In nature, lightning is a spark discharge or a brief arc between clouds or between clouds and the earth . As a rule, lightning occurs during a thunderstorm as a result of an electrostatic charge in the cloud-forming water droplets or raindrops. He is accompanied by thunder and belongs to the electrometeors . In the process, electrical charges (electrons or gas ions) are exchanged, which means that electrical currents flow . Depending on the polarity of the electrostatic charge, lightning can also come from the earth.
Lightning bolts, which are artificially generated in the laboratory with high-voltage pulses, are used to study them or to check electrical network equipment with regard to the effects of lightning strikes and the effectiveness of protective measures.
A lightning discharge is significantly more complex than a pure spark discharge . The physical principles underlying the natural occurrence of lightning have not yet been conclusively researched.
We owe Benjamin Franklin the inspiration for experiments that have proven that during thunderstorms there is an electrical voltage between the clouds and the earth, which is discharged in a flash. His kite experiment of 1752, in which a sparking over a damp hemp string during a thunderstorm was observed later, became particularly famous. In a newspaper publication from 1752 Franklin reported about it without explicitly mentioning whether he had done it himself, which Joseph Priestley claimed in a book from 1767 that probably got it from Franklin. Franklin also suggested experiments with an isolated metal tip during thunderstorms, which were the inspiration for a corresponding experiment in France by Thomas François Dalibard (1752). The dangerousness of these experiments became evident as early as 1753 with the death of Georg Wilhelm Richmann . Franklin's research was the beginning of modern lightning research. To date, however, not all forms of lightning and the associated effects have been comprehensively and undisputedly scientifically explained, in particular how the charge differences that lead to lightning arise.
Today, various methods for investigating lightning have become established, which also take care to keep the risk for the researchers as low as possible (in contrast to Franklin's method). Often rockets are launched that pull a metallic wire behind them. The lightning passes through the wire to the measuring station, where it can be analyzed. Other methods rely on weather balloons or measurements by airplanes.
For a long time there was little research interest in natural lightning, as it was believed that they could be treated like spark discharges, which can easily be generated in the laboratory. This has only changed since the late 1990s, when inconsistencies arose that could not be explained by the simple model. It turned out to be impossible to use lightning to generate energy with today's means.
Some of the most recent research projects are:
- On the Hohen Peißenberg in the Bavarian foothills of the Alps is the lightning measuring station operated by the University of the Federal Armed Forces in Munich , which is located in the Hohenpeißenberg transmitter of the same name . The station is operated by Fridolin Heidler's Institute for High Voltage Technology and Lightning Research. In the event of a direct lightning strike in the telecommunications tower, the current and magnetic as well as the electric field course are recorded with high-resolution measuring technology.
- In Austria , ALDIS ( Austrian Lightning Detection & Information System ) is running a lightning research project on the Gaisberg transmitter in Salzburg . Direct lightning strikes in the transmitter tower are evaluated and, among other things, the course of the lightning current is recorded using measurements.
- In Brazil, the DLR Falcon research aircraft is investigating the formation of nitrogen oxides from lightning in tropical thunderstorms.
- Since 1994 it has been known from the (then misaligned) BATSE satellite experiment that gamma radiation pulses occur in the atmosphere and, as it later turned out, these are up to 50 times a day with energies of up to 40 MeV ( AGILE measured energies of up to 100 MeV) and they are associated with thunderstorms (often a few minutes before the lightning discharge). In 2001 it was also possible to prove in thunderstorms that lightning bolts also emit X-rays and gamma rays (energies above 1 MeV). These results were confirmed many times in the following years, especially through the detection of gamma radiation from thunderstorm zones by the NASA research satellite RHESSI (2005) and the Fermi Gamma-ray Space Telescope (2010). According to theoretical calculations, these gamma-ray bursts can generate secondary particles such as electrons , positrons , neutrons and protons with energies of up to 50 MeV. The production of neutrons in laboratory discharges was proven by Fleischer and colleagues as early as 1974 and predicted for lightning and later also measured for lightning. For this purpose, fusion reactions with deuterium or photonuclear reactions come into consideration (LP Babich 2007), with Babich assigning fusion reactions a subordinate role based on theoretical considerations. Finally, the origin of photonuclear reactions was conclusively proven in 2017 by scientists from the University of Tokyo in thunderstorms. They were able to correlate gamma rays with an energy of 511 keV , the annihilation energy of an electron and a positron, with lightning . In a photonuclear process, photons of more than 10 MeV hit a neutron from a nitrogen-14 nucleus, which then disintegrated into a carbon-13 nucleus with beta decay, which also produced a positron. Since this also creates carbon nuclei, this has an impact on the C14 dating method .
Theories of origin
Most often, lightning strikes are observed between special types of clouds such as cumulonimbus and earth, almost daily in the tropics, and in moderate latitudes mainly during the summer months. A great number of lightning bolts are also observed in volcanic eruptions, for which rising damp is probably not the cause. In both cases, it has not yet been possible to fully clarify what leads to the enormous charge separation that must have taken place beforehand. The obvious difference to laboratory experiments with gases is puzzling, where the good mobility of the molecules makes it difficult to create and maintain charge separation for a long time without metallic conductors and insulators.
