What's scarier: thunder or lightning? Why is there thunder?

What is thunder? Thunder is the sound that accompanies a lightning strike during a thunderstorm. Sounds simple enough, but why does lightning sound the way it does? Any sound consists of vibrations that create sound waves in the air. Lightning is a huge bolt of electricity that shoots through the air, causing vibrations. Many people have repeatedly wondered where lightning and thunder come from and why thunder precedes lightning. There are quite understandable reasons for this phenomenon.

How does thunder thunder?

Electricity passes through the air and causes air particles to vibrate. Lightning accompanied incredibly high temperature, so the air around it also gets very hot. Hot air expands, increasing the strength and number of vibrations. What is thunder? That's what it is sound vibrations arising from lightning strikes.

Why does thunder not thunder at the same time as lightning?

We see lightning before we hear thunder because light travels faster than sound. Eat old myth that by counting the seconds between a flash of lightning and thunder, you can find out the distance to the place where the storm is raging. However, from a mathematical point of view, this assumption is not valid. scientific justification, since the speed of sound is approximately 330 meters per second.

Thus, for thunder to travel one kilometer, it will take 3 seconds. Therefore, it would be more correct to count the number of seconds between the flash of lightning and the sound of thunder, and then divide this number by five, this will be the distance to the thunderstorm.

This mysterious phenomenon- lightning

The heat from lightning's electricity raises the temperature of the surrounding air to 27,000°C. Since lightning moves at incredible speeds, the heated air simply does not have time to expand. Heated air is compressed, it Atmosphere pressure at the same time it increases several times and becomes from 10 to 100 times more than normal. Compressed air rushes out from the lightning channel, forming a shock wave of compressed particles in each direction. Like an explosion, fast-moving waves of compressed air create a loud, booming burst of noise.

Based on the fact that electricity follows the shortest path, the predominant number of lightning strikes are close to vertical. However, lightning can also branch, as a result of which the sound color of the thunder roar also changes. Shock waves from different lightning forks bounce off each other, and low-hanging clouds and nearby hills help create the continuous rumble of thunder. Why is there thunder? Thunder is caused by the rapid expansion of air surrounding the lightning path.

What causes lightning?

Lightning is an electric current. Inside a thundercloud high in the sky, numerous small pieces of ice (frozen raindrops) collide with each other as they move through the air. All these collisions create an electrical charge. After some time, the whole cloud is filled with electrical charges. Positive charges, protons, form at the top of the cloud, and negative charges, electrons, form at the bottom of the cloud. And as we know, opposites attract. The main electrical charge is concentrated around everything that protrudes above the surface. These could be mountains, people or lonely trees. The charge goes up from these points and eventually combines with the charge going down from the clouds.

What causes thunder?

What is thunder? This is the sound caused by lightning, which is essentially a stream of electrons flowing between or within a cloud, or between a cloud and the ground. The air around these streams heats up to such an extent that it becomes three times hotter than the surface of the Sun. Simply put, lightning is a bright flash of electricity.

This stunning and at the same time terrifying spectacle of thunder and lightning is a combination of dynamic vibrations of air molecules and their disruption through electrical forces. This magnificent show once again reminds everyone of the powerful force of nature. If you heard the roar of thunder, lightning will soon flash; it is better not to be outside at this time.

Thunder: Fun Facts

• You can judge how close the lightning is by counting the seconds between the flash and the clap of thunder. For every second there are about 300 meters.
• During a large thunderstorm, seeing lightning and hearing thunder is a common occurrence; thunder during snowfall is very rare.
• Lightning is not always accompanied by thunder. In April 1885, five lightning bolts struck the Washington Monument during a thunderstorm, but no one heard the thunder.

Be careful, lightning!

Lightning is quite dangerous a natural phenomenon, and it’s better to stay away from her. When indoors during a thunderstorm, you should avoid water. It is an excellent conductor of electricity, so do not shower, wash your hands, wash dishes or do laundry. Do not use the telephone, as lightning may strike external telephone lines. Do not include electrical equipment, computers or household appliances during a storm. Knowing what thunder and lightning are, it is important to behave correctly if suddenly a thunderstorm takes you by surprise. You should stay away from windows and doors. If someone is struck by lightning, they need to call for help and an ambulance.

Ancient people did not always consider thunderstorms and lightning, as well as the accompanying clap of thunder, to be a manifestation of the wrath of the gods. For example, for the Hellenes, thunder and lightning were symbols of supreme power, while the Etruscans considered them signs: if a flash of lightning was seen from the east, it meant that everything would be fine, and if it flashed in the west or northwest, it meant the opposite.

