What is lightning? How is this natural phenomenon formed and where does it come from? Atmospheric physics: how, why and where lightning comes from
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Lightning is a giant electrical spark discharge in the atmosphere that can usually occur during a thunderstorm, manifested by a bright flash of light and accompanying thunder. Lightning has also been recorded on Venus, Jupiter, Saturn and Uranus, etc. The current in a lightning discharge reaches 10-100 thousand amperes, the voltage ranges from tens of millions to billions of volts, however, only 47.3% die after lightning strikes a person. of people
Story:
The electrical nature of lightning has been revealed in research American physicist B. Franklin, based 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.
Physical properties of lightning:
The average length of lightning is 2.5 km, some discharges extend up to 20 km in the atmosphere.
Lightning Formation:
Most often, lightning occurs in cumulonimbus clouds, then they are called thunderstorms; Lightning sometimes forms in nimbostratus clouds, as well as during volcanic eruptions, tornadoes and dust storms.
Typically observed are linear lightning, which belongs 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 km?. 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 for a cloud to form in a relatively small (but not less than some critical) volume. electric field(see atmospheric electricity) with a intensity sufficient to initiate an electrical discharge (~ 1 MV/m), and in a significant part of the cloud there would be a field with an average intensity sufficient to maintain the initiated discharge (~ 0.1-0.2 MV/ m). In the lightning Electric Energy clouds transform into heat, light and sound.
Ground lightning:
The development process of ground lightning consists of several stages. At the first stage, in the zone where the electric field reaches critical value, impact ionization begins, created initially by free charges, always present in small quantities in the air, which, under the influence of an electric field, acquire significant speeds towards the ground and, colliding with the molecules that make up the air, ionize them.
According to more modern concepts, ionization of the atmosphere for the passage of a discharge occurs under the influence of high-energy cosmic radiation - particles with energies of 1012-1015 eV, forming a wide air shower (EAS) with a decrease in the breakdown voltage of the air by an order of magnitude from that under normal conditions.
According to one hypothesis, particles trigger a process called runaway electron breakdown (the “trigger” of the process is cosmic rays). Thus, electron avalanches arise, turning into threads of electrical discharges - streamers, which are well-conducting channels, which, merging, give rise to a bright thermally ionized channel with high conductivity - a stepped lightning leader.
The movement of the leader towards the 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 greatly weakens; 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 as the leader moves to the surface of the earth at an average speed of 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 20000-30000 °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. But the ground is not charged, so it is generally accepted that a lightning discharge occurs from the cloud towards the ground (from top to bottom).
The main discharge often discharges only part of the cloud. Charges located at high altitudes can give rise to a new (swept) leader moving continuously at speeds of thousands of kilometers per second. The brightness of its glow is close to the brightness of the stepped leader. When the swept leader reaches the surface of the earth, a second main blow follows, similar to the first. Typically, lightning includes several repeated discharges, but their number can reach several dozen. The duration of multiple lightning can exceed 1 second. The displacement of the channel of multiple lightning by the wind creates the so-called ribbon lightning - a luminous strip.
Intra-cloud lightning:
Intracloud lightning usually includes only leader stages; their length ranges from 1 to 150 km. The proportion of intracloud lightning increases as it moves toward the equator, changing from 0.5 in temperate latitudes to 0.9 in the equatorial zone. The passage of lightning is accompanied by changes in electric and magnetic fields and radio emissions, the so-called atmospherics.
Flight from Kolkata to Mumbai.
The probability of a ground object being struck by lightning increases as its height increases and with an increase in the electrical conductivity of the soil on the surface or at some depth (the action of a lightning rod is based on these factors). If there is an electric field in the cloud that is sufficient to maintain a discharge, but not sufficient to cause it to occur, a long metal cable or an airplane can act as the lightning initiator - especially if it is highly electrically charged. In this way, lightning is sometimes “provoked” in nimbostratus and powerful cumulus clouds.
Lightning in the upper atmosphere:
In 1989 it was discovered special kind lightning - elves, lightning in the upper atmosphere. In 1995, another type of lightning in the upper atmosphere was discovered - jets.
Elves:
Elves (Emissions of Light and Very Low Frequency Perturbations from Electromagnetic Pulse Sources) are huge but faintly luminous flash cones with a diameter of about 400 km, which appear directly from the top of a thundercloud. The height of the elves can reach 100 km, the duration of the flashes is up to 5 ms (on average 3 ms).
Jets:
Jets are tube-cones of blue color. The height of the jets can reach 40-70 km (the lower boundary of the ionosphere); jets live relatively longer than elves.
Sprites:
Sprites are difficult to distinguish, but they appear in almost any thunderstorm at an altitude of 55 to 130 kilometers (the altitude of “ordinary” lightning is no more than 16 kilometers). This is a kind of lightning striking upward from a cloud. This phenomenon was first recorded in 1989 by accident. Currently, very little is known about the physical nature of sprites.
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 a shock of air, 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.[...]
A visible electrical discharge between clouds, separate parts of one cloud, or between a cloud and the earth's surface. The most common typical look lightning - linear M. - spark discharge with branches, an average length of 2-3 km, and sometimes up to 20 km or more; the diameter of M is about tens of centimeters. Flat, square and ball M. have a special character (see). Next we talk about linear M.[...]
In addition to linear, there are, although much less frequently, lightning of other types. Of these, we will consider one, the most interesting - ball lightning.[...]
In addition to linear lightning, flat lightning is observed in thunderclouds. The observer sees a cumulonimbus cloud flare up from within in a considerable thickness. Flat lightning is the cumulative effect of the simultaneous action of a large number of corona discharges in the intracloud mass. In this case, a significant part of the cloud is illuminated from the inside, and outside the cloud a reddish glow emanates in the form of a flash. Flat lightning does not create acoustic effects. Flat lightning, illuminating the cloud from the inside, should not be confused with lightning - reflections of other lightning, sometimes beyond the horizon, illuminating the cloud from the outside, as well as the sky near the horizon.[...]
FLAT ZIPPER. An electrical discharge on the surface of clouds, which is not linear in nature and apparently consists of luminous quiet discharges emitted by individual droplets. The PM spectrum is striped, mainly consisting of nitrogen bands. PM should not be confused with lightning, which is the illumination of distant clouds by linear lightning.[...]
BALL LIGHTNING. A phenomenon sometimes observed during a thunderstorm; is a brightly glowing ball of various colors and sizes (usually on the order of tens of centimeters near the earth’s surface). Sh. M. appears after a linear lightning discharge; moves in the air slowly and silently, can penetrate into buildings through cracks, chimneys, pipes, and sometimes bursts with a deafening crash. The phenomenon can last from a few seconds to half a minute. This is a little-studied physico-chemical process in the air, accompanied by an electrical discharge.[...]