Formation of electrical charge in a thundercloud
The basic requirement for the occurrence of lightning is charge separation . As far as we know today, a number of mechanisms within thunderclouds can contribute to this. A distinction is made between charging mechanisms with induction and without can act induction, the latter representing the far more important category.
The basic requirement for the separation of electrical charge is the friction caused by strong updrafts within a cumulonimbus cloud , which can reach 5–20 m / s and more. Over-saturated water vapor condenses in the cloud to form small but constantly growing water droplets. The condensation releases heat . This gives the air a higher temperature than it would have at the same height without condensation. This increases their buoyancy compared to the air outside the cloud. The climb accelerates. During the ascent, the air cools adiabatically due to the pressure dropping with altitude , which increases the condensation and accelerates the ascent further. At a height of a few kilometers, the temperature drops below zero , and the water droplets freeze to form ice particles that continue to grow through resublimation . Over time, the sleet particles become heavy enough that they fall to the ground against the direction of the updrafts.
At this stage, smaller, still light ice crystals probably collide with the sleet particles and give up electrons to the sleet particles. These take on a negative charge and so continue to sink charged into the lower part of the cloud. The light, now positively charged ice crystals are carried further upwards by the updrafts. If the rate of rise is sufficiently high, there is a charge separation and considerable space charges arise . The Tropical Rainfall Measurement Mission (TRMM) found that the strength of the space charges depends directly on the ice content of the cloud. This means a strong correlation between the amount of ice in a cloud and the frequency of lightning.
In cloud areas with a high percentage of sleet, air masses are carried down by the falling sleet particles and downdraft channels are created in the thundercloud. In them, the negatively charged sleet particles first reach the lower part of the cloud. The lower part of the cloud, which is now negatively charged, causes the ground below the cloud to become positively charged by means of influence ; the classic charge distribution in a thundercloud occurs. In addition, in the lower part of the thundercloud, the sleet particles melt again and become positively charged. The common explanation is that when the sleet particle grows in height, air pockets form which, when thawing later, leave the water droplets, taking with them negative charges on the surface. In this way, the precipitation falling under the cloud becomes electrically neutral or - as has been observed - even positively charged, while the negative charge remains in the lower part of the cloud. The sometimes extremely strong turbulence within thunderclouds makes an experimental verification of these assumptions very difficult.
One can imagine other processes that support this charge distribution: The sleet particles that grow through resublimation can become positively charged and, in the event of collisions, transfer their charge to lighter ice crystals before or while they fall towards the ground. The opposite effect, i.e. the negative charge of sublimating ice, would then come into play in the downdraft channels.
In the already charged thundercloud, further charge separation mechanisms can be added: In 1929 the Nobel laureate Charles Thomson Rees Wilson proposed that, due to the space charge present, dipole-like charged and appropriately aligned precipitation particles in the air either trap or repel ions depending on their polarity (regardless of their physical state ).
In practice, it can be measured with electric field meters that the charge distribution shown above often applies in thunderstorms, but that there can also be strong deviations depending on the type of thunderstorm (frontal thunderstorm, heat thunderstorm) and the stage of maturity, such as far in the lower part Positive space charges reaching the cloud, negative areas on the ground or positive cloud base in the late stage of a thunderstorm. A clarification of all connections has not yet been made.
Tensions within a thundercloud: cloud lightning and earth lightning
Lightning is a potential equalization within the cloud ( cloud lightning) or between the ground and the lower part of the cloud (earth lightning) . For lightning strikes between the cloud and the earth, the potential difference (voltage) must be a few tens of millions of volts . In the air there is only an electrical spark discharge at an electrical field strength of approx. Three million volts per meter (the so-called breakdown field strength ); however, this value drops sharply with increasing humidity . However, such field strengths have never been measured in a thundercloud. Measurements only extremely rarely show field strengths of over 200,000 V / m, which is well below the value for the breakthrough. It is therefore now assumed that the air must first be made conductive by ionization so that a lightning discharge can occur.
Formation of a lightning channel through ionization: lead lightning, catch discharge and main lightning
Some researchers, the first Wilson in 1925, assume that electrons excited by cosmic rays are the beginning of a lightning strike. If such an electron hits an air molecule in a thundercloud, further high-energy electrons are released. A chain reaction occurs , resulting in an electron avalanche (called runaway electrons , the exact mechanism is explained in the article Runaway Breakdown ).
A lightning discharge is preceded by a series of pre-discharges directed towards the surface of the earth. A lightning channel (beacon) is created, i.e. That is, an electrically conductive channel is formed by the impact ionization of air molecules by the runaway electrons . The ionized lightning channel builds up in stages (hence stepped leader ) until it is established between the earth's surface and the cloud. The pre-discharges are directed towards the ground, but vary their direction within a few meters and can split up in places. This creates the zigzag shape and the branches of the lightning bolt. As new research shows, the beacon also emits X-rays with an energy of 250,000 electron volts (see the literature references). In 2004, researchers at the University of Florida demonstrated that the measured bursts of X-rays coincide with the formation of the individual stages of the guide flash. The intensity of the radiation increases with the number of stages, i.e. the longer the lightning channel becomes. No X-rays were measured during the main discharges. It is not yet known why the electrons in the guide light are accelerated so strongly. The runaway breakdown process alone is not sufficient for the measured radiation (see also the web links).
