Message on the topic of lightning. How lightning occurs

Just recently the clear, clear sky was covered with clouds. The first drops of rain fell. And soon the elements demonstrated their power to the earth. Thunder and lightning pierced the stormy sky. Where do such phenomena come from? For many centuries, humanity has seen in them a manifestation of divine power. Today we know about the occurrence of such phenomena.

Origin of thunderclouds

Clouds appear in the sky from condensation rising high above the ground and float in the sky. The clouds are heavier and larger. They bring with them all the “special effects” that come with bad weather.

Thunderclouds differ from ordinary clouds in that they are charged with electricity. Moreover, there are clouds with a positive charge, and there are clouds with a negative one.

To understand where thunder and lightning come from, you need to rise higher above the ground. In the sky, where there are no obstacles to free flight, the winds blow stronger than on the ground. They are the ones who provoke the charge in the clouds.

The origin of thunder and lightning can be explained by just one drop of water. It has a positive charge of electricity in the center and a negative charge on the outside. The wind breaks it into pieces. One of them remains with a negative charge and has less weight. Heavier positively charged drops form the same clouds.

Rain and electricity

Before thunder and lightning appear in a stormy sky, the wind separates the clouds into positively and negatively charged ones. Rain falling on the ground takes some of this electricity with it. An attraction forms between the cloud and the surface of the earth.

The negative charge of the cloud will attract the positive one on the ground. This attraction will be located evenly on all surfaces that are elevated and conduct current.

And now the rain creates all the conditions for the appearance of thunder and lightning. The higher the object is to the cloud, the easier it is for lightning to break through to it.

Origin of lightning

The weather has prepared all the conditions that will help all its effects appear. She created the clouds from which thunder and lightning come.

A roof charged with negative electricity attracts the positive charge of the most exalted object. Its negative electricity will go into the ground.

Both of these opposites tend to attract each other. The more electricity there is in a cloud, the more it is in the most elevated object.

Accumulating in a cloud, electricity can break through the layer of air located between it and the object, and sparkling lightning will appear and thunder will thunder.

How lightning develops

When a thunderstorm rages, lightning and thunder accompany it incessantly. Most often, the spark comes from a negatively charged cloud. It develops gradually.

First, a small stream of electrons flows from the cloud through a channel directed toward the ground. In this place of the cloud, electrons moving at high speed accumulate. Due to this, electrons collide with air atoms and break them up. Individual nuclei are obtained, as well as electrons. The latter also rush to the ground. While they move along the channel, all primary and secondary electrons again split the air atoms standing in their way into nuclei and electrons.

The whole process is like an avalanche. It is moving upward. The air heats up and its conductivity increases.

More and more electricity from the cloud flows to the ground at a speed of 100 km/s. At this moment, lightning makes its way to the ground. Along this road laid by the leader, electricity begins to flow even faster. A discharge of enormous force occurs. Reaching its peak, the discharge decreases. The channel, heated by such a powerful current, glows. And lightning becomes visible in the sky. Such a discharge does not last long.

After the first discharge, a second one often follows along a laid channel.

How does thunder appear?

Thunder, lightning, and rain are inseparable during a thunderstorm.

Thunder occurs for the following reason. The current in the lightning channel is generated very quickly. The air becomes very hot. This makes it expand.

It happens so quickly that it resembles an explosion. Such a shock shakes the air violently. These vibrations lead to the appearance of a loud sound. This is where lightning and thunder come from.

As soon as the electricity from the cloud reaches the ground and disappears from the channel, it cools very quickly. Compressing air also causes thunder to sound.

The more lightning that passes through the channel (there can be up to 50 of them), the longer the air tremors. This sound is reflected from objects and clouds, and an echo occurs.

Why is there an interval between lightning and thunder?

In a thunderstorm, lightning is followed by thunder. Its delay from lightning occurs due to the different speeds of their movement. Sound moves at a relatively low speed (330 m/s). This is only 1.5 times faster than the movement of a modern Boeing. The speed of light is much greater than the speed of sound.

Thanks to this interval, it is possible to determine how far flashing lightning and thunder are from the observer.

For example, if 5 s passed between lightning and thunder, this means that the sound traveled 330 m 5 times. By multiplying, it is easy to calculate that the lightning from the observer was at a distance of 1650 m. If a thunderstorm passes closer than 3 km from a person, it is considered close. If the distance, in accordance with the appearance of lightning and thunder, is further, then the thunderstorm is distant.