If ball lightning consists of charged particles, then in the absence of an influx of energy from the outside, these particles must recombine and quickly transfer the heat released to the surrounding atmosphere (recombination time 10 10-10-11 s, and taking into account the time of energy removal from the volume - no more than 10 -3 s). Thus, after the current stops, the linear lightning channel cools down and disappears in a time of the order of several milliseconds. [...]
So, ball lightning does not always occur in connection with a linear lightning discharge, although perhaps in most cases this is the case. It can be assumed that it occurs where significant amounts accumulate and cannot be neutralized. electric charges. Slow spreading of these charges leads to coronation or the appearance of St. Elmo's fire, fast spreading - to the appearance of ball lightning. This can happen, for example, in places where the linear lightning channel is suddenly interrupted and a significant charge is thrown into a relatively small area of air by a powerful corona discharge. However, probably similar situations can arise without a linear lightning discharge.[...]
Further, ball lightning is silent. Its movement is completely silent or accompanied by a faint hissing or crackling sound. Although in rare cases ball lightning flies several tens of meters per second and forms a short luminous stripe several meters long (this is due to the inability of our visual analyzers to distinguish events separated by a time interval of less than 0.1 s), nevertheless this stripe cannot be confused with a channel linear lightning, the formation of which is accompanied by deafening thunder. The consequences of a ball lightning explosion are also, as a rule, much weaker than those of a linear lightning discharge. In particular, an explosion is most often a bang, in strong cases a rifle or pistol shot, while thunder from close linear lightning is more reminiscent in strength of the roar of an exploding shell.[...]
Since ball lightning is most often associated with lightning and thunderstorms, it was natural for early researchers to try to use atmospheric lightning in laboratory experiments. In the works, the first scientifically recorded study of a phenomenon similar to ball lightning is associated with the name of Professor Richman from St. Petersburg. It is believed that the discharge, similar to ball lightning, was accidentally formed during a thunderstorm. This case became widely known among researchers of phenomena associated with linear and ball lightning. This fame is due not so much to the results of the experiment itself, but to the fact that ball lightning was reported to have struck Richmann in the forehead, as a result of which he died on August 6, 1753. [...]
The appearance of ball lightning is usually associated with thunderstorm activity. Statistics show that 73% of 513 cases according to McNelli, 62% of 112 cases according to Raleigh and 70% of 1006 according to Stakhanov are related to thunderstorm weather. According to Barry, in 90% of the cases he collected, ball lightning was observed during a thunderstorm. At the same time, many studies reported that ball lightning occurred immediately after a linear lightning strike.[...]
Note that ball lightning did not appear immediately, but 3-4 s after the discharge of linear lightning. In addition, the author of the letter provided too many details of the event, so that what he saw can hardly be considered a hallucination. Such observations are not isolated.[...]
From the point of view under consideration, the formation of ball lightning from a linear lightning channel is presented as follows. Some hot dissociated air expelled shock wave from the linear lightning channel, mixes with the surrounding cold air and cools so quickly that the small fraction of atomic oxygen in it does not have time to recombine. For the reasons stated above, this oxygen should turn into ozone in 10 5 s. The permissible proportion of hot air in the resulting mixture is greatly limited, since the temperature of the mixture should not exceed 400 K, otherwise the resulting ozone will quickly decompose. This limits the amount of ozone in the mixture to about 0.5-1%. To obtain higher ozone concentrations, the excitation of oxygen by lightning current is considered. The author concludes that this can lead to a mixture containing up to 2.6% ozone. Thus, in this case, the lightning discharge is actually included in the proposed scheme as required part paintings. This favorably distinguishes the hypothesis under consideration from other chemical hypotheses, where the discharge itself does not, at first glance, play any role and it remains unclear why ball lightning is so closely related to thunderstorms.[...]
Real ball lightning usually appears during a thunderstorm, often with strong winds. The linear lightning channel is resumed by the swept leader every 30-40 ms, and it exists for no more than 0.1 - 0.2 s.[...]
The occurrence of ball lightning can be represented from this point of view as follows. After a linear lightning strike, a small part of its channel remains, heated to a high temperature. When the discharge ends, the current does not stop. Now the bright spark discharge is replaced by a dark, non-luminous discharge, in which the current flows along the extinguished linear lightning channel. The air here contains an increased amount of ions that have not had time to recombine. The conductivity of this column of air filled with ions, the width of which is assumed to be much larger than the initial diameter of the lightning channel, is assumed to be of the order of 10“3 - -10 4 m 1 Ohm 1. The movement of ball lightning arises from the action of the magnetic field of the current on the same current when cylindrical symmetry is violated. The explosion is considered as an implosion resulting from the cessation of current. However, with a sharp and strong increase in current, an explosion in the usual sense of the word can occur. Silent extinction occurs when the current slowly stops. [...]
It is known that a discharge of ordinary linear lightning has a complex, sometimes very tortuous trajectory in the atmosphere. The development of a discharge can be studied by photography using high-speed cameras. In cameras used to photograph lightning, the film can move quickly in a horizontal or vertical direction. Typical film speed is 500-1000 cm/s. This speed is necessary because the speed of movement of the lightning channel reaches a value of 5 108 cm/s.[...]
It is generally accepted that bead lightning arises from an anomalous lightning channel between two clouds. The discharge channel of ordinary lightning breaks up into a number of luminous fragments unrelated to each other. The completed form of bead lightning consists of a large number of parts, apparently existing simultaneously, and is not the apparent result of the movement of a single luminous object with periodically varying brightness. To observers, it appears as a stable glow along the trajectory of ordinary linear lightning, which exists for quite some time. for a long time after the last outbreak. According to reports, the lifetime of such beaded lightning is 1-2 s.[...]
According to reports, bead lightning usually appears between two clouds, forming a broken line of luminous "spots" that remains for some time after the appearance of normal line lightning. The luminous "spots" have the same angular size as the diameter of the line lightning channel, and, according to - Apparently, they have a spherical shape. Each “spot” is separated from the neighboring one by a non-luminous area. The size of the dark gap can be several diameters of the luminous parts.[...]
The appearance of ball lightning was observed when linear lightning struck water. I. A. Gulidov from Kharkov told us about it. [...]