Shortly before the pre-discharges reach the ground, one or more catch discharges emanate from the ground , which are bluish and very faint. A catch discharge usually occurs with pointed objects (such as trees, masts or church towers), which stand out in their height from the surroundings. Mostly - but not always - one of the catch discharges meets the previous discharges and forms a closed lightning channel between the cloud and the ground. The lightning channel has a maximum diameter of 12 mm. The main discharge then occurs through this channel , which is very bright and is perceived as an actual lightning bolt. The lightning flash is caused by the formation of plasma .
Duration, amperage and polarity of lightning
On average, four to five main discharges form a lightning bolt. The total pre-discharges take about 0.01 seconds, the main discharge takes only 30 µs (0.00003 s). After a recovery pause between 0.03 s and 0.05 s, a new discharge takes place. Up to 42 consecutive discharges have been observed. This creates the flickering of a lightning bolt.
According to the World Meteorological Organization, the longest lasting lightning strikes were measured on March 4, 2019 with 16.73 seconds over northern Argentina and in 2012 over southern France with 7.74 seconds. Due to the jerky different stages of the discharge, the lightning can be interpreted as a short-term, pulsating direct current .
The amperage of the main discharge of a negative lightning bolt is on average about 30 kilo amperes (kA). However, positive lightning strikes can reach several 100 kA, which means that a strong magnetic field surrounds the lightning channel. The combination of current and magnetic field causes compression of the conductive plasma channel ( pinch effect ), which has a diameter of only a few centimeters.
Mostly the negative charge flows from the underside of the cloud to the ground, one speaks of negative lightning . More rarely, positive charge is added to the earth's surface (positive lightning) . Usually it is a particularly intense discharge, the main discharge of which also lasts significantly longer than with negative flash. The positive flash usually consists of only one main discharge. The current strength of a main discharge in positive lightning is given as up to 400,000 amperes. They are therefore far more dangerous than negative lightning, but only make up about 5% of all earth lightning. Positive lightning often comes from the upper, positively charged part of the thundercloud or the cloud screen. They can also emerge from the cloud and make their way through the cloud-free space to an impact target on the ground. The point of impact can be a few kilometers from the thunderstorm cell. Positive flashes also occur in the rear, stratiform areas of the thunderstorm as well as in their dissolution phase. In addition, winter thunderstorms, in which the precipitation falls in frozen form, have a high proportion of positive lightning.
The rate of rise of the lightning current is significantly lower for the main discharge than for the subsequent discharges. During the first flash, the rate of increase in current is usually less than 2 · 10 10 A / s, while subsequent flashes reach 2 · 10 11 A / s. Accordingly, the subsequent lightning strikes are more dangerous in terms of induced interference voltages despite the lower current strength. Even at a distance of several kilometers, lightning can induce electrical voltages that destroy electronic equipment.
During the flash time, often after the main discharge, the ionized flash channel can cause a longer charge equalization that lasts for 10 to a few 100 ms. An almost constant current of 10 to 1000 A. This introductory long-term current also contains current peaks in the kiloampere range and often occurs after positive lightning strikes. At the end of the lightning strike, the last surge current is often followed by a subsequent long-term current, also known as a "current tail" .
Length of lightning
The average length of an earth lightning bolt (negative lightning bolt) is 1 to 2 km in middle latitudes and 2 to 3 km in the tropics due to the higher humidity. Positive lightning strikes often reach from the upper regions of the thundercloud to the ground and therefore come to lengths of well over 10 km. A bolt of cloud is about five to seven kilometers long.
However, lightning can also develop enormous lengths. On June 25, 2020, the World Meteorological Organization announced that on October 31, 2018, a lightning bolt with a length of 700 km was measured in a thunderstorm in Brazil. The longest lightning bolt to date was recorded over Oklahoma in 2007 with a horizontal length of 321 km.
Origin of thunder
In the lightning duct, the air is suddenly heated up to 30,000 ° C. The tubular magnetic field surrounding the lightning channel prevents the expansion of the ionized and thus magnetically influenceable air molecules. The result is extremely high pressure. With the end of the beacon and with it the current, the magnetic field collapses and the hot air expands explosively, causing the crack of thunder. The rumbling of the thunder comes about through echo effects, through different distances to the lightning channel and through dispersion (dependence of the sound propagation on the wavelength). The lightning itself reaches about a tenth to a third of the speed of light, whereby the pre-discharge, which is imperceptible to the eye, only runs at a thousandth of the speed of light, i.e. at 300 kilometers per second. Lightning discharges within the cloud are usually accompanied by a longer-lasting and less sharp rumbling noise. On the one hand, this is related to the usually greater distance, but is mainly due to the different orientation and structure of earth lightning and cloud lightning.
At the point where the lightning goes into the ground (or out of it), a strong field of tension (high potential) forms, which decreases in a circular manner from the point of impact towards the outside and continues in a conical shape in the ground, hence the name . The area, depth and potential of the cone are e.g. B. depending on the strength of the lightning, the soil and moisture. Rock melt can occur in the center of the cone. Then a fulgurite is formed .
