Aurora: photos, latitudes, causes of the phenomenon. Aurora: photos, latitudes, causes of the phenomenon Disturbance of the geomagnetic field
The natural phenomenon known as airglow was discovered in 1868 by Swedish scientist Anders Angström.
This natural celestial glow occurs all the time and all over the globe. There are three types: dayglow, twilightglow and nightglow. Each of them is the result of the interaction of sunlight with molecules in our atmosphere, but has its own special way of formation.
Dayglow occurs when sunlight hits the atmosphere during the daytime. Some of it is absorbed by molecules in the atmosphere, giving them excess energy, which they then release as light, either at the same or slightly lower frequency (color). This light is much weaker than normal daylight, so we cannot see it with the naked eye.
Twilight glow is essentially the same as daylight, but in this case only the upper layers of the atmosphere are illuminated by the Sun. The rest of it and observers on Earth are in darkness. Unlike daytime glow, it is visible to the naked eye.
Night glow is generated not by sunlight falling on the night atmosphere, but by another process called chemiluminescence. During the day, sunlight stores energy in the atmosphere containing oxygen molecules. This extra energy causes the oxygen molecules to break apart into individual atoms. This mainly occurs at an altitude of about 100 km.
Unlike auroras, night glows are spread across the entire sky and are uniform.
The brightness of the glow correlates with the level of ultraviolet (UV) light coming from the Sun, which changes over time. The strength of the glow depends on the time of year.
To increase your chances of spotting the skyglow, you should capture a dark and clear night sky with a long exposure. The glow can be seen in any direction free from light pollution, 10–20 degrees above the horizon.
The sky glows like a giant multiple rainbow. Various disturbances, such as an approaching storm, can create ripples in the Earth's atmosphere, similar to waves. These gravitational waves are vibrations of the surfaces of layers of air and are similar to the waves caused by throwing a stone into calm water.
Long exposure photography taken towards the vertical layers of airglow made this wave-like structure visible.
The mechanism of occurrence of this phenomenon is as follows. During the day, solar radiation (sunlight) breaks down air molecules into atoms (charged atoms, ions), and electrons are knocked out. When the ions meet again (or attract an electron), a molecule is formed, and the excess energy is lost in the form of light. At an altitude of 80-120 km, mainly oxygen and sodium molecules recombine, emitting green and yellow light, respectively; At an altitude of 250-300 km, electron-ion recombination occurs, but the radiation of this layer lies in the infratastic (invisible) region of the electromagnetic spectrum.
The most common mechanism leading to the appearance of luminescence is the combination of a nitrogen atom with an oxygen atom to form a molecule of nitric oxide (NO). During this reaction, a photon is emitted. Other substances that can contribute to skyglow include hydroxyl radical (OH), molecular oxygen, sodium and lithium. The dark red glow is most likely produced by OH molecules located at an altitude of about 87 kilometers and excited by ultraviolet solar radiation. The orange and green glow comes from the sodium and oxygen atoms located just above.
During periods of activity, flares are observed on the Sun. A flare is something similar to an explosion, which results in the formation of a directed flow of very fast charged particles (electrons, protons, etc.). Streams of charged particles rushing at tremendous speed change the Earth's magnetic field, that is, they lead to the appearance of magnetic storms on our planet.
Charged particles captured by the Earth's magnetic field move along magnetic field lines and penetrate closest to the Earth's surface into the regions of the Earth's magnetic poles. As a result of collisions of charged particles with air molecules, electromagnetic radiation occurs - the aurora.
The color of the aurora is determined by the chemical composition of the atmosphere. At altitudes from 300 to 500 km, where the air is thin, oxygen predominates. The color of the glow here can be green or reddish. Below, nitrogen already predominates, giving bright red and violet aurora.
The most convincing evidence that we correctly understand the nature of the aurora is its repetition in the laboratory. Such an experiment, called “Araks,” was carried out in 1985 jointly by Russian and French researchers.
For the experiment, two points on the Earth's surface were chosen, lying on the same magnetic field line. These points were the French island of Kerguelen in the Indian Ocean in the Southern Hemisphere and the village of Sogra in the Arkhangelsk region in the Northern Hemisphere.
A geophysical rocket was launched from Kerguelen Island with a small particle accelerator, which at a certain altitude created a stream of electrons. Moving along the magnetic field line, these electrons penetrated into the Northern Hemisphere and caused an artificial aurora over Sogra.
- Task No. 2E0B2C
According to modern ideas, auroras on other planets of the solar system may have the same nature as auroras on Earth. On which planets presented in the table is it possible to observe auroras?
Explain your answer.
- Task No. 3B56A0
According to modern ideas, auroras on other planets of the solar system may have the same nature as auroras on Earth. On which planets presented in the table can auroras be observed?