First of all, we note that ball lightning does not always appear after a certain discharge of linear lightning. According to our data, in 75% of cases the observer cannot definitely indicate whether a linear lightning strike preceded the appearance of ball lightning. Apparently, it can appear as a result of a distant discharge of linear lightning, which is not detected by an observer, for example, during a discharge between clouds, and then descend down to the ground. In many cases (approximately 20-30%) it is not associated with a thunderstorm at all. According to our data, this happens in approximately 25% of cases, approximately the same figure - 30% - is given by a survey in the UK. However, even in cases where ball lightning appears after a certain strike of linear lightning, the observer does not always see the flash; sometimes he only hears thunder. This was the case, for example, with all four eyewitnesses who saw ball lightning in the Kremlin (see No. 1). Proponents of the theory of image inertia must, therefore, admit that an afterimage can arise not only from a flash of lightning, but also from the sound of thunder. Sometimes a flash of lightning is separated from the appearance of ball lightning by several seconds, which is required for the ball lightning to come into the field of view of the observer or for him to pay attention to it. Here are a few examples from the correspondence received.[...]
If, as is often believed, ball lightning is formed by a discharge of linear lightning, then the probability of its observation can be significantly increased. To do this, it is enough to organize regular monitoring of those objects that are often struck by linear lightning (high-rise spiers, television towers, power line supports, etc.). Thus, the frequency of linear lightning hitting the Ostankino Tower is several dozen cases per year. If the probability of ball lightning appearing during a linear lightning discharge is not less than 0.1-0.01, then there is a good chance of detecting ball lightning within one season. In this case, of course, it is necessary to assume that lightning striking the tower does not exclude the appearance of ball lightning for one reason or another. In addition, it is necessary to use appropriate equipment, since, if we take into account the large height of the tower, the angular size of ball lightning (when observed from the ground) will be very small, and its brightness is negligible compared to the brightness of the linear lightning channel.[...]
A drop of molten metal, falling into the channel of linear lightning, can also form a luminous sphere, the movement of which, however, will differ significantly from the movement of ball lightning. Due to their high specific gravity, such drops will inevitably flow down or fall quickly, while ball lightning can float, move horizontally, or rise. Even if we assume that a molten drop of metal acquires a significant impulse at the moment of formation, its movement, due to its large inertia, will bear little resemblance to the movements that are usually attributed to ball lightning. Finally, in this case we can only talk about ball lightning small size, the diameter of which is several centimeters, while the vast majority of lightning is much larger (10-20 cm, and sometimes more).[...]
Only a few eyewitnesses who observed ball lightning also see the moment of its origin. Of the 1,500 responses to the first questionnaire, only 150 people gave a definite answer to the question of how ball lightning occurs. In the responses to the second questionnaire we received a detailed description of almost all of these events.[...]
There is no doubt that the origin of ball lightning in most cases is closely related to the discharge of linear lightning. Regarding the first question, there is practically no doubt that, at least in those cases when the birth of ball lightning is accompanied by a discharge of linear lightning, energy is supplied to it through the linear lightning channel, and then, according to the cluster hypothesis, is stored in the form of ionization energy of cluster ions. Assuming that the potential difference between the cloud and the ground can reach 108 V, and the charge carried by a lightning discharge is 20-30 K, we find that the energy released in a linear lightning discharge is (2h-3) 109 J. With an average channel length 3-5 km energy per unit length is about 5-105 J/m. During charging, this energy is distributed along the channel and can give rise to ball lightning. In some cases, it can be transmitted through conductors to a considerable distance from the point of linear lightning strike.[...]
The most likely place for the occurrence of ball lightning is, in our opinion, the corona of a linear lightning discharge. Like any conductor under high potential, the linear lightning channel is surrounded by a corona discharge, which occupies a wide area (about 1 m in diameter), in which a large number of ions are formed during the discharge. The temperature of this region is many times lower than the temperature of the lightning channel and hardly exceeds, especially in its peripheral parts, several hundred degrees. Under such conditions: ions can easily become covered with hydration shells, turning into ionic hydrates or other cluster ions. We see that both dimensions and temperature conditions, existing in the corona, are much better suited for the formation of ball lightning than the conditions characteristic of a current-carrying discharge channel. [...]
A letter from V.V. Mosharov reports that ball lightning occurred after linear lightning struck the TV antenna.[...]
So, the discharge currents that appeared during the explosion of ball lightning flowed at a considerable distance from the explosion site. In this case, it is completely impossible to blame these consequences on a linear lightning discharge, since the thunderstorm had already ended at that time. The appearance of strong current pulses can also lead to the melting of metals; therefore, these currents may, at least partially, be responsible for the melting caused by ball lightning. Of course, the energy spent on melting is not contained in the ball lightning itself, and this may explain the large spread of heat release.[...]
Note that, according to the last observation, ball lightning arose, although near the tree that was struck by linear lightning, but still somewhat to the side, two meters from it.[...]
To protect overhead lines from damage by a direct lightning strike, linear tubular arresters are used, installed on supports during the thunderstorm season. The arresters are inspected at each next round of lines, and especially carefully after a thunderstorm.[...]
The second argument is that the formation of ball lightning takes a time interval of several seconds. Although ball lightning appears after a discharge of linear lightning, however, judging by the testimony of eyewitnesses, it takes some time for it to “flare up” or grow in diameter to a stationary size or to form into an independent spherical body. This time (1-2 s) is approximately an order of magnitude longer than the total duration of the linear lightning channel (0.1-0.2 s) and more than two orders of magnitude longer than the channel decay time (10 ms).[...]
Above we described mainly cases of the appearance of ball lightning from conductors during a close strike of linear lightning or, at least, when the possibility of such a strike was not excluded. The question arises: can ball lightning occur without a previous discharge of linear lightning. Based on an analysis of a number of cases, we can definitely answer this question in the affirmative. As one example, we can recall the case (No. 47) described at the beginning of § 2.6, when “ball lightning appeared on the terminals battery. Let us give a few more examples that describe in detail the occurrence of ball lightning.[...]
Let us return again to the question of the objective frequency of occurrences of ball lightning. A natural scale for comparison is the frequency of occurrence of linear lightning. The preliminary survey conducted by NABA also included questions about the observation of bead lightning and the location of strike by linear lightning. In the last question, they mean observing an area with a diameter of about 3 m, located where the linear lightning channel goes into the ground or into objects located on it. An affirmative answer to this question meant that the observer saw this place clearly enough to be able to notice a small, faintly luminous ball near the ground.[...]
This class of photographs is characterized by the presence, near the trace of ordinary linear lightning, of a separate small luminous area, clearly formed by lightning and remaining as something separated from the main discharge.[...]
I.P. Stakhanov specifically analyzed the description of observations of ball lightning from the point of view of their occurrence. He selected 67 cases in which the moment of the appearance of ball lightning was recorded. Of these, in 31 cases, ball lightning arose in the immediate vicinity of the linear lightning channel, in 29 cases it appeared from metal objects and devices - sockets, radios, antennas, telephones, etc., in 7 cases it ignited in the air “from Nothing".[ ...]
