Cold ultraviolet glow in the upper atmosphere. The sky over the UK was lit up by “non-polar lights. What is isochasm

During the period of activity on the Sun, flares are observed. A flash is something similar to an explosion, which results in a directed stream of very fast charged particles (electrons, protons, etc.). Streams of charged particles, rushing at great speed, change the Earth's magnetic field, that is, lead to the appearance of magnetic storms on our planet.

Captured by the Earth's magnetic field, charged particles move along magnetic field lines and penetrate the Earth's magnetic poles closest to the Earth's surface. As a result of collisions of charged particles with air molecules, electromagnetic radiation is produced - 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 rarefied, oxygen predominates. The color of the radiance here can be green or reddish. Below, nitrogen already predominates, giving glows of bright red and purple.

The most compelling argument for our correct understanding of 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.

Two points on the Earth's surface were chosen for the experiment, 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 with a small particle accelerator was launched from Kerguelen Island, which created a stream of electrons at a certain height. Moving along the magnetic field line, these electrons penetrated the Northern Hemisphere and caused an artificial aurora over Sogra.

• Task #2E0B2C

According to modern concepts, the auroras on other planets of the solar system may have the same nature as the auroras on Earth. On which planets in the table is it possible to observe auroras?

Explain the answer.

• Task #3B56A0

According to modern concepts, the auroras on other planets of the solar system may have the same nature as the auroras on Earth. On which planets in the table can auroras be observed?

• • 1) only on Mercury
  • 2) only on Venus
  • 3) only on Mars
  • 4) on all planets
• Task #A26A40

Magnetic storms on Earth are

• • 1) outbreaks of radioactivity
  • 2) streams of charged particles
  • 3) rapid and continuous changes in cloudiness
  • 4) rapid and continuous changes in the planet's magnetic field
• Task #AA26A6

The color of the aurora, which occurs at an altitude of 100 km, is determined mainly by radiation

• • 1) nitrogen
  • 2) oxygen
  • 3) hydrogen
  • 4) helium

auroras

The aurora borealis is one of the most beautiful phenomena in nature. The forms of the aurora borealis are very diverse: either they are peculiar light pillars, or emerald green with red fringe, flaming long ribbons, diverging numerous rays-arrows, 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 game of natural forces lasts for several hours, then fading, then flaring up.

Auroras are most often observed in the circumpolar regions, hence the name. Polar lights can be seen not only in the far 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 great Russian scientist M.V. Lomonosov, who put forward the hypothesis that the cause of this phenomenon is electric discharges in rarefied air.

The experiments confirmed the scientific assumption of the scientist.

Auroras are the electrical glow of the upper very rarefied layers of the atmosphere at an altitude (usually) from 80 to 1000 km. This glow occurs under the influence of rapidly 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 bring the atoms into an excited state. Releasing excess energy, oxygen atoms give 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 auroras a beautiful, often changing color. Such processes can occur only in the upper layers of the atmosphere, because, firstly, in the lower dense layers, collisions of atoms and molecules of air 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 on the days when powerful flares appear on the Sun and other forms of increased solar activity, since with its increase the intensity of the solar wind increases, which is the cause of the auroras.

• Task #2F4F0E

In what parts of the earth's atmosphere is the most active auroras observed?

• • 1) only near the North Pole
  • 2) only in equatorial latitudes
  • 3) Near the Earth's magnetic poles
  • 4) in any place of the earth's atmosphere
• Task №A0E5A3

Is it possible to argue that the Earth is the only planet in the solar system where auroras are possible? Explain the answer.

• Task #F3B537

They call it the aurora borealis

A. mirages in the sky.

B. rainbow formation.

V. 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 phenomena of nature is the aurora borealis. 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 of 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 rarefied, oxygen predominates. The color of the radiance here can be green or reddish. Below, nitrogen already predominates, giving glows of bright red and purple.