The Etruscan idea was adopted by the Romans, who were convinced that a lightning strike from the right side was sufficient reason to postpone all plans for a day. The Japanese had an interesting interpretation of heavenly sparks. Two vajras (lightning bolts) were considered symbols of Aizen-meo, the god of compassion: one spark was on the deity’s head, the other he held in his hands, suppressing all the negative desires of humanity with it.

Lightning is a huge electrical discharge, which is always accompanied by a flash and thunderclaps (a shining discharge channel resembling a tree is clearly visible in the atmosphere). At the same time, there is almost never just one flash of lightning; it is usually followed by two or three, often reaching several dozen sparks.

These discharges almost always form in cumulonimbus clouds, sometimes in large-sized nimbostratus clouds: the upper boundary often reaches seven kilometers above the surface of the planet, while the lower part can almost touch the ground, staying no higher than five hundred meters. Lightning can form both in one cloud and between nearby electrified clouds, as well as between a cloud and the ground.

A thundercloud consists of large quantity steam condensed in the form of ice flakes (at an altitude exceeding three kilometers these are almost always ice crystals, since temperature indicators here they do not rise above zero). Before a cloud becomes a thunderstorm, ice crystals begin to actively move inside it, and they are helped to move by rising currents of warm air from the heated surface.

Air masses carry upward smaller pieces of ice, which during movement constantly collide with larger crystals. As a result, smaller crystals become positively charged, while larger ones become negatively charged.

After small ice crystals collect at the top and large ones at the bottom, top part The cloud turns out to be positively charged, the lower one – negatively. So the tension electric field in a cloud reaches extremely high levels: a million volts per meter.

When these oppositely charged areas collide with each other, ions and electrons at the points of contact form a channel through which all charged elements rush down and an electrical discharge is formed - lightning. At this time, such powerful energy is released that its strength would be enough to power a 100 W light bulb for 90 days.

The channel heats up to almost 30 thousand degrees Celsius, which is five times higher than the temperature of the Sun, producing a bright light (the flash usually lasts only three quarters of a second). After the channel is formed, the thundercloud begins to discharge: the first discharge is followed by two, three, four or more sparks.

A lightning strike resembles an explosion and causes the formation of a shock wave, which is extremely dangerous for any living creature near the canal. A shock wave of a strong electrical discharge a few meters away is quite capable of breaking trees, injuring or concussing even without direct electric shock:

• At a distance of up to 0.5 m from the channel, lightning can destroy weak structures and injure a person;
• At a distance of up to 5 meters, buildings remain intact, but can break windows and stun a person;
• At long distances the shock wave negative consequences does not carry and turns into a sound wave known as thunderclaps.

Rolling thunder

A few seconds after a lightning strike was recorded, due to a sharp increase in pressure along the channel, the atmosphere heats up to 30 thousand degrees Celsius. As a result, explosive vibrations of the air occur and thunder occurs. Thunder and lightning are closely interrelated with each other: the length of the discharge is often about eight kilometers, so the sound from different parts of it reaches the different time, forming thunderclaps.

Interestingly, by measuring the time that passes between thunder and lightning, you can find out how far the epicenter of the thunderstorm is from the observer.

To do this, you need to multiply the time between lightning and thunder by the speed of sound, which is from 300 to 360 m/s (for example, if the time interval is two seconds, the epicenter of the thunderstorm is a little more than 600 meters from the observer, and if three - at a distance kilometer). This will help determine whether a storm is moving away or approaching.

Amazing fireball

One of the least studied, and therefore most mysterious, natural phenomena is considered to be ball lightning - a glowing plasma ball moving through the air. It is mysterious because the principle of the formation of ball lightning is unknown to this day: despite the fact that there are a large number of hypotheses explaining the reasons for the appearance of this amazing phenomenon nature, there were objections to each of them. Scientists have never been able to experimentally achieve the formation of ball lightning.

Ball lightning can exist long time and move along an unpredictable trajectory. For example, it is quite capable of hovering in the air for several seconds and then darting to the side.

Unlike a simple discharge, there is always only one plasma ball: until two or more fiery lightning bolts are detected simultaneously. The dimensions of ball lightning range from 10 to 20 cm. Ball lightning is characterized by white, orange or blue tones, although other colors, even black, are often found.

