Every second, approximately 700 lightning, and every year about 3000 people are killed by lightning strikes. The physical nature of lightning has not been fully explained, and most people have only a rough idea of what it is. Some discharges collide in the clouds, or something like that. Today we turned to our physics authors to learn more about the nature of lightning. How lightning appears, where lightning strikes, and why thunder rumbles. After reading the article, you will know the answer to these and many other questions.
What is lightning
Lightning- spark electric discharge in the atmosphere.
electrical discharge- this is the process of current flow in the medium, associated with a significant increase in its electrical conductivity relative to the normal state. There are different types of electrical discharges in gas: spark, arc, smoldering.
Spark discharge occurs at atmospheric pressure and is accompanied by a characteristic spark crack. A spark discharge is a collection of disappearing and replacing each other filamentous spark channels. Spark channels are also called streamers. The spark channels are filled with ionized gas, i.e. plasma. Lightning is a giant spark, and thunder is a very loud crack. But not everything is so simple.
The physical nature of lightning
How is the origin of lightning explained? System cloud-earth or cloud-cloud is a kind of capacitor. Air plays the role of a dielectric between clouds. The lower part of the cloud has a negative charge. With a sufficient potential difference between the cloud and the ground, conditions arise in which lightning occurs in nature.
Stepped leader
Before the main lightning flash, you can observe a small spot moving from the cloud to the ground. This is the so-called step leader. Electrons under the action of a potential difference begin to move towards the ground. As they move, they collide with air molecules, ionizing them. An ionized channel is being laid from the cloud to the ground. Due to the ionization of air by free electrons, the electrical conductivity in the zone of the leader trajectory increases significantly. The leader, as it were, paves the way for the main discharge, moving from one electrode (cloud) to another (ground). Ionization occurs unevenly, so the leader can branch out.
Backfire
The moment the leader approaches the ground, the tension at his end rises. From the ground or from objects protruding above the surface (trees, roofs of buildings), a response streamer (channel) is thrown towards the leader. This property of lightning is used to protect against them by installing a lightning rod. Why does lightning strike a person or a tree? In fact, she doesn't care where to hit. After all, lightning is looking for the shortest path between earth and sky. That is why during a thunderstorm it is dangerous to be on the plain or on the surface of the water.
When the leader reaches the ground, a current begins to flow through the laid channel. It is at this moment that the main lightning flash is observed, accompanied by a sharp increase in current strength and energy release. Here is the question, where does lightning come from? It is interesting that the leader spreads from the cloud to the ground, but the reverse bright flash, which we are used to seeing, spreads from the ground to the cloud. It is more correct to say that lightning does not go from heaven to earth, but occurs between them.
Why does lightning strike?
Thunder is the result of a shock wave generated by the rapid expansion of ionized channels. Why do we see lightning first and then hear thunder? It's all about the difference in the speeds of sound (340.29 m/s) and light (299,792,458 m/s). By counting the seconds between thunder and lightning and multiplying them by the speed of sound, you can find out at what distance the lightning struck from you.
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Types of lightning and facts about lightning
Lightning between heaven and earth is not the most common lightning. Most often, lightning occurs between clouds and does not pose a threat. In addition to terrestrial and intracloud lightning, there are lightnings that form in the upper atmosphere. What are the types of lightning in nature?
- Intra-cloud lightning;
- Ball lightning;
- "Elves";
- Jets;
- Sprites.
The last three types of lightning cannot be observed without special instruments, as they form at an altitude of 40 kilometers and above.
Here are the facts about lightning:
- The length of the longest recorded lightning on Earth was 321 km. This lightning was seen in Oklahoma, 2007.
- The longest lightning lasted 7,74 seconds and was recorded in the Alps.
- Lightning is formed not only on Earth. Know exactly about lightning on Venus, Jupiter, Saturn and Uranus. Saturn's lightning is millions of times more powerful than Earth's.