Lightning channel, i.e. The path along which the spark discharge jumps, judging by photographs of lightning taken with special cameras, has a diameter of 0.1 to 0.4 m. The duration of the discharge is estimated in microseconds. Observations of lightning developing in such a short time do not contradict the theory of visibility in the atmosphere, where the time required for observation, as discussed earlier, should exceed 0.5 s. During the microseconds of lightning development, a very bright area of the lightning channel has such a strong impact on the human visual apparatus that during the time required for vision readaptation, he manages to comprehend what happened. The visual effect of being blinded by, say, a photo flash is similar to this. For the same reason, linear lightning is perceived by us as a single spark discharge, less often - two, although, according to special photography, it almost always consists of 2-3 pulses or more, up to tens.[...]
The research carried out allows us to unambiguously answer the question of whether ball lightning exists at all as a physical phenomenon. At one time, a hypothesis was put forward that ball lightning is optical illusion. This hypothesis still exists today (see, for example,). The essence of this hypothesis is that a strong flash of linear lightning as a result of photochemical processes can leave a mark on the retina of the observer's eye, which remains on it in the form of a spot for 2-10 s; This spot is perceived as ball lightning. This statement is rejected by all authors of reviews and monographs on ball lightning, which have previously been processed big number observations. This is done for two reasons. Firstly, each of the numerous observations used as an argument in favor of the existence of ball lightning, in the process of observing it, includes many details that could not arise in the observer's brain as an aftereffect of a flash of ball lightning. Secondly, there are a number of reliable photographs of ball lightning, and this objectively proves its existence. Thus, based on the totality of data on the observation of ball lightning and their analysis, we can say with complete confidence that ball lightning is a real phenomenon. [...]
When setting up their experiments, Andrianov and Sinitsyn proceeded from the assumption that ball lightning arises as a secondary effect of linear lightning from the material evaporated after its action. To model this phenomenon, the authors used a so-called erosion discharge - a pulsed discharge that creates plasma from evaporating material. The stored energy under the experimental conditions was 5 kJ, the potential difference was 12 kV, and the capacitance of the discharged capacitor was 80 μF. The discharge was directed to a dielectric material; the maximum discharge current was 12 kA. The discharge area was initially separated from the normal atmosphere by a thin membrane, which was torn when the discharge was turned on, so that the erosive plasma was released into the atmosphere. The moving luminous area took on a spherical or toroidal shape, and visible radiation plasma was observed for a time of about 0.01 s, and in general the plasma glow was recorded for no more than 0.4 s. These experiments once again show that the lifetime of plasma formations in atmospheric air is significantly less than the observed lifetime of ball lightning.[...]
In Fig. 2.4 shows a photograph from, the features of the image in which are close to the described characteristics of beaded lightning. The intermittent glow has been reported to occur in conjunction with normal linear lightning. As you can see, the trace of beaded lightning, unlike ordinary lightning discharges, does not branch. This feature, completely unusual for the trace of ordinary lightning, is, according to eyewitnesses, a distinctive feature of rosary lightning. However, the origin of this particular trace in Fig. 2.4 is questionable because at the top of the photograph there is a part of the trace that repeats the trace just described (its shape clearly coincides with the shape of the main image of the bead lightning). It is incredible that two or more discharges could acquire such similar shapes under the influence of atmospheric electric fields and space charges widely separated from each other. Thus, the photograph of Fig. 2.4 is questionable. It appears to be related to the movement of the camera, and does not represent a true trace of bead lightning.[...]
Finding this water close to the ground is not difficult. It can be contained in the air and on the surface of the earth, on leaves in the form of dew and on other objects. During the lightning discharge (0.1-0.2 s), it evaporates and can fill a significant volume. In the air (in particular, in clouds) water is distributed in the form of droplets and vapors. Since the substance of ball lightning has surface tension, it will tend to gather in one place like a stretched elastic film. Therefore, one can think that the ions that make up ball lightning are formed and dressed in hydrate shells in a fairly large volume, many times larger than the volume of ball lightning itself, and only after that they are compressed and combined into one body. Eyewitnesses also point to this (see Chapter 2). Let us recall that one of them, in particular, says that after linear lightning struck a plowed field, “lights” ran across its surface, which then gathered into one ball, which came off the ground and floated through the air (see No. 67).
Federal Agency for Education
State educational institution of higher professional education
PETROZAVODSK STATE UNIVERSITY
Linear lightning.
Its birth and methods of use.
Petrozavodsk 2009
List of performers:
Egorova Elena,
1st year, gr.21102
Lebedev Pavel,
1st year, group 21112
Shelegina Irina,
1st year, gr.21102
Lightning. General information………………………………….4
Story. Theories of origin……………………………5
Formation of lightning……………………………………………………….6
Lightning. General information
Lightning is a spark discharge of static electricity accumulated in thunderclouds.
The length of linear lightning is several kilometers, but can reach 20 km or more.
The shape of lightning is usually similar to the branched roots of a tree that has grown in the sky.
The main lightning channel has several branches 2-3 km long.
The diameter of the lightning channel ranges from 10 to 45 cm.
The duration of lightning is tenths of a second.
The average speed of lightning is 150 km/s.
The current strength inside the lightning channel reaches 200,000 A.
The plasma temperature in lightning exceeds 10,000°C.
The electric field strength inside a thundercloud ranges from 100 to 300 volts/cm, but before a lightning discharge in individual small volumes it can reach up to 1600 volts/cm.
The average charge of a thundercloud is 30-50 coulombs.
Each lightning discharge carries from 1 to 10 coulombs of electricity.
Along with the most common linear lightning, rocket, bead and ball lightning are sometimes found. Rocket lightning is observed very rarely. It lasts 1-1.5 seconds and is a discharge slowly developing between the clouds. Beaded lightning is also a very rare type of lightning. It has a total duration of 0.5 seconds and appears to the eye against the background of clouds in the form of luminous rosaries with a diameter of about 7 cm. Ball lightning in most cases is a spherical formation with a diameter of 10-20 cm at the earth’s surface, and up to 10 m at a cloud height.
On Earth, on average, about 100 discharges of linear lightning are observed every second; the average power that is spent on the scale of the entire Earth for the formation of thunderstorms is 1018 erg/sec. That is, the energy released when precipitation falls from a thundercloud significantly exceeds its electrical energy.
