Thursday, September 6, 2012

Lightning :massive electrostatic discharge

Lightning is a massive electrostatic discharge caused by unbalanced electric charge in the atmosphere. Lightning can be either inside clouds (IC), cloud to cloud (CC) or cloud to ground (CG) and is accompanied by the loud sound ofthunder. Sony VAIO PCG-3B1M Battery
Because the speed of sound in air (~340 m/s) is so much slower than the speed of light (300,000,000 m/s) from the lightning flash the distance to a lightning strike can be closely approximated by dividing the flash-thunder interval, T (sec) by 3--T(sec)/3 = km distance or T(sec)/5 = mile distance. Sony VAIO PCG-3C1T Battery
Thunder often lasts several seconds because the sounds from different parts of the lightning strike arrive at different times.
A typical cloud to ground lightning strike is often over 5-6 km (3-4 mi) long[1] but may be many kilometers longer. Sony VAIO PCG-3D1M Battery
A typical thunderstorm may have three or more strikes per minute at its peak.[2] Lightning is usually associated with and produced by cumulonimbus clouds which may reach up to 15 km high (10 mi) high and often have a base 5-6 km (3-4 mi) above the ground. Sony VAIO PCG-3G2M Battery
The sun heats the earth and water causing massive up-drafts of warm moisture-filled air to rise like a giant hot air balloon that go through different temperature zones and electric fields typical of athunderstorm formation. Once the moisture in the air cools and condenses into rain droplets or ice crystals it falls in massive turbulent down drafts typical of rain storms. Sony VAIO PCG-5R1M Battery
The temperature of the moisture filled air typically falls about 6° C (11° F) for each 1,000 metres (3,300 ft) of higher elevations causing much of the water vapor to freeze into ice crystals or super cooled water droplets at higher elevations. Sony VAIO PCG-7141M Battery
As the ice crystals, graupel or water droplet laden masses of air rise or fall they tend to either accumulate or get rid of electrons depending on the type of ice or water particles in the air and the electric fields and temperatures they are rising or falling through.Sony VAIO PCG-7143M Battery
The rising and falling particles in the air acts like a massive Van de Graaf generator belt that is used to separate the negatively charge electrons and positively charged molecules missing electrons. These accumulations of charge of different signs generate large powerful electric fields in the clouds and between the clouds and ground much like what would occur in a massive parallel plate capacitor. Sony VAIO PCG-7151M Battery
Strong electric fields between clouds with too many or not enough electrons or clouds and the ground accelerate these electrons towards areas deficient in electrons.[4]
The turbulent airflow typical of clouds may move different charged parts of clouds into different locations. Sony VAIO PCG-7154M Battery
If the local electric field is strong enough to exceed the dielectric strength of moisture filled air (about 3 million Volts/m) there will be a massive flow of electrons away from where there are too many electrons (negative charge) towards places where there are not enough electrons (positive charge). Sony VAIO PCG-7162M Battery
There are local variations in dielectric strength and charge distributions that cause the lightning charge flows to follow a tortuous path through the atmosphere. These powerful electric fields also accelerate the molecules deficient in electrons but since they typically weigh at least 30,000 times more than electrons they are much harder to move in air. Sony VAIO PCG-7181M Battery
Massive amounts of unbalanced charge can accumulate in different areas of the clouds or between the clouds and the ground. Observation by satellite show that about 75% of all lightning strikes are from regions inside clouds or from cloud to cloud with only about 25% reaching the ground. Sony VAIO PCG-41112M Battery
When the electric fields are strong enough these massive charge imbalances are discharged as electrons flow towards areas deficient in electrons. A lightning strike reestablishes a local charge equilibrium. Sony VAIO PCG-7153M Battery
Once a lightning strike has established a low resistance path to an unbalanced charge region there are usually three or more return strokes following the same ionized lightning channel that drain other adjacent volumes of unbalanced charge a few milliseconds later. Sony VAIO PCG-71312M Battery
Lightning may also occur during snow storms (thundersnow), volcanic eruptions, dust storms, forest fires or tornadoes which all have large flows of rising particles in the atmosphere which can and do accumulate massive amounts of differing charge in different locations and conditions inside clouds of rising and falling snow, Sony VAIO PCG-7144M Battery
dust, volcanic or smoke particles and dissipate these charge accumulations with lightning strikes.[5] [6] Hurricanes typically generate some lightning in the hurricane eyewall and inner and outer rainbands circling the hurricane center. The rainbands in a strong hurricane can be as much as 160 km (100 mi) from the center and typically contains the majority of the lightning strikes.[7] Sony VAIO PCG-7191L Battery
Very strong tropical cyclones (hurricanes) generate more lightning activity near the eyewall of the hurricane; but the total number of lightning strikes in the rainbands remains even higher. Hurricane lightning strikes are at a low level when the hurricane is over the ocean and their number increases as the hurricane makes land fall. Sony VAIO PCG-3C1M Battery