“Lightning strike” means not only the direct hit, but also damage caused by the voltage cone. Is z. B. a victim of lightning with both legs on the ground, each leg is at a slightly different potential. The potential difference in the body, the so-called step voltage , leads to damage to organs. These are not fatal if the difference is small, e.g. B. if the victim has both feet close to each other at the moment of the impact and the tension difference is minimized. For someone with their head or feet in the direction of the impact point, the voltage difference is u. U. but very large. Then even an impact further away can cause serious damage. For this reason, four-legged animals (e.g. cows in the pasture) are particularly at risk. The strength and shape of the stress cone are usually not predictable.
“Blue Jets” are bluish glowing fountains of light that spread above thunderstorm cells at around 100 km / s up to 50 km high.
An Elmsfeuer is a spark discharge against the surrounding air. From a physical point of view, it is a pre-discharge due to the high field strength. It mostly occurs on tall objects such as antenna masts , ship masts, airplanes (when flying near thunderstorms or a layer of air soaked with ash particles) or summit crosses . Elm fires can initiate a lightning discharge. Mountaineers often report that this so-called peak discharge also occurs on the pimple , which therefore should not be carried in hand during thunderstorms .
"Elves" are lightning discharges that cause the gases in the ionosphere to vibrate so that they briefly shine in a ring. They appear above large storm clouds as a colored ring at a height of about 90 km and are probably induced by cloud lightning.
Lightning discharges can also be triggered by a volcanic eruption .
A surface lightning shows numerous branches from the main lightning channel.
Ball lightning are rare, spherical luminous phenomena that have been observed during thunderstorms. The cases, which are mostly based on eyewitness reports, cannot be adequately explained physically.
A line lightning has no branches. However, he does not always look for the direct path to the ground, but can also describe arcs that can be seen from a certain perspective as knots and circular interconnections. The line flash is seen more often than other flashes.
Pearl cord lightning
The pearl cord lightning is a type of lightning in which the lightning is not characterized by a continuous lightning channel, but rather breaks up into individual segments, usually only a few meters long. These individual segments shine brighter and usually a little longer than a "normal" line flash. Viewed from a distance, the short, glowing segments of lightning look like pearls strung on a string.
Like ball lightning, lightning bolts of pearls are very rare lightning phenomena. Laboratories have already succeeded in artificially generating lightning bolts of pearls, but their origin has not yet been fully understood. The cause could be instabilities in the plasma of the lightning channel.
A positive lightning bolt is a lightning bolt in which the discharge occurs from the upper, positively charged part of the cloud to the ground. These lightning bolts are much stronger than negative lightning bolts and can strike kilometers away from the actual thundercloud; they often occur on the back of the anvil when thunderclouds are withdrawn, which is why one should not leave a safe place too early. They also last longer than negative flash. Because of all of this, positive lightning can cause far greater damage. The thunderclap is also louder due to the stronger potential equalization.
"Red Sprites" are short (approx. 5 ms), up to 100 km high, polar lights- like discharge phenomena in the mesosphere above large thunderstorms. They are related to lightning and are mainly observable from airplanes, from a further distance (approx. 200 km) with appropriate visibility also from the ground. They usually appear reddish - the red color is caused by the fluorescence of nitrogen that was stimulated by lightning from the thunderstorm below - and have different shapes, from mushroom-like to picket fence-like .
Under "weather lights" (Middle High German weterleichen to "weter" (weather) + "corpses" (dance, hop), folk etymology based on the unrelated glow ) is usually understood to be the reflection of lightning when you cannot see it yourself. It occurs in thunderstorms further away or in lightning that discharges within clouds. The associated thunder can usually not be heard or only weakly because of the great distances. In typical Central European thunderstorms, the thunder can be heard about 5 to 20 km away (depending on wind direction, background noise, temperature and humidity, terrain and surface, buildings, forest, etc.), which corresponds to a time span between lightning and thunder of about 15 to 60 Seconds equals.
Frequency of lightning
Lightning event and lightning density
A discharge is known as a lightning strike . For statistical purposes it combines multiple flashes part (strokes) which are measured within a or 1.5 seconds at the same location, a lightning event, flash '(English flash ) together. According to the CATS (Computer Aided Thunderstorm Surveillance System) database of EUCLID ( European Cooperation for Lightning Detection ), a ratio of 100 million partial flashes to 65 million flashes can be determined, i.e. about 3: 2.
In order to record the lightning frequency (number of lightning events) in a comparable manner and to estimate the risk of lightning, the lightning density N g is determined in events (lightning) per square kilometer . Since the development of electromagnetic lightning localization, the lightning density can now be precisely measured; in the past it was estimated from the Keraunian level of the thunderstorm frequency. As average date of this value (km generally 1 × 1 km) from the underlying unit area depends, for estimating the single object you put your local lightning density (about 62305 -2 lightning protection - Risk Management ) is based.
