people, as well as those who suffer from chronic diseases, need to monitor information about the geomagnetic field for a week in order to eliminate physical and emotional stress, as well as any actions and events that could lead to stress, when possible approaching magnetic storms occur.
Magnetic field deficiency syndrome
The weakening of the geomagnetic field in rooms (hypogeomagnetic field) occurs due to the design features of various buildings, wall materials, and magnetized structures. When staying in a room with a weakened GP, blood circulation and the supply of oxygen and nutrients to tissues and organs are disrupted. Weakening of the magnetic shield also affects the nervous, cardiovascular, endocrine, respiratory, skeletal and muscular systems.
The Japanese doctor Nakagawa “called” this phenomenon “human magnetic field deficiency syndrome.” In terms of its importance, this concept may well compete with a deficiency of vitamins and minerals.
The main symptoms indicating the presence of this syndrome are:
- increased fatigue;
- decreased performance;
- insomnia;
- headache and joint pain;
- hypo- and hypertension;
- disruptions in the digestive system;
- disturbances in the functioning of the cardiovascular system.
- Solar cosmic rays (SCR) are protons, electrons, nuclei formed in solar flares and reaching the Earth's orbit after interacting with the interplanetary medium.
- Magnetospheric storms and substorms caused by the arrival of an interplanetary shock wave to the Earth associated with both CMEs and COEs, and with high-speed solar wind streams;
- Ionizing electromagnetic radiation (IER) from solar flares, causing heating and additional ionization of the upper atmosphere;
- Increases in the fluxes of relativistic electrons in the Earth's outer radiation belt associated with the arrival of high-speed solar wind streams to the Earth.
Solar cosmic rays (SCR)
The energetic particles formed in flares - protons, electrons, nuclei - after interacting with the interplanetary medium can reach the Earth's orbit. It is generally accepted that the largest contribution to the total dose comes from solar protons with an energy of 20-500 MeV. The maximum flux of protons with energies above 100 MeV from a powerful flare on February 23, 1956 was 5000 particles per cm -2 s -1 .
(See the materials on the topic “Solar Cosmic Rays” for more details).
Main source of SCR– solar flares, in rare cases - decay of a prominence (fiber).
SCR as the main source of radiation hazard in OKP
Fluxes of solar cosmic rays significantly increase the level of radiation hazard for astronauts, as well as crews and passengers of high-altitude aircraft on polar routes; lead to the loss of satellites and failure of equipment used on space objects. The harm that radiation causes to living beings is quite well known (for more details, see the materials on the topic “How does space weather affect our lives?”), but in addition, a large dose of radiation can also damage electronic equipment installed on spacecraft (see Read more about Lecture 4 and materials on topics on the impact of the external environment on spacecraft, their elements and materials).
The more complex and modern the microcircuit, the smaller sizes each element and the greater the likelihood of failures, which can lead to its incorrect operation and even stopping the processor.
Let us give a clear example of how high-energy SCR fluxes affect the state of scientific equipment installed on spacecraft.
For comparison, the figure shows photographs of the Sun taken by the EIT (SOHO) instrument, taken before (07:06 UT 28/10/2003) and after a powerful solar flare that occurred around 11:00 UT 28/10/2003, after which NCP fluxes of protons with energies of 40-80 MeV increased by almost 4 orders of magnitude. The amount of “snow” in the right figure shows how damaged the recording matrix of the device is by the fluxes of flare particles.
The influence of increases in SCR fluxes on the Earth's ozone layer
Since the sources of nitrogen and hydrogen oxides, the content of which determines the amount of ozone in the middle atmosphere, can also be high-energy particles (protons and electrons) of SCRs, their influence should be taken into account in photochemical modeling and interpretation of observational data at the moments of solar proton events or strong geomagnetic disturbances.