2. History of the study of the nature of lightning and the initial “theories” to explain this natural phenomenon
Lightning and thunder were originally perceived by people as an expression of the will of the gods and,
in particular, as a manifestation of God's wrath. At the same time, inquisitive human
the mind has been trying for a long time to comprehend the nature of lightning and thunder, to understand them
natural reasons. In ancient times, Aristotle pondered this. Above
Lucretius thought about the nature of lightning. It is very naive to imagine him
attempts to explain thunder as a consequence of the fact that “the clouds are colliding there under
the onslaught of the winds."
steam trapped in the water vapor of clouds. Expanding, it breaks through them at the most
weak spot and quickly rushes down to the surface of the earth. In 1929, J. Simpson proposed a theory that explains electrification by the fragmentation of raindrops by air currents. As a result of fragmentation, the falling larger drops are charged positively, and the smaller ones remaining in the upper part of the cloud are charged negatively. In Charles Wilson's theory of free ionization, it is assumed that electrification occurs as a result of the selective accumulation of ions by droplets in the atmosphere different sizes. It is possible that the electrification of thunderclouds is carried out by the combined action of all these mechanisms, and the main one is the fall of sufficiently large particles, electrified by friction with the atmospheric air.
In 1752, Benjamin Franklin experimentally proved that lightning is
strong electrical discharge. The scientist performed the famous experiment with an air
a kite that was launched into the air as a thunderstorm approached.
Experience: A sharpened wire was attached to the serpent's crosspiece,
tied to the end of the rope was a key and a silk ribbon, which he held with his hand.
As soon as the thundercloud was over the kite, the sharpened wire became
extract an electric charge from it, and the kite, along with the string, is electrified.
After the rain wets the kite along with the string, thereby making them
free to conduct an electric charge, can be observed as an electric
the charge will “drain” when the finger approaches.
Simultaneously with Franklin's research into the electrical nature of lightning
were engaged in M.V. Lomonosov and G.V.Rikhman. Thanks to their research, the electrical nature of lightning was proven in the mid-18th century. From that time on, it became clear that lightning is a powerful electrical discharge that occurs when clouds are sufficiently electrified.
3. Lightning Formation
Most often, lightning occurs in cumulonimbus clouds, then they are called thunderstorms; Lightning sometimes forms in nimbostratus clouds, as well as during volcanic eruptions, tornadoes and dust storms.
Linear lightning is usually observed, which refers to electrodeless discharges, since they begin (and end) in accumulations of charged particles. This determines some of their 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 myriads 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 with a strength sufficient to initiate an electrical discharge (~ 1 MV/m) is formed, and in a significant part of the cloud there is a 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.
Lightning discharges can occur between adjacent electrified clouds or between an electrified cloud and the ground. The discharge is preceded by the occurrence of a significant difference in electrical potential between neighboring clouds or between a cloud and the ground due to the separation and accumulation of atmospheric electricity as a result of natural processes such as rain, snowfall, etc. The resulting potential difference can reach a billion volts, and the subsequent discharge of stored electrical energy through the atmosphere can create short-term currents of 3 to 200 kA.
4.Main phases of the first and subsequent
lightning components
The relationship between lightning and spark discharge was proven by the work of Benjamin Franklin two and a half centuries ago. When pronouncing a similar phrase today, it is more correct to mention these two forms of electrical discharge in reverse order, because the most important structural elements of the spark were initially observed in lightning and only then were discovered in the laboratory. The reason for such a non-standard sequence of events is simple: the lightning discharge has a significantly longer length, its development takes longer, and therefore optical recording of lightning does not require equipment with particularly high spatial and temporal resolution. The first and still impressive time sweeps of lightning discharges were made using simple cameras with mechanical mutual movement of the lens and film (Beuys cameras) back in the 30s. They made it possible to identify two main phases of the process: leadership And home stages.
During leader stage, in the cloud-ground gap or between the clouds, a conducting plasma channel grows - the leader. It is born in the region of a strong electric field, certainly sufficient to ionize the air by electron impact, but the leader has to lay the main part of the path where the external field strength (from the charge of thunderclouds) does not exceed several hundred volts per centimeter. However, the length of the leader channel increases, which means that intense ionization occurs at its head, turning neutral air into a highly conductive plasma. This is possible because the leader himself carries his own strong field. It is created by a space charge concentrated in the area of the channel head and moves with it. The function of a conductor galvanically connecting the leader head with the lightning starting point is performed by the plasma channel of the leader. The leader grows for quite a long time, up to 0.01 s - an eternity on the scale of fleeting phenomena of a pulsed electric discharge. All this time, the plasma in the channel must maintain high conductivity. This is impossible without heating the gas to temperatures approaching those of an electric arc (over 5000-6000 K). The question of the balance of energy in the channel, which is required for
warming it up and to compensate for losses is one of the most important in the theory of a leader.
The leader is a necessary element of any lightning. In a multicomponent outbreak, not only the first, but also all subsequent components begin with the leader process. Depending on the polarity of the lightning, the direction of its development and the number of the component (the first or any of the subsequent ones), the leader mechanism may change, but the essence of the phenomenon remains the same. It consists in the formation of a highly conductive plasma channel due to a local increase in the electric field in the immediate vicinity of the leader head.
Main stage of lightning(return stroke) begins from the moment the leader contacts the surface of the earth or a grounded object. Most often, this is not direct contact. From the top of the object, its own leader channel, called the counter leader, can arise and move towards the lightning leader. Their meeting marks the beginning of the main stage. While moving in the cloud-ground gap, the head of the lightning leader carried a high potential, comparable to the potential of a thunderstorm
clouds at the lightning start point (they differ in the voltage drop across the channel). After contact, the leader head accepts the ground potential, and its charge flows into the ground. Over time, the same thing happens to others.
sections of the canal with high potential. This “unloading” occurs by propagating a wave of neutralization of the leader charge along the channel from the ground to the cloud. The wave speed approaches the speed of light, up to 108 m/s. Between the wave front and the ground, the channel flows
a strong current that carries charge to the ground from the “unloading” sections of the channel. The current amplitude depends on the initial potential distribution along the channel. On average it is close to 30 kA, and for the most
powerful lightning reaches 200-250 kA. The transfer of such a strong current is accompanied by an intense release of energy. Due to this, the gas in the channel quickly heats up and expands; a shock wave occurs. The sound of thunder is one of its manifestations. Energetically, the main stage is the most powerful. It is also characterized by the fastest change in current. The steepness of its increase can exceed 1011 A/s - hence the extremely powerful electromagnetic radiation that accompanies a lightning discharge. This is why a working radio or television reacts intensely to a thunderstorm.
significant interference, and this occurs at distances of tens of kilometers.