Scientists have not yet determined the temperature indicators of ball lightning: despite the fact that, according to their calculations, it should range from one hundred to a thousand degrees Celsius, people who were close to this phenomenon did not feel the heat emanating from the ball lightning.

The main difficulty in studying this phenomenon is that scientists are rarely able to record its occurrence, and eyewitness testimony often casts doubt on the fact that the phenomenon they observed was indeed ball lightning. First of all, testimonies differ regarding the conditions under which she appeared: she was mainly seen during a thunderstorm.

There are also indications that ball lightning can appear on a fine day: it can descend from the clouds, appear in the air, or appear from behind an object (a tree or a pole).

One more characteristic feature ball lightning is its penetration into closed rooms, it has even been noticed in pilot cockpits (the fireball can penetrate through windows, go down ventilation ducts and even fly out of sockets or a TV). Situations have also been repeatedly documented when a plasma ball was fixed in one place and constantly appeared there.

Often the appearance of ball lightning does not cause trouble (it moves calmly in air currents and after some time flies away or disappears). But sad consequences were also noticed when it exploded, instantly evaporating the liquid located nearby, melting glass and metal.

Possible dangers

Since the appearance of ball lightning is always unexpected, when you see this unique phenomenon near you, the main thing is not to panic, not to move abruptly and not to run anywhere: fire lightning is very susceptible to air vibrations. It is necessary to quietly leave the trajectory of the ball and try to stay as far away from it as possible. If a person is indoors, you need to slowly walk to the window opening and open the window: there are many stories when a dangerous ball left the apartment.

You cannot throw anything into a plasma ball: it is quite capable of exploding, and this is fraught not only with burns or loss of consciousness, but also with cardiac arrest. If it happens that the electric ball catches a person, you need to move him to a ventilated room, wrap him warmly, perform a heart massage, perform artificial respiration and immediately call a doctor.

What to do in a thunderstorm

When a thunderstorm begins and you see lightning approaching, you need to find shelter and hide from the weather: a lightning strike is often fatal, and if people survive, they often remain disabled.

If there are no buildings nearby, and a person is in the field at that time, he must take into account that it is better to hide from a thunderstorm in a cave. But it is advisable to avoid tall trees: lightning usually hits the largest plant, and if the trees are the same height, it hits something that conducts electricity better.

To protect a free-standing building or structure from lightning, a high mast is usually installed near it, at the top of which there is a pointed metal rod securely connected to a thick wire; at the other end there is a metal object buried deep in the ground. The operation scheme is simple: the rod from a thundercloud is always charged with a charge opposite to the cloud, which, flowing down the wire underground, neutralizes the charge of the cloud. This device is called a lightning rod and is installed on all buildings in cities and other human settlements.

Fog that rises high above the ground consists of water particles and forms clouds. Larger and heavier clouds are called clouds. Some clouds are simple - they do not cause lightning or thunder. Others are called thunderstorms, since they are the ones who create a thunderstorm, form lightning and thunder. Thunderclouds differ from simple rain clouds in that they are charged with electricity: some are positive, others are negative.

How do thunderclouds form?

Everyone knows how strong the wind can be during a thunderstorm. But even stronger air vortices form higher above the ground, where forests and mountains do not interfere with the movement of air. This wind mainly creates positive and negative electricity in the clouds. To understand this, consider how electricity is distributed in each drop of water. Such a drop is shown enlarged in Fig. 8. In its center there is positive electricity, and equal negative electricity is located on the surface of the drop. Falling raindrops are picked up by the wind and fall into air currents. The wind hitting the drop with force breaks it into pieces. In this case, the breakaway outer particles of the drop become charged with negative electricity. The remaining larger and heavier part of the drop is charged with positive electricity. That part of the cloud in which heavy droplet particles accumulate is charged with positive electricity.

Rice. 8. This is how electricity is distributed in a raindrop. Positive electricity inside the drop is represented by a single (large) “+” sign.

How stronger wind, the sooner the cloud is charged with electricity. The wind expends a certain amount of work to separate positive and negative electricity.

Rain falling from a cloud carries some of the cloud's electricity to the ground and, thus, an electrical attraction is created between the cloud and the ground.

In Fig. Figure 9 shows the distribution of electricity in a cloud and on the surface of the earth. If a cloud is charged with negative electricity, then, trying to be attracted to it, the positive electricity of the earth will be distributed on the surface of all elevated objects that conduct electric current. The higher the object standing on the ground, the smaller the distance between its top and the bottom of the cloud and the smaller the layer of air remaining here that separates opposite electricity. Obviously, in such places it is easier for lightning to reach the ground. We will talk about this in more detail later.

