Causes of monstrous lightning. Physics of the atmosphere: how, why and where do lightning come from

Can there be thunder without lightning and vice versa, lightning without thunder?

Can there be a thunderstorm at other times of the year, for example, 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 which is more terrible 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 influence on the state of man and animals; the state of nature after a thunderstorm;

Draw your own conclusions.

Hypotheses:

1. If the weather is hot for several days, 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, therefore it is dangerous for human life.

Research product:

Compile a collection of folk signs and mysteries 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 are afraid of thunderstorms, 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.

Once, 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, and thunder was heard. The rain poured down. It was very scary. We continued to drive in the pouring rain. I was very afraid of thunder. As thunder strikes - the earth seems to have split. Why is it thundering? What makes thunder? I was curious to know about this.

About a thunderstorm in ancient mythology

The most important god among the ancient Greeks - Zeus - was also the god of lightning and thunder. He was called the thunderer, the cloud-killer. Zeus frowns - and the clouds are gathering. In anger, he strikes with lightning, frightens with thunder.

The Romans had Jupiter as the god of thunder. 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 quick,

What he wants - so now.

Sparks sparks, throws sparks

From the pupils of the sparkling eyes.

Perun was armed with a club, a bow with arrows (lightning are arrows that God threw), and an ax. The ax was considered one of the main symbols of God.

Perun is often closely associated, in addition to fire, with the cult of water, wood and stone. He is considered the ancestor of the heavenly fire, which, descending to earth, gives life. With the onset of spring warmth, he fertilizes the earth with rains and brings out the clear sun from behind the clouds. Through his efforts, the world is, as it were, reborn every time.

The Slavs represented Perun in the form of a rider galloping across the heavens on a horse or riding a chariot. People mistook the rumble from the chariot for thunder. And also Perun was imagined in the form of a middle-aged angry man with a red curly beard. It is noted that a red beard is an indispensable feature of the God of a thunderstorm among various nations. In particular, the Thunderbolt Thor in the Scandinavian pantheon was considered red-bearded. Perun knows for sure that the hair was like a thundercloud - black and silver. Perun's chariot was harnessed by winged stallions, whites and crows.

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 in the white world, willingly takes the form of the forest bull of Tour, therefore the bull was considered a sacred animal of Perun.

The sanctuaries of Perun were set up in the open air. They were in the shape of a flower; in those sanctuaries that have been excavated by archaeologists, there are usually eight "petals", but in ancient times, according to scientists, there were six of them. The "petals" were pits in which inextinguishable 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 made there and sacrificial blood was shed: most often animal blood.

Scientific explanation of the origin of thunder and lightning

Thunder comes from lightning. This is because of them all the noise and crackling. And lightning comes from the collision of clouds. Moist air rises upward, rain clouds are obtained. Since it is cold at the top, the droplets turn into ice crystals. Crystals in the clouds rub against each other, electricity is formed, and a flash is obtained - this is lightning. The sky is illuminated by lightning, the air on its way heats up and expands rapidly. There is a blast wave and we hear thunder. There is even a poem about this:

The cloud spoke to the cloud:

Get out of the way, volatile steam!

You can't see - I'm in a hurry.

I will heal and crush!

The cloud answered the cloud:

You better roll it yourself.

You won't get out of the way - I

I'll blow you to shreds.

Laughter broke out in response:

Give way? No!

I will strike with a thunderous saber -

And you will say goodbye to your head!

Do not scare, for this case

I have an explosive charge.

I will fight with you

Electric boom.

Both clouds have turned black

Foreheads are like stone slopes.

And, like two bulls in the field,

Clouds collided in the sky.

In a moment everything went dark around,

The world closed its eyes in fear.

Both clouds now and then

Fire arrows are thrown

Cut to death with sabers.

Thunder rolled across the sky

Shaking everything around

It sparkles here, it shines there -

Fuck! - and the sky in half!

And forests, fields tremble:

What if the earth breaks apart ?!