A connection between the auroras and the activity of the Sun has been noticed:
in the years of maximum solar activity (maximum solar flares), the number of auroras also reaches a maximum. During flares on the Sun, charged particles (including electrons) are ejected, moving at great speed. Getting into the upper layers of the Earth's atmosphere, the electrons cause the gases that make up the Earth to glow.

But why are auroras observed predominantly at high latitudes, because the sun's rays illuminate the entire Earth? The fact is that the Earth has a fairly strong magnetic field. Getting into the earth's magnetic field, electrons deviate from their original direct path and are ejected into the subpolar regions of the globe. The same electrons change the Earth's magnetic field, causing the appearance of magnetic storms, and also affect the conditions for the propagation of radio waves near the earth's surface.

• Task #7CF82A

According to modern concepts, the auroras on other planets of the solar system may have the same nature as the auroras on Earth. A sufficient condition for observing auroras on a planet is that it has

• • 1) only atmospheres
  • 2) magnetic field only
  • 3) natural satellites
  • 4) atmosphere and magnetic field
• Task #A62C62

The color of the aurora, which occurs at an altitude of 80 km, is determined mainly by radiation

• • 1) nitrogen
  • 2) oxygen
  • 3) hydrogen
  • 4) helium
• Task #A779CF

Magnetic storms are

• • 1) spots on the sun
  • 2) streams of charged particles
  • 3) rapid and continuous changes in the magnetic field of the Sun
  • 4) rapid and continuous changes in the magnetic field of our planet

Mirage of ultra-long vision

The nature of these mirages is the least studied. It is clear that the atmosphere must be transparent, free from water vapor and pollution. But this is not enough. A stable layer of cooled air should form at some height above the ground. Below and above this layer, the air should be warmer. A light beam that has fallen inside a dense cold layer of air is, as it were, “locked” inside it and propagates in it like a kind of light guide. The trajectory of the beam must be convex all the time towards the less dense regions of the air.

auroras

Aurora is 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 dancing in the sky, or that they are the spirits of fallen enemies who want to awaken again.

In most cases, auroras are green or blue-green in color, with occasional patches or borders 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 on the form of ribbons. Losing intensity, it turns into spots. However, many ribbons disappear before they 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 stars can be seen through it. The lower edge of the curtain is quite sharply and distinctly outlined and often tinted in red or pinkish color, reminiscent of the border of the curtain, the upper one is gradually lost in height and this creates a particularly spectacular impression of the depth of space.

There are four types of auroras

Uniform arc - the luminous strip has the most simple, calm form. It is brighter from below and gradually disappears upward against the background of the glow of the sky;

radiant arc - the tape becomes somewhat more active and mobile, it forms small folds and streams;

radiant band - with an increase in activity, larger folds are superimposed on smaller ones;

With increased activity, the folds or loops expand to enormous sizes, the lower edge of the ribbon shines brightly with a pink glow. When the activity subsides, the wrinkles disappear and the tape returns to a uniform shape. This suggests that the uniform structure is the main form of the aurora, and the folds are associated with an increase in activity.

Often there are aurora of a different kind. They capture the entire polar region and are very intense. They occur during an increase in solar activity. These lights appear as a whitish-green cap. Such lights are calledflurries.

According to 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 aurora, barely noticeable and approximately equal in brightness to the Milky Way, while the radiance of the fourth class illuminates the Earth as brightly as the full moon.

It should be noted that the aurora that has arisen propagates to the west at a speed of 1 km/sec. The upper layers of the atmosphere in the area of ​​auroral flashes are heated and rush upwards. During auroras, eddy electric currents arise in the Earth's atmosphere, capturing large areas. They excite additional unstable magnetic fields, the so-called magnetic storms. During aurora, the atmosphere emits X-rays, which appear to be the result of electron deceleration in the atmosphere.

Intense flashes of radiance are often accompanied by sounds resembling noise, crackling. Auroras cause strong changes in the ionosphere, which in turn affects radio conditions. In most cases, radio communication deteriorates significantly. There is strong interference, and sometimes a complete loss of reception.

How do aurorae occur?