- The current in lightning can reach hundreds of thousands of amperes, and the voltage can reach billions of volts.
- The temperature of the lightning channel can reach 30000 degrees Celsius is 6 times the surface temperature of the sun.
Fireball
Ball lightning is a separate type of lightning, the nature of which remains a mystery. Such lightning is a luminous object moving in the air in the form of a ball. According to the limited evidence, ball lightning can move along an unpredictable trajectory, split into smaller lightning bolts, explode, or simply disappear unexpectedly. There are many hypotheses about the origin of ball lightning, but none can be recognized as reliable. The fact is that no one knows how ball lightning appears. Some hypotheses reduce the observation of this phenomenon to hallucinations. Ball lightning has never been observed in the laboratory. All scientists can be content with is eyewitness accounts.
Finally, we invite you to watch the video and remind you: if the course paper or control fell on your head like lightning on a sunny day, do not despair. Student Services Specialists have been helping students since 2000. Seek qualified help at any time. 24 hours a day, 7 days a week we are ready to help you.
In 1992, the Russian physicist Alexander Gurevich from the Physical Institute. PN Lebedev RAS suggested that lightning is caused by cosmic rays that enter the Earth's atmosphere.
No, of course, we have all heard about Benjamin Franklin's hypothesis, according to which lightning is a discharge that occurs between clouds and the Earth's surface simply because of the difference in their charges. This concept, however, has a rather weak point. For a discharge to occur, it is necessary that there is too much difference in charges between the clouds and the surface (or neighboring clouds). As it turned out from the information received by weather balloons in the 1990s, in practice there is no more than one tenth of such a difference. However, lightning seems to still happen. So for what?
Alexander Gurevich and Co. believe that high-energy particles in the atmosphere trigger a process called runaway electron breakdown (RTE). And the "trigger" of the PUE is cosmic rays. These streams of charged particles, mainly protons, generated by distant supernova explosions (and other processes), entering the atmosphere and colliding with the nuclei of air atoms, cause an avalanche-like process of the formation of free electrons with significant energy (extensive air showers).
Electric fields in thunderclouds accelerate electrons to near-light speeds. Further collisions of electrons with air atoms give rise to additional free electrons, as well as X-ray and gamma radiation (“dark lightning”, about which “KL” does not tire of writing), turning into threads of electrical discharges - streamers, well-conducting channels, upon merging of which arises thermal ionized channel with high conductivity (aka stepped lightning leader).
In theory, everything looks very harmonious: RB appears in the atmosphere in a constant electric field, an order of magnitude smaller than the normal breakdown field, that is, in the presence of cosmic rays, the observed atmospheric electric fields are finally enough to explain the phenomenon of both dark lightning and its visible counterpart .
But until very recently, all this remained only a theory: there was no concrete evidence that it was cosmic rays that were responsible for the onset of breakdown by runaway electrons.
Alas, it turned out to be rather difficult to reproduce such processes in the laboratory, and the point is not only that this requires a voltage of 10 million volts. It has long been known that cosmic rays entering the earth's atmosphere generate radio pulses, and during thunderstorms there are more radio pulses with similar parameters than when there are no thunderstorms.
To check the hypothesis with observations, Alexander Gurevich and Anatoly Karashtin from the Research Institute of Radiophysics (Nizhny Novgorod) analyzed data from radio interferometers taken during 3,800 lightning strikes over Russia and Kazakhstan. Since radio interferometers allow the radio waves they register to be tied to specific directions, scientists have been able to unequivocally correlate hundreds and even thousands of short and strong radio pulses with moments immediately preceding lightning strikes. Moreover, it turned out that the specific parameters of radio pulses coincide with the theoretically predicted features of their generation by cosmic rays.
So what, it turns out, the observations explained everything? In fact, although it has been confirmed that cosmic rays play the role of a "seed" for dark and accompanying ordinary lightning, an important ambiguity remains. Over Russia and Kazakhstan, there is simply not enough cosmic rays with the necessary energies to generate the observed "collapse" of lightning.