Can there be thunder without lightning? In a thunderstorm, thunder and lightning occur at the same time, but we see lightning first, and then we hear thunder. Thunder is just the sound of a thunderstorm that triggers lightning.

Which is correct: lightning rods or lightning rods?

Which is scarier: thunder or lightning?

There is no harm in real thunder. You need 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 instantly heats up. An explosion occurs. The sound from it is thunder. Lightning is a bad joke.

Hit the haystack - set it on fire, start a fire. Therefore, residential buildings, factory pipes are protected by lightning rods. It is such a metal rod. One end of it rises above the buildings, the other is buried in the ground. Lightning immediately finds a short path and, without causing harm to anyone or anything, goes into the ground. By 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, I tried to correlate them with folk signs.

I analyzed the results and made conclusions:

1. A thunderstorm is most often expected after a prolonged heat wave.

2. Before a thunderstorm: It's hot and stuffy in the morning. “Soars! There will be a thunderstorm, ”people say.

In the evening, a huge black cloud is approaching the firmament. It expands, grows before our eyes and now hangs ominously overhead. Gusts of strong wind raise columns of dust from the ground, broken off branches, and tear off leaves. Twilight is deepening. Lightning flashes brightly, blinding with instant light. Thunder rumbles deafeningly. And now streams of water fall from above.

3. During a thunderstorm. It is pouring rain. Nothing can be seen around. Puddles form on the ground, all pits and depressions are filled with water. They overflow with water and streams flowed. Gradually brightens. The rain subsides. A gentle sun appears.

4. After a thunderstorm.

Freshness in the air. A sense of relief. Joy in the soul. Chirping birds. I would like to say to the storm: “Thank you! How fresh it became! 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 rain.

2. Swallows fly low - to rain.

3. Frogs jump on land - before the rain.

4. The birds fell silent - before the storm, waiting for the thunder.

Thunder and lightning can be compared to the work of an electric welder. When welding, a spark also flashes - lightning. And the crackling from it is like thunder. The welder is protected from the impact of such a lightning by canvas gloves, from the dazzling light - by black glasses. I also saw how welders work in the summer.

Once my mother's iron burned out - it sparkled and crackled.

In the uncorrected outlet, when the appliance was turned on, it also flashed and a crackling sound was heard. Dad said that this is also lightning and thunder, only small, but just as dangerous as real ones.

Safe conduct during a thunderstorm

How to behave during a thunderstorm?

I read the story of Lev Nikolaevich 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 tree, and lightning hit him and smashed the oak into chips. The boy fell and lay there until the storm ended. And then he took the mushrooms and ran home.

Conclusion: you can't hide under trees during a thunderstorm!

I have compiled the rules for 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 for cover - 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 severely injured.

3. During a thunderstorm, do not hide under freestanding trees. Don't hide under tall trees. They are most often struck by lightning.

4. It is best to wait out the thunderstorm 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 playing tenderly

Like a bucket banging from a distance.

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, do not know fear,

And I'm running out of the pond

And hiding from the thunderstorm in the bushes.

I love the storm in early May.

Let the thunder rumble and the rain fall

And the lightning flashes brightly

It won't hit me!

Collection of riddles, folk signs about a thunderstorm

1. She approached - rumbled, arrows on the field of metal.

It seemed to us that she was in trouble, it turned out she was walking with water.

Came up and spilled. The arable land is drunk to its fullest. (Cloud).

2. First - shine, after shine - crackle, after crackle - splash. (Storm).

3. Knocks loudly,

Shouts loudly

And what does he say

Nobody understands

And the sages do not know. (Thunder).

4. Blazing-hot arrow

I dumped an oak near the village. (Lightning).

5. Will sparkle, rumble,

Blink, scare everyone. (Thunder and lightning).

7. The horse runs, the earth trembles. (Thunder).

8. It knocks in the sky, it is heard on the ground. (Thunder).

9. The earth trembles from heavenly knocking. (Thunder).

10. An eagle flies across the blue sky,

Spread my wings

The sun is overcast. (Cloud).

11. No legs, but walking,

No eyes, but crying. (Cloud).