The earth is a huge magnet, the south pole of which is located near the north geographic pole, and the north is close to the south. The lines of force of the Earth's magnetic field, called geomagnetic lines, leave the area adjacent to the north magnetic pole of the Earth, cover the globe and enter it in the area of ​​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 about the earth's axis. It has now become clear that the so-called "solar wind" - a stream of protons and electrons emitted by the Sun - hits 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" near the Earth.

An electron or a proton that has fallen into the Earth's magnetic field moves in a spiral, as if winding itself on a geomagnetic line. Electrons and protons that have fallen from the solar wind into the Earth's magnetic field are divided into two parts. Some of them flow down the magnetic field lines immediately 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 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. To do this, they have enough energy, since protons arrive at the Earth with energies of 10000-20000 eV (1 eV = 1.6 10 J), and electrons with energies of 10-20 eV. For the ionization of atoms, it is necessary: ​​for hydrogen - 13.56 eV, for oxygen - 13.56 eV, for nitrogen - 124.47 eV, and even less for excitation.

Excited gas atoms give back the received energy in the form of light, just as it happens in tubes with a rarefied gas when currents are passed through them.

A spectral study shows that the green and red glow belongs to excited oxygen atoms, infrared and violet - to ionized nitrogen molecules. Some emission lines of oxygen and nitrogen are formed at an altitude of 110 km, and the red glow of oxygen is formed at an altitude of 200-400 km. Another weak source of red light is hydrogen atoms formed in the upper atmosphere from protons arriving from the Sun. Having captured an electron, such a proton turns into an excited hydrogen atom and emits red light.

Aurora flares usually occur a day or two after solar flares. This confirms the connection between these phenomena. Recently, scientists have found that the auroras are more intense off the coast of the oceans and seas.

Auroras can occur not only on Earth, but also on other planets.

Aurora on Saturn, combined ultraviolet and visible light (Hubble Space Telescope)

But the scientific explanation of all the phenomena associated with aurora encounters a number of difficulties. For example, the exact mechanism of particle acceleration to the indicated energies is not known, their trajectories in near-Earth space are not quite clear, not everything agrees quantitatively in the energy balance of ionization and excitation of particles, the mechanism for the formation of various types of luminescence is not quite clear, the origin of sounds is unclear.

Parade of superstitions. Methodological aspects

In the school course of physics, optical atmospheric phenomena are studied little and rather superficially. This is due to the certain complexity of the material and the relatively small number of physics hours provided in secondary general education schools. However, additional study of the subject is still possible in optional classes. At the same time, the visibility of the material and the appeal to the personal experience of students 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 halo).

The study of optical phenomena in the school course is further 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).

When it comes to teaching in specialized philological classes, then more attention should be paid not to a detailed consideration of the physical causes of the occurrence of this or that optical phenomenon, but to the legends and superstitions associated with them. The same applies to 7th and 8th grade students.

In specialized physical and mathematical 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 mirages, chrono-mirages, tracker mirages and other not entirely scientific phenomena. It is best to consider such material in a specially conducted delusion lesson, or if time does not allow, you can touch it in an abstract form.

At the present stage of human development, it is easy to explain how luminous crosses appear in the sky, which in our century frighten other people.

The scientific explanation of the halo is a vivid example of how sometimes the external form of a natural phenomenon can be deceptive. It seems that something is extremely mysterious, mysterious, but upon closer examination, there is no trace of the “inexplicable”.

However, the search for rational explanations for frightening optical phenomena sometimes took years, decades and even centuries. Today, every person, interested in something, can look into the reference book, look through the textbook, immerse himself in the study of special literature. But such opportunities for humanity appeared only recently. Of course, things were very different in the Middle Ages. After all, then such knowledge had not yet been accumulated, and loners were engaged in science. Religion was the dominant worldview, and faith was the usual worldview.

The French scientist K. Flammarion looked through the historical chronicles from this angle. And this is what turned out: the compilers of the chronicles did not at all doubt 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 appeared simultaneously in the sky, one in the west and the other in the east. In the same year, the king was victorious in battle.