To explain this "inconsistency", physicists analyzed the nature of the possible interaction of waves recorded by radio interferometers with water drops and hailstones (hydrometeors). It turned out that when low-energy electrons accompanying high-energy free electrons pass by drops and hailstones in the atmosphere, a series of micro-discharges is launched, radically amplifying both the electric field in the area where the future lightning occurs, and the radio pulse, later recorded by devices.
Top: frequency of cosmic rays hitting the Earth's atmosphere. Bottom: frequency of lightning strikes per unit area. It is clearly seen that cosmic rays alone are not enough to generate lightning: they need interaction with water drops.
Even 250 years ago, the famous American scientist and public figure Benjamin Franklin established that lightning is an electrical discharge. But so far, it has not been possible to fully reveal all the secrets that lightning holds: it is difficult and dangerous to study this natural phenomenon.
(20 photos of lightning + video Lightning in slow motion)
Inside the clouds
You can't confuse a thundercloud with an ordinary cloud. Its gloomy, leaden color is explained by its great thickness: the lower edge of such a cloud hangs at a distance of no more than a kilometer above the ground, while the upper one can reach a height of 6-7 kilometers. 
What is going on inside this cloud? The water vapor that makes up clouds freezes and exists as ice crystals. Ascending currents of air coming from the heated ground carry small pieces of ice up, forcing them to constantly collide with large ones settling down. 
By the way, in winter the earth heats up less, and at this time of the year, there are practically no powerful updrafts. Therefore, winter thunderstorms are extremely rare. 
In the process of collisions, the ice floes become electrified, just as it happens when various objects are rubbed against one another, for example, combs against hair. Moreover, small pieces of ice acquire a positive charge, and large ones - a negative one. For this reason, the upper part of the lightning-forming cloud acquires a positive charge, and the lower part acquires a negative one. There is a potential difference of hundreds of thousands of volts at every meter of distance - both between the cloud and the ground, and between parts of the cloud. 
Development of lightning
The development of lightning begins with the fact that in some place of the cloud a focus appears with an increased concentration of ions - water molecules and gases that make up air, from which electrons have been taken away or to which electrons have been added. 
According to some hypotheses, such an ionization center is obtained due to the acceleration of free electrons in the electric field, which are always present in the air in small quantities, and their collision with neutral molecules, which are immediately ionized. 
According to another hypothesis, the initial push is caused by cosmic rays, which penetrate our atmosphere all the time, ionizing air molecules. 
Ionized gas serves as a good conductor of electricity, so current begins to flow through ionized areas. Further - more: the passing current heats up the area of ionization, causing more and more high-energy particles that ionize nearby areas - the lightning channel spreads very quickly. 
Follow the leader
In practice, the development of lightning occurs in several stages. First, the leading edge of the conducting channel, called the "leader", moves in jumps of several tens of meters, each time changing direction slightly (this makes the lightning turn tortuous). Moreover, the speed of advancement of the "leader" can, at some moments, reach 50 thousand kilometers in one single second. 
In the end, the "leader" reaches the ground or another part of the cloud, but this is not yet the main stage of the further development of lightning. After the ionized channel, the thickness of which can reach several centimeters, is “pierced”, charged particles rush along it at a tremendous speed - up to 100 thousand kilometers in just one second, this is lightning itself. 
The current in the channel is hundreds and thousands of amperes, and the temperature inside the channel, at the same time, reaches 25 thousand degrees - that's why lightning gives such a bright flash, visible from tens of kilometers away. And instantaneous temperature drops, thousands of degrees, create the strongest drops in air pressure, propagating in the form of a sound wave - thunder. This stage lasts a very short time - thousandths of a second, but the energy that is released during this is huge. 
final stage
At the final stage, the speed and intensity of movement of charges in the channel decreases, but still remain sufficiently large. It is this moment that is most dangerous: the final stage can last only tenths (and even less) of a second. Such a rather long-term impact on objects on the ground (for example, on dry trees) often leads to fires and destruction. 