Lightning in numbers

Thunder and lightning have been modified by scientists, and the results of their research are presented to the public.

It has been found that the potential difference preceding lightning reaches billions of volts. The current strength at the moment of discharge reaches 100 thousand A.

The temperature in the channel heats up to 30 thousand degrees and exceeds the temperature on the surface of the Sun. From the clouds to the ground, lightning travels at a speed of 1000 km/s (in 0.002 s).

The internal channel through which the current flows does not exceed 1 cm, although the visible one reaches 1 m.

There are about 1,800 thunderstorms occurring continuously around the world. The chance of being killed by lightning is 1:2000000 (the same as dying from falling out of bed). The chance of seeing ball lightning is 1 in 10,000.

Ball lightning

On the path to studying where thunder and lightning come from in nature, the most mysterious phenomenon is ball lightning. These round fiery discharges have not yet been fully studied.

Most often, the shape of such lightning resembles a pear or watermelon. It lasts up to several minutes. Appears at the end of a thunderstorm in the form of red clumps from 10 to 20 cm in diameter. The largest ball lightning ever photographed was about 10 m in diameter. It makes a buzzing, hissing sound.

It may disappear quietly or with a slight crash, leaving a burning smell and smoke.

The movement of lightning does not depend on the wind. They are drawn into closed spaces through windows, doors and even cracks. If they come into contact with a person, they leave severe burns and can be fatal.

Until now, the reasons for the appearance of ball lightning were unknown. However, this is not evidence of its mystical origin. Research is being conducted in this area that can explain the essence of this phenomenon.

By becoming familiar with phenomena such as thunder and lightning, you can understand the mechanism of their occurrence. This is a consistent and rather complex physical and chemical process. It is one of the most interesting natural phenomena that occurs everywhere and therefore affects almost every person on the planet. Scientists have solved the mysteries of almost all types of lightning and even measured them. Ball lightning today is the only unsolved mystery of nature in the field of formation of such natural phenomena.

Lightning is a powerful electrical discharge. It occurs when clouds or ground are highly electrified. Therefore, lightning discharges can occur either inside a cloud, or between neighboring electrified clouds, or between an electrified cloud and the ground. A lightning discharge is preceded by the occurrence of an electrical potential difference 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.

What causes clouds to electrify? 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 floes of ice. The top of a thundercloud can be at an altitude of 6-7 km, and the bottom can hang above the ground at an altitude 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 pieces of ice are in constant motion, caused by rising currents of warm air from the heated surface of the earth. Small pieces of ice are more easily carried away by rising air currents than large ones. Therefore, “nimble” small pieces of ice, moving to the top of the cloud, constantly collide with large ones. Each such collision leads to electrification. In this case, large pieces of ice are charged negatively, and small ones - positively. Over time, positively charged small pieces of ice end up at the top of the cloud, and negatively charged large ones end up at the bottom. In other words, the top of a thundercloud is positively charged and the bottom is negatively charged.

The electric field of a 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 other charged particles rush after them. This is how a lightning discharge occurs.

During this discharge, enormous 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 external manifestations of these atmospheric phenomena in the form of lightning.

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

We ourselves can simulate lightning, even a miniature one. The experiment should be carried out in a dark room, otherwise nothing will be visible. We will need two oblong balloons. Let's inflate them and tie them. Then, making sure that they do not touch, we simultaneously rub them with a woolen cloth. The air filling them is electrified. If the balls are brought closer together, leaving a minimum gap between them, then sparks will begin to jump from one to another through a thin layer of air, creating light flashes. At the same time, we will hear a faint crackling sound - 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 forming a conductive channel for a lightning discharge is called its “step leader”. Each of these “steps” is a place where 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 whose dielectric is air, and the plates are clouds and earth. The capacity of such a capacitor is small - approximately 0.15 μF, but the energy reserve is enormous, 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 in shape and direction of discharge. Discharges can occur:

• between a thundercloud and the ground,
• between two clouds
• inside the cloud,
• leaving the clouds for clear skies.

Just recently the clear, clear sky was covered with clouds. The first drops of rain fell. And soon the elements demonstrated their power to the earth. Thunder and lightning pierced the stormy sky. Where do such phenomena come from? For many centuries, humanity has seen in them a manifestation of divine power. Today we know about the occurrence of such phenomena.

Origin of thunderclouds

Clouds appear in the sky from condensation rising high above the ground and float in the sky. The clouds are heavier and larger. They bring with them all the “special effects” that come with bad weather.