Lightning causes strong electromagnetic interference in radio communications ( atmospheric interference ). On unused radio frequencies of the long and medium waves, lightning strikes are noticeable through clear cracking or scratching. This phenomenon is used to automatically locate lightning strikes. For this purpose, according to today's standard technology of lightning location systems, the differences in transit time are measured using at least three sensors, and the position is determined from this ( time of arrival systems, TOA, similar to the function of GPS bearings). The results are available as lightning cards on various websites, such as BLIDS from Siemens AG or the Austrian system ALDIS and other members of EUCLID (European Cooperation for Lightning Detection) , or NALDN ( North American Lightning Detection Network ) and that of volunteers operated network Blitzortung.org .
The technique of magnetic direction finding is used by around 50,000 aircraft in the form of the Stormscope invented in 1975 . The devices of the 70s and 80s had their own screen in the cockpit. Since small aircraft have also been using screen cockpits, the existing screens are used for display in the vast majority of cases. The Stormscope WX-500, a direct descendant of the 70s devices, no longer has its own screen. In addition to the original Stormscope, Avidyne markets its TWX670 under a different name.
Another method is the satellite-based global lightning detection, which is based on optical or electromagnetic measurement methods: The important lightning detection satellites and systems include: MicroLab-1 Optical Transient Detector (OTD) ; TRMM Lightning Imaging Sensor (LIS) ; GOES-R Geostationary Lightning Mapper (GLM) , Lightning Mapper Sensor (LMS) ; The third generation of Meteosat from 2021 will also have a tracking system.
Locating via the Schumann resonance is also possible.
Distance estimate over the time interval to the thunder
In order to get an approximate distance information during a thunderstorm without measuring equipment, the time between lightning and thunder can be measured. The transit time of the light is neglected as slightly. This time in seconds, multiplied by the speed of sound (343 m / s), gives the distance in meters. The time in seconds divided by three for the approximate distance in kilometers can also be calculated as an approximation. To determine the time of the thunder, the first perceptible sound signal must always be used, which reaches the observer by the shortest route from the lightning and thus reproduces the distance to this section of the lightning channel relatively precisely. Depending on the type of lightning, this lightning channel section is generally either the part of a cloud lightning that is closest to the observer or that part of a ground lightning that is slightly above the ground. The sound signals from more distant sections of the lightning canal, together with components delayed by reflections and diffraction, form the rumble of thunder, which can be considerably louder than the primary event.
Worldwide there are 2000 to 3000 thunderstorms at any given point in time, which results in 10 to 30 million lightning strikes every day on the entire earth (other estimates only assume 4 million). That's over 100 lightning bolts every second. But only 10% of all lightning strikes the ground.
In 2003 there were over 2 million lightning bolts in the Federal Republic of Germany . In Austria the number registered since 1992 fluctuates between 100,000 and 222,000, of which 70% are in the south-eastern half of the country and only 10% in Alpine Tyrol. The assumption that more lightning occurs in the mountains could not be confirmed on the basis of the measurement data.
The general frequency of lightning in Germany is between 0.5 and ten strikes per square kilometer and year. The average in Bavaria is less than one lightning per km² annually, in Austria and Northern Italy 1–2, in Slovenia 3. Almost everywhere there are smaller areas where the lightning frequency is two to three times as high as in the surrounding area and vice versa. Above all, however, the frequency of lightning depends very much on the season. There are many lightning strikes in July and August, and almost none in January. In addition, there are more lightning bolts in large cities, which is probably related to air pollution and air temperature ( urban climate ). The most frequent lightning flashes in Germany are in the Black Forest, closely followed by the Rhine-Main area and the Rhine-Neckar triangle, and in Austria and Italy in the Southern Limestone Alps .
Research by NASA (e.g. LIS ) has shown that the world's largest lightning frequency is in the Congo Basin , especially in the lee , i.e. H. west of the Central African Threshold . Further centers are the north of Colombia up to Lake Maracaibo in Venezuela (see Catatumbo thunderstorm ), the extreme north of the Indus plain surrounded by the high mountains in Pakistan , the Strait of Malacca including the southern part of the Malay Peninsula , Paraguay and northern Argentina about along the Río Paraná as well as the southern states of the USA (namely Florida) and the offshore Caribbean islands.
While there is lightning all year round in the Congo Basin with slight shifts, in the other areas mentioned the lightning maximum coincides significantly with the summer of the respective hemisphere or the occurrence of the monsoons . The reason that intense thunderstorms occur so frequently, especially in these areas, is almost always of an orographic nature; In other words, the prevailing wind direction forces the air masses to ascend mountain ranges and this is the trigger for thunderstorm rain.