Moreover, as a rule, the matter is not limited to one category - new “leaders” can move along the beaten path, causing repeated discharges in the same place, reaching up to several dozen in number. 
Despite the fact that lightning has been known to mankind since the appearance of man himself on Earth, it has not yet been fully studied to date. 
Learn: What is thunder? What is lightning?
Can there be thunder without lightning and vice versa, lightning without thunder?
Can there be a thunderstorm at other times of the year, such as in winter?
How do thunder and lightning affect the human psyche?
How do folk signs about a thunderstorm correspond to reality?
Purpose of the article:
Find out the origin of thunder and lightning and find out what is scarier and more dangerous - thunder or lightning?
Check the conformity of folk signs about a thunderstorm
Find scientific information about the origin of lightning and thunder;
Find folk signs about these natural phenomena;
Observe: why there is a thunderstorm, how it passes; its impact on the condition of man and animals; state of nature after a thunderstorm;
Draw your own conclusions.
Hypotheses:
1. If the weather is hot for several days, then there will certainly be a thunderstorm.
2. The approach of a thunderstorm is felt by animals and birds.
3. Lightning is a very large electric charge, so it is dangerous for human life.
Research product:
Compile a collection of folk signs and riddles about a thunderstorm.
Research methods:
Literature analysis, observations
We do not attach much importance to many natural phenomena, taking them for granted. But the thunderstorm, apparently, does not leave indifferent any person on earth.
Many people are afraid of a thunderstorm, especially when it passes directly overhead, when the whole sky is in lightning and thunder rumbles.
I am always very scared when there is a thunderstorm.
One day, returning from the south by car, we were caught in a severe thunderstorm. It was a hot July day. It was very stuffy. Suddenly clouds began to gather, thunder was heard. Rain poured down. It was very scary. We continued driving through the pouring rain. I was very afraid of thunder. As thunder strikes, it seems the earth has split. Why is he thundering? What causes thunder? I became interested in learning about it.
About a thunderstorm in ancient mythology
The most important god of the ancient Greeks - Zeus - was also the god of lightning and thunder. He was called the thunderer, the cloudmaker. Zeus furrows his brows - and the clouds are gathering. In anger, he strikes with lightning, frightens with thunder.
The Roman god of thunder was Jupiter. Like the ancient Greeks Zeus, so the Romans considered Jupiter the main god. Among the Hindus, the god of thunder was the god Indra, among the Scandinavians - the god Thor, among the Slavs - the god Perun.
Perun is the god of thunderclouds, thunder and lightning. A very expressive portrait of the Thunderer was given by the poet Konstantin Balmont:
Perun's thoughts are fast,
Whatever he wants, so now.
Throws sparks, throws sparks
From the pupils of sparkling eyes.
Perun was armed with a club, a bow with arrows (lightning bolts are arrows that God threw), and an ax. The ax was considered one of the main symbols of God.
Perun often turns out to be closely connected, in addition to fire, with the cult of water, wood and stone. He is considered the ancestor of heavenly fire, which, descending to earth, gives life. With the onset of spring warmth, it fertilizes the earth with rains and brings the clear sun out from behind the clouds. Through his efforts, the world is every time as if born anew.
The Slavs represented Perun in the form of a rider galloping through the heavens on a horse or riding a chariot. The roar from the chariot people mistook for thunder. And also Perun was imagined as a middle-aged angry man with a red swirling beard. It is noted that a red beard is an indispensable feature of the Thunder God among various peoples. In particular, the Thunderer Thor in the Scandinavian pantheon was considered red-bearded. Perun knows for sure that his hair was like a thundercloud - black and silver. Perun's chariot was harnessed by winged stallions, whites and ravens.