Thunderclouds differ from ordinary clouds in that they are charged with electricity. Moreover, there are clouds with a positive charge, and there are clouds with a negative one.

To understand where thunder and lightning come from, you need to rise higher above the ground. In the sky, where there are no obstacles to free flight, the winds blow stronger than on the ground. They are the ones who provoke the charge in the clouds.

The origin of thunder and lightning can be explained by just one drop of water. It has a positive charge of electricity in the center and a negative charge on the outside. The wind breaks it into pieces. One of them remains with a negative charge and has less weight. Heavier positively charged drops form the same clouds.

Rain and electricity

Before thunder and lightning appear in a stormy sky, the wind separates the clouds into positively and negatively charged ones. Rain falling on the ground takes some of this electricity with it. An attraction forms between the cloud and the surface of the earth.

The negative charge of the cloud will attract the positive one on the ground. This attraction will be located evenly on all surfaces that are elevated and conduct current.

And now the rain creates all the conditions for the appearance of thunder and lightning. The higher the object is to the cloud, the easier it is for lightning to break through to it.

Origin of lightning

The weather has prepared all the conditions that will help all its effects appear. She created the clouds from which thunder and lightning come.

A roof charged with negative electricity attracts the positive charge of the most exalted object. Its negative electricity will go into the ground.

Both of these opposites tend to attract each other. The more electricity there is in a cloud, the more it is in the most elevated object.

Accumulating in a cloud, electricity can break through the layer of air located between it and the object, and sparkling lightning will appear and thunder will thunder.

How lightning develops

When a thunderstorm rages, lightning and thunder accompany it incessantly. Most often, the spark comes from a negatively charged cloud. It develops gradually.

First, a small stream of electrons flows from the cloud through a channel directed toward the ground. In this place of the cloud, electrons moving at high speed accumulate. Due to this, electrons collide with air atoms and break them up. Individual nuclei are obtained, as well as electrons. The latter also rush to the ground. While they move along the channel, all primary and secondary electrons again split the air atoms standing in their way into nuclei and electrons.

The whole process is like an avalanche. It is moving upward. The air heats up and its conductivity increases.

More and more electricity from the cloud flows to the ground at a speed of 100 km/s. At this moment, lightning makes its way to the ground. Along this road laid by the leader, electricity begins to flow even faster. A discharge of enormous force occurs. Reaching its peak, the discharge decreases. The channel, heated by such a powerful current, glows. And lightning becomes visible in the sky. Such a discharge does not last long.

After the first discharge, a second one often follows along a laid channel.

How does thunder appear?

Thunder, lightning, and rain are inseparable during a thunderstorm.

Thunder occurs for the following reason. The current in the lightning channel is generated very quickly. The air becomes very hot. This makes it expand.

It happens so quickly that it resembles an explosion. Such a shock shakes the air violently. These vibrations lead to the appearance of a loud sound. This is where lightning and thunder come from.

As soon as the electricity from the cloud reaches the ground and disappears from the channel, it cools very quickly. Compressing air also causes thunder to sound.

The more lightning that passes through the channel (there can be up to 50 of them), the longer the air tremors. This sound is reflected from objects and clouds, and an echo occurs.

Why is there an interval between lightning and thunder?

In a thunderstorm, lightning is followed by thunder. Its delay from lightning occurs due to the different speeds of their movement. Sound moves at a relatively low speed (330 m/s). This is only 1.5 times faster than the movement of a modern Boeing. The speed of light is much greater than the speed of sound.

Thanks to this interval, it is possible to determine how far flashing lightning and thunder are from the observer.

For example, if 5 s passed between lightning and thunder, this means that the sound traveled 330 m 5 times. By multiplying, it is easy to calculate that the lightning from the observer was at a distance of 1650 m. If a thunderstorm passes closer than 3 km from a person, it is considered close. If the distance, in accordance with the appearance of lightning and thunder, is further, then the thunderstorm is distant.

Lightning in numbers

Thunder and lightning have been modified by scientists, and the results of their research are presented to the public.

It has been found that the potential difference preceding lightning reaches billions of volts. The current strength at the moment of discharge reaches 100 thousand A.

The temperature in the channel heats up to 30 thousand degrees and exceeds the temperature on the surface of the Sun. From the clouds to the ground, lightning travels at a speed of 1000 km/s (in 0.002 s).

The internal channel through which the current flows does not exceed 1 cm, although the visible one reaches 1 m.