- 1) only on Mercury
- 2) only on Venus
- 3) only on Mars
- 4) on all planets
- Task No. A26A40
Magnetic storms on Earth are
- 1) outbreaks of radioactivity
- 2) flows of charged particles
- 3) rapid and continuous changes in cloudiness
- 4) rapid and continuous changes in the planet’s magnetic field
- Task No. AA26A6
The color of the aurora occurring at an altitude of 100 km is determined primarily by radiation
- 1) nitrogen
- 2) oxygen
- 3) hydrogen
- 4) helium
Auroras
The polar lights are one of the most beautiful phenomena in nature. The forms of the aurora are very diverse: sometimes they are peculiar light pillars, sometimes long flaming ribbons of emerald green with red fringe, diverging numerous arrow-rays, or even just shapeless light, sometimes colored spots in the sky.
A bizarre light in the sky sparkles like a flame, sometimes covering more than half the sky. This fantastic play of natural forces lasts for several hours, then fading away and then flaring up.
Auroras are most often observed in the subpolar regions, hence the name. Auroras can be visible not only in the distant North, but also to the south. For example, in 1938, the aurora was observed on the southern coast of Crimea, which is explained by an increase in the power of the luminescence causative agent - the solar wind.
The study of auroras was started by the great Russian scientist M.V. Lomonosov, who hypothesized that the cause of this phenomenon is electrical discharges in rarefied air.
The experiments confirmed the scientist’s scientific assumption.
Auroras are the electric glow of the upper, very rarefied layers of the atmosphere at an altitude (usually) of 80 to 1000 km. This glow occurs under the influence of fast moving electrically charged particles (electrons and protons) coming from the Sun. The interaction of the solar wind with the Earth's magnetic field leads to an increased concentration of charged particles in the zones surrounding the Earth's geomagnetic poles. It is in these zones that the greatest activity of auroras is observed.
Collisions of fast electrons and protons with oxygen and nitrogen atoms lead the atoms to an excited state. Releasing excess energy, oxygen atoms emit bright radiation in the green and red regions of the spectrum, nitrogen molecules in the violet. The combination of all these radiations
and gives the aurora a beautiful, often changing color. Such processes can only occur in the upper layers of the atmosphere, because, firstly, in the lower dense layers, collisions of atoms and air molecules with each other immediately take away from them the energy received from solar particles, and secondly, cosmic particles themselves cannot penetrate deep into the earth's atmosphere.
Auroras occur more often and are brighter during the years of maximum solar activity, as well as during the days when powerful flares and other forms of increased solar activity appear on the Sun, since with its increase the intensity of the solar wind increases, which is the cause of the occurrence of auroras.
- Task No. 2F4F0E
In which parts of the earth's atmosphere is the greatest activity of auroras observed?
- 1) only near the North Pole
- 2) only in equatorial latitudes
- 3) Near the magnetic poles of the Earth
- 4) in any place in the earth’s atmosphere
- Task No. A0E5A3
Is it possible to say that the Earth is the only planet in the solar system where auroras are possible? Explain your answer.
- Task No. F3B537
The polar lights are called
A. mirages in the sky.
B. rainbow formation.
B. glow of some layers of the atmosphere.
The correct answer is
- 1) only A
- 2) only B
- 3) only B
- 4) B and C
Auroras
One of the most beautiful and majestic natural phenomena is the polar lights. In places on the globe located at high latitudes, mainly beyond the northern or southern Arctic Circle, during the long polar night, glows of various colors and shapes often flash in the sky. Auroras occur at an altitude of 80 to 1000 km above the Earth's surface and represent the glow of rarefied gases in the Earth's atmosphere. The color of the aurora is determined by the chemical composition of the atmosphere. At altitudes from 300 to 500 km, where the air is thin, oxygen predominates. The color of the glow here can be green or reddish. Below, nitrogen already predominates, giving bright red and violet aurora.
A connection has been noted between auroras and solar activity:
During the years of maximum solar activity (maximum solar flares), the number of auroras also reaches its maximum. During solar flares, charged particles (including electrons) are released, moving at enormous speed. When electrons enter the upper layers of the Earth's atmosphere, they cause its constituent gases to glow.
But why are auroras observed mainly at high latitudes, since the sun's rays illuminate the entire Earth? The fact is that the Earth has a fairly strong magnetic field. When electrons enter the earth's magnetic field, they are diverted from their original direct path and ejected into the polar regions of the globe. These same electrons change the Earth's magnetic field, causing the appearance of magnetic storms, and also influence the conditions for the propagation of radio waves near the earth's surface.