In 1120, a cross and a man appeared among the blood-red clouds, consisting of flames. Everyone expected the doomsday, but the matter ended only 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 an allusion to the king's quarrel with the Bishop of Canterbury in England and to the destruction after the seven-year siege of Milan in Italy.

The following year, three suns reappeared, and a white cross was visible in the middle of the moon; of course, the chronicler immediately associated this with the strife that accompanied the election of a new pope.

In January 1514, three suns were visible in Württemberg, of which the average is 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. Then the Turks were defeated by the Persians in Armenia.

Most often, a bad meaning was attributed to celestial phenomena.

In this regard, a curious 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 firm, the siege had lasted for more than a year. Finally, the irritated king gave the order to prepare for a decisive attack. But then an unprecedented thing happened: a few hours before the assault, three suns shone over the besieged city. The mortally frightened king decided that heaven was protecting Magdeburg and ordered the siege to be lifted.

Something similar is known in Russian history. Yes, in"The Tale of Igor's Campaign"it is mentioned that before the offensive of the Polovtsians and the capture of Igor, "four suns shone over the Russian land." The warriors took this as a sign of impending big trouble.

In other legends, it is reported that Ivan the Terrible saw the omen of his death in the "sign of the cross in heaven."

Whether all these phenomena actually existed is not so important for us now. It is important that with their help, on their basis, real historical events were interpreted; 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 paintings painted by the authors of the chronicles "exemplars 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 some distance, not only in space, but also in time. The mirages of battles and battles that once took place on earth were especially famous. In November 1956, several tourists spent the night in the mountains of Scotland. At about three o'clock in the morning they woke up from a strange noise, looked out of the tent and saw dozens of Scottish archers in ancient military uniforms, who, shooting, fled through a rocky field! Then the vision disappeared, leaving no traces, but a day later it happened again. The Scottish archers, all wounded, plodded across the field, stumbling over the stones.

And this is not the only evidence of this phenomenon. So, the famous battle of Waterloo (June 18, 1815) was observed a week later by the inhabitants 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 such mirages were observed at large distances - up to 1000 km.

According to one theory, with a special combination of natural factors, visual information is imprinted in time and space. And with the coincidence of certain atmospheric, weather, etc. conditions, it again becomes visible to outside observers.

Mirages - trackers

A class of phenomena that also has not received scientific justification. It includes mirages, which, after their disappearance, leave material traces. It is known that in March 1997, fresh ripe nuts fell from the sky in England. Put forward several explanations of the nature of the occurrence of these traces.

First, these traces are not directly related to the mirage. “After this” does not mean “because of this”. The most difficult thing is to establish the general reliability of the very facts of such phenomena.

Another explanation is that the difference in temperature layers leads to the formation of a vortex effect that sucks various garbage into the atmosphere. The movement of air currents delivers "absorbed" to the area of ​​mirage formation. After the temperatures equalize, the "heavenly picture" disappears, and the debris falls to the ground.

It is difficult to speak about the reliability of such phenomena. But they still arouse a certain “mystical” interest. Therefore, they may well be considered in the lesson-delusion.

By studying various phenomena associated with the passage of light in the atmosphere, scientists use the acquired knowledge for the development of science. Thus, the observation of crowns helps to determine the size of ice crystals and water drops, 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, portends the onset of dry and cloudy weather.

Conclusion

The physical nature of light has interested people since time immemorial. Many eminent 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 show signs inherent in both material elements and the nature of electromagnetic radiation. The 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 an accuracy of a micron, 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 beam found its application in human life, many optical phenomena that occur everywhere in the earth's atmosphere were identified, described, scientifically substantiated and experimentally confirmed, from the rainbow known to everyone to complex, periodic mirages. But, despite this, the bizarre play of light has always attracted and still attracts a person. Neither the contemplation of the winter halo, nor the bright sunset, nor the wide, half-sky strip of the northern lights, nor the modest moonlit path on the water surface leaves anyone indifferent. A light beam, passing through the atmosphere of our planet, not only illuminates it, but also gives it a unique look, making it beautiful.