There are about 1,800 thunderstorms occurring continuously around the world. The chance of being killed by lightning is 1:2000000 (the same as dying from falling out of bed). The chance of seeing ball lightning is 1 in 10,000.

Ball lightning

On the path to studying where thunder and lightning come from in nature, the most mysterious phenomenon is ball lightning. These round fiery discharges have not yet been fully studied.

Most often, the shape of such lightning resembles a pear or watermelon. It lasts up to several minutes. Appears at the end of a thunderstorm in the form of red clumps from 10 to 20 cm in diameter. The largest ball lightning ever photographed was about 10 m in diameter. It makes a buzzing, hissing sound.

It may disappear quietly or with a slight crash, leaving a burning smell and smoke.

The movement of lightning does not depend on the wind. They are drawn into closed spaces through windows, doors and even cracks. If they come into contact with a person, they leave severe burns and can be fatal.

Until now, the reasons for the appearance of ball lightning were unknown. However, this is not evidence of its mystical origin. Research is being conducted in this area that can explain the essence of this phenomenon.

By becoming familiar with phenomena such as thunder and lightning, you can understand the mechanism of their occurrence. This is a consistent and rather complex physical and chemical process. It is one of the most interesting natural phenomena that occurs everywhere and therefore affects almost every person on the planet. Scientists have solved the mysteries of almost all types of lightning and even measured them. Ball lightning today is the only unsolved mystery of nature in the field of formation of such natural phenomena.

Lightning discharges ( lightning) is the most common source of naturally occurring powerful 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 a thundercloud. Lightning The cause of lightning is the formation of a large volumetric electric charge.

Ordinary source of lightning are thunderstorm cumulonimbus clouds that carry an accumulation of positive and negative electrical charges in the upper and lower parts of the cloud and form electric fields of increasing intensity around this cloud. The formation of such space charges of different polarities in the cloud (cloud polarization) is associated with condensation due to the cooling of water vapor of rising warm air flows on positive and negative ions (condensation centers) and the separation of charged droplets of moisture in the cloud under the influence of intense ascending thermal air flows. Due to the fact that several charge clusters isolated from each other are formed in the cloud (mainly charges of negative polarity accumulate in the lower part of the cloud).

Lightning discharges can be divided into several types based on external signs. Regular type - linear lightning, with varieties: ribbon, rocket, zigzag and branched. The rarest type of discharge is ball lightning. There are known discharges called “St. Elmo’s Fire” and “Glow of the Andes.” Lightning usually occurs multiple times, i.e. consists of several single discharges developing along the same path, and each discharge, just like the discharge obtained in laboratory conditions, begins with a leader and ends with a reverse (main) discharge. The descent speed of the leader of the first single discharge is approximately 1500 km/s, the speed of the leaders of subsequent discharges reaches 2000 km/s, and the speed of the reverse discharge varies within 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, so part of the charges of this center flows 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 head is small and, to a first approximation, the channel can be considered uniformly charged with a linear charge density S. The total charge in the leader channel in this case is equal to Q = S*l, where l is the channel length , and its value is usually 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 channel moves, under the influence of the electric field it creates in the ground, charges shift, and charges opposite in sign to the leader charges (usually positive charges) tend to be located as close as possible to the head of the leader channel. In the case of homogeneous soil, these charges accumulate directly under the leader channel.

If the soil is heterogeneous and its main part has a high resistivity, charges are concentrated in areas with high conductivity (rivers, groundwater). In the presence of grounded, towering objects (lightning rods, chimneys, tall buildings, rain-drenched trees), the charges are drawn to the top of the object, creating significant field strength there. At the first stages of development of the leader channel, the electric field strength at its head is determined by the leader’s own charges and clusters of space charges located under the cloud. The leader's trajectory is not connected with earthly objects. As the leader descends, accumulations of charges on the ground and elevated objects begin to have 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 greatest, and the leader is oriented towards one of the ground objects. Naturally, in this case, elevated objects and areas of land with increased conductivity are predominantly affected (selective susceptibility). From very high objects, counter leaders develop towards the leader, the presence of which helps to orient the lightning towards a 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 almost equal to the ground potential. At the head of the upwardly developing reverse discharge there is an area of ​​​​increased electric field strength, under the influence of which a restructuring of the channel occurs, 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 a 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 to the reverse discharge is in many ways similar to the process of a vertical charged wire shorting to ground.

