Lightning. Report: Electrical phenomena in nature: lightning What is lightning definition

26.10.2019

Lightning is a powerful electrical discharge. It occurs when there is a strong electrification of the clouds or the earth. Therefore, lightning discharges can occur either within a cloud, or between neighboring electrified clouds, or between an electrified cloud and the ground. A lightning discharge is preceded by the occurrence of a difference in electrical potentials between neighboring clouds or between a cloud and the ground.

Electrization, that is, the formation of attractive forces of an electrical nature, is well known to everyone from everyday experience.

If you comb clean dry hair with a plastic comb, they begin to be attracted to it, or even sparkle. After that, the comb can attract other small objects, such as small pieces of paper. This phenomenon is called electrification by friction.

What causes clouds to become electrified? After all, they do not rub against each other, as happens when an electrostatic charge forms on the hair and on the comb.

A thundercloud is a huge amount of steam, some of which is condensed in the form of tiny droplets or ice floes. The top of a thundercloud can be at a height of 6-7 km, and the bottom hangs above the ground at a height of 0.5-1 km. Above 3-4 km, the clouds consist of ice floes of different sizes, since the temperature there is always below zero. These ice floes are in constant motion, caused by ascending currents of warm air from the heated surface of the earth. Small pieces of ice are easier than large ones to be carried away by ascending air currents. Therefore, "nimble" small ice floes, moving to the upper part of the cloud, all the time collide with large ones. Each such collision leads to electrification. In this case, large pieces of ice are charged negatively, and small pieces are positively charged. Over time, positively charged small pieces of ice are at the top of the cloud, and negatively charged large ones at the bottom. In other words, the top of a thundercloud is positively charged, while the bottom is negatively charged.

The electric field of the cloud has a huge intensity - about a million V/m. When large oppositely charged regions come close enough to each other, some electrons and ions, running between them, create a glowing plasma channel through which the rest of the charged particles rush after them. This is how lightning occurs.

During this discharge, huge energy is released - up to a billion J. The temperature of the channel reaches 10,000 K, which gives rise to the bright light that we observe during a lightning discharge. Clouds are constantly discharged through these channels, and we see the external manifestations of these atmospheric phenomena in the form of lightning.

The incandescent medium expands explosively and causes a shock wave, perceived as thunder.

We ourselves can simulate lightning, albeit a miniature one. The experiment should be carried out in a dark room, otherwise nothing will be visible. We need two oblong balloons. Let's inflate them and tie them up. Then, making sure that they do not touch, simultaneously rub them with a woolen cloth. The air that fills them is electrified. If the balls are brought together, leaving a minimum gap between them, then sparks will begin to jump from one to the other through a thin layer of air, creating light flashes. At the same time, we will hear a faint crackle - a miniature copy of thunder during a thunderstorm.

Everyone who has seen lightning has noticed that it is not a brightly glowing straight line, but a broken line. Therefore, the process of formation of a conductive channel for a lightning discharge is called its "step leader". Each of these "steps" is the place where the electrons accelerated to near-light speeds stopped due to collisions with air molecules and changed the direction of movement.

Thus, lightning is a breakdown of a capacitor, in which the dielectric is air, and the plates are clouds and earth. The capacitance of such a capacitor is small - about 0.15 microfarads, but the energy reserve is huge, since the voltage reaches a billion volts.

One lightning usually consists of several discharges, each of which lasts only a few tens of millionths of a second.

Lightning most often occurs in cumulonimbus clouds. Lightning also occurs during volcanic eruptions, tornadoes, and dust storms.

There are several types of lightning according to the shape and direction of the discharge. Discharges can occur:

between the storm cloud and the earth,
between two clouds
inside the cloud
move out of the clouds into the clear sky.

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Lightning as a natural phenomenon

Lightning is a giant electric spark discharge between clouds or between clouds and the earth's surface, several kilometers long, tens of centimeters in diameter and tenths of a second long. Lightning is accompanied by thunder. In addition to linear lightning, ball lightning is occasionally observed.