Solar proton events
The role of 11-year GCR variations in assessing the radiation safety of long-term space flights
When assessing the radiation safety of long-term space flights (such as, for example, the planned expedition to Mars), it becomes necessary to take into account the contribution of galactic cosmic rays (GCRs) to the radiation dose (for more details, see lecture 4). In addition, for protons with energies above 1000 MeV, the magnitude of the GCR and SCR fluxes becomes comparable. By revising various phenomena on the Sun and in the heliosphere, over time intervals of several decades or more, their determining factor is the 11-year and 22-year cyclicity of the solar process. As can be seen from the figure, the GCR intensity changes in antiphase with the Wolf number. This is very important, since at SA minimum the interplanetary medium is weakly disturbed and GCR fluxes are maximum. Having a high degree of ionization and being all-pervasive, during periods of minimum SA GCRs determine dose loads on humans in space and aviation flights. However, solar modulation processes turn out to be quite complex and cannot be reduced only to anti-correlation with the Wolf number. .
The figure shows the modulation of CR intensity in the 11-year solar cycle.
Solar electrons
High-energy solar electrons can cause volume ionization of spacecraft, and also act as “killer electrons” for microcircuits installed on spacecraft. Due to SCR fluxes, short-wave communications in the polar regions are disrupted and failures occur in navigation systems.
Magnetospheric storms and substorms
Other important consequences of solar activity that affect the state of near-Earth space are magnetic storms– strong (tens and hundreds of nT) changes in the horizontal component of the geomagnetic field measured on the Earth’s surface at low latitudes. Magnetospheric storm is a set of processes occurring in the Earth’s magnetosphere during a magnetic storm, when there is a strong compression of the magnetosphere boundary on the day side, other significant deformations of the structure of the magnetosphere, and a ring current of energetic particles is formed in the inner magnetosphere.
The term "substorm" was introduced in 1961. S-I. Akasofu to designate auroral disturbances in the auroral zone lasting about an hour. In the magnetic data, bay-shaped disturbances were identified even earlier, coinciding in time with a substorm in the auroras. Magnetospheric substorm is a set of processes in the magnetosphere and ionosphere, which in the most general case can be characterized as a sequence of processes of energy accumulation in the magnetosphere and its explosive release. Source of magnetic storms− the arrival of high-speed solar plasma (solar wind), as well as COW and the associated shock wave, to the Earth. High-speed solar plasma flows, in turn, are divided into sporadic, associated with solar flares and CMEs, and quasi-stationary, arising above coronal holes. Magnetic storms, in accordance with their source, are divided into sporadic and recurrent. (See lecture 2 for more details).
Geomagnetic indices – Dst, AL, AU, AE
Numerical characteristics reflecting geomagnetic disturbances are various geomagnetic indices - Dst, Kp, Ap, AA and others.
The amplitude of variations in the Earth's magnetic field is often used as the most general characteristic of the strength of magnetic storms. Geomagnetic index Dst contains information about planetary disturbances during geomagnetic storms.
The three-hour index is not suitable for studying substorm processes; during this time a substorm can begin and end. Detailed structure of magnetic field fluctuations due to auroral zone currents ( auroral electric jet) characterizes auroral electric jet index AE. To calculate the AE index, we use magnetograms of H-components observatories located at auroral or subauroral latitudes and evenly distributed in longitude. Currently, AE indices are calculated from data from 12 observatories located in the northern hemisphere at different longitudes between 60 and 70° geomagnetic latitude. To numerically describe substorm activity, geomagnetic indices AL (the largest negative variation of the magnetic field), AU (the largest positive variation of the magnetic field) and AE (the difference between AL and AU) are also used.