Rice. 9. Distribution of electricity in a thundercloud and ground objects.

2. What causes lightning?

Approaching close to a tall tree or house, a thundercloud charged with electricity acts on it in exactly the same way as in the one we considered. latest experience the charged rod acted on the electroscope. On the top of a tree or on the roof of a house, electricity of a different kind is generated through influence than that carried by a cloud. So, for example, in Fig. 9, a cloud charged with negative electricity attracts positive electricity to the roof, and the negative electricity of the house goes into the ground.

Both electricity - in the cloud and in the roof of the house - tend to attract each other. If there is a lot of electricity in the cloud, then a lot of electricity is generated in the house through the influence. Just as rising water can wash away a dam and rush into a torrent, flooding a valley in its uncontrollable movement, so electricity, all in more what accumulates in the cloud can eventually break through the layer of air separating it from the surface of the earth and rush down towards the earth, towards the opposite electricity. A strong discharge will occur - an electric spark will jump between the cloud and the house.

This is lightning striking the house.

Lightning discharges can occur not only between a cloud and the ground, but also between two clouds charged with electricity various kinds.

3. How does lightning develop?

Most often, lightning striking the ground comes from clouds charged with negative electricity. Lightning striking from such a cloud develops like this.

First, electrons begin to flow from the cloud towards the ground in small quantities, in a narrow channel, forming something like a stream in the air. In Fig. Figure 10 shows this beginning of lightning formation. In the part of the cloud where the formation of the channel begins, electrons have accumulated and have a high speed of movement, due to which, when they collide with air atoms, they break them into nuclei and electrons. The electrons released in this case also rush towards the ground and, again colliding with air atoms, split them. This is similar to the fall of snow in the mountains, when at first a small lump, rolling down, becomes overgrown with snowflakes sticking to it, and, accelerating its run, turns into a formidable avalanche. And here the electron avalanche captures more and more volumes of air, splitting its atoms into pieces. At the same time, the air heats up, and as the temperature rises, its conductivity increases; it turns from an insulator into a conductor. Through the resulting conductive channel of air, electricity begins to flow out of the cloud in increasing quantities. Electricity is approaching the earth at enormous speeds, reaching 100 kilometers per second. For comparison, let us recall that the flight speed of a projectile from modern guns does not exceed two kilometers per second.

Rice. 10. Lightning begins to form in the cloud.

After hundredths of a second, the electron avalanche reaches the ground. This ends only the first, so to speak, “preparatory” part of the lightning: the lightning has made its way to the ground. The second, main part of the development of lightning is still ahead.

The considered part of the lightning formation is called the leader. This foreign word means "leading" in Russian. The leader paved the way for the second, more powerful part of the lightning; this part is called the main part.

Once the channel has reached the ground, electricity begins to flow through it much more violently and quickly. Now there is a connection between the negative electricity accumulated in the channel and the positive electricity that entered the ground with raindrops and through electrical influence - a discharge of electricity occurs between the cloud and the ground. This discharge is an electric current enormous power- this force is much greater than the current in a conventional electrical network. The current flowing in the channel increases very quickly, and having reached its greatest strength, it begins to gradually decrease. The lightning channel through which such a strong current flows becomes very hot and therefore glows brightly. But the time of current flow in a lightning discharge is very short. The discharge lasts for very small fractions of a second, and therefore Electric Energy, which is obtained during discharge, is relatively small.

In Fig. Figure 11 shows the gradual movement of the lightning leader towards the ground (the first three figures on the left). The last three pictures show individual moments of the formation of the second (main) part of the lightning.

Rice. 11. Gradual development of the leader of the lightning (the first three pictures) and its main part (the last three pictures).

A person looking at lightning, of course, will not be able to distinguish its leader from the main part, since they follow each other extremely quickly, along the same path. But with the help of a photographic camera you can clearly see both processes. The photographic apparatus used in these cases is special. Its main difference from conventional cameras is that its plate has round shape and rotates during shooting - exactly the same as a gramophone record. Therefore, a picture taken with such a device is stretched and “smeared.”

After connecting two different types of electricity, the current is interrupted. However, the lightning usually doesn't end there. Often along the path laid out by the first discharge, new leader, and behind it, along the same path, comes the main part of the discharge again. This completes the second category.

Up to 50 such separate discharges, each consisting of its own leader and main part, can be formed. Most often there are 2-3 of them. The appearance of individual discharges makes the lightning intermittent, and often a person looking at the lightning sees it flickering.