The nature and causes of lightning

A thunderstorm is a complex atmospheric process, and its occurrence is due to the formation of cumulonimbus clouds. Strong cloudiness is a consequence of the significant instability of the atmosphere. Thunderstorms are characterized by strong winds, often heavy rain (snow), sometimes with hail. Before a thunderstorm (an hour or two before a thunderstorm), atmospheric pressure begins to drop rapidly until the wind suddenly picks up, and then begins to rise.

Thunderstorms can be divided into local, frontal, night, in the mountains. Most often, a person encounters local or thermal thunderstorms. These thunderstorms occur only in hot weather with high atmospheric humidity. As a rule, they occur in the summer at noon or afternoon (12-16 hours). The water vapor in the ascending stream of warm air condenses at a height, while a lot of heat is released and the ascending air streams are heated. The rising air is warmer than the surrounding air and expands until it becomes a thundercloud. Large storm clouds are constantly filled with ice crystals and water droplets. As a result of their crushing and friction between themselves and against the air, positive and negative charges are formed, under the influence of which a strong electrostatic field arises (the strength of the electrostatic field can reach 100,000 V / m). And the potential difference between the individual parts of the cloud, the clouds or the cloud and the earth reaches enormous values. When the critical tension of the electric air is reached, an avalanche-like air ionization occurs - a spark discharge of lightning.

A frontal thunderstorm occurs when masses of cold air enter an area dominated by warm weather. Cold air displaces warm air, while the latter rises to a height of 5-7 km. Warm layers of air invade vortices of various directions, a squall is formed, strong friction between the layers of air, which contributes to the accumulation of electric charges. The length of a frontal thunderstorm can reach 100 km. Unlike local thunderstorms, it usually gets colder after frontal thunderstorms. A night thunderstorm is associated with the cooling of the earth at night and the formation of eddy currents of the ascending air. The thunderstorm in the mountains is explained by the difference in solar radiation to which the southern and northern slopes of the mountains are exposed. Night and mountain thunderstorms are not strong and short.

Thunderstorm activity in different regions of our planet is different. World centers of thunderstorms: Java Island - 220, Equatorial Africa -150, Southern Mexico - 142, Panama - 132, Central Brazil - 106 thunderstorm days a year. Russia: Murmansk - 5, Arkhangelsk - 10, St. Petersburg - 15, Moscow - 20 thunderstorm days a year.

By type of lightning are divided into linear, pearl and ball. Pearl and ball lightning is quite rare.

The lightning discharge develops in a few thousandths of a second; at such high currents, the air in the zone of the lightning channel almost instantly heats up to a temperature of 30,000-33,000 ° C. As a result, the pressure rises sharply, the air expands - a shock wave occurs, accompanied by a sound impulse - thunder. Due to the fact that on high pointed objects the electric field strength created by the static electric charge of the cloud is especially high, a glow occurs; as a result, air ionization begins, a glow discharge occurs and reddish glow tongues appear, sometimes shortening and again lengthening. Do not attempt to extinguish these fires, as there is no combustion. At a high electric field strength, a beam of luminous filaments may appear - a corona discharge, which is accompanied by a hiss. Linear lightning can also occasionally occur in the absence of thunderclouds. It is no coincidence that the saying arose - "thunder from a clear sky."

The discovery of ball lightning

lightning discharge ball electric

As often happens, the systematic study of ball lightning began with a denial of their existence: at the beginning of the 19th century, all isolated observations known by that time were recognized as either mysticism or, at best, an optical illusion.