Dst index for May 2005
Kr, Ar, AA indices
The geomagnetic activity index Kp is calculated every three hours based on magnetic field measurements at several stations located in various parts Earth. It has levels from 0 to 9, each next level of the scale corresponds to variations 1.6-2 times greater than the previous one. Strong magnetic storms correspond to levels of Kp greater than 4. So-called superstorms with Kp = 9 occur quite rarely. Along with Kp, the Ap index is also used, equal to the average amplitude of geomagnetic field variations across the globe per day. It is measured in nanoteslas (the earth's field is approximately
50,000 nT). The level Kp = 4 approximately corresponds to an Ap equal to 30, and the level Kp = 9 corresponds to an Ap greater than 400. The expected values of such indices constitute the main content of the geomagnetic forecast. The Ap index began to be calculated in 1932, so for earlier periods the AA index is used - the average daily amplitude of variations, calculated from two antipodal observatories (Greenwich and Melbourne) since 1867.
The complex influence of SCRs and storms on space weather due to the penetration of SCRs into the Earth's magnetosphere during magnetic storms
From the point of view of the radiation hazard posed by SCR fluxes for high-latitude segments of the orbits of spacecraft such as the ISS, it is necessary to take into account not only the intensity of SCR events, but also the boundaries of their penetration into the Earth’s magnetosphere(See Lecture 4 for more details.) Moreover, as can be seen from the figure above, SCRs penetrate quite deeply even for magnetic storms of small amplitude (-100 nT or less).
Assessment of radiation hazard in high-latitude regions of the ISS trajectory based on data from low-orbit polar satellites
Estimates of radiation doses in high-latitude regions of the ISS trajectory, obtained based on data on the spectra and limits of SCR penetration into the Earth's magnetosphere according to the Universitetsky-Tatyana satellite data during solar flares and magnetic storms of September 2005, were compared with doses experimentally measured on the ISS in high latitude areas. From the given figures it is clearly seen that the calculated and experimental values are consistent, which indicates the possibility of estimating radiation doses in different orbits using data from low-altitude polar satellites.
Map of doses on the ISS (IBS) and comparison of calculated and experimental doses.
Magnetic storms as a cause of radio communication disruption
Magnetic storms lead to strong disturbances in the ionosphere, which in turn negatively affect the state radio broadcast. In the subpolar regions and auroral oval zones, the ionosphere is associated with the most dynamic regions of the magnetosphere and is therefore most sensitive to such influences. Magnetic storms in high latitudes can almost completely block radio broadcasts for several days. At the same time, other areas of activity, for example, air travel, also suffer. Another negative effect associated with geomagnetic storms is the loss of orientation of satellites, the navigation of which is carried out along the geomagnetic field, which experiences strong disturbances during the storm. Naturally, during geomagnetic disturbances, problems arise with radar.
The influence of magnetic storms on the functioning of telegraph and power lines, pipelines, railways
Variations in the geomagnetic field that occur during magnetic storms in polar and auroral latitudes (according to the well-known law of electromagnetic induction) generate secondary electric currents in the conductive layers of the Earth's lithosphere, in salt water and in artificial conductors. The induced potential difference is small and amounts to approximately a few volts per kilometer, but in long conductors with low resistance - communication and power lines (power lines), pipelines, rails railways
− the total strength of induced currents can reach tens and hundreds of amperes.
The least protected from such influence are overhead low-voltage communication lines. Thus, significant interference that occurred during magnetic storms was noted already on the very first telegraph lines built in Europe in the first half of the 19th century. Geomagnetic activity can also cause significant problems for railway automation, especially in the polar regions. And in oil and gas pipelines stretching for many thousands of kilometers, induced currents can significantly accelerate the process of metal corrosion, which must be taken into account when designing and operating pipelines.
Examples of the impact of magnetic storms on the functioning of power lines
A major accident that occurred during the severe magnetic storm of 1989 in Canada's power grid clearly demonstrated the danger of magnetic storms for power lines. Investigations showed that transformers were the cause of the accident. The fact is that the constant current component introduces the transformer into a non-optimal operating mode with excessive magnetic saturation of the core. This leads to excessive energy absorption, overheating of the windings and, ultimately, to a breakdown of the entire system. A subsequent analysis of the performance of all power plants in North America revealed a statistical relationship between the number of failures in high-risk areas and the level of geomagnetic activity.