This is the reason for the flickering of lightning.

Since lightning consists of several rapidly alternating flashes of light, individual images appear on a rotating photographic plate, located at a certain distance from one another. The faster the plate rotates, the greater the distance between the images.

The time between the formation of individual discharges is very short; it does not exceed hundredths of a second. If the number of discharges is very large, then the duration of lightning can reach a whole second or even several seconds. Lightning is not as “fast” as it was previously imagined!

We looked at only one type of lightning, which is the most common. This lightning is called line lightning because to the naked eye it appears as a line - a narrow bright stripe of white, light blue or hot pink color. Linear lightning has a length from hundreds of meters to many kilometers. The path of lightning is usually zigzag. Lightning often has many branches. As already mentioned, linear lightning discharges can occur not only between a cloud and the ground, but also between clouds.

In Fig. 12 shows linear lightning.

Rice. 12. Linear lightning.

4. What causes thunder?

Linear lightning is usually accompanied by a strong booming sound called thunder. Thunder occurs for the following reason. We have seen that the current in the lightning channel is generated within a very short period of time. At the same time, the air in the channel heats up very quickly and strongly, and when heated it expands. The expansion occurs so quickly that it resembles an explosion. This explosion produces air concussion, which is accompanied by strong sounds. After a sudden cessation of current, the temperature in the lightning channel drops rapidly as heat escapes into the atmosphere. The channel cools quickly, and the air in it is therefore sharply compressed. This also causes the air to shake, which again produces sound. It is clear that repeated lightning strikes can cause prolonged rumble and noise. In turn, the sound is reflected from clouds, the ground, houses and other objects and, creating multiple echoes, lengthens the thunder. That's why thunderclaps occur.

Like any sound, thunder travels through the air at a relatively low speed - approximately 330 meters per second. This speed is only one and a half times the speed of a modern aircraft. If an observer first sees lightning and only after some time hears thunder, then he can determine the distance that separates him from the lightning. Let, for example, 5 seconds pass between lightning and thunder. Since in every second sound travels 330 meters, in five seconds thunder has traveled a distance five times greater, namely 1650 meters. This means that lightning struck less than two kilometers from the observer.

In calm weather, thunder is heard after 70–90 seconds, traveling 25–30 kilometers. Thunderstorms that pass from the observer at a distance of less than three kilometers are considered close, and thunderstorms that pass at a greater distance are considered distant.

5. Ball lightning

In addition to linear, there are, although much less frequently, lightning of other types. Of these, we will consider one of the most interesting - ball lightning.

Sometimes lightning discharges are observed, which are fireballs. How ball lightning is formed has not yet been studied, but existing observations of this interesting view lightning discharges allow us to draw some conclusions. Here we present one of the most interesting descriptions ball lightning.

This is what the famous French scientist Flammarion reports:

“On June 7, 1886, at half past seven in the evening, during a thunderstorm that broke out over French city Gray, the sky suddenly lit up with wide red lightning, and with a terrible crash, a fireball fell from the sky, apparently 30–40 centimeters in diameter. Scattering sparks, it hit the end of the roof ridge, knocked off a piece more than half a meter long from its main beam, and split it into small pieces, filled the attic with debris and brought down the plaster from the ceiling of the upper floor. Then this ball jumped onto the roof of the entrance, punched a hole in it, fell onto the street and, having rolled along it for some distance, gradually disappeared. The balloon did not cause a fire and did not harm anyone, despite the fact that there were a lot of people on the street.”

In Fig. 13 shows ball lightning captured by a photographic camera, and Fig. 14 shows a picture of an artist who painted a ball of lightning that fell into the yard.

Rice. 13. Ball lightning.

Rice. 14. Ball lightning. (From a painting by the artist.)

Most often, ball lightning has the shape of a watermelon or pear. It lasts for a relatively long time - from a small fraction of a second to several minutes. The most common duration of ball lightning is from 3 to 5 seconds. Ball lightning most often appears at the end of a thunderstorm in the form of red luminous balls with a diameter of 10 to 20 centimeters. In more rare cases, it also has big sizes. For example, a lightning bolt with a diameter of about 10 meters was photographed.

The ball can sometimes be dazzling white and have a very sharp outline. Typically, ball lightning makes a whistling, buzzing or hissing sound.