12. Pours fire, splashes water. (Thundercloud).

13. No one sees me, but everyone hears, but everyone can see my faithful companion, but no one hears. (Thunder and lightning).

14. A bird is flying an eagle, carrying fire in its teeth, in the middle of it - human death. (Lightning).

15. The bear roared at all the mountains, at 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 - bang! - a woman rides on the mountains, knocks with a lamb, 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,

A hunter beats 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 hysterically, flap their wings, dive - they call a thunderstorm.

3. Swallows fly low - to rain, to thunderstorms.

4. The larks are ruffled - to be a thunderstorm.

5. Mosquitoes bite harder than usual, usually during a thunderstorm.

6. Ants hide in their houses - to a thunderstorm.

7. If the stars twinkle strongly at night, 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 on land jump - to the rain.

10. Thunder is heard in the morning - rain in the evening.

11. Lightning in the west - followed by rain.

12. Thunder thunders for a long time and not abruptly - to bad weather; if it is abrupt and short, it will be clear.

13. If thunder thunders continuously, there will be hail.

14. If thunder rumbles in cold, rainy summer weather, you should expect prolonged cool weather, often with a further drop in temperature.

15. Water darkens in rivers before a thunderstorm.

16. The sun's rays darken - to a strong thunderstorm.

17. Thunder in early spring - before the cold.

18. The first thunder with the north wind is a cold spring, with the east wind - dry and warm, with the south - warm, with the west - wet.

19. Thunder in September - warm autumn.

There is no need to be afraid of a thunderstorm, but care must be taken during a thunderstorm. Discharges of atmospheric electricity can cause great damage to the national economy and turn out to be life-threatening if precautions are not taken in time. It is necessary to fear lightning, not thunder. The renowned American expert on thunderstorms, Dr. KV McIhron, said that if you hear thunder, lightning will not strike you anymore; if you see lightning, it will no longer hit you, and if it strikes you, you will not know about it.

So I learned how thunder and lightning are made and which of them is worse?

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

As early as 250 years ago, the famous American scientist and public figure Benjamin Franklin established that lightning is an electrical discharge. But until now, it has not been possible to fully reveal all the secrets that lightning keeps: it is difficult and dangerous to study this natural phenomenon.

(20 photos of lightning + video Lightning in slow motion)

Inside the clouds

A thundercloud cannot be confused with an ordinary cloud. Its gloomy, lead 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's going on inside this cloud? The water vapor that makes up the clouds freezes and exists in the form of ice crystals. Upward currents of air coming from the heated earth carry small pieces of ice upward, forcing them to collide with large ones that settle down all the time.

By the way, in winter the earth heats up less, and at this time of the year, practically no powerful ascending currents are formed. Therefore, winter thunderstorms are extremely rare.

In the process of collisions, the ice floes are electrified, just as it happens when various objects rub against each other, for example, a combs on hair. Moreover, small pieces of ice acquire a positive charge, and large ones - negative. For this reason, the upper part of the lightning cloud acquires a positive charge, and the lower one - 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.

Lightning development

The development of lightning begins with the fact that in some place in the cloud a focus appears with an increased concentration of ions - water molecules and gases that make up air, from which electrons were taken away or to which they were added.

According to some hypotheses, such an ionization center is obtained due to the acceleration in an electric field of free electrons, 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 shock is caused by cosmic rays, which constantly penetrate our atmosphere, ionizing air molecules.

Ionized gas serves as a good conductor of electricity, so a current begins to flow through the ionized areas. Further - more: the passing current heats up the ionization region, causing more and more high-energy particles that ionize the nearby regions - the lightning channel spreads very quickly.

Following the leader

In practice, the development of lightning occurs in several stages. First, the leading edge of the conductive channel, called the "leader", moves in leaps of several tens of meters, each time slightly changing direction (this makes the lightning winding). Moreover, the speed of advancement of the "leader" can, at some moments, reach 50 thousand kilometers in one single second.