The influence of magnetic storms on human health
Currently, there are results of medical studies proving the existence of a human reaction to geomagnetic disturbances. These studies show that there is a fairly large category of people on whom magnetic storms have a negative effect: human activity is inhibited, attention is dulled, and chronic diseases are exacerbated. It should be noted that studies of the impact of geomagnetic disturbances on human health are just beginning, and their results are quite controversial and contradictory (for more details, see the materials on the topic “How does space weather affect our lives?”).
However, most researchers agree that in this case there are three categories of people: for some, geomagnetic disturbances have a depressing effect, for others, on the contrary, they have an exciting effect, and for others, no reaction is observed.
Ionospheric substorms as a space weather factor
Substorms are a powerful source electrons in the outer magnetosphere. The fluxes of low-energy electrons increase greatly, which leads to a significant increase in electrification of spacecraft(for more details, see the materials on the topic "Electrification of spacecraft"). During strong substorm activity, electron fluxes in the Earth's outer radiation belt (ERB) increase by several orders of magnitude, which poses a serious danger to satellites whose orbits cross this region, since a sufficiently large amount of electrons accumulates inside the spacecraft. volumetric charge leading to failure of on-board electronics. As an example, we can cite problems with the operation of electronic instruments on the Equator-S, Polag and Calaxy-4 satellites, which arose against the background of prolonged substorm activity and, as a consequence, very high fluxes of relativistic electrons in the outer magnetosphere in May 1998.
Substorms are an integral companion of geomagnetic storms, however, the intensity and duration of substorm activity has an ambiguous relationship with the power of the magnetic storm. An important manifestation of the “storm-substorm” connection is the direct influence of the power of a geomagnetic storm on the minimum geomagnetic latitude at which substorms develop. During strong geomagnetic storms, substorm activity can descend from high geomagnetic latitudes, reaching mid-latitudes. In this case, at mid-latitudes there will be a disruption of radio communications caused by the disturbing effect on the ionosphere of energetic charged particles generated during substorm activity.
The relationship between solar and geomagnetic activity - current trends
In some contemporary works devoted to the problem of space weather and space climate, the idea is expressed about the need to separate solar and geomagnetic activity. The figure shows the difference between monthly average sunspot values, traditionally considered an indicator of the SA (red), and the AA index (blue), which shows the level of geomagnetic activity. It can be seen from the figure that the coincidence is not observed for all SA cycles.
The fact is that a large proportion of SA maxima are made up of sporadic storms, for which flares and CMEs are responsible, that is, phenomena occurring in regions of the Sun with closed field lines. But at SA minima, most storms are recurrent, caused by the arrival to Earth of high-speed solar wind streams flowing from coronal holes - regions with open field lines. Thus, the sources of geomagnetic activity, at least for SA minima, have a significantly different nature.
Ionizing electromagnetic radiation from solar flares
As another important factor space weather Ionizing electromagnetic radiation (IER) from solar flares should be noted separately. During quiet times, EI is almost completely absorbed at high altitudes, causing ionization of air atoms. During solar flares, EI fluxes from the Sun increase by several orders of magnitude, which leads to warming up And additional ionization of the upper atmosphere.
As a result heating under the influence of electrical energy, the atmosphere is “inflated”, i.e. its density at a fixed height increases greatly. This poses a serious danger for low-altitude satellites and manned spacecraft, since when entering the dense layers of the atmosphere, the spacecraft can quickly lose altitude. This fate befell the American space station Skylab in 1972 during a powerful solar flare - the station did not have enough fuel to return to its previous orbit.
Absorption of shortwave radio waves
Absorption of shortwave radio waves is the result of the fact that the arrival of ionizing electromagnetic radiation - UV and X-ray radiation from solar flares causes additional ionization of the upper atmosphere (for more details, see the materials on the topic “Transient light phenomena in the upper atmosphere of the Earth”). This leads to a deterioration or even complete cessation of radio communications on the illuminated side of the Earth for several hours