The very name of Perun is very ancient. Translated into modern language, it means "The one who hits harder", "smashing". Perun was considered the founder of the moral law and the very first defender of Truth.
People believed that Perun, walking around the world, willingly takes the form of a forest bull Tura, so the bull was considered a sacred animal of Perun.
The sanctuaries of Perun were arranged in the open air. They were flower-shaped; in those sanctuaries that have been excavated by archaeologists, there are usually eight "petals", but in ancient times, according to scientists, there were six. "Petals" were pits in which unquenchable sacred fires burned. In the middle was a sculptural image of Perun. An altar was placed in front of the image of God, usually in the form of a stone ring. Offerings were piled there and sacrificial blood was shed: most often animal blood.
Scientific explanation of the origin of thunder and lightning
Thunder comes from lightning. It is because of them that all the noise and crackling. And lightning is obtained due to the collision of clouds. Moist air rises and rain clouds form. Since it is cold at the top, the droplets turn into ice crystals. The crystals in the clouds rub against each other, electricity is generated, and a flash is obtained - this is lightning. The sky is illuminated by lightning, the air in its path is heated and expands rapidly. There is a blast wave, and we hear thunder. There is even a poem about it:
The cloud spoke to the cloud:
Get out of the way, flying steam!
Can't you see I'm in a hurry.
I'll fly and crush!
Cloud cloud answered:
You better roll it yourself.
You won't get out of the way - I
I'll tear you to shreds.
Laughter erupted in response.
Give way? Not!
Gryan saber thunder -
And say goodbye to your head!
Don't worry, just in case
I have an explosive charge.
I will fight with you
Electric arrow.
Both clouds turned black
Foreheads are like stone steeps.
And, like two bulls in a field,
Clouds collided in the sky.
All around darkened,
The world closed its eyes in fear.
Both clouds now and then
Shooting fire arrows
Slashed to death with sabers.
Thunder rolled across the sky
Shaking all around
It sparkles here, it sparkles there -
Fuck! - and the sky in half!
And the forests and fields tremble:
Will the earth break apart?
Can there be thunder without lightning? During a thunderstorm, thunder and lightning occur at the same time, but we first see the lightning, and then we hear the thunder. Thunder is just the sound of lightning that causes lightning.
What is right: lightning rods or lightning rods?
Which is scarier: thunder or lightning?
Real thunder does no harm. It is necessary to be afraid of the lightning that gave birth to it. Lightning is a huge electrical spark. In a matter of fractions of a second, it flies several kilometers. The air in its path is instantly heated. There is an explosion. The sound from it is thunder. With lightning jokes are bad.
If he strikes a haystack, he will set it on fire, start a fire. Therefore, residential buildings, factory pipes are protected by lightning rods. This is such a metal rod. One of its ends rises above the buildings, the other is buried in the ground. Lightning immediately finds a short path and, without harming anyone or anything, goes into the ground. Out of habit, people say - lightning rods. But it's not right. That's right - lightning rods.
My observations and conclusions
In the summer, I made observations on what signs one can expect the onset of a thunderstorm, tried to correlate them with folk signs.
I analyzed the results and concluded:
1. A thunderstorm is most often expected after a prolonged heat wave.
2. Before a thunderstorm: It is hot and stuffy in the morning. “Soars! There will be a thunderstorm,” people say.
By evening, a huge black cloud is approaching the sky. It expands, grows before our eyes, and now ominously hangs overhead. Gusts of strong wind raise columns of dust from the ground, broken branches, and pluck leaves. Twilight is falling. Lightning flashes brightly, blinding with instant light. Thunder rumbles deafeningly. And from above, streams of water fall.
3. During a thunderstorm. The pouring rain is coming. Nothing is visible around. Puddles form on the ground, all pits and depressions are filled with water. They overflowed with water and streams flowed. Gradually brightens. The rain subsides. The gentle sun appears.