- Task No. 7CF82A
According to modern ideas, auroras on other planets of the solar system may have the same nature as auroras on Earth. A sufficient condition for observing auroras on a planet is that it has
- 1) only atmospheres
- 2) only magnetic field
- 3) natural satellites
- 4) atmosphere and magnetic field
- Task No. A62C62
The color of the aurora occurring at an altitude of 80 km is determined primarily by radiation
- 1) nitrogen
- 2) oxygen
- 3) hydrogen
- 4) helium
- Task No. A779CF
Magnetic storms are
- 1) sunspots
- 2) flows of charged particles
- 3) rapid and continuous changes in the solar magnetic field
- 4) rapid and continuous changes in the magnetic field of our planet
Ultra Long Vision Mirage
The nature of these mirages is least studied. It is clear that the atmosphere must be transparent, free of water vapor and pollution. But this is not enough. A stable layer of cooled air should form at a certain height above the earth's surface. Below and above this layer the air should be warmer. A light beam that gets inside a dense cold layer of air is, as it were, “locked” inside it and spreads through it as if through a kind of light guide. The beam path should always be convex towards less dense areas of air.
Auroras
Aurora - the glow (luminescence) of the upper layers of the atmospheres of planets with a magnetosphere due to their interaction with charged particles of the solar wind.
Eskimo and Indian legends say that it is the spirits of animals that dance in the sky, or that they are the spirits of fallen enemies who want to awaken again.
In most cases, auroras have a green or blue-green hue with occasional spots or a border of pink or red.
Auroras are observed in two main forms - in the form of ribbons and in the form of cloud-like spots. When the radiance is intense, it takes the form of ribbons. Losing intensity, it turns into spots. However, many tapes disappear before they have time to break into spots. The ribbons seem to hang in the dark space of the sky, resembling a giant curtain or drapery, usually stretching from east to west for thousands of kilometers. The height of this curtain is several hundred kilometers, the thickness does not exceed several hundred meters, and it is so delicate and transparent that the stars are visible through it. The lower edge of the curtain is quite sharply and clearly outlined and is often tinted in a red or pinkish color, reminiscent of a curtain border; the upper edge is gradually lost in height and this creates a particularly impressive impression of the depth of space.
There are four types of auroras
Homogeneous arc - the luminous stripe has the simplest, calmest shape. It is brighter from below and gradually disappears upward against the background of the sky glow;
Radiant arc - the tape becomes somewhat more active and mobile, it forms small folds and streams;
Radiant stripe - with increasing activity, larger folds are superimposed on smaller ones;
As activity increases, the folds or loops expand to enormous sizes, and the bottom edge of the ribbon glows brightly with a pink glow. When activity subsides, the folds disappear and the tape returns to a uniform shape. This suggests that a homogeneous structure is the main form of the aurora, and folds are associated with increasing activity.
Radiances of a different type often appear. They cover the entire polar region and are very intense. They occur during an increase in solar activity. These auroras appear as a whitish-green cap. Such lights are calledsqualls.
Based on the brightness of the aurora, they are divided into four classes, differing from each other by one order of magnitude (that is, 10 times). The first class includes auroras that are barely noticeable and approximately equal in brightness to the Milky Way, while the fourth class auroras illuminate the Earth as brightly as the full Moon.
It should be noted that the resulting aurora spreads to the west at a speed of 1 km/sec. The upper layers of the atmosphere in the area of auroral flashes heat up and rush upward. During auroras, eddy electric currents arise in the Earth's atmosphere, covering large areas. They excite additional unstable magnetic fields, so-called magnetic storms. During auroras, the atmosphere emits X-rays, which apparently result from the deceleration of electrons in the atmosphere.
Intense flashes of radiance are often accompanied by sounds reminiscent of noise and crackling. Auroras cause strong changes in the ionosphere, which in turn affects radio communication conditions. In most cases, radio communications deteriorate significantly. There is strong interference, and sometimes a complete loss of reception.
How do auroras occur?
The Earth is a huge magnet, the south pole of which is located near the north geographic pole, and the north pole is located near the south. The Earth's magnetic field lines, called geomagnetic lines, emerge from the region adjacent to the Earth's magnetic north pole, envelop the globe, and enter it at the south magnetic pole, forming a toroidal lattice around the Earth.
It has long been believed that the location of magnetic field lines is symmetrical relative to the earth's axis. Now it has become clear that the so-called “solar wind” - a stream of protons and electrons emitted by the Sun, strikes the geomagnetic shell of the Earth from a height of about 20,000 km, pulls it back, away from the Sun, forming a kind of magnetic “tail” on the Earth.
An electron or proton caught in the Earth's magnetic field moves in a spiral, as if winding around a geomagnetic line. Electrons and protons that enter the Earth's magnetic field from the solar wind are divided into two parts. Some of them immediately flow along magnetic lines of force into the polar regions of the Earth; others get inside the teroid and move inside it, along a closed curve. These protons and electrons eventually also flow along geomagnetic lines to the region of the poles, where their increased concentration occurs. Protons and electrons produce ionization and excitation of atoms and molecules of gases. For this they have enough energy, since protons arrive on Earth with energies of 10,000-20,000 eV (1 eV = 1.6 10 J), and electrons with energies of 10-20 eV. To ionize atoms you need: for hydrogen - 13.56 eV, for oxygen - 13.56 eV, for nitrogen - 124.47 eV, and for excitation even less.