Ball lightning may disappear quietly, but may also produce a faint crackling sound or even a deafening explosion. When it disappears, it often leaves a pungent-smelling haze. Near the ground or in enclosed spaces, ball lightning moves at the speed of a running person - approximately two meters per second. It can remain at rest for some time, and such a “settled” ball hisses and throws out sparks until it disappears. Sometimes it seems that ball lightning is driven by the wind, but usually its movement does not depend on the wind.

Ball lightning is attracted to enclosed spaces, into which they penetrate through open windows or doors, and sometimes even through small cracks. The pipes represent for them good way; Therefore, ball lightning often appears from ovens in kitchens. After circling around the room, ball lightning leaves the room, often leaving along the very path along which it entered.

Sometimes lightning rises and falls two or three times over distances from several centimeters to several meters. Simultaneously with these ascents and descents, the fireball sometimes moves in a horizontal direction, and then it seems that the ball lightning is making leaps.

Often ball lightning “settles” on conductors, preferring the most high points, or roll along conductors, for example, along drainpipes. Moving over people's bodies, sometimes under clothes, ball lightning causes severe burns and even death. There are many descriptions of cases of fatal damage to people and animals by ball lightning. Ball lightning can cause very severe damage to buildings.

There is no complete scientific explanation for ball lightning yet. Scientists have persistently studied ball lightning, but so far all its various manifestations have not been explained. Much more remains to be done in this area. scientific work. Of course, there is nothing mysterious or “supernatural” about ball lightning. This is an electrical discharge, the origin of which is the same as that of linear lightning. Undoubtedly, in the near future, scientists will be able to explain all the details of ball lightning as well as they were able to explain all the details of linear lightning.

Report

Thunder and lightning

Thunder is a sound phenomenon in the atmosphere that accompanies a lightning strike. Thunder is the vibration of air under the influence of a very rapid increase in pressure along the path of lightning, due to heating to approximately 30,000 ° C. Thunderclaps occur due to the fact that lightning has a significant length and sound from different parts of it and does not reach the observer’s ear at the same time; in addition, the occurrence of thunderclaps is facilitated by the reflection of sound from clouds, and also because, due to refraction, the sound wave spreads across in different ways and comes with different delays, in addition, the discharge itself does not occur instantly, but lasts a finite time.

The volume of thunder can reach 120 decibels.

By measuring the time interval between a flash of lightning and a clap of thunder, you can approximately determine the distance at which the thunderstorm is located. Since the speed of light is very high compared to the speed of sound, it can be neglected, taking into account only the speed of sound, which is approximately 350 meters per second. (But the speed of sound is very variable, depending on the air temperature; the lower it is, the lower the speed.) Thus, by multiplying the time between a flash of lightning and a clap of thunder in seconds by this value, one can judge the proximity of a thunderstorm, and by comparing similar measurements, one can judge whether a thunderstorm is approaching the observer (the interval between lightning and thunder is decreasing) or moving away (the interval is increasing). Typically, thunder can be heard at a distance of up to 15-20 kilometers, so if an observer sees lightning but does not hear thunder, then the thunderstorm is at least 20 kilometers away.

Spark discharge (electric spark)- a non-stationary form of electrical discharge occurring in gases. Such a discharge usually occurs at pressures on the order of atmospheric pressure and is accompanied by a characteristic sound effect - the “crackling” of a spark. The temperature in the main channel of the spark discharge can reach 10,000 K. In nature, spark discharges often occur in the form of lightning. The distance “pierced” by a spark in the air depends on the voltage and is considered equal to 10 kV per 1 centimeter.

A spark discharge usually occurs when the energy source is not powerful enough to support a steady arc or glow discharge. In this case, simultaneously with a sharp increase in the discharge current, the voltage across the discharge gap for a very short time (from several microseconds to several hundred microseconds) drops below the extinction voltage of the spark discharge, which leads to the termination of the discharge. Then the potential difference between the electrodes increases again, reaches the ignition voltage, and the process repeats. In other cases, when the power of the energy source is sufficiently large, the whole set of phenomena characteristic of this discharge is also observed, but they are only a transition process leading to the establishment of a discharge of another type - most often an arc one. If the current source is not capable of maintaining a self-sustained electrical discharge for a long time, then a form of self-sustained discharge called a spark discharge is observed.