4. After a thunderstorm.
Freshness in the air. Feeling of relief. Joy in the soul. Twitter of birds. I want to say to the storm: “Thank you! How fresh it is! It's not scary at all!" She, as if, having heard grateful words, sends us a wonderful rainbow.
I checked some folk signs. Really:
1. Mosquitoes bite harder before it rains.
2. Swallows fly low - to the rain.
3. Frogs jump on land - before the rain.
4. The birds fell silent - before a thunderstorm, they are waiting for thunder.
Thunder and lightning can be compared to the work of an electric welder. When welding, a spark also flares up - lightning. And the crackle from it is like thunder. Tarpaulin gloves protect the welder from such a lightning strike, and black glasses protect him from blinding light. I also saw how welders work in the summer.
Once my mother's iron burned out - it sparkled and crackled.
In an uncorrected socket, when the electrical appliance was turned on, it also sparkled and crackled. Papa said that this is also lightning and thunder, only small, but just as dangerous as real ones.
Rules for safe behavior during a thunderstorm
How to behave during a thunderstorm?
I read the story of Leo Tolstoy "How a thunderstorm caught me in the forest" In this story, the author tells an incident from his childhood. How he went to the forest for mushrooms and got caught in a thunderstorm. He hid under a large oak, and lightning hit him and smashed the oak to pieces. The boy fell and lay there until the storm ended. And then he took the mushrooms and ran home.
Conclusion: you can not hide under the trees during a thunderstorm!
I made up the rules of safe behavior during a thunderstorm:
1. If a thunderstorm caught you in an open place, lie down on the ground, hide in a hole or hollow, run to a shelter - a car or a building. After all, lightning always strikes high places.
2. If a thunderstorm caught you in the water, go ashore immediately.
If lightning strikes a body of water, you can be seriously injured.
3. During a thunderstorm, you can not hide under free-standing trees. Do not hide under tall trees. They are most often struck by lightning.
4. It is best to wait out the storm in the bush. Lightning won't get there.
I also really liked the poem on safety rules during a thunderstorm:
I love the storm in early May,
When the first spring thunder
As if gently playing
How it smells like a bucket from afar.
But my whole village knows
And all my friends know
What's under the tall trees
You can't hide from lightning.
Let it go far to home
But we, friends, are not afraid,
And I'm running from the pond
And I hide from the storm in the bushes.
I love the storm in early May.
Let the thunder rumble and the rain fall
And bright lightning sparkles
She won't hit me!
Collection of riddles, folk signs about a thunderstorm
1. Approached - rumbled, threw arrows on the field.
It seemed to us - it was a disaster, it turned out it was with water.
Came up and spilled. Plenty of arable land got drunk. (Cloud).
2. First - shine, after shine - crackle, after crackle - splash. (Thunderstorm).
3. Loud knocking,
screaming loudly,
And what does he say
Nobody understand
And the wise do not know. (Thunder).
4. Molten Arrow
The oak fell down near the village. (Lightning).
5. Sparkle, rumble,
Blink, scare everyone. (Thunder and lightning).
7. The horse is running, the earth is trembling. (Thunder).
8. It will knock in the sky, it will be heard on the earth. (Thunder).
9. The earth trembles from heavenly knocks. (Thunder).
10. An eagle flies across the blue sky,
Wings spread out
The sun has dimmed. (Cloud).
11. No legs, but walking,
No eyes, but crying. (Cloud).
12. Sprinkles with fire, splashes with water. (Thundercloud).
13. No one sees me, but everyone hears, and everyone can see my faithful companion, but no one hears. (Thunder and lightning).
14. An eagle bird flies, carries fire in its teeth, in the middle of it is human death. (Lightning).
15. The bear roared over all the mountains, over all the seas. (Thunder).
16. The horse is running, the earth is trembling. (Thunder).
17. Raven croaked
For a hundred cities
For a thousand lakes. (Thunder).