Of course, much more optical phenomena occur in the atmosphere of our planet than is considered in this term paper. Among them there are both well-known to us and solved by scientists, and those who are still waiting for their discoverers. And we can only hope that, over time, we will witness more and more new 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. "Course of General Physics"

Korolev F.A. "Physics course" M., "Enlightenment" 1988

"Physics 10", authors - G. Ya. Myakishev B. B. Bukhovtsev, publishing house "Prosveshchenie", Moscow, 1987. atmosphere of ideological purges, psychotechnics actually stopped ... - vision) - subjective light phenomena(feelings) having no character...

A natural phenomenon known as airglow was discovered in 1868 by the Swedish scientist Anders Angström.

This celestial glow of natural nature occurs all the time and all over the globe. There are three types of it: day (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 specific way of formation.

Dayglow is formed when sunlight hits the atmosphere during the daytime. Some of it is absorbed by the molecules in the atmosphere, which gives them an excess of energy, which they then release as light, either at the same or at a slightly lower frequency (color). This light is much weaker than ordinary daylight, so we cannot see it with the naked eye.

The twilight glow is essentially the same as the daytime one, 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, it is visible to the naked eye.

The night glow is not generated by sunlight falling on the night atmosphere, but by a different process called chemiluminescence. Sunlight during the day accumulates energy in the atmosphere containing oxygen molecules. This extra energy causes the oxygen molecules to break up into individual atoms. This mainly occurs at an altitude of about 100 km.

Unlike the auroras, nightglows are spread throughout the 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 season.

To increase your chances of spotting celestial glow, you should capture dark and clear night skies in long exposure mode. The glow can be seen in any direction free of light pollution, 10 to 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 oscillations of the surfaces of layers of air and are similar to the waves caused by throwing a stone into calm water.

A long exposure photograph taken in the direction of the vertical airglow layers made this undulating structure visible.

The mechanism of occurrence of this phenomenon is as follows. During the day, solar radiation (sunlight) destroys air molecules into atoms (charged atoms, ions), electrons are knocked out. When the ions meet again (or attract an electron), a molecule is formed, and the excess energy escapes in the form of light. At an altitude of 80-120 km, mainly oxygen and sodium molecules recombine with the emission of 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 infra-tonic (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 nitric oxide (NO) molecule. During this reaction, a photon is emitted. Other substances that can contribute to skyglow are the hydroxyl radical (OH), molecular oxygen, sodium and lithium. The dark red glow is most likely formed 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, which are slightly higher.

The intrinsic glow of the atmosphere is a very weak emission of light by the planet's atmosphere.

The glow of the sky above the horizon, taken from the ISS.

In the case of the Earth's atmosphere, this optical phenomenon means that the night sky is never completely dark, even if we exclude the light of stars and the scattered light of the Sun from the day side.

Skyglow is 1000 times more intense during the daytime, but the study of the phenomenon of daytime airglow is difficult due to the fact that it is lost in the bright light of the Sun.

The sky glow phenomenon was discovered in 1868 by a Swedish scientist. Anders Angstrom. Since then, his observation and laboratory research has been carried out. Various chemical reactions were discovered, during which the formation of electromagnetic radiation is possible, and those processes that can occur in the Earth's atmosphere were identified. Astronomical observations have confirmed the existence of just such radiation.

Anders Jonas Ångström (Ongström; Swedish. Anders Jonas Ångström; August 13, 1814, Lögdö, Medelpad - June 21, 1874, Uppsala) - Swedish astrophysicist, one of the founders of spectral analysis.

The glow of the sky is caused by various processes in the upper atmosphere, in particular, the recombination of ions formed in the process of photoionization under the influence of solar radiation in the daytime; luminescence caused by the passage of cosmic rays through the upper atmosphere, as well as chemiluminescence associated mainly with reactions between oxygen, nitrogen and hydroxyl radical at an altitude of several hundred kilometers.