A spark discharge is a bunch of bright, quickly disappearing or replacing each other thread-like, often highly branched stripes - spark channels. These channels are filled with plasma, which in a powerful spark discharge includes not only ions of the source gas, but also ions of the electrode substance, which intensively evaporates under the action of the discharge. The mechanism for the formation of spark channels (and, consequently, the occurrence of a spark discharge) is explained by the streamer theory of electrical breakdown of gases. According to this theory, from electron avalanches arising in the electric field of the discharge gap, under certain conditions, streamers are formed - dimly glowing thin branched channels that contain ionized gas atoms and free electrons split off from them. Among them we can highlight the so-called. leader - a weakly glowing discharge that “paves” the path for the main discharge. Moving from one electrode to another, it closes the discharge gap and connects the electrodes with a continuous conductive channel. Then the main discharge passes in the opposite direction along the laid path, accompanied by a sharp increase in the current strength and the amount of energy released in them. Each channel rapidly expands, resulting in a shock wave at its boundaries. The combination of shock waves from the expanding spark channels generates a sound perceived as the “crack” of a spark (in the case of lightning, thunder).

The ignition voltage of a spark discharge is usually quite high. The electric field strength in the spark decreases from several tens of kilovolts per centimeter (kV/cm) at the moment of breakdown to ~100 volts per centimeter (V/cm) after a few microseconds. The maximum current in a powerful spark discharge can reach values ​​of the order of several hundred thousand amperes.

A special type of spark discharge is a sliding spark discharge that occurs along the interface between a gas and a solid dielectric placed between the electrodes, provided that the field strength exceeds the breakdown strength of air. Areas of a sliding spark discharge, in which charges of one sign predominate, induce charges of a different sign on the surface of the dielectric, as a result of which spark channels spread along the surface of the dielectric, forming the so-called Lichtenberg figures. Processes similar to those occurring during a spark discharge are also characteristic of a brush discharge, which is a transition stage between corona and spark.

Lightning- a giant electrical spark discharge in the atmosphere, usually occurring during a thunderstorm, manifested by a bright flash of light and accompanying thunder. Lightning has also been recorded on Venus, Jupiter, Saturn and Uranus. The current in a lightning discharge reaches 10-20 thousand amperes, so few people manage to survive after being struck by lightning.

The electrical nature of lightning was revealed in the research of the American physicist B. Franklin, on whose idea an experiment was carried out to extract electricity from a thundercloud. Franklin's experience in elucidating the electrical nature of lightning is widely known. In 1750, he published a work that described an experiment using a kite launched into a thunderstorm. Franklin's experience was described in the work of Joseph Priestley.

The average length of lightning is 2.5 km, some discharges extend up to 20 km in the atmosphere. The current in a lightning discharge reaches 10-20 thousand amperes.

Lightning Formation

Most often, lightning occurs in cumulonimbus clouds, then they are called thunderstorms; Sometimes lightning forms in nimbostratus clouds, as well as when volcanic eruptions, tornadoes and dust storms.

Usually observed linear zippers, which belong to the so-called electrodeless discharges, since they begin (and end) in accumulations of charged particles. This determines their some still unexplained properties that distinguish lightning from discharges between electrodes. Thus, lightning does not occur shorter than several hundred meters; they arise in electric fields much weaker than the fields during interelectrode discharges; The collection of charges carried by lightning occurs in thousandths of a second from billions of small particles, well isolated from each other, located in a volume of several km³. The most studied process of lightning development in thunderclouds, while lightning can pass in the clouds themselves - intracloud lightning, or can strike the ground - ground lightning. For lightning to occur, it is necessary that in a relatively small (but not less than a certain critical) volume of the cloud an electric field (see atmospheric electricity) with a strength sufficient to initiate an electrical discharge (~ 1 MV/m) must be formed, and in a significant part of the cloud there would be field with an average strength sufficient to maintain the started discharge (~ 0.1-0.2 MV/m). In lightning, the electrical energy of the cloud is converted into heat and light.

Ground lightning

The development process of ground lightning consists of several stages. At the first stage, in the zone where the electric field reaches a critical value, impact ionization begins, created initially by free charges, always present in small quantities in the air, which, under the influence of the electric field, acquire significant speeds towards the ground and, colliding with the molecules that make up air, ionize them. For more modern ideas, the discharge is initiated by high-energy cosmic rays, which trigger a process called runaway breakdown. Thus, electron avalanches arise, turning into filaments electrical discharges- streamers, which are highly conductive channels, which, merging, give rise to a bright thermally ionized channel with high conductivity - a stepped lightning leader.