Current pulses of the main stage accompany not only the first, but also all subsequent components of downward lightning. This means that the leader of each successive component charges the one moving towards the ground
channel, and during the main stage, part of this charge is neutralized and redistributed. Long rumbles of thunder are the result of the superposition of sound waves excited by current pulses of the entire set
subsequent components. For ascending lightning the picture is somewhat different. Leader of the first component
starts from a point with zero potential. As the channel grows, the potential of the head changes gradually until the leader process slows down somewhere in the depths of the thundercloud. This is not accompanied by any rapid changes in charge, and therefore the first component of the ascending lightning has the main
no stage. It is observed only in subsequent components, which start from the cloud and move towards the ground, no different from subsequent components of downward lightning.
From a scientific point of view, the main stage of intercloud lightning is of great interest. The fact that it exists is indicated by thunderclaps, no less loud than when discharges into the ground. It is clear that the leader of intercloud lightning starts somewhere within the volume of one charged region of a thundercloud (thunderstorm cell) and moves in the direction of another, of the opposite sign. Charged areas in the cloud cannot be imagined in the form of some kind of conducting bodies, similar to the plates of a high-voltage capacitor, because the charges there are distributed throughout the volume with a radius of hundreds of meters and are located on small drops of water and ice crystals (hydrometeors) that are not in contact with each other. The emergence of the main stage in its own way physical essence necessary involves contact of the lightning leader with a highly conductive body of large electrical capacity, comparable or larger capacity leader. It must be assumed that during an intercloud lightning discharge, the role of such a body is played by some other plasma channel that simultaneously appeared and then comes into contact with the first one.
In measurements near the earth's surface, the main stage current pulse decreases by half its amplitude value on average in about 10 -4 s. The spread of this parameter is very large - deviations from the average in each direction reach almost an order of magnitude. Positive lightning current pulses, as a rule, are longer than negative ones, and pulses of the first components last longer than subsequent ones.
After the main stage, a weakly varying current of the order of 100 A can flow through the lightning channel for hundredths and sometimes tenths of a second. In this final stage of continuous current, the lightning channel retains its conducting state, and its temperature is kept at the arc level. A continuous current stage can follow each lightning component, including the first component of an upgoing lightning that does not have a main stage. Sometimes against the background of continuous current
current bursts are observed with a duration of about 10 -3 s and an amplitude of up to 1 kA. They are accompanied by an increase in the brightness of the channel.
5. Linear zippers
The common linear lightning, which every person encounters many times, has the appearance of a branching line. The current strength in the linear lightning channel is on average 60 - 170 kA; lightning with a current of 290 kA has been recorded. The average lightning carries energy of 250 kW/hour (900 MJ). energy is mainly realized in the form of light, heat and sound energies.
The 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 appears, accompanied by a sound pulse - thunder.
Before and during a thunderstorm, occasionally dark time on the tops of tall pointed objects (tops of trees, masts, tops of sharp rocks in the mountains, crosses of churches, lightning rods, sometimes in the mountains on people’s heads, raised hands or animals) a glow can be observed, called “St. Elmo’s lights”. This name was given in ancient times by sailors who observed the glow at the tops of the masts of sailing ships. The glow occurs due to the fact that on tall, pointed objects the electric field strength created by the static electric charge of the cloud is especially high; as a result, ionization of the air begins, a glow discharge occurs and reddish tongues of glow appear, at times shortening and lengthening again. You should not try to extinguish these fires, because there is no combustion. at high electric field strength, a bunch of luminous filaments may appear - a corona discharge, which is accompanied by hissing. Linear lightning can also occasionally occur in the absence of thunderclouds. It is no coincidence that the saying “bolt from the blue” arose.
Linear lightning
6.Physical processes during lightning discharge.
Lightning starts not only from a cloud to the ground, or from a grounded object to a cloud, but also from bodies isolated from the ground (airplanes, rockets, etc.). Attempts to clarify the mechanisms of the listed processes are of little help from experimental data related to lightning itself. There are almost no observations that would shed light on the physical essence of phenomena. Therefore, we have to build speculative schemes, actively drawing on the results of experiment and the theory of a long laboratory spark. Lightning is very interesting for its physical beginning, but it is most important to consider in detail the main stage of lightning
G 
The main stage, or the process of lightning channel discharge, begins from the moment the gap between the cloud and the ground is blocked by the downward leader. By touching the ground or a grounded object, the leader channel (to be specific, let it be a negative leader) must acquire its zero potential, since the capacity of the earth is “infinite”. The channel of the ascending leader, which is a continuation of its “twin”, the descending one, also acquires zero potential. Grounding of a leader channel carrying a high potential is accompanied by a strong change in the charge distributed along it. Before the start of the main stage, the charge τ 0 = C 0 was distributed along the channel. Here and henceforth, the potential brought to the ground, the “initial” for the main stage, is denoted by Ui. We continue to assume that it is constant along the length of both leaders, ignoring the voltage drop along the channel, which is of little significance for our purposes. Let us assume that during the main stage, as well as in the leader, the channel can be characterized by a linear capacity Co, which does not change either along its length or in time. When the entire channel acquires zero potential (U = 0), the charge per unit length becomes equal to τ 1 = -CoUо(x). The part of the channel belonging to the negative descending leader not only loses its negative charge, but acquires a positive charge (Uо 0). It not only discharges, but also recharges. The channel of the conjugate positive ascending leader high in the cloud becomes even more positively charged (see figure). Change in linear charge during the main stage ∆τ = τ-τ o = -C o U i . When U i (x) = const, the charge change is the same along the entire length of the channel. It is as if a long conductor (long line), previously charged to voltage Ui, is completely discharged.
Measurements near ground show that the downward leader channel discharges a very high current. In the case of negative lightning, the main stage current pulse with an amplitude IM ~ 10-100 kA lasts 50-100 μs at a level of 0.5. For approximately the same time, a short bright section, the head of the main channel, runs up the channel, clearly visible on photographic scans. Speed it v r≈(1-0.5)s is only several times less than the speed of light. It is natural to interpret this as the propagation of a discharge wave along the channel, i.e. waves of potential decrease and the appearance of strong current. In the region of the wave front, where the potential sharply drops in value from U i and a strong current is formed, due to the intense release energy, the former leader channel is heated to a high temperature (according to measurements - up to 30-35 kK). That's why the wave front glows so brightly. Behind it, the channel, expanding, cools down and, losing energy to radiation, glows weaker. The main stage process has much in common with the discharge of an ordinary long line formed by a metal conductor.