Eventually, the "leader" reaches the ground or another part of the cloud, but this is not yet the main stage in 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 the 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 the lightning gives such a bright flash visible from tens of kilometers away. And instantaneous temperature drops, in thousands of degrees, create the strongest air pressure drops, spreading in the form of a sound wave - thunder. This stage does not last long - thousandths of a second, but the energy that is released is enormous.

Final stage

At the final stage, the speed and intensity of the movement of charges in the channel decreases, but, all the same, they remain rather large. It is this moment that is most dangerous: the final stage can last only tenths (or even less) of a second. Such long-term exposure to objects on the ground (for example, dry trees) often leads to fires and destruction.

Moreover, as a rule, the matter is not limited to one discharge - new "leaders" can move along the beaten path, causing repeated discharges in the same place, reaching up to several dozen.

Despite the fact that lightning has been known to mankind since the appearance of man himself on Earth, until now it has not yet been fully studied.

Lightning discharges ( lightning) is the most common source of powerful natural electromagnetic fields. Lightning is a type of gas discharge with a very long spark length. The total length of the lightning channel reaches several kilometers, and a significant part of this channel is located inside the thundercloud. lightning The cause of lightning is the formation of a large volumetric electric charge.

Ordinary lightning source are thunderstorm cumulonimbus clouds, which carry an accumulation of positive and negative electric charges in the upper and lower parts of the cloud and form electric fields of increasing intensity around this cloud. The formation of such volumetric charges of different polarity in the cloud (cloud polarization) is associated with condensation due to the cooling of water vapors of the ascending streams of warm air on positive and negative ions (condensation centers) and the separation of charged moisture droplets in the cloud under the action of intense ascending thermal air currents. Due to the fact that several accumulations of charges isolated from each other are formed in the cloud (charges of negative polarity accumulate in the lower part of the cloud).

Lightning discharges can be divided into several types based on their external features. The usual type is line zipper, with varieties: tape, rocket, zigzag and branched. The rarest type of discharges is ball lightning. There are known categories that bear the names "St. Elmo's Fire" and "Andean Glow". Lightning is usually multiple, i.e. consists of several unit discharges developing along the same path, and each discharge, like the discharge obtained in laboratory conditions, begins with a leader and ends with a reverse (main) discharge. The rate of descent of the leader of the first unit discharge is approximately equal to 1500 km / s, the velocities of the leaders of subsequent discharges reach 2000 km / s, and the speed of the reverse discharge varies within the range of 15000 -150000 km / s, i.e., from 0.05 to 0.5 speed Sveta. The leader channel, like the channel of any streamer, is filled with plasma and, therefore, has a certain conductivity.

The upper end of the leader channel is connected to one of the charged centers in the cloud; therefore, part of the charges from this center flows down into the leader channel. The charge distribution in the channel should be uneven, increasing towards its end. However, some indirect measurements suggest that the absolute value of the charge on the leader's head is small and, in the first approximation, the channel can be considered uniformly charged with a linear charge density S. The total charge in the leader's channel in this case is Q = S * l, where l is the channel length , and usually its value is about 10% of the value of the charge flowing into the ground during a single lightning discharge. In 70-80% of all cases, this charge has a negative polarity. As the leader's channel moves under the action of the electric field created by him, the charges shift in the ground, and the charges opposite in sign to the leader's charges (usually positive charges) tend to be located as close as possible to the leader channel head. In the case of a homogeneous soil, these charges accumulate directly under the leader channel.

If the soil is heterogeneous and its main part has a high resistivity, the charges are concentrated in areas with increased conductivity (rivers, groundwater). In the presence of earthed towering objects (lightning rods, chimneys, tall buildings, rain-soaked trees), charges are drawn to the top of the object, creating a significant field strength there. At the first stages of the development of the leader channel, the strength of the electric field at its head is determined by the leader's own charges and the accumulations of space charges located under the cloud. The leader's trajectory is not associated with terrestrial objects. As the leader descends, accumulations of charges on the ground and towering objects begin to exert an increasing influence. Starting from a certain height of the leader's head (orientation height), the field strength in one of the directions turns out to be the highest, and the leader is oriented to one of the ground objects. Naturally, in this case, towering objects and areas of the earth with increased conductivity (selective attack) are mainly affected. From very high objects, counter leaders develop towards the leader, the presence of which contributes to the orientation of the lightning towards the given object.