Excited gas atoms give back the received energy in the form of light, similar to what happens in tubes with rarefied gas when currents are passed through them.
A spectral study shows that the green and red glow belongs to excited oxygen atoms, while the infrared and violet glow belongs to ionized nitrogen molecules. Some oxygen and nitrogen emission lines form at an altitude of 110 km, and the red glow of oxygen occurs at an altitude of 200-400 km. Another weak source of red light is hydrogen atoms, formed in the upper layers of the atmosphere from protons arriving from the Sun. Having captured an electron, such a proton turns into an excited hydrogen atom and emits red light.
Auroral flares usually occur a day or two after solar flares. This confirms the connection between these phenomena. Recently, scientists have found that auroras are more intense near the coasts of oceans and seas.
Auroras can occur not only on Earth, but also on other planets.
Aurora on Saturn, combined image in ultraviolet and visible light (Hubble Space Telescope)
But the scientific explanation of all phenomena associated with auroras encounters a number of difficulties. For example, the exact mechanism for accelerating particles to the indicated energies is unknown, their trajectories in near-Earth space are not entirely clear, not everything quantitatively converges in the energy balance of ionization and excitation of particles, the mechanism for the formation of various types of luminescence is not entirely clear, and the origin of sounds is unclear.
Parade of superstitions. Methodological aspects
In the school physics course, optical atmospheric phenomena are studied little and rather superficially. This is explained by a certain complexity of the material and the relatively small number of hours of physics provided in secondary schools. However, additional study of the subject is still possible in elective classes. In this case, the clarity of the material and the appeal to students’ personal experience in observing this or that optical phenomenon are of great importance (if we are talking about students in central Russia, then most often this concerns the observation of the color of the sky, including during the morning and evening dawn, rainbows, less often - crowns or haloes).
The study of optical phenomena in a school course is also complicated by the fact that not all of them can be explained only from the point of view of physics. Sometimes you have to resort to other sciences to explain (for example, when studying the northern lights, information from astronomy is used, which is not taught in all schools).
If it comes to teaching in specialized philological classes, then more attention should be paid not to a detailed consideration of the physical reasons for the occurrence of this or that optical phenomenon, but to the legends and superstitions associated with them. The same applies to students in 7th and 8th grades.
In specialized physics and mathematics classes, on the contrary, the most complete and comprehensive consideration of these phenomena is possible.
Optical phenomena, which have not yet received a clear physical explanation, are also of great interest to students. Here we can mention ultra-long-range vision mirages, chronomirages, trail mirages and other not entirely scientific phenomena. It is best to consider such material in a specially conducted misconception lesson, or if time does not allow, you can touch on it in abstract form.
At the present stage of human development, it is not difficult to explain how luminous crosses appear in the sky, which even in our age frighten other people.
The scientific explanation of the halo is a vivid example of how deceptive the external form of any natural phenomenon can sometimes be. It seems like something extremely mysterious, mysterious, but upon closer examination, not a trace remains of the “inexplicable”.
However, the search for rational explanations for frightening optical phenomena sometimes took years, decades and even centuries. Today, anyone who becomes interested in something can look into a reference book, leaf through a textbook, or immerse themselves in the study of specialized literature. But such opportunities appeared to humanity only recently. Of course, in the Middle Ages everything was completely different. After all, at that time such knowledge had not yet been accumulated, and science was carried out alone. The dominant worldview was religion, and the usual attitude was faith.
The French scientist K. Flammarion looked at historical chronicles from this angle. And this is what turned out to be: the compilers of the chronicles did not doubt at all the existence of a direct causal connection between the mysterious phenomena of nature and earthly affairs.
In 1118, during the reign of King Henry I of England, two full moons simultaneously appeared in the sky, one in the west and the other in the east. That same year the king won the battle.
In 1120, a cross and a man made of flames appeared among the blood-red clouds. Everyone expected the end of the world, but it only ended in civil war.
In 1156, three rainbow circles shone around the sun for several hours in a row, and when they disappeared, three suns appeared. The compiler of the chronicle saw in this phenomenon a hint of the king's quarrel with the Bishop of Canterbury in England and the destruction after the seven-year siege of Milan in Italy.
The next year, three suns appeared again, and in the middle of the moon a white cross was visible; Of course, the chronicler immediately connected this with the discord that accompanied the election of the new Pope.
In January 1514, three suns were visible in Württemberg, of which the middle one was larger than the side ones. At the same time, bloody and flaming swords appeared in the sky. In March of the same year, three suns and three moons were again visible. At the same time, the Turks were defeated by the Persians in Armenia.
Most often, celestial phenomena were assigned a bad meaning.