|year||number||Per km²||Strongest month||number||proportion of||Strongest week||number||Strongest day||number|
|2004||1,752,455||4.9||July||747.330||43%||Week 30||326.246||July 23, 2004||125,696|
|2005||1,927,941||5.4||July||869.882||45%||Week 30||475.230||July 29, 2005||277,768|
|2006||2,484,791||7.0||July||1,029,761||41%||Week 25||360.410||June 25, 2006||159,254|
|2007||2,662,409||7.5||June||1,023,778||38%||Week 21||452.160||June 21, 2007||162.139|
|2008||2,153,171||6.0||July||722.830||34%||Week 31||274,444||June 25, 2008||106.923|
|2009||2,354,567||6.6||July||1,047,679||44%||Week 27||595,767||July 3, 2009||191,636|
|2010||1,349,049||3.8||July||686.337||51%||Week 28||389,672||July 17, 2010||143,748|
Lightning / km² over time (1992–2010) for Austria with federal states
|1992||4,071 (1.0)||13,265 (1.4)||19,094 (1.0)||9304 (0.8)||12,878 (1.8)||29,013 (1.8)||14,771 (1.2)||2,328 (0.9)||194 (0.5)||104,918 (1.3)|
|1993||7,979 (2.0)||31,293 (3.3)||40,701 (2.1)||28,291 (2.4)||22,614 (3.2)||59,656 (3.6)||28,155 (2.2)||3,384 (1.3)||296 (0.7)||222,369 (2.7)|
|1994||5,233 (1.3)||27,712 (2.9)||22,766 (1.2)||12,395 (1.0)||15,343 (2.1)||41,881 (2.6)||25,715 (2.0)||3,190 (1.2)||244 (0.6)||154,479 (1.8)|
|1995||5,560 (1.4)||24,294 (2.5)||23,892 (1.2)||10,467 (0.9)||12,295 (1.7)||34,423 (2.1)||17,992 (1.4)||2,120 (0.8)||426 (1.0)||131,469 (1.6)|
|1996||6,014 (1.5)||14,756 (1.5)||21,262 (1.1)||14,153 (1.2)||11,853 (1.7)||32,690 (2.0)||16,665 (1.3)||1,835 (0.7)||373 (0.9)||119,601 (1.4)|
|1997||5,164 (1.3)||23,893 (2.5)||20,043 (1.0)||12,299 (1.0)||10,380 (1.5)||39,761 (2.4)||10,793 (0.9)||962 (0.4)||241 (0.6)||123,536 (1.5)|
|1998||10,521 (2.7)||30,567 (3.2)||28,340 (1.5)||16,032 (1.3)||15,110 (2.1)||55,805 (3.4)||21,770 (1.7)||1,349 (0.5)||664 (1.6)||180,158 (2.1)|
|1999||3,770 (1.0)||17,771 (1.9)||20,592 (1.1)||10,261 (0.9)||7,786 (1.1)||28,270 (1.7)||10,252 (0.8)||1,224 (0.5)||256 (0.6)||100,182 (1.2)|
|2000||7,849 (2.0)||29,079 (3.0)||34,074 (1.8)||21,522 (1.8)||18,993 (2.7)||54,673 (3.3)||23,286 (1.8)||3,745 (1.4)||707 (1.7)||193,928 (2.3)|
|2001||5,973 (1.5)||17,263 (1.8)||24,456 (1.3)||16,986 (1.4)||10,055 (1.4)||29,022 (1.8)||14,538 (1.1)||1,897 (0.7)||368 (0.9)||120,558 (1.4)|
|2002||8,642 (2.2)||21,588 (2.3)||39,506 (2.1)||27,328 (2.3)||14,148 (2.0)||41,864 (2.6)||24,241 (1.9)||3,874 (1.5)||613 (1.5)||181,804 (2.2)|
|2003||7,620 (1.9)||41,241 (4.3)||32,510 (1.7)||23,636 (2.0)||20,555 (2.9)||53,095 (3.2)||28,483 (2.3)||3,419 (1.3)||1,196 (2.9)||211,755 (2.5)|
|2004||4,834 (1.2)||17,941 (1.9)||20,249 (1.1)||17,600 (1.5)||9,813 (1.4)||36,050 (2.2)||12,596 (1.0)||2,942 (1.1)||476 (1.1)||122,501 (1.5)|
|2005||3,996 (1.0)||18,923 (2.0)||36,400 (1.9)||31,584 (2.6)||12,289 (1.7)||58,585 (3.6)||14,318 (1.1)||1,577 (0.6)||317 (0.8)||177,989 (2.1)|
|2006||8,305 (2.1)||43,715 (4.6)||50,672 (2.6)||38,662 (3.2)||28,975 (4.1)||72,777 (4.4)||37,073 (2.9)||3,300 (1.3)||501 (1.2)||283,980 (3.4)|
|2007||8,143 (2.1)||33,531 (3.5)||57,540 (3.0)||38,414 (3.2)||26,225 (3.7)||54,401 (3.3)||26,024 (2.1)||2,175 (0.8)||1,142 (2.8)||247,595 (3.0)|
|2008||14,828 (3.7)||37,521 (3.9)||49,778 (2.6)||26,821 (2.2)||20,109 (2.8)||66,386 (4.1)||33,938 (2.7)||3,475 (1.3)||1,235 (3.0)||254.091 (3.0)|
|2009||10,850 (2.7)||45,675 (4.8)||54,537 (2.8)||29,099 (2.4)||21,049 (2.9)||92,255 (5.6)||24,289 (1.9)||4,298 (1.7)||792 (1.9)||282,844 (3.4)|
|2010||14,584 (3.7)||20,539 (2.1)||44,526 (2.3)||30,468 (2.5)||11,542 (1.6)||53,071 (3.2)||13,583 (1.1)||2,119 (0.8)||1,205 (2.9)||191,637 (2.3)|
|2011||5,855 (1.5)||18,220 (1.9)||22,182 (1.2)||16,821 (1.4)||7,276 (1.0)||34,245 (2.1)||12,784 (1.0)||1,890 (0.7)||274 (0.7)||119,547 (1.4)|
|Ø (1992–2011)||7,490 (1.9)||26,439 (2.8)||33,156 (1.7)||21,607 (1.8)||15,464 (2.2)||48,396 (3.0)||20,563 (1.6)||2,555 (1.0)||576 (1.4)||176,246 (2.1)|
- Color legend:
- The lightning frequencies shown are so-called non-homogenized data. This means that part of the apparent increase in the number of lightning strikes in recent years is due to technical improvements in lightning location and is not necessarily due to climatic factors. The homogenization of the ALDIS lightning data series is a complex issue and is to be carried out as part of a cooperation project with the ZAMG experts .