The line discharge also has a wave character, and this process served as a prototype in the formation of ideas about the main stage of lightning. The lightning channel discharges much faster than it charged during its growth at the speed of the leaders v l
10 -3 -10 -2)v r. But changes in potential and charge per unit length during charging and discharging are of the same order of magnitude: τ o =∆t. According to the speed, the channel is discharged v t /v l ~ 10 2 --10 3 times with a stronger current i M ~ ∆tv r than the leader one i L ~ t 0 V L ~ 100 A. The linear resistance of the channel R 0 approximately decreases by the same amount at transition from the leader stage to the main stage. The reason for the decrease in resistance is the heating of the channel when a strong current passes, which increases the conductivity of the plasma. Consequently, the resistances of the channel and the streamer zone, through which the same current flows, are comparable. This means that per unit length of the leader channel, energy of the same order of magnitude is dissipated and it is expressed through the parameters of the leader 
This also gives that the average electric field in the leader channel and behind the discharge wave in the already transformed channel is of the same order. This is consistent with a similar conclusion that can be made by directly considering the steady states in the channels of the leader and main stages of lightning. The situation there is similar to that in a stationary arc. But in high-current arcs, the field in the channel actually weakly depends on the current. From the above it follows that if in the leader and , then in the steady state behind the main stage wave front there should be , and the total ohmic resistance of the entire lightning channel several kilometers long is about 102 Ohms. This is comparable to the characteristic impedance of a perfectly conducting long line in air Z, while for a leader channel of the same length the total resistance is 2 orders of magnitude greater than Z. The relationship between the ohmic resistance of the section of the line passed by the wave and the characteristic impedance characterizes the degree of attenuation of the wave as it propagates along the line If the resistance of the channel did not change, remaining at the level of the leader, the discharge wave of the lightning channel would fade and spread out without passing even a small fraction of the channel. The current through the point where the channel closes to ground would also die out too quickly. Experience suggests the opposite: the visible luminous head has a sharp front, and a large current near the ground is recorded during the entire time of its rise. The transformation of the leader channel during the passage of the wave, leading to a sharp decrease in its linear resistance, determines the entire course of the process of the main stage of lightning.
Hazardous factors of lightning exposure.
Due to the fact that lightning is characterized by large values of currents, voltages and discharge temperatures, the impact of lightning on a person, as a rule, results in very serious consequences - usually death. On average, about 3,000 people die from lightning strikes in the world every year, and there are known cases of several people being struck at the same time.
A lightning discharge follows the path of least electrical resistance. Since the distance, and therefore the electrical resistance, is smaller between a tall object and a thundercloud, lightning, as a rule, strikes tall objects, but not necessarily. for example, if you place two masts next to each other - a metal one and a taller wooden one, then lightning will most likely strike the metal mast, although it is lower, because the electrical conductivity of metal is higher. lightning also strikes clayey and wet areas much more often than dry and sandy ones, because the former have greater electrical conductivity.
For example, in a forest, lightning also acts selectively. A tree splits when struck by lightning. the mechanism of this is as follows: tree sap and moisture in the discharge area instantly evaporate and expand, creating enormous pressures,
which tear the wood. A similar effect, accompanied by the scattering of wood chips, can occur when lightning strikes the wall of a wooden building. therefore, being under a tall tree during a thunderstorm is dangerous.
It is dangerous to be on or near water during a thunderstorm, because... water and areas of land near water have high electrical conductivity. at the same time being inside during a thunderstorm reinforced concrete buildings, metal buildings (for example, metal garages) are safe for humans.
In addition to damaging people and animals, linear lightning quite often causes forest fires, as well as residential and industrial buildings, especially in rural areas.
During a thunderstorm, being in a city is less dangerous than being in open area, since steel structures and tall buildings perform well as lightning rods.
A completely or partially closed electrically conductive surface forms a so-called “Faraday chamber” inside which no significant potential that is dangerous to humans can form. Therefore, passengers inside a car with an all-metal body, a tram, a trolleybus, or a train carriage are safe during a thunderstorm until they go outside or start opening the windows.
Lightning can strike an airplane, but since modern airplanes are made of all metal, passengers are fairly reliably protected from lightning.
Statistics show that every 5,000-10,000 flight hours there is one lightning strike on an aircraft; fortunately, almost all damaged aircraft continue to fly. Among the various causes of aircraft accidents, such as glaciation, rain, fog, snow, storm, tornado, lightning ranks last, but aircraft flights during a thunderstorm are still prohibited.
The world-famous Eiffel Tower in Paris is almost always struck by lightning during a thunderstorm, but this does not pose a danger to people on the observation deck, because The openwork metal lattice of the tower forms a Faraday chamber, which is excellent protection against electric lightning.
A sign that you are in an electric field may be your hair standing on end and making a slight crackling noise. But this is only dry hair.
If you are struck by lightning but are still able to think, you should consult a doctor as soon as possible. Doctors believe that a person who survives a lightning strike, even without receiving severe burns to the head and body, may subsequently suffer complications in the form of deviations in cardiovascular and neuralgic activity from the norm.
Lightning strikes the Eiffel Tower, photograph from 1902.
8.How often does lightning strike?
Lightning strikes to ground structures. From everyday experience we know that lightning most often strikes tall structures, especially those that dominate the surrounding area. On the plain, most blows fall on free-standing masts, towers, chimneys and so on. In mountainous areas, low-rise structures often suffer if they stand on isolated high hills or on top of a mountain. At the everyday level, the explanation for this is simple: it is easier for an electrical discharge, such as lightning, to cover a shorter distance to a towering object. Thus, on average in Europe, a mast 30 m high receives 0.1 lightning strikes per year (one strike per 10 years), while for a secluded 100-meter object there are almost 10 times more. Upon closer inspection, such a sharp dependence of the number of impacts on height no longer seems trivial. The average height of the starting point of downward lightning is about 3 km and even a 100 meter height is only 3% of the distance between the cloud and the ground. Random curvatures change the total length of the trajectory tens of times more strongly. We have to assume that the final ground stage of lightning development is distinguished by some special processes that quite strictly predetermine the last part of the path. These processes lead to the orientation of the descending leader, his attraction to high objects.