At night, the airglow can be bright enough to be noticed by an observer and is usually bluish in color. Although the airglow is almost uniform, to a terrestrial observer it appears brightest at a distance of 10 degrees from the horizon.

One of the mechanisms of atmospheric glow 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 are the hydroxyl radical (OH), molecular oxygen, sodium and lithium.

Night glow is not constant in brightness. Probably, its intensity depends on geomagnetic activity.

Comet Lovejoy passing behind Earth's skyglow on December 22, 2011.

Alex Rivest. The land you've never seen before

An interval video that introduces us to an amazing phenomenon - the own glow of the earth's atmosphere.

We have already begun to get used to the wonderful pictures of the Earth obtained by cosmonauts and astronauts from the ISS. But in vain! Some of them look very unusual. First of all, this concerns images of the night side of the Earth. The photographs taken with a long exposure clearly show the bright lights of cities, thunderstorms, and auroras. But besides them, we observe a completely amazing phenomenon - own glow of the earth's atmosphere.

It turns out that our planet is never completely dark at night. Even if we exclude urban illumination, the Moon and stars, there will still be an extremely weak (but quite detectable) airglow. It is caused by a number of factors, among which the Sun plays an important role (at night, air ions are recombined, born during the day under the influence of starlight), cosmic rays and chemical reactions involving oxygen, nitrogen and hydroxyl radicals.

American photographer Alex Rivest invites us to look at this phenomenon from the point of view of art. He collected a large number of photographs of the Earth at night and created a wonderful time-lapse video from them, which we bring to your attention.

The structure of the airglow itself is quite complex (see, for example, at 00:37 after the start of the video). We see that the phenomenon is formed by three layers of luminescence: the red layer (the most extended and rarefied), the yellow layer and the green layer (thin layer between red and yellow). Different colors are due to the glow of different atoms. So, meteors are responsible for the yellow color, which, burning up in the upper atmosphere, spray sodium atoms - they glow yellow. The green glow is produced by nitrogen and oxygen atoms. Finally, the red glow is generated by hydroxyl ions -OH.

Red, green and yellow glow of the Earth's night atmosphere. Photo: NASA

When watching a video, we notice more than once another type of earth's atmosphere glow: auroras (for example, after 00:24 after the start). Auroras are caused by the solar wind, high-energy particles flying from the Sun and colliding with the Earth's atmosphere at altitudes of about 100 km.

Big Universe

The aurora borealis is one of the many wonders of nature. It can also be observed in Russia. In the north of our country there is a strip where the auroras manifest themselves most often and brightly. A magnificent spectacle can cover most of the sky.

The beginning of the phenomenon

The aurora begins with the appearance of a bright band. Rays come out of it. The brightness may increase. The area of ​​the sky covered by the miraculous phenomenon is increasing. The height of the rays of light, falling closer to the surface of the Earth, also increases.

Bright flashes and play of color delight observers. The movements of the waves of light are mesmerizing. This phenomenon is associated with the activity of the Sun - a source of light and heat.

What it is

The auroras are called the rapidly changing glow of the upper rarefied layers of air in certain parts of the night sky. This phenomenon, along with the sunrise, is sometimes referred to as the aurora. During the day, the light show is not visible, but the devices record the flow of charged particles at any time of the day.

Causes of the aurora

A magnificent natural phenomenon occurs due to the Sun and the presence of the planet's atmosphere. For the formation of the aurora, the presence of a geomagnetic field is also necessary.

The sun is constantly ejecting charged particles. A solar flare is a factor due to which electrons and protons enter outer space. They fly at high speed towards the rotating planets. This phenomenon is called the solar wind. It could be dangerous for all life on our planet. The magnetic field protects against the penetration of the solar wind. It sends charged particles to the poles of the planet, according to the location of the geomagnetic field lines. However, in the case of more powerful flares on the Sun, the population of the Earth observes auroras in temperate latitudes. This happens if the magnetic field does not have time to send a large stream of charged particles to the poles.