In this regard, an interesting fact has been recorded in the history of mankind. In 1551, the German city of Magdeburg was besieged by the troops of the Spanish king Charles V. The defenders of the city held out steadfastly, and the siege lasted for more than a year. Finally, the irritated king gave the order to prepare for a decisive attack. But then the unprecedented happened: a few hours before the assault, three suns shone over the besieged city. The mortally frightened king decided that Magdeburg was protected by heaven and ordered the siege to be lifted.
Something similar is known in Russian history. So, in"The Tale of Igor's Campaign"it is mentioned that before the advance of the Polovtsians and the capture of Igor, “four suns shone over the Russian land.” The warriors took this as a sign of impending great trouble.
Other legends say that Ivan the Terrible saw an omen of his death in the “sign of the cross in the sky.”
Whether all these phenomena actually happened is not so important for us now. It is important that with their help, real historical events were interpreted on their basis; that people then looked at the world through the prism of their distorted ideas and therefore saw what they wanted to see. Their imagination sometimes knew no bounds. Flammarion called the incredible fantastic pictures drawn by the authors of the chronicles “examples of artistic exaggeration.”
Chronomirages
Chronomirages are mysterious phenomena that have not received a scientific explanation. No known laws of physics can explain why mirages can reflect events occurring at a certain distance, not only in space, but also in time. Mirages of battles and battles that once took place on earth have become especially famous. In November 1956, several tourists spent the night in the mountains of Scotland. At about three in the morning they woke up from a strange noise, looked out of the tent and saw dozens of Scottish riflemen in ancient military uniforms, who were running across the rocky field, shooting! Then the vision disappeared, leaving no traces, but a day later it repeated itself. The Scottish riflemen, all wounded, wandered across the field, stumbling over stones.
And this is not the only evidence of such a phenomenon. Thus, the famous Battle of Waterloo (June 18, 1815) was observed a week later by residents of the Belgian town of Verviers. The distance from Waterloo to Verviers in a straight line is more than 100 km. There are cases when similar mirages were observed at large distances - up to 1000 km.
According to one theory, with a special confluence of natural factors, visual information is imprinted in time and space. And if certain atmospheric, weather, etc. coincide. conditions, it again becomes visible to outside observers.
Mirages - tracers
A class of phenomena that has also not received scientific substantiation. It includes mirages, which leave material traces after their disappearance. It is known that in March 1997, fresh ripe nuts fell from the sky in England. Several explanations have been put forward for the nature of the occurrence of these traces.
First, these traces are not directly related to the mirage. “After this” does not mean “as a result of this”. The most difficult thing is to establish the general reliability of the facts of such phenomena.
Another explanation is that the difference in temperature layers leads to the formation of a vortex effect, sucking various debris into the atmosphere. The movement of air currents delivers the “absorbed” to the area where the mirage is formed. After the temperatures equalize, the “sky picture” disappears and the debris falls to the ground.
It is difficult to talk about the reliability of such phenomena. But they still evoke a certain “mystical” interest. Therefore, they may well be considered a misconception in the lesson.
By studying various phenomena associated with the passage of light in the atmosphere, scientists use the acquired knowledge to develop science. Thus, observing the crowns helps determine the size of ice crystals and water droplets from which various clouds are formed. Observations of crowns and halos also make it possible to predict the weather. So, if the crown that appears gradually decreases, precipitation can be expected. An increase in crowns, on the contrary, foreshadows the onset of dry and partly cloudy weather.
Conclusion
The physical nature of light has interested people since time immemorial. Many outstanding scientists, throughout the development of scientific thought, struggled to solve this problem. Over time, the complexity of an ordinary white ray was discovered, and its ability to change its behavior depending on the environment, and its ability to exhibit signs inherent in both material elements and the nature of electromagnetic radiation. A light beam, subjected to various technical influences, began to be used in science and technology in the range from a cutting tool capable of processing the desired part with micron accuracy, to a weightless information transmission channel with practically inexhaustible possibilities.
But before the modern view of the nature of light was established, and the light ray found its application in human life, many optical phenomena were identified, described, scientifically substantiated and experimentally confirmed, occurring everywhere in the earth’s atmosphere, from the rainbow known to everyone, to complex, periodic mirages. But, despite this, the bizarre play of light has always attracted and attracts people. Neither the contemplation of a winter halo, nor a bright sunset, nor a wide, half-sky strip of northern lights, nor a modest lunar path on the surface of the water leaves anyone indifferent. A light beam passing through the atmosphere of our planet not only illuminates it, but also gives it a unique appearance, making it beautiful.
Of course, much more optical phenomena occur in the atmosphere of our planet than is discussed in this course work. Among them there are those that are well known to us and have been solved by scientists, as well as those that are still waiting for their discoverers. And we can only hope that, over time, we will witness more and more discoveries in the field of optical atmospheric phenomena, indicating the versatility of an ordinary light beam.