From the experience of scientific observations of lightning, we can speak of an approximately quadratic dependence of the number of strikes N M from height h concentrated objects (they have h much larger than all other sizes); for extended ones, length I, such as overhead line power transmission, N M ~ h i . This suggests the existence of some equivalent lightning contraction radius R uh~h. All lightning displaced horizontally from the object by a distance r R uh fall into it, the rest pass by. Such a primitive orientation scheme generally leads to the correct result. For assessments you can use R uh~ 3h, and the number of lightning strikes per unit of undisturbed earth surface per unit time n m is extracted from meteorological observation data. Based on them, special maps of the intensity of thunderstorm activity are constructed. In the European tundra n m R uh= 0.3 km and for her
blow per year, if we focus on the average figure n m = 3.5 km -2 year -1 The assessment makes sense for flat terrain and only for objects that are not too high h
Human Defeat
The radius of lightning contraction into a person is only 5-6 m, the area of contraction is no more than 10 -4 km 2. In fact, lightning has many more casualties and a direct strike has nothing to do with it. Human experience does not recommend being in the forest during a thunderstorm, especially in open areas, near tall trees. And it is right. A tree is about 10 times taller than a person and is struck by lightning 100 times more often. Being under a tree crown, a person has a noticeable chance of ending up in the lightning current spreading zone, which is not safe. After lightning strikes the top of a tree, its current I M spreads along a well-conducting trunk, and then spreads through the roots into the ground. Root system the tree becomes like a natural grounding agent. Thanks to the current, an electric field appears in the ground, where p - resistivity soil, j - current density. Let the current spread in the ground strictly symmetrically. Then the equipotentials are hemispheres with a diametrical plane on the surface of the earth. Current density at a distance r from the tree trunk j(r) =,
the potential difference between close points is equal to ∆ U=. If, for example, a person stands at a distance r ≈ 1 m from the center of a tree trunk with his side to the tree, and the distance between his feet is ∆r ≈ 0.3 m, then for an average intensity lightning with current Im= 30 kA, the voltage drop on the ground surface with p = is . This voltage is applied to the soles of shoes, and after their inevitable very rapid breakdown - to the human body. There is no doubt that a person will suffer, and most likely be killed - the stress acting on him is too great. Note that it is proportional to ∆r. This means that standing with your legs spread wide apart is much more dangerous than standing at attention with your feet tightly clenched, and lying along a radius from a tree is even more dangerous, because in this case the distance between the extreme points in contact with the ground becomes equal to your height
person. It is best to stand still on one leg, like a stork, but such advice is easier to give than to implement. By the way, large animals are struck by lightning more often than humans, also because they have a larger distance between their legs.
If you have a dacha with a lightning rod and a special grounding rod has been built for it, make sure that during a thunderstorm there are no people near the grounding rod and the grounding descent to it. The situation here is similar to that just discussed.
7. Rules of conduct during a thunderstorm.
We see a flash of lightning almost instantly, because... light travels at a speed of 300,000 km/s. the speed of sound propagation in air is approximately 344 m/s, i.e. In about 3 seconds, sound travels 1 kilometer. Thus, dividing the time in seconds between the flash of lightning and the first clap of thunder that followed it, we determine the distance in kilometers until the thunderstorm is found.
If these periods of time decrease, then a thunderstorm is approaching, and it is necessary to take measures to protect against lightning damage. Lightning is dangerous when the flash is immediately followed by a clap of thunder, i.e. a thundercloud is above you and the danger of a lightning strike is most likely. Your actions before and during a thunderstorm should be as follows:
do not leave the house, close windows, doors and chimneys, make sure that there is no draft that can attract ball lightning.
During a thunderstorm, do not light the stove, because the smoke coming out of the chimney has high electrical conductivity, and the likelihood of a lightning strike into the chimney rising above the roof increases;
disconnect radios and televisions from the network, do not use electrical appliances and telephones (especially important for rural areas);
While walking, hide in the nearest building. A thunderstorm in a field is especially dangerous. When looking for shelter, give preference to a large metal structure or one with a metal frame, residential building or another building protected by a lightning rod; if it is not possible to hide in a building, there is no need to hide in small sheds, under lonely trees;
do not be on hills and open unprotected places, near metal or mesh fences, large metal objects, damp walls, lightning rod grounding;
in the absence of shelter, lie on the ground, and preference should be given to dry sandy soil, far from the reservoir;
If a thunderstorm finds you in the forest, you need to take shelter in a low-growing area. You cannot take shelter under tall trees, especially pine trees, oaks, and poplars. It is better to be at a distance of 30 m from a separate tall tree. Pay attention to whether there are any split trees nearby that were previously damaged by a thunderstorm. It is better to stay away from this place in this case.
the abundance of trees struck by lightning indicates that the soil in this area has high electrical conductivity, and a lightning strike in this area of the area is very likely;
In the mountains, move away from mountain ridges, sharp towering rocks and peaks. When a thunderstorm approaches in the mountains, you need to go as low as possible.
collect metal objects - climbing pitons, ice axes, saucepans - into a backpack and lower them on a rope 20-30 m down the slope; do not exercise during a thunderstorm outdoors
, do not run, because it is believed that sweat and rapid movement “attract” lightning;
if you are caught in a thunderstorm on a bicycle or motorcycle, stop driving and wait out the thunderstorm at a distance of about 30 m from them;
8. Technology of using lightning energy.
Chinese scientists have developed technology for using lightning energy for scientific and industrial purposes,
“The new development makes it possible to capture lightning in the air and redirect it to collectors on the ground for research and use,” said Tse Xiushu, an employee at the Institute of Atmospheric Physics.
To capture lightning, rockets equipped with special lightning rods will be used, which will be launched into the center of a thundercloud. The YL-1 rocket must launch a few minutes before the lightning strike.
“Checks have shown that the launch accuracy is 70%,” the device’s developers said.
Lightning energy, as well as the electromagnetic radiation it produces, will be used for genetic modification of agricultural breeds and the production of semiconductors.
In addition, the new technology will significantly reduce the economic damage from thunderstorms, since the discharges will go to safe places. According to statistics, about a thousand people die from lightning strikes in China every year. Economic damage from thunderstorms in China reaches $143 million per year.
Researchers are also trying to find a way to use lightning for energy. According to scientists, a single lightning strike produces billions of kilowatts of electricity. Around the world, 100 lightning strikes occur every second - this is a huge source of electricity.
Bibliography:
Stekolnikov I.K., Physics of lightning and lightning protection, M. - L., 1943;
Imyanitov I.M., Chubarina E.V., Shvarts Ya.M., Electricity of clouds, Leningrad, 1971; Renema.py, Lightning.URL::// http. www. renema/ ru/ Info_ lightning. priroda
shtml History of lightning. URL:Lightning
http://ru.wikipedia.org/wiki/
Imenitov I.M., Chubarina E.V., Shvarts Ya.M. Electricity of the clouds. L., 1971
Science and technology: Physics. URL: http://www.krugosvet.ru/enc/nauka_i_tehnika/fizika/MOLNIYA.html
Bazelyan E.M., Raiser Yu.P. Physics of lightning and lightning protection.
M.: Fizmatlit, 2001.
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. This is why there are amazing thunderstorms after a heat wave. 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 a thundercloud and the ground. These are the same “ribbons” that we are used to.
Between a tall tree and a cloud. 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.
- 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.
- A type of lightning with a 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!