The solar wind interacts with the molecules and atoms of the planet's atmosphere. This is what causes the glow. The greater the number of charged particles that reached the Earth, the brighter the glow of the upper layers of the atmosphere: the thermosphere and exosphere. Sometimes even the mesosphere - the middle layer of the atmosphere - reaches the particles of the solar wind.

Aurora types

The types of auroras are different and can smoothly transition from one to another. Light spots, rays and stripes, as well as coronas are observed. The northern lights can be almost stationary or streaming, which is especially mesmerizing for observers.

Earth's auroras

Our planet has a fairly powerful geomagnetic field. It is strong enough to constantly send charged particles towards the poles. That is why we can observe a bright glow on the territory of the band, where the isochasm of the most frequent auroras passes. Their brightness directly depends on the work of the geomagnetic field.

The atmosphere of our planet is rich in various chemical elements. This explains the different colors of the sky glow. So, an oxygen molecule at an altitude of 80 kilometers, when interacting with a charged particle of the solar wind, gives a pale green color. At an altitude of 300 kilometers above the Earth, the color will be red. The nitrogen molecule exhibits a blue or bright red color. In the photo of the aurora, bands of different colors are clearly distinguishable.

The northern lights are brighter than the southern ones. Because protons are moving towards the north magnetic pole. They are heavier than the electrons rushing towards the south magnetic pole. Radiance, formed as a result of the interaction of protons with atmospheric molecules, is somewhat brighter.

The device of the planet Earth

Where does the geomagnetic field come from, protecting all living things from the destructive solar wind and moving charged particles towards the poles? Scientists believe that the center of our planet is filled with iron, which is molten from heat. That is, iron is liquid and is constantly in motion. From this movement, electricity and the planet's magnetic field arise. However, in some parts of the atmosphere, the magnetic field weakens for some unknown reason. This happens, for example, over the South Atlantic Ocean. Here, only a third of the magnetic field from the norm. This worries scientists because the field continues to weaken at the present time. Experts have calculated that over the past 150 years, the Earth's geomagnetic field has weakened by another ten percent.

The area of ​​occurrence of a natural phenomenon

Aurora zones do not have clear boundaries. However, the brightest and most frequent are those that appear as a ring near the Arctic Circle. In the Northern Hemisphere, you can draw a line on which the auroras are the strongest: the northern part of Norway - the islands of Novaya Zemlya - the Taimyr Peninsula - the north of Alaska - Canada - the south of Greenland. At this latitude - about 67 degrees - the auroras are observed almost every night.

The peak of phenomena often occurs at 23:00. The brightest and longest auroras are on the days of the equinoxes and dates close to them.

More often, auroras occur in areas of magnetic anomalies. Here their brightness is higher. The greatest activity of the phenomenon is observed on the territory of the East Siberian magnetic anomaly.

The height of the glow

As a rule, about 90 percent of all auroras occur at an altitude of 90 to 130 kilometers. Auroras were recorded at an altitude of 60 kilometers. The maximum recorded figure is 1130 kilometers from the Earth's surface. At different heights, different forms of luminescence are observed.

Features of a natural phenomenon

A number of unknown dependences of the beauty of the northern lights on some factors were discovered by observers and confirmed by scientists:

1. Auroras appearing over sea space are more mobile than those appearing over land.
2. There is less glow over small islands, as well as over desalinated water, even in the middle of the sea surface.
3. Above the coastline, the phenomenon is observed much lower. Towards the land, as well as towards the ocean, the height of the aurora increases.

The speed of flight of charged particles of the Sun

The distance from the Earth to the Sun is about 150 million kilometers. Light reaches our planet in 8 minutes. The solar wind moves more slowly. From the moment scientists notice, more than a day must pass before the aurora begins. On September 6, 2017, experts noticed a powerful solar flare and warned Muscovites that on September 8, the northern lights might be visible in the capital. Thus, the forecast of an impressive natural phenomenon is possible, but only in a day or two. In which region the radiance will appear brighter, no one can predict with accuracy.