List of used literature
Gershenzon E.M., Malov N.N., Mansurov A.N. "General Physics Course"
Korolev F.A. “Physics course” M., “Enlightenment” 1988
“Physics 10”, authors - G. Ya. Myakishev B. B. Bukhovtsev, Prosveshchenie publishing house, Moscow, 1987. in an atmosphere of ideological cleansing, psychotechnics actually stopped... - vision) - subjective light phenomena(feelings) without character...
The phenomenon of glow, to some extent close to the auroras, called “glow of the night sky,” can be observed using special instruments at any latitude.
Forms of auroras. In recent years, aurorae have been observed visually and photographed, in particular using a new type of instrument called an all-round camera. Aurorae have a wide variety of forms, including flashes, spots, uniform arcs and stripes, pulsating arcs and surfaces, flashes, rays, radiant arcs, drapes and coronas. The glow, as a rule, begins in the form of a solid arc, which is one of the most common forms and does not have a radiant structure. The brightness can be fairly constant over time or pulsate with a period of less than a minute. If the brightness of the radiance increases, the homogeneous form often breaks up into rays, radiant arcs, drapery or coronas, in which the rays seem to converge to the top. Flashes in the form of rapidly moving upward waves of light are often crowned with a crown.Altitudinal and latitudinal distribution. Calculations based on many photographic observations in Alaska, Canada and especially Norway show that ca. 94% of auroras are confined to altitudes from 90 to 130 km above the earth's surface, although different forms of auroras are characterized by their own altitude position. The maximum height of aurora appearance recorded so far is approx. 1130 km, minimum 60 km.Based on a large number of observations in the Arctic, Herman Fritz and Harry Vestein established geographic patterns of occurrence of auroras and characterized their relative frequency at each specific point as the average number of days of their appearance per year. Lines of equal frequency of occurrence of auroras (isochasms) have the shape of several deformed circles with a center approximately coinciding with the Earth's North Magnetic Pole, located in the Thule region in northern Greenland (
cm . rice. ). The isochasm of maximum frequencies passes through Alaska, Great Bear Lake, crosses Hudson Bay, southern Greenland and Iceland, northern Norway and Siberia. A similar isochasm of maximum frequencies of auroras for the Antarctic region was revealed during studies carried out within the framework of the International Geophysical Year (IGY, July 1957 December 1958). These belts of maximum frequency of auroras, which are almost regular rings, are called the northern and southern aurora zones. Observations during the IGY confirmed that auroras appear almost simultaneously in both zones. Some researchers have suggested the existence of a spiral or double ring zone of auroras, which, however, has not been confirmed. Auroras can also appear outside the mentioned zones (see below ). Historical materials indicate that auroras were sometimes observed even at very low latitudes, for example, on the Hindustan Peninsula. Aurora activity and related phenomena. Auroras are studied using radar. Radio waves with frequencies from 10 to 100 MHz, under certain conditions, are reflected by ionization regions that arise in the high layers of the atmosphere under the influence of auroras. By using high-frequency radio signals and long-range antennas, reflected waves can be obtained at frequencies up to 800 MHz. The radar method detects ionization even during the day in sunlight, and very fast movements of auroras are also recorded. The results of photo and radar observations indicate that the activity of auroras is subject to both daily and seasonal changes. Maximum activity during the day is approx. 23 hours, while the seasonal peak of activity occurs on the days of the equinox and time intervals close to them (March - April and September - October). These peaks of auroral activity repeat at relatively regular intervals, and the duration of the main cycles is approximately 27 days and approx. 11 years. All these figures show that there is a correlation between auroras and changes in the Earth's magnetic field, since their activity peaks coincide, i.e. auroras typically occur during periods of high magnetic field activity called "disturbances" and "magnetic storms." It is during strong magnetic storms that auroras are visible at lower latitudes than usual.Pulsating auroras are usually accompanied by pulsations of the magnetic field and very rarely by faint whistling sounds. They also appear to generate radio waves at 3000 MHz. Ionospheric observations in the radio wave range show that ionization increases at altitudes of 80150 km during auroras. Geophysical rocket observations indicate that dense nuclei of increased ionization along magnetic field lines are associated with auroras, and during intense auroras the temperature of the upper atmosphere increases.