Lightning in hurricanes is now studied by data obtained from the Long Range Lightning Detection Network (LLCN) which can detect lightning up to 2000 km (1200 mi) from their detector stations.[9]
The complicated details of the mechanisms that cause lightning are still a matter of scientific investigation. Sony VAIO PCG-3F1M Battery
The rise and fall of water droplets, icecrystals (graupel, etc.) inside a cloud as they are carried aloft through different temperature zones and electric fields in updrafts or down in downdrafts are thought to be a key elements in lightning development, Sony VAIO PCG-3H1M Battery
and may cause a forcible separation of positive and negative charges which are transferred by collisions within the cloud, thus assisting in the formation of the large charge differences in the atmosphere that cause lightning. The "typical" thunderstorm cloud accumulates positive charge in the colder upper part of the cloud, Sony VAIO PCG-3J1M Battery
negative charge in the middle and lower parts and possibly a small positive charge at the base of the cloud. Collisions of moving water droplets, ice particles and smoke or dust particles, which are bipolar in charge distribution, in the presence of a strong electric fields are thought to possibly enhance charge buildup of different polarity.[11] Sony VAIO PCG-8141M Battery
The fear of lightning (and thunder) is called astraphobia. Because of the severe danger of a close lightning strike this fear may be appropriate. The study or science of lightning is called fulminology, and someone who studies lightning is referred to as a fulminologistSony VAIO PCG-8161M Battery
The turbulent rising moist warm air flow combined with rain drops and ice crystals rising and falling though different temperature zones and electrical fields typical of cumulonimbus clouds may cause different parts of the cloud to accumulate an excess of positive or negative charge. Sony VAIO PCG-3C2M Battery
Usually the top of the cloud which may be as cold as -40°C (-40°F) is composed of small ice crystals charged positively with the middle of the cloud charged negative with a possible small zone at the base of the cloud of positive charge. A large accumulation of charge gives rise to strong electrical fields in the clouds and induces fields on the ground of the opposite polarity. Sony VAIO PCG-5N2M Battery
Electric fields accelerate charged particles.Air is a great insulator but when this potential difference between either parts of a cloud charged differently or the cloud and ground exceed the local dielectric strength of air (about 2 to 3,000,000 volts/m (2 to 3 MV/m) a inside cloud (IC), cloud to cloud (CC), or cloud to ground (CG), Sony VAIO PCG-5P1M Battery
a massive flow of electrons in a lightning stroke may be initiated. Paths in the air with higher electric fields or lower dielectric strength cause the electrons in a lightning strike to go though a tortuous path in the air, changing directions slightly or significantly every few centimeters or inches. Sony VAIO PCG-5S1M Battery
Each major stroke of a lightning strike is usually about 50 m (150 ft) long and lasts about 1 to 2 microseconds with a pause of about 50 microseconds as more charge is accumulated before resuming another stroke in a slightly or significantly different direction. Sony VAIO PCG-9Z1M Battery
The front of a lightning strike is called a stepped leader and may split into many different paths--not all of them reach the ground giving rise to the phrase: forked lightning. The part of the stroke that reaches the ground nearly always carries most of the charge and is seen as the Sony VAIO PCG-7171M Battery
lightning bolt as electrons rush to the newly found highly conductive ionized air and low resistance path. In a typical cloud-to-ground strike, electrons descend from cloud base to ground. Just before the strike leader reaches the ground, the charge in the step leader induces a huge electric potential in objects connected to the ground (some 10's of million volts), Sony VAIO PCG-7186M Battery
that brings up spikes of positive charge flow from high sharp objects, lightning rods, people, trees, etc., connected to the ground or water. After the descending and rising charge paths meet, massive amounts of charge flow in the 1 to 4 cm (.5 to 1.5 in) thick ionized channel of air centered in a lightning bolt channel—Sony VAIO PCG-81112M Battery
this massive flow of charged particles heats the air and gives the brightest part of a lightning strike. The stepped leader of a bolt of lightning may take on average about 20 milliseconds to reach the ground. Occasionally much longer lightning strokes occur which take more time. Sony VAIO PCG-31311M Battery
Once the downward and upward current flow impulses meet—a few metres or tens of metres above earth—a much more conductive connection is established between the cloud and the ground and the front edge of the return stroke electrons zip from the cloud at about 0.3-0.5 times the speed of light, c, on the highly ionized lightning stepped leader stroke path. Sony VAIO PCG-8152M Battery
Return currents may continue for several microseconds with three or more repeat strokes common. Subsequent lightning strokes following the ionized lightning channel are initiated by dart leaders.[13]
The return stroke with its much larger current flow produces the highly visible intense Sony VAIO PCG-31111M Battery
main lightning strike as it heats and ionizes the surrounding air in the lightning channel to about 30,000 degrees C (54,000 degrees F). This fast and massively heated ionized air in the lightning channel “explodes” creating theshock waves that within a few yards decay to loud sound waves we hear as thunder. Sony VAIO PCG-61111M Battery