What is isochasm

Experts put points on the map of the earth's surface with notes on the frequency of occurrence of auroras. Connected by lines points with a similar frequency. So we got isochasms - lines of equal frequency of occurrence of auroras. Let us describe once again the isochasm of the highest frequency, but relying on some other objects of the area: Alaska - the Great Bear Lake - Hudson Bay - the south of Greenland - Iceland - the north of Norway - the north of Siberia.

Earth's magnetic pole

The Earth's magnetic pole does not coincide with the geographic pole. It is located in the northwestern part of Greenland. Here, the northern lights occur much less frequently than in the band of the highest frequency of the phenomenon: only about 5-10 times a year. Thus, if the observer is located to the north of the main isochasm, then he sees auroras more often in the southern side of the sky. If a person is located south of this band, then the aurora is more often manifested in the north. This is typical for the Northern Hemisphere. For the South, it's exactly the opposite.

On the territory of the North Geographic Pole, auroras occur about 30 times a year. Conclusion: you do not need to go to the most severe conditions to enjoy a natural phenomenon. In the main isochasm band, the glow is repeated almost every day.

Why do the northern lights sometimes have no color?

Travelers sometimes get frustrated if they don't get to see a color light show during their stay in the north or south. People can often observe only a glow that has no color. This is not due to the peculiarity of a natural phenomenon. The fact is that the human eye is not able to capture colors in low light. In a gloomy room, we see everything in black and white. The same thing happens when observing a natural phenomenon in the sky: if it is not bright enough, then our eyes will not pick up colors.

Experts measure the brightness of the glow in points from one to four. Only three- and four-magnitude auroras appear colored. The fourth degree is close in brightness to moonlight in the night sky.

Cycles of solar activity

The emergence of the aurora is always associated with solar flares. Once every 11 years, the activity of the luminary increases. This always leads to an increase in the intensity of aurora.

Northern lights over the planets of the solar system

Auroras appear not only on our planet. Earth's auroras are bright and beautiful, but Jupiter's phenomena are brighter than Earth's. Because the magnetic field of the giant planet is several times stronger. It sends the solar wind in opposite directions even more productively. All light accumulates in certain areas near the planet's magnetic poles.

Jupiter's moons affect the aurora. Especially Io. Behind it is a bright light, because the natural phenomenon follows the direction of the magnetic field lines. In the photo - the aurora in the atmosphere of the planet Jupiter. The bright band left by Io's satellite is clearly visible.

Auroras have also been discovered on Saturn, Uranus, Neptune. Only Venus has almost no magnetic field of its own. Flashes of light arising from the interaction of the solar wind with the atoms and molecules of the atmosphere of Venus are special. They cover the entire atmosphere of the planet entirely. Moreover, the solar wind reaches up to However, such auroras are never bright. Charged particles of the solar wind do not accumulate anywhere in large quantities. From space, Venus, when attacked by charged particles, looks like a faintly luminous ball.

Disturbance of the geomagnetic field

The solar wind is trying to break through our planet's magnetosphere. in this case does not remain calm. There are disturbances on it. Each person has their own electric and magnetic fields. It is these fields that are affected by the resulting perturbations. This is felt by people all over the planet, especially those with poor health. People with good health do not notice such an impact. During the attack of charged particles, sensitive people may have a headache. But it is the solar wind that is a necessary factor for the occurrence of auroras.

The attitude of peoples to a natural phenomenon

Usually the locals associated the aurora with something not very good. Perhaps because they have a bad effect on the well-being of people. The radiance itself does not pose any danger.

Residents of more southern regions, not used to such phenomena, felt something mysterious when bright flashes appeared in the sky.

Currently, residents of temperate and more southern latitudes are eager to see this miracle of nature. Tourists travel to the North or to the Antarctic Circle. They do not wait for the phenomenon to be observed at their native latitude.

The aurora borealis is an enchanting natural phenomenon. It is unusual for residents of warm regions and familiar to the population of the tundra. It often happens that in order to learn something new, you need to go on a trip.