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

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

By measuring this magnetization, it is possible to determine the maximum value of the magnetizing current using calibration curves. Measurements with magnetic recorders do not provide great accuracy, but this disadvantage is partially compensated by the huge number of measurements, which currently number in the tens of thousands. By placing a frame closed to an inductive coil near the affected object, you can measure the slope of the lightning current using a magnetic recorder placed inside the coil. Measurements have shown that lightning currents vary widely from several kiloamperes to hundreds of kiloamperes, therefore the measurement results are presented in the form of probability curves (distribution functions) of lightning currents, on which the probability of lightning currents with a maximum value exceeding the value indicated is plotted on the abscissa axis. ordinate.

In Ukraine, when calculating lightning protection, the curve is used. For mountainous areas, the ordinates of the curve are reduced by 2 times, since at short 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. It is much more difficult to experimentally determine the steepness and duration of a lightning current pulse, so the amount of experimental data on these parameters is relatively small. The duration of the lightning current pulse is mainly determined by the time of propagation 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 a lightning current pulse is close to 50 μs, which determined the choice of the standard pulse.

The most important from the point of view of assessing the lightning resistance of RES are: the amount of charge transferred by lightning, the current in the lightning channel, the number of repeated strikes along one channel and the intensity of lightning activity. All these parameters are not determined unambiguously and are probabilistic in nature. The charge transferred by lightning fluctuates during the discharge process in the range from fractions of a coulomb to several tens of coulombs. The average charge dropped into the ground by repeated 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 channel, which amounts to 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 into television towers the charge reaches 160 C.

When lightning strikes into the ground, the overwhelming majority (85 - 90%) transfer a negative charge to the ground. The charge flowing into the ground during multiple lightning varies from fractions of a coulomb to 100 C or 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 of the ground. The intensity of thunderstorm activity in different climatic regions varies greatly. As a rule, the number of thunderstorms throughout the year is minimal in the northern regions and gradually increases to the south, where increased air humidity and high temperatures contribute to the formation of thunderclouds. However, this trend is not always followed. There are centers of thunderstorm activity in mid-latitudes (for example, in the Kyiv 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 maps of thunderstorm activity, on which lines of equal duration of thunderstorms are plotted - isokeranic lines. The average duration of thunderstorms per thunderstorm day for the territory of the European part of Russia and Ukraine is 1.5-2 hours.

In the warm season, thunderstorms occur quite often - impressive natural phenomena, however, causing not only curiosity, but also fear. During a thunderstorm, electrical discharges arise between the clouds and the Earth, which are clearly visible and audible: lightning is observed in the form of branching luminous lines piercing the sky, and a little later we hear the rolling sound of thunder. In this case, as a rule, there is heavy rain, accompanied by heavy winds and hail. Thunderstorms are one of the most dangerous atmospheric phenomena: only floods are associated with a greater number of human casualties than thunderstorms. Interest in the study of natural electricity arose in ancient times. The first to explore the electrical nature of lightning was Benjamin Franklin, an American politician, but at the same time a scientist and inventor. It was he who proposed the first lightning rod project back in 1752. Let's try to figure out what danger a thunderstorm poses, and what you need to know and do to protect yourself.

At the same time, there are about one and a half thousand thunderstorms on Earth, the average intensity of discharges is estimated as 100 lightning strikes per second or over 8 million per day. Thunderstorms are distributed unevenly across the planet's surface. There are approximately ten times fewer thunderstorms over the ocean than over the continents. About 78% of all lightning discharges are concentrated in the tropical and equatorial zone (from 30° north latitude to 30° south latitude). Maximum thunderstorm activity occurs in Central Africa. In the polar regions of the Arctic and Antarctic and over the poles, there are practically no thunderstorms. The intensity of thunderstorms follows the sun, with maximum thunderstorms occurring in the summer (at mid-latitudes) and during the daytime afternoon hours. The minimum of recorded thunderstorms occurs before sunrise. Thunderstorms are also influenced by geographic features of the area: strong thunderstorm centers are located in the mountainous regions of the Himalayas and Cordillera.