After the leader channel reaches the ground or the counter leader, a reverse discharge begins, during which the leader channel acquires a potential that is almost equal to that of the ground. On the head of the upwardly developing reverse discharge there is a region of increased electric field strength, under the influence of which the channel is rearranged, accompanied by an increase in the plasma charge density from 10 ^ 13 - 10 ^ 14 to 10 ^ 16 - 10 ^ 19 1 / m3, due to which the channel conductivity increases at least 100 times. During the development of the reverse discharge, a current iM = v passes through the impact site, where v is the speed of the reverse discharge. The process that occurs during the transition of the leader discharge into the reverse discharge is in many respects similar to the process of a vertical charged wire shorted to ground.

If a charged wire is closed to ground through a resistance r, then the current at the grounding point is: where z = the characteristic impedance of the wire. Thus, even with a lightning discharge, the current at the point of impact will be equal to v only with the grounding resistance equal to zero. With grounding resistances other than zero, the current at the impact site decreases. It is rather difficult to quantify this decrease, since the wave impedance of the lightning channel can be estimated only roughly approximately. There is reason to believe that the wave impedance of the lightning channel decreases with increasing current, and the average value is approximately equal to 200 - 300 Ohm. In this case, when the grounding resistance of the object changes from 0 to 30 Ohm, the current in the object changes by only 10%. In what follows, we will call such objects well grounded and assume that the total lightning current iM = v passes through them. The main parameters of lightning and the intensity of thunderstorm activity Lightning with large currents occur extremely rarely. So, lightning with currents of 200 kA occurs in 0.7 ... 1.0% of cases of the total number of observed discharges.

The number of lightning strikes with a current of 20 kA is about 50%. Therefore, it is customary to represent the values ​​of the amplitudes of lightning currents in the form of probability curves (distribution functions), for which the probability of occurrence of lightning currents with a maximum value is plotted along the ordinate. The main quantitative characteristic of lightning is the current flowing through the struck object, which is characterized by the maximum value of iM, the average steepness of the front and the pulse duration tp, which is equal to the time the current decreases to half the maximum value. Currently, the largest amount of data is available on the maximum values ​​of the lightning current, the measurement of which is carried out by the simplest measuring instruments - magnetorecorders, which are cylindrical rods made of steel filings or wires pressed into plastic. Magnetorecorders are mounted near towering objects (lightning rods, transmission line supports) and are located along the lines of force of the magnetic field that occurs when the lightning current passes through the object. Since materials with a high coercive force are used for the manufacture of recorders, they retain a large residual magnetization.

By measuring this magnetization, you can use the calibration curves to determine the maximum value of the magnetizing current. Measurements by magnetorecorders do not provide high accuracy, however, this drawback is partially compensated by the huge number of measurements, which by now amount to tens of thousands. By placing a frame closed on an inductive coil close to the object being struck, it is possible to measure the lightning current steepness using a magnetorecorder placed inside the coil. Measurements have shown that lightning currents vary over a wide range from several kiloamperes to hundreds of kiloamperes, therefore the measurement results are presented as probability curves (distribution functions) of lightning currents, on which the probability of lightning currents with a maximum value exceeding the value indicated ordinate.

In Ukraine, when calculating lightning protection, a curve is used For mountainous areas, the ordinates of the curve are halved, since at small distances from the ground to the clouds, lightning occurs at a lower density of charges in clusters, i.e., the probability of large currents decreases. Experimental determination of the steepness and duration of the lightning current impulse presents much greater difficulties; therefore, the amount of experimental data on these parameters is relatively small. The duration of the lightning current pulse is mainly determined by the propagation time of the reverse discharge from the ground to the cloud and, therefore, varies within a relatively narrow range from 20 to 80-100 μs. The average duration of the lightning current impulse is close to 50 μs, which determined the choice of the standard impulse.