The leader's movement towards earth's surface occurs in steps of several tens of meters at a speed of ~ 50,000 kilometers per second, after which its movement stops for several tens of microseconds, and the glow weakens greatly; then, in the subsequent stage, the leader again advances several tens of meters. A bright glow covers all the steps passed; then a stop and weakening of the glow follows again. These processes are repeated when the leader moves to the surface of the earth from average speed 200,000 meters per second.

As the leader moves toward the ground, the field intensity at its end increases and under its action, a response streamer is ejected from objects protruding on the surface of the Earth, connecting to the leader. This feature of lightning is used to create a lightning rod.

In the final stage, a reverse (from bottom to top), or main, lightning discharge follows along the channel ionized by the leader, characterized by currents from tens to hundreds of thousands of amperes, a brightness noticeably exceeding the brightness of the leader, and a high speed of progress, initially reaching ~ 100,000 kilometers per second , and at the end decreasing to ~ 10,000 kilometers per second. The channel temperature during the main discharge can exceed 25,000 °C. The length of the lightning channel can be from 1 to 10 km, the diameter can be several centimeters. After the passage of the current pulse, the ionization of the channel and its glow weaken. In the final stage, the lightning current can last hundredths and even tenths of a second, reaching hundreds and thousands of amperes. Such lightning is called prolonged lightning and most often causes fires.

The clouds spread their wings and blocked the sun from us...

Why do we sometimes hear thunder and see lightning when it rains? Where do these outbreaks come from? Now we will tell you about this in detail.

What is lightning?

What is lightning? This is an amazing and very mysterious natural phenomenon. It almost always happens during a thunderstorm. Some are amazed, some are frightened. Poets write about lightning, scientists study this phenomenon. But much remains unsolved.

One thing is certain - it is a giant spark. It's like a billion light bulbs exploded! Its length is enormous - several hundred kilometers! And she is very far from us. That is why we see it first, and only then hear it. Thunder is the “voice” of lightning. After all, light reaches us faster than sound.

And lightning also happens on other planets. For example, on Mars or Venus. Normal lightning lasts only a fraction of a second. It consists of several categories. Lightning sometimes appears quite unexpectedly.

How is lightning formed?

Lightning is usually born in a thundercloud, high above the ground. Thunderclouds appear when the air begins to become very hot. That's why after extreme heat There are amazing thunderstorms. Billions of charged particles literally fly to the place where it originates. And when there are very, very many of them, they burst into flames. That's where lightning comes from - from a thundercloud. She can hit the ground. The earth attracts her. But it can also explode in the cloud itself. It all depends on what kind of lightning it is.

What types of lightning are there?

There are different types of lightning. And you need to know about this. This is not just a “ribbon” in the sky. All these “ribbons” are different from each other.

Lightning is always a strike, it is always a discharge between something. There are more than ten of them! For now, let’s name only the most basic ones, attaching pictures of lightning to them:

• Between thundercloud and earth. These are the same “ribbons” that we are used to.

Between tall tree and clouds. The same “ribbon”, but the blow is directed in the other direction.

Ribbon zipper - when there is not one “ribbon”, but several in parallel.

• Between cloud and cloud, or simply “played out” in one cloud. This type of lightning can often be seen during a thunderstorm. You just need to be careful.

• There are also horizontal lightning that do not touch the ground at all. They are endowed with colossal strength and are considered the most dangerous

• And everyone has heard about ball lightning! Only a few have seen them. There are even fewer who would like to see them. And there are also people who do not believe in their existence. But ball lightning exists! It is difficult to photograph such lightning. It explodes quickly, although it can “take a walk”, but it’s better for the person next to it not to move - it’s dangerous. So there’s no time for a camera here.

• View of lightning with very beautiful name- "St. Elmo's Fire." But it's not exactly lightning. This is the glow that appears at the end of a thunderstorm on pointed buildings, lanterns, and ship masts. Also a spark, but not fading and not dangerous. St. Elmo's Fire is very beautiful.

• Volcanic lightning occurs when a volcano erupts. The volcano itself already has a charge. This is probably what causes lightning.

• Sprite lightning is something that you cannot see from Earth. They appear above the clouds and few people are studying them yet. These lightning bolts look like jellyfish.

• The dotted lightning has hardly been studied. It can be seen extremely rarely. Visually, it really looks like a dotted line - as if a lightning ribbon is melting.

These are the different kinds of lightning. There is only one law for them - electric discharge.

Conclusion.

Even in ancient times, lightning was considered both a sign and the wrath of the Gods. She was a mystery before and remains one now. No matter how they break it down into the smallest atoms and molecules! And it’s always incredibly beautiful!