During a thunderstorm, a huge voltage arises between the clouds and the Earth, reaching a value of 1000000000 V. At this voltage, the air is ionized, turning into plasma, and a giant electric discharge occurs with a current of up to 300,000 A. The temperature of the plasma in lightning exceeds 10,000 ° C. Lightning manifests itself as a bright flash of light and a shock wave of sound, which is heard a little later as thunder. Lightning is also dangerous because it can strike completely unexpectedly, and its path can be unpredictable. However, the distance to the thunderstorm front and the speed of its approach or retreat can be easily determined using a stopwatch. To do this, you need to detect the time between the flash of lightning and the clap of thunder. The speed of sound in air is approximately 340 m/s, so if you hear thunder 10 seconds after the flash of light, then the thunderstorm front is approximately 3.4 km away. By measuring in this way the time between a flash of light and thunder, as well as the time between different lightning strikes, it is possible to determine not only the distance to them, but also the speed of approach or retreat of the thunderstorm front:

where is the speed of sound, is the time between the flash of light and the thunder of the first lightning, is the time between the flash of light and the thunder of the second lightning, is the time between lightning. If the speed value turns out to be positive, then the thunderstorm front is approaching, and if it is negative, it is moving away. It must be taken into account that the direction of the wind does not always coincide with the direction of movement of the thunderstorm.

If you do find yourself in a thunderstorm, you should follow a number of simple rules to protect yourself:

Firstly, during a thunderstorm it is advisable to avoid open areas. Lightning is more likely to strike the highest point; a lonely person in a field is that very point. If for some reason you are left alone in a field with a thunderstorm, hide in any possible depression: a ditch, hollow or the lowest place in the field, squat down and bend your head. It should be remembered that sandy and stone soils have lower electrical conductivity, which means they are safer than clay soils. You should not hide under isolated trees, as they are primarily susceptible to lightning strikes. And if you are in the forest, then it is best to hide under low-growing trees with a dense crown.

Secondly, during a thunderstorm, avoid water, as natural water is a good conductor of current. A lightning strike spreads around a body of water within a radius of about 100 meters. It often hits the banks. Therefore, during a thunderstorm, it is necessary to move away from the shore, and you cannot swim or fish. In addition, during a thunderstorm, it is advisable to get rid of metal objects. Watches, chains, and even an umbrella open over your head are potential targets for a strike. There are known cases of lightning striking a bunch of keys in a pocket.

Third, if a thunderstorm finds you in the car, then it protects quite well from lightning, since even when lightning strikes, the discharge occurs on the surface of the metal. Therefore, close the windows, turn off the radio and GPS navigator. Do not touch any metal parts of the car. It is very dangerous to talk on a cell phone during a thunderstorm. It is best to turn it off during a thunderstorm. There have been cases when an incoming call was caused by lightning. A bicycle and a motorcycle, unlike a car, will not save you from a thunderstorm. It is necessary to dismount, place the vehicle on the ground and move away to a distance of approximately 30 m from it.

There are different types of lightning in nature: linear (ground-based, intracloud, lightning in the upper atmosphere) and ball lightning - luminous formations floating in the air, a uniquely rare natural phenomenon. If the nature of linear lightning is clear and its behavior is more predictable, then the nature of ball lightning still holds many secrets. Despite the fact that the probability of a person being hit by ball lightning is small, it nevertheless poses a serious danger, since there are no reliable methods and rules for protecting against it.

The behavior of ball lightning is unpredictable. It can suddenly appear anywhere, including indoors. There have been cases of ball lightning appearing from a telephone handset, an electric razor, a switch, a socket, or a loudspeaker. Quite often it enters buildings through pipes, open windows and doors. There are known cases when ball lightning penetrated into a room through narrow cracks and even a keyhole. The dimensions of ball lightning can vary: from a few centimeters to several meters. In most cases, ball lightning easily hovers or rolls above the ground, sometimes jumping, but it can also hover above the surface of the earth. According to eyewitnesses, ball lightning reacts to wind, draft, ascending and descending air currents. But this is not always the case: there are cases where ball lightning did not react in any way to air currents.

Ball lightning can suddenly appear and just as suddenly disappear without causing harm to a person or premises. For example, it can fly into a window and fly out of the room through an open door or chimney, flying past you. However, you should know that any contact with a person leads to severe injuries, burns, and in most cases, death. Therefore, if you see ball lightning, the safest thing to do is to move as far away from it as possible.

In addition, ball lightning often explodes. The resulting shock air wave can injure a person or lead to destruction. For example, there are known cases of lightning explosions in stoves and chimneys, which led to serious damage. The temperature inside ball lightning reaches 5000 °C, so it can cause a fire. Statistics on the behavior of ball lightning indicate that in 80% of cases the explosions were not dangerous, but serious consequences still occurred in 10% of the explosions.

Using the proposed method, we suggest that you calculate the distance to the lightning discharge and its speed if the first thunder was heard 20 seconds after observing the first lightning, and the second 15 seconds after observing the second lightning. The time between lightning flashes is 1 minute.