The most important from the point of view of assessing the lightning resistance of RES are: the value of the charge carried by the lightning, the current in the lightning channel, the number of repeated strikes in one channel and the intensity of thunderstorm activity. All these parameters are not uniquely determined and are probabilistic in nature. The charge carried by lightning fluctuates in the course of the discharge in the range from fractions of a coulomb to several tens of coulombs. The average charge lowered into the ground by multiple lightning is 15 - 25 C. Considering that, on average, a lightning discharge contains three components, therefore, during one component, about 5 - 8 C are transferred to the ground. Of these, about 60% of the entire given accumulation of charges flows into the leader's channel, which is 3 - 5 C. A lightning strike into flat areas of the earth's surface carries a charge of 10 - 50 C (on average 25 C), with lightning strikes in the mountains - a charge of 30 - 100 C (on average 60 C), with discharges to television towers, the charge reaches 160 C.

In the case of lightning strikes into the ground, the overwhelming majority (85 - 90%) carry a negative charge into the ground. The charge flowing into the ground during multiple lightning varies from fractions of a pendant to 100 C and more. The average value of this charge is close to 20 C. The charge released into the ground during thunderstorms appears to play a significant role in maintaining the negative charge on the ground. The intensity of thunderstorm activity in different climatic regions varies greatly. As a rule, the number of thunderstorms during the year is minimal in the northern regions and gradually increases to the south, where high air humidity and high temperatures contribute to the formation of thunderclouds. However, this trend is not always observed. There are centers of thunderstorm activity in the middle latitudes (for example, in the Kiev region), where favorable conditions are created for the formation of local thunderstorms.

The intensity of thunderstorm activity is usually characterized by the number of thunderstorm days per year or the total annual duration of thunderstorms in hours. The latter characteristic is more correct, since the number of lightning strikes into the ground does not depend on the number of thunderstorms, but on their total duration. The number of thunderstorm days or hours per year is determined on the basis of long-term observations of meteorological stations, the generalization of which makes it possible to draw up maps of thunderstorm activity, on which lines of equal duration of thunderstorms are drawn - isokeranic lines. The average duration of thunderstorms in one thunderstorm day for the territory of the European part of Russia and Ukraine is 1.5-2 hours.

Every second, approximately 700 lightning, and every year about 3000 people are killed by a lightning strike. 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 reached out to our physics authors to learn more about the nature of lightning. How lightning appears, where lightning strikes, and why thunder thunders. 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.

Electric discharge Is the process of current flow in a 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.

The spark discharge occurs at atmospheric pressure and is accompanied by a characteristic spark crackle. A spark discharge is a set of filamentary spark channels disappearing and replacing each other. Spark channels are also called streamers... The spark channels are filled with ionized gas, that is, 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 acts as a dielectric between the 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 is formed in nature.

Step leader

Before the main flash of lightning, a small spot can be observed moving from the cloud to the ground. This is the so-called step leader. Electrons, under the influence of a potential difference, begin to move towards the earth. As they move, they collide with air molecules, ionizing them. An ionized channel is 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's 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 a leader approaches the ground, the tension at his end grows. 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 the earth and the sky. That is why it is dangerous to be on the plain or on the surface of the water during a thunderstorm.

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 the current strength and the release of energy. The question is pertinent here, Where does the 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 observing, 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 is lightning thundering?

Thunder occurs as a result of a shockwave generated by the rapid expansion of ionized channels. Why do we first see lightning and then hear thunder? It's all about the difference between 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 from you the lightning struck.

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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 ground-based and intra-cloud lightning, there are lightning strikes 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 devices, since they are formed at an altitude of 40 kilometers and higher.

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 year.
• The longest lightning bolt lasted 7,74 seconds and was recorded in the Alps.
• Lightning is not only formed on Earth... It is known exactly about lightning on Venus, Jupiter, Saturn and Uranus... The lightning bolts of Saturn are millions of times more powerful than earthly ones.
• Lightning current 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 in 6 times the temperature of the sun's surface.

Ball lightning