But already in 1838, a survey compiled by the famous astronomer and physicist Dominique Francois Arago was published in the Yearbook of the French Bureau of Geographic Longitudes. Subsequently, he initiated the experiments of Fizeau and Foucault to measure the speed of light, as well as the work that led Le Verrier to the discovery of Neptune. Based on the then known descriptions of ball lightning, Arago came to the conclusion that many of these observations cannot be considered an illusion. In the 137 years that have passed since the publication of Arago's review, new eyewitness accounts and photographs have appeared. Dozens of theories were created, extravagant, witty, those that explained some of the known properties of ball lightning, and those that could not withstand elementary criticism. Faraday, Kelvin, Arrhenius, Soviet physicists Ya.I. Frenkel and P.L. Kapitsa, many well-known chemists, and finally, specialists from the American National Commission for Astronautics and Aeronautics, NASA tried to investigate and explain this interesting and formidable phenomenon. And ball lightning still continues to be largely a mystery.

The nature of ball lightning

What facts must link scientists with a single theory in order to explain the nature of the occurrence of ball lightning? What are the limitations of observation on our imagination?

In 1966, NASA circulated a questionnaire to 2,000 people, the first part of which asked two questions: "Have you seen ball lightning?" and “Have you seen a linear lightning strike in the immediate vicinity?” The answers made it possible to compare the frequency of observation of ball lightning with the frequency of observation of ordinary lightning. The result turned out to be stunning: 409 out of 2,000 people saw a linear lightning strike near, and two times less than a ball lightning. There was even a lucky person who met ball lightning 8 times - another indirect proof that this is not at all such a rare phenomenon as it is commonly thought.

Analysis of the second part of the questionnaire confirmed many previously known facts: ball lightning has an average diameter of about 20 cm; does not glow very brightly; the color is most often red, orange, white. Interestingly, even observers who saw ball lightning up close often did not feel its thermal radiation, although it burns when touched directly.

There is such lightning from a few seconds to a minute; can penetrate into the premises through small holes, then restoring its shape. Many observers report that it throws out some kind of sparks and rotates. It usually hovers a short distance from the ground, although it has also been seen in the clouds. Sometimes ball lightning quietly disappears, but sometimes it explodes, causing noticeable destruction.

Ball lightning carries a lot of energy. True, deliberately overestimated estimates are often found in the literature, but even a modest realistic figure - 105 joules - is very impressive for a lightning bolt with a diameter of 20 cm. If such energy were spent only on light radiation, it could glow for many hours. Some scientists believe that lightning is constantly receiving energy from outside. For example, P.L. Kapitsa suggested that it occurs when a powerful beam of decimeter radio waves is absorbed, which can be emitted during a thunderstorm. In reality, for the formation of an ionized bunch, which is ball lightning in this hypothesis, the existence of a standing wave of electromagnetic radiation with a very high field strength in the antinodes is necessary. During the explosion of ball lightning, a power of a million kilowatts can develop, since this explosion proceeds very quickly. Explosions, however, a person can arrange even more powerful ones, but if compared with “calm” energy sources, then the comparison will not be in their favor.

Why ball lightning glows

Let us dwell on one more riddle of ball lightning: if its temperature is low (in the cluster theory it is considered that the temperature of ball lightning is about 1000°K), then why does it glow? It turns out that this can be explained.

During the recombination of clusters, the released heat is rapidly distributed among colder molecules. But at some point, the temperature of the "volume" near the recombined particles can exceed the average temperature of the lightning substance by more than 10 times. This "volume" glows like a gas heated to 10,000-15,000 degrees. There are relatively few such "hot spots", so the substance of ball lightning remains translucent. The color of ball lightning is determined not only by the energy of the solvate shells and the temperature of the hot "volumes", but also by the chemical composition of its substance. It is known that if ball lightning appears when linear lightning strikes copper wires, it is often colored blue or green - the usual "colors" of copper ions. The residual electrical charge explains such interesting properties of ball lightning as its ability to move against the wind, be attracted to objects and hang over high places.