Glow intensity and color. The intensity of the aurora glow is usually assessed visually and expressed in points according to the accepted international scale. Weak auroras, roughly equivalent in intensity to the Milky Way, are rated I. Auroras with an intensity similar to the lunar coherence of thin cirrus clouds in the II point, and cumulus clouds in the III point, the light of the full Moon in the IV point. For example, an intensity of grade III emanating from the arc of the aurora corresponds to the light of several microcandles per 1 square meter. see. An objective method for determining the intensity of the aurora glow is to measure the total illumination using photocells. It has been established that the ratio of the intensity of the brightest to the weakest auroras is 1000:1.Aurorae with glow intensities of points I, II and III (near the lower limit) do not appear multi-colored, since the intensity of individual colors in them is below the threshold of perception. Auroras with luminescence intensity of IV and III (at the upper limit) points appear colored, usually yellowish-green, sometimes violet and red. Since Anders Ångström first pointed a spectroscope at the auroras in 1867, a large number of spectral lines and bands have been discovered and studied in them. The bulk of the radiation is emitted by nitrogen and oxygen, the main components of the high layers of the atmosphere. Atomic oxygen usually gives auroras yellowish tones, sometimes there is no color at all, a green line with a wavelength of 5577 appears in the spectrum
, and there are also red radiant auroras with a wavelength of 6300(type A). Strong emission from molecular nitrogen at wavelengths 4278 and 3914 observed in red and violet auroras in the lower part of arcs or drapes (type B). Hydrogen emission has been detected in some forms of auroras, which is important for understanding the nature of auroras, since this emission indicates the arrival of a flux of protons. Theories of the origin of auroras. As mentioned above, it has long been known that auroral displays and disturbances in the Earth's magnetic field, or magnetic storms, share some important characteristics. Therefore, any theory proposed to explain one of these phenomena must also explain the other.The frequency of disturbances in the Earth's magnetic field and auroras with a period of 27 days and an 11-year cycle indicate the connection of these phenomena with solar activity, since the rotation period of the Sun is approx. 27 days, and solar activity is subject to cyclical fluctuations with an average period of approx. 11 years. The fact that both auroras and disturbances of the Earth's magnetic field are concentrated in the same belts leads to the conclusion that both are caused by the influence of high-speed electrically charged particles (protons and electrons) emitted by active regions on the Sun (flares) and penetrating into the zones of auroras under the influence of the Earth’s magnetic field
SPACE EXPLORATION AND USE) .This idea was put forward by Eugen Goldstein back in 1881 and was confirmed by laboratory experiments first carried out by Christian Birkeland. He placed an iron ball inside the cathode tube, which he called a “terrella,” which is a model of the Earth and is an electromagnet covered with a shell that phosphorescent under the action of cathode rays. When Birkeland exposed the ball to cathode rays emitted directly in the chamber, they fell on the surface of the ball around the magnetic poles, forming belts of luminescence similar to the belts of auroras.
Later, the mathematical development of this problem was carried out by Karl Frederick Störmer. It became known as the theory of Birkeland Störmer, but it was based on the assumption that a stream of particles with identical electrical charges emanates from the Sun. The validity of this assumption is highly controversial, since such a flow of particles could not approach the Earth due to electrostatic repulsion between similarly charged particles.
Frederick A. Lindeman proposed in 1919 that the flow of charged particles is generally electrically neutral, since it consists of equal numbers of positive and negative charges. This idea was developed by Sidney Chapman and Vincent S.A. Ferraro and slightly modified by David F. Martin. However, this theory also raises doubts. It suggests the existence of a vacuum in the exosphere and beyond the atmosphere, but recent observations in these regions of space indicate the presence of charged particles.
Some researchers have hypothesized that a cloud of solar gas (plasma), which likely consists of electrons and protons, may approach our planet at a distance of about six Earth radii from the center of the Earth. When plasma acts on the Earth's magnetic field, magnetohydrodynamic waves arise. These waves and accelerated charged particles moving along geomagnetic field lines cause magnetic storms. Accelerated particles penetrate to a height of approx. 95 km into the aurora zones, forming dense ionization nuclei along geomagnetic field lines and causing electromagnetic emission of auroras as a result of interaction with the main components of the upper atmosphere - oxygen and hydrogen.
The toroidal region of charged particles surrounding the Earth (the so-called Van Allen radiation belt) can also play an important role, especially as a cause of geomagnetic field disturbances and associated auroras. Ultraviolet radiation from the Sun, meteors and winds in the high atmosphere have been considered as possible causes of the formation of auroras. However, none of these phenomena can be the primary cause, since the magnitudes of their changes are not large enough to explain the main characteristics of auroras. It is necessary to carry out further observations in the high layers of the Earth's atmosphere and beyond using rockets and artificial satellites, to study radio emission, as well as X-ray emission from the Sun and the behavior of high-energy particles in the stratosphere using weather balloons during magnetic storms and when auroras appear.