In June 2017, the ORF published a map with the district-specific lightning density (per year and km 2 ) averaged over the years 2010-2016.
|year||number||per km²||strongest month||number||proportion of|
- Source: BLIDS (area averages and percentages calculated)
Lightning damage and protective measures
In Germany, lightning causes damage amounting to several million euros every year. In 2014, lightning caused insured damage amounting to 340 million euros. Lightning strikes can cause house and forest fires, but electrical equipment is increasingly damaged. Many buildings are therefore provided with a lightning protection system for protection. However, insurance companies do not expressly require lightning protection for private buildings.
However, damage is not only caused by direct impact, but also by potential differences in electrical systems or the ground as well as by electromagnetic induction in longer cable runs. Surge protection sockets for electronic devices such as computers are therefore rather insufficient links in a chain of measures for lightning protection. If they are used alone, they hardly provide any protection, especially if other lines are connected to the devices (telephone line, antenna system, cable television). It is more effective to route all lines (electricity, gas, water, telephone, antenna, cable television) to a common equipotential bonding rail when entering the building. In addition, the power and signal lines should be provided with surge arresters (coarse and fine protection). In the case of antenna systems, the old rule still applies to pull the antenna connector off the device before a thunderstorm. In the past, long wire antennas were used for radio reception on medium and short wave . When a thunderstorm was approaching, the antenna was separated from the device by a flip switch and connected to the earth. There was always a multi-tooth spark gap with an air gap of 1 mm between the "antenna" and "earth" of the switch. The same applies to amateur radio.
Overhead lines are often spanned by one or more earth cables that function as lightning conductors and often have fiber optic data lines integrated inside.
Before and when rockets are launched , they can be struck by lightning. Today launch ramps are often surrounded by around four more than rocket-high lightning rod masts connected with earth ropes. In May 2019, a lightning struck one in Plesetsk cosmodrome a launched missile that their flight and payload, a GLONASS did not affect -Stelliten. After two lightning bolts hit the rocket when the Apollo 12 manned lunar mission took off in November 1969 , parts of the on-board electronics temporarily failed, but the mission continued without any major problems. In March 1987, an unmanned US Atlas G rocket was launched, struck by lightning, disrupting the flight path control computer. The missile went off course and broke.
A particularly spectacular lightning damage occurred in 1970 on the long-wave transmitter Orlunda in Sweden . At that time, a lightning strike destroyed the base insulator of the 250-meter-high central mast of the long-wave transmitter and caused it to collapse.
Effect on people
During a thunderstorm, one is exposed to the risk of lightning strikes outdoors, especially from an elevated position. The effects of a direct lightning strike correspond roughly to those of an electrical accident with the injuries typical of high-voltage accidents such as burns and effects on the nervous system (such as the brain , spinal cord ), muscles including the heart and other organs . (Permanent) damage is possible, which u. a. can lead to unconsciousness ( coma ), paralysis and fatal cardiac , circulatory and respiratory arrest . Skin injuries in the form of a Lichtenberg figure can develop within one hour of the accident . Direct lightning strikes in people are often fatal, especially with stronger lightning strikes.
In around 50% of lightning victims who survive, neurological damage occurs after months to years.
In addition to the direct effects of the electric current, the pressure wave resulting from the lightning bolt represents a danger. Depending on the strength of the lightning bolt, this can correspond to an explosive effect of around 30 kg TNT and, at some distance, secondary injuries such as hearing loss , for example sudden hearing loss , tinnitus or Cracks in the eardrum, but can also cause life-threatening tears in the lungs or injuries to internal organs and fractures .
Depending on the situation, there may be other indirect effects, for example frightening or dazzling, which can lead to secondary accidents. People who have been in the vicinity of a lightning strike sometimes have physiological or psychological disorders or changes that can even result in a permanent change in personality .
Fatal lightning strikes are rare; the average of three to seven fatalities per year in Germany could be further reduced by further precautionary measures. In the 19th century, around 300 people were still killed by lightning in Germany each year, as significantly more people worked in the open fields in agriculture and could not retreat to protective objects such as cars, tractors or combine harvesters.
Behavior in thunderstorms
The best protection is to observe the short-term weather development en route and to identify places of refuge that can be reached when there is a thunderstorm. Today, weather forecasts are still too imprecise to predict the exact location and time of a thunderstorm. Short-term severe weather warnings via mobile phone app can be helpful, but still do not replace the specific decisions that have to be made depending on the situation.