Cause of ball lightning

To explain the conditions for the occurrence and properties of ball lightning, researchers have proposed many different hypotheses. One of the extraordinary hypotheses is the alien theory, which proceeds from the assumption that ball lightning is nothing more than a type of UFO. This assumption has a basis, since many eyewitnesses claim that ball lightning behaved like a living intelligent being. Most often, it looks like a ball, which is why in the old days it was called a fireball. However, this is not always the case: variants of ball lightning also occur. It can be the shape of a mushroom, a jellyfish, a bagel, a drop, a flat disk, an ellipsoid. The color of lightning is most often yellow, orange or red, white, blue, green, black is less common. The appearance of ball lightning does not depend on the weather. They can occur in different weather and completely independent of power lines. A meeting with a person or animal can also take place in different ways: mysterious balls either hover peacefully at some distance, or attack with fury, causing burns or even killing. After that, they may quietly disappear or explode loudly. It should be noted that the number of those killed and injured from fiery objects is approximately 9% of the total number of witnesses. In the case of a person being struck by ball lightning, in many cases no traces remain on the body, and the body of the person killed by lightning for an inexplicable reason does not decompose for a long time. In connection with this circumstance, a theory appeared that lightning is able to influence the course of the individual time of the organism.

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Inside the cloud

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 regions. 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.

Lightning as a natural phenomenon

The nature and causes of lightning

By type of lightning are divided into linear, pearl and ball. Pearl and ball lightning is quite rare.

The clouds spread their wings and closed 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 talk about this in detail.

What is lightning?

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

One thing is known for sure - it's a giant spark. Like a billion light bulbs exploded! Its length is huge - several hundred kilometers! And it is very far from us. That is why we first see it, and only then we hear it. Thunder is the "voice" of lightning. After all, light reaches us faster than sound.

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

How is lightning formed?

Lightning is usually born in a thundercloud, high above the ground. Thunderclouds appear when the air starts to get very hot. That's why after a heat wave there are amazing thunderstorms. Billions of charged particles literally flock to the place where it originates. And when there are very, very many of them, they flare up. That's where lightning comes from - from a thundercloud. She can hit the ground. The earth draws her. But it can break in the cloud itself. It all depends on what kind of lightning it is.

What are lightning bolts?

There are different types of lightning. And you need to know about it. This is not only 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, we will name only the most basic ones, attaching pictures of lightning to them:

Between thundercloud and earth. These are the very "ribbons" to which we are accustomed.

Between a tall tree and a cloud. The same "ribbon", but the blow is directed in the other direction.

Tape lightning - when not one "ribbon", but several in parallel.

Between cloud and cloud, or simply “play out” in one cloud. This type of lightning is often seen during thunderstorms. You just need to be careful.

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

Everyone has heard of ball lightning! Few people have seen them. There are even fewer who would like to see them. And there are people who do not believe in their existence. But fireballs do exist! Photographing such lightning is difficult. It explodes quickly, although it can “walk”, but it’s better for a person next to her not to move - it’s dangerous. So - not up to the camera here.

A type of lightning with a very beautiful name - "Fires of St. Elmo". But it's not really lightning. This is the glow that appears at the end of a thunderstorm on pointed buildings, lanterns, ship masts. Also a spark, only not damped and not dangerous. The fires of St. Elmo are 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 you can't see from Earth. They arise above the clouds and so far few people are studying them. These lightning bolts look like jellyfish.

Dotted lightning is almost not studied. It is extremely rare to see it. Visually, it really looks like a dotted line - as if the lightning-ribbon is melting.

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

Conclusion.

Even in ancient times, lightning was considered both a sign and the fury of the Gods. She was a mystery before and remains so now. No matter how they decompose it into the smallest atoms and molecules! And it's always amazingly beautiful!

Lightning. Report: Electrical phenomena in nature: lightning What is lightning definition

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Inside the cloud

Development of lightning

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The nature and causes of lightning

What is lightning?

How is lightning formed?

What are lightning bolts?

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