Artificial auroras. Glows similar to auroras arose as a result of nuclear explosions in the high layers of the atmosphere carried out by the US Department of Defense during the IGY. These experiments were important for studying the Van Allen radiation belt and the nature of natural auroras. This kind of aurora was observed in the area of the islands of Maui (Hawaii Islands) and Apia (Samoa Islands) shortly after the Teak and Orange nuclear explosions, which were carried out at altitudes of approx. 70 and 40 km over Johnston Atoll in the central Pacific Ocean on August 1 and 12, 1958. The glow visible over Apia on August 1 consisted of a crimson arc and rays that were first violet, then red and gradually turning green. Other artificially induced auroras associated with the Argus I, II and III explosions carried out at an altitude of ca. 480 km on August 27 and 30 and September 6, 1958, were observed in the area of explosions in the South Atlantic Ocean. Their color was red mixed with yellowish-green. During the Argus III explosion, a red artificial aurora was also observed near the Azores Islands, at the end of the corresponding magnetic field lines of the Earth opposite the explosion site (i.e., in the territory geomagnetically conjugate with this one).These observations clearly show that artificial auroras in the area of the explosion and in the geomagnetically associated area were caused by such high-energy particles as electrons formed as a result
b - disintegration during a nuclear explosion. In other words, the high-energy particles produced by the explosion moved along the geomagnetic field lines, forming artificial Van Allen radiation belts, and led to the formation of “auuroras” at both ends of the field lines. Judging by the height of appearance and color range of these auroras, it can be assumed that the cause of their occurrence is the excitation of atmospheric oxygen and nitrogen as a result of collisions with charged particles with high energy, which is very similar to the mechanism of formation of natural auroras.The aforementioned explosions in the high layers of the atmosphere, especially the Teak and Orange experiments, were also associated with significant disturbances in the Earth's magnetic field and ionosphere. Thus, as a result of the experiments, important information was obtained about natural auroras and related phenomena.
There is another anthropogenic phenomenon of glow in the high layers of the atmosphere, caused by emissions of sodium or potassium gas from rockets. This phenomenon can be called an artificial glow, in contrast to the artificial aurora, since its causes are close to those that cause the natural glow of the air.
LITERATURE Isaev S. I., Pushkov N. V.Auroras . M., 1958Omholt A. Auroras . M., 1974
Vorontsov-Velyaminov B. A.Essays on the Universe . M., 1980
Amateur astronomers and aurora hunters have reported seeing a green glow in the skies over the UK. A phenomenon that can easily be confused with aurora borealis, is called the atmospheric glow. airglow).
KAMRUL ARIFIN | shutterstock
This natural celestial glow occurs all the time and all over the globe. There are three types: daytime ( dayglow), twilight ( twilightglow) and night ( nightglow). Each of them is the result of the interaction of sunlight with molecules in our atmosphere, but has its own special way of formation.
Dayglow occurs when sunlight hits the atmosphere during the daytime. Some of it is absorbed by molecules in the atmosphere, giving them excess energy, which they then release as light, either at the same or slightly lower frequency (color). This light is much weaker than normal daylight, so we cannot see it with the naked eye.
Twilight glow is essentially the same as daylight, but in this case only the upper layers of the atmosphere are illuminated by the Sun. The rest of it and observers on Earth are in darkness. Unlike daylight, twilightglow visible to the naked eye.
Chemoluminescence
Night glow is generated not by sunlight falling on the night atmosphere, but by another process called chemiluminescence.
During the day, sunlight stores energy in the atmosphere containing oxygen molecules. This extra energy causes the oxygen molecules to break apart into individual atoms. This mainly occurs at an altitude of about 100 km. However, atomic oxygen is not able to easily get rid of this excess energy and, as a result, turns into a kind of “energy store” for several hours.
Eventually, atomic oxygen manages to “recombine,” again forming molecular oxygen. In doing so, it releases energy, again in the form of light. This produces several different colors, including the night green emission, which is not actually very bright, but is the brightest of all the emission in this category.
Light pollution and cloudiness may interfere with observation. But if you're lucky, the night glow can be seen with the naked eye or captured in a photograph using a long exposure.
Yuri Zvezdny | shutterstock
How are glows different from auroras?
The green glow in the night sky is very similar to the famous green color we see in the northern lights, which is not surprising since they are produced by the same oxygen molecules. However, these two phenomena are in no way related to each other.
Polar Lights. ZinaidaSopina | shutterstock
Auroras form when charged particles, such as electrons, “bombard” the Earth's atmosphere. These charged particles, which were launched from the Sun and accelerated in the Earth's magnetosphere, collide with atmospheric gases and transfer energy to them, causing the gases to emit light.
Additionally, auroras are known to form a ring around the magnetic poles (auroral oval), while nightglows are spread across the entire sky. The auroras are very structured (due to the Earth's magnetic field), and the glows are generally quite uniform. The degree of auroras depends on the strength of the solar wind, and atmospheric glows occur constantly.
Auroral oval. NOAA
But why then did observers from the UK only see him the other day? The fact is that the brightness of the glow correlates with the level of ultraviolet (UV) light coming from the Sun, which changes over time. The strength of the glow depends on the time of year.
To increase your chances of spotting the skyglow, you should capture a dark and clear night sky with a long exposure. The glow can be seen in any direction free from light pollution, 1020 degrees above the horizon.