According to the 30/30 rule, it is assumed that the risk of being struck by lightning is high as soon as there are less than 30 seconds between lightning and thunder when a thunderstorm is approaching (the thunderstorm is then about 10 kilometers away) until 30 minutes have passed after the last thunder or lightning bolt. During this time, a safe place should be sought and not left again.
- Looking for protection in buildings or vehicles: Vehicles with a closed metal body and buildings with a lightning protection system or made of reinforced concrete act like a Faraday cage . The metallic cage must, however, be dimensioned accordingly in order to be able to absorb the high pulse currents without mechanical deformation. Occasionally it is reported that cars struck by lightning have caught fire. The areas on the ground under high-voltage lines , which have metallic masts and whose masts are connected by earth cables , are also a good shelter . The lightning current is distributed to several earthed masts through the earth wire, thus reducing the step voltage in the area of the earthing point.
- There is also danger from indirect effects such as the sound effect (bang), the dazzling effect and a startle reaction . This can trigger secondary accidents such as falls and car accidents. When climbing, you should secure yourself with a rope, but keep your distance from metallic objects such as snap hooks .
If protection cannot be found in buildings or vehicles, the following rules apply:
- Avoid open terrain, hills and ridges, as well as solitary and isolated trees and forest edges (risk of rollover). Forests with trees of about the same height, however, are safe inside. If you are looking for protection in the forest, a distance of at least 10 meters to the next tree should be kept because of the possible bark of the tree.
- Rock walls and building walls offer some protection (see chart at right).
- Avoid standing on or in water and pools.
- Because of the step tension, put your feet together, crouch down, hold your arms against your body, draw your head, look for a recess. Do not lay on the floor, but minimize the contact area with the floor (e.g. sit on a backpack).
- Keep a distance of at least 3 m from all larger objects, including other people (risk of rollover).
- Put away metallic objects (e.g. walking sticks).
However, other dangers of thunderstorms must also be taken into account: Flash floods can occur in streams and rivers , and the temperature can drop very quickly and sharply, especially in the mountains. Paths can also get wet and slippery or be covered by hailstones.
Building law and lightning protection
In Germany, a lightning rod is not mandatory for residential buildings. In the building regulations of the pending model building regulations , section 46 of the lightning protection systems only says briefly:
"Structural systems in which, depending on their location, design or use, lightning strikes can easily occur or lead to serious consequences, must be provided with permanently effective lightning protection systems."
Every building project therefore requires a case-by-case assessment with regard to the probability of lightning strikes (for example based on the location and expansion of the building) and an impact assessment (for example personal injury).
The corresponding wording in Austrian building law reads: "Buildings are to be equipped with lightning protection systems if they are at risk from lightning strikes due to their location, size or construction or if the purpose or the cultural and historical significance of the structure so requires".
Risk analysis - proof of lightning protection
The legislator does not specify any technical rule according to which this test should be carried out. In principle, the building owner / architect is therefore free to provide evidence provided that all influencing factors named in the legal text (location, type of construction, use, consequences) are considered in detail.
In practice, this turns out to be not that easy at all, because the necessary estimates usually require appropriate experience. The amount of work that can be put into a professional risk assessment can be seen from EN 62305-11 Part 2 (Germany: VDE 0185-305). This standard fulfills the minimum legal requirements in terms of scope, so its use is permissible under building law. On the other hand, the effort involved in data acquisition and calculation is inappropriately high for many construction projects. However, it is particularly problematic that in individual cases the calculation results are not in accordance with the applicable building law. The legislature or the case law have made other stipulations for certain building types / user groups. If the calculation results of the risk assessment deviate from the legal requirements, the higher requirements must generally be implemented.
The risk assessment will always be only the first step in the planning of a lightning protection system; in a further step, the particularities of building law must be taken into account, and then the assumptions made in the risk assessment (selected reduction factors, damage factors etc.) must be implemented. Further statements are also made in EN 62305-11 Parts 1 to 4 for the subsequent planning of the lightning protection of a structural system.
Use of lightning energy
In the Bible, lightning (and thunder) are used, for example, for the wrath of God ( Ex 9.24 EU ; 2 Sam 22.15 EU ; Hi 37 EU ; Ps 18 EU ), for God's judgment ( Zech 9,14 EU ) , for God's revelation to men ( Ex 20.18 EU ; Rev 4.5 EU ), for the coming of the Son of Man ( Mt 24.27 EU ; Lk 17.24 EU ), for the fall of Satan ( Lk 10.18 EU ) and for the nature of the angels and the risen ( Eze 1.14 EU ; Dan 10.6 EU ; Mt 28.3 EU ).
In ancient Greece, lightning was assigned to Zeus as Astrapaios ( lightning bolt ), and to Jupiter by the Romans . A lightning bolt in the hand as an attribute of the lightning thrower can be found in literary sources (e.g. Homer ) and in representations since then. The Etruscans saw oracles in flashes through which they could interpret the present and the future. Only the priests ( haruspices ) were authorized to interpret the lightning according to the lightning doctrine . Already at this time (between 800 and 600 BC) lightning was categorized and observed.
Lightning on other planets
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