18. Fuck - rattle! - a woman rides on the mountains, knocks with a batog, grumbles to the whole world. (Thundercloud).
19. It burns without fire, flies without wings, runs without legs. (Thundercloud).
20. A bird flies without a wing,
Beats a hunter without a gun,
The cook fries without fire,
The ram eats without a mouth. (Cloud, thunder, sun and earth).
Folk signs:
1. The birds are silent - wait for the thunder.
2. Ducks scream angrily, flap their wings, dive - they call a thunderstorm.
3. Swallows fly low - to rain, to a thunderstorm.
4. Larks fluffed up - to be a thunderstorm.
5. Mosquitoes bite harder than usual usually by a thunderstorm.
6. Ants hide in their houses - to a thunderstorm.
7. If at night the stars twinkle strongly, and in the morning the sky is covered with clouds, then at noon there will be a thunderstorm.
8. The frogs croaked before the rain.
9. Frogs jump on land - to the rain.
10. Thunder is heard in the morning - rain in the evening.
11. Lightning in the west - rain following.
12. Thunder rumbles for a long time and not sharply - to bad weather; if it is abrupt and short, it will be clear.
13. If the thunder rumbles continuously, there will be hail.
14. If thunder rumbles during cold rainy weather in summer, long cool weather should be expected, often with a further drop in temperature.
15. Water darkens in the rivers before a thunderstorm.
16. The rays of the sun darken - to a strong thunderstorm.
17. Thunder in early spring - before the cold.
18. The first thunder in the north wind is a cold spring, in the east it is dry and warm, in the south it is warm, in the west it is wet.
19. Thunder in September - warm autumn.
It is not necessary to be afraid of a thunderstorm, but it is necessary to be careful during a thunderstorm. Discharges of atmospheric electricity can cause great damage to the national economy and be life-threatening if precautions are not taken in a timely manner. Lightning is to be feared, not thunder. Dr. C. W. McEachron, a well-known American expert on thunderstorms, said that if you hear thunder, lightning will not strike you; if you see lightning, it will not hit you, and if it hits you, you will not know about it.
So I found out how thunder and lightning are made and which one is scarier?
Now I am not afraid of thunder, and in order to protect myself from lightning, I will follow the rules. I concluded: there is no need to be afraid of thunder, lightning is dangerous.
My hypotheses were confirmed
Russian physicists have come close to unraveling the mechanism of the occurrence of lightning during a thunderstorm. The assumption about how this could happen was expressed back in 1992 by the domestic scientist Alexander Gurevich. But only recently has it become possible to test his hypothesis experimentally. The very first stage of lightning formation is currently being studied.
Thus, in the laboratory of problems of new accelerators of the Lebedev Physical Institute, an experimental setup was put into operation, which makes it possible to study the processes of the formation of a long spark in air - the closest analogue of the well-known lightning that occurs during a thunderstorm. Experiments on the new facility are carried out in accordance with the provisions of the "Theory of Breakdown on Runaway Electrons", developed by Academician Alexander Gurevich.
Despite the fact that lightning is not a rare phenomenon (probably all the inhabitants of our planet have seen it at least once in their lives), the mechanism of the occurrence of this formidable and beautiful natural phenomenon has not been practically studied so far.
Moreover, the knowledge that scientists have suggests that lightning cannot occur during a thunderstorm, since, according to the available data, the electric fields near thunderclouds are significantly less than what is necessary for the occurrence of electrical discharges. However, they nevertheless occur, and sometimes even several per minute.
Back in 1992, trying to somehow solve this paradox, Russian physicist Alexander Gurevich formulated the so-called "Theory of runaway breakdown". Briefly, its essence is as follows.
Numerous observations and calculations have shown that in air, most electrons have a mean free path (that is, the distance that a particle travels between two collisions with surrounding molecules, atoms, and particles) of about one centimeter.
However, there are so-called fast electrons that move at a speed close to the speed of light. Accordingly, they have a free path 100 times greater, that is, about a meter.
Gurevich suggested that if these fast electrons (they are called runaway electrons), rushing at great speed, collide with air molecules, then as a result, several more of the same fast electrons will be released from the latter. Thus, several "pioneers" stimulate the appearance of a horde of secondary runaway electrons. They, in turn, are also accelerated by the field.
As a result, an exponentially growing avalanche of runaway electrons appears, along with which the number of slow (thermal) electrons also grows. They are also ejected as a result of collisions of fast electrons with molecules. This situation resembles the fall of a line made up of dominoes, the only difference is that in this case some chips fall slowly and do not touch others, and some fall quickly, dropping their neighbors.
It is assumed that all this should lead to a rapid increase in the electrical conductivity of the medium (which, as we know, increases with an increase in the concentration of free charge carriers). The result is a phenomenon that physicists call "electrical breakdown."
By the way, a similar phenomenon is familiar to every motorist - it is the presence of such a breakdown of the air-fuel mixture on a candle in an internal combustion engine that allows you to start the engine (in this situation it is usually called a "spark"). During the breakdown, the charge carrier at the mean free path acquires energy sufficient to ionize the molecules of the crystal lattice or gas.
This ionization occurs when particles snatch electrons from them, without which the molecules turn into positively charged ions. The ejected electrons, in turn, also become free charge carriers, which make the main contribution to the total current.
However, the breakdown itself is not yet lightning. However, as a result of this phenomenon, a multi-kilometer layer of conducting plasma is formed. But it is already capable of creating the same lightning discharge, which we call lightning.
Calculations carried out by Gurevich showed that in the atmosphere, a breakdown can occur at an electric field strength much lower than that required for a normal breakdown (like what happens on the candles of a car).
Thus, at a pressure of one atmosphere, the threshold field for ordinary breakdown is 23 kV/cm, and for runaway breakdown it is 2.16 kV/cm. It turns out that runaway electrons may well create all the conditions necessary for the occurrence of this phenomenon.
But where do the very first runaway electrons come from? The scientist suggested that they appear under the influence of cosmic radiation. In the upper atmosphere, it ionizes air molecules, releasing a small amount of runaway electrons, which, falling into the thunderstorm region, cause a breakdown.
By the way, in this case, powerful flashes of X-ray radiation should occur. And, as shown by the data obtained during experiments conducted on airplanes and balloons, this really takes place (the first such flash during a thunderstorm was recorded back in 1960, but then no one could explain where it came from).
A series of field experiments carried out at the end of the last - beginning of this century at the Tien Shan high-mountain scientific station of the Lebedev Physical Institute, seemed to confirm this theory. However, now it is possible to study this mechanism in the laboratory.
True, scientists immediately declared that no one is going to create artificial lightning yet. . “Our task is not to simulate lightning, since it is a multi-stage process, but its initial, that is, pre-breakdown stage,” says Alexander Oginov, Ph.D. However, this is also very interesting for scientists.
An experimental setup for modeling an analog of a high-altitude atmospheric discharge was created by the staff of the Physics Institute of the Russian Academy of Sciences and the Institute of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences (Tomsk) based on an electronic relativistic generator, which includes a pulsed voltage generator.
It can be used to detect the presence of runaway electrons in the air. Scientists study their behavior, find out the main characteristics and observe their effect on the molecules of the surrounding air.
“Now the stage of accumulation of experimental data is underway, but many new interesting results have already been obtained. The plans are to obtain not a statistical, but a dynamic effect, that is, not to wait for the appearance of a “seed” electron, but to learn how to create it.
And then, by injecting a seed beam of electrons, I hope we will unambiguously detect amplification. And thus, we will confirm the possibility of a breakdown on runaway electrons in accordance with the conclusions of the theory,” Alexander Oginov comments on the results of the experiments.