Thunder, under ideal conditions, can be heard from over 20 km or 12 miles away. The relatively slow speed of sound (~340 m/s) and the extended length (5-6 km) of a typical lightning strike extends the sound of thunder over several seconds. Sony VAIO PCG-51112M Battery
Multiple return strokes over the highly conductive ionized channel to different local charge locations about 0.5 km (0.3 mi) away from the original sources in the cloud may be needed to establish a larger volume of charge equilibrium. Sometimes return strokes take long enough to recur that they cause the lightning to flicker. Sony VAIO PCG-51211M Battery
A typical lightning flash has four return strokes spaced a few tens of milliseconds apart but over 30 return strokes have been observed. Although resolvable with high speed photography and other instruments a typical lightning strike occurs much faster than the human eye can see it so it appears as a single bright flash of lightning lasting a few tenths of a second. Sony VAIO PCG-51212M Battery
Dependent on the location and time of year about 5 to 10% of lightning is positive lightning that originates mainly in the "anvil" of cumulonimbus clouds near the top of the typical thunderstorm, where a high positive charge (electron deficient) often resides.Sony VAIO PCG-41111M Battery
"Positive lightning" that forms in this region has a descending stepped leader that will carry an apparent positive charge as electrons rush to the top of the cloud leaving positive charged molecules behind. When this "positive pulse" reaches the ground electrons will flow from the ground to cloud—the opposite of the usual electron flow. Sony VAIO PCG-41111V Battery
Positive lightning is particularly dangerous since it originates in the upper levels of a storm cloud several kilometers higher than a typical lightning strike.[15]
The amount of air the strike must "burn through" to reach the ground requires a much stronger electric field. Sony VAIO PCG-61412V Battery
The current flow is typically much stronger than a negative strike. Its flash duration is longer, and its peak charge and potential can be ten times greater than a negative strike; as much as 300,000 amperes and well over several billion volts. Positive lightning, though typically rarer, Sony VAIO PCG-71112M Battery
can be the dominate type of cloud-to-ground (CG) lightning during the winter months and in the last stages of a thunderstorm. Positive lightning typically strikes at the edge of a storm but can strike up to 10 km (6 mi) from a storm. The positively charged upper parts of the cumulonimbus cloud has been identified as a major source of the recently discovered spriteselvesSony VAIO PCG-81111V Battery
blue flashes and other lightning like phenomena observed well above the clouds, 30 to 95 km (20 to 60 mi) in altitude, well above the parent thunderstorm clouds which typically stop at about 15 km.
High speed photographs of a lightning storm show the step wise development of lightning strikes. Sony VAIO PCG-81111V Battery
An average bolt of negative lightning carries an electric current of about 30,000 to 100,000 amperes (30-100 kA) at a voltage of over a billion volts.
The current in a lightning strike can raise the temperature of sand high enough to fuse the silica in it into glass channels known asfulgurites, Sony VAIO PCG-81212M Battery
which are normally hollow and can sometimes extend as much as several meters into the ground. Water in trees can be heated enough to cause them to explode and/or set the tree on fire--a leading cause of forest fires.[17][18]
The most lightning deaths occur to people exposed in an open field or on water where they are the highest local object and most likely to attract a lightning strike. Sony VAIO PCG-81212V Battery
Lightning hitting a tree with people under it is the second leading cause of lightning deaths. Isolated trees are typically the highest object around and attract lightning--the danger in a forest of trees is reduced. The safest places to be if lightning threatens are inside a building with metal plumbing and wiring which conduct the electricity away from you, Sony VAIO PCG-51111M Battery
or inside a metal-bodied and metal-roofed vehicle which acts as a faraday cage. Cars are usually safe because lightning induced current and voltage stay outside the metal surrounding the typical passenger compartment and do not penetrate inside--the skin effect that makes Faraday cages work. Sony VAIO VPCS13X9E/B battery
The rubber tires on a motorcycle, etc. or the fabric topped convertible offer no protection. IfLightning Roars Stay Indoors.[19]
The average peak power output of a single lightning stroke is about one trillion watts — one terawatt (1012 W), and the stroke lasts for about 30 to 90microseconds. Sony VAIO VPCS12V9E/B battery
Most of the energy is dissipated in creating the ionized air channel and thunder.
Lightning strikes 40–50 times a second worldwide, for a total of nearly 1.4 billion flashes per year.[21]
Cloud-to-ground (CG) lightning accounts for 25% of lightning globally. Sony VAIO VPCS12V9E/B battery
The base of the negative region in a cloud is typically at the elevation where freezing occurs. The closer this region is to the ground, the more likely cloud-to-ground strikes are. In the tropics, where the freeze zone is higher, 10% of lightning is CG. At the latitude of Norway (60° lat.) where the freezing elevation is lower, 50% of lightning is CG.Sony VAIO VPCF13M8E/B battery
Lightning is not distributed evenly around the planet.[24] About 70% of lightning occurs on land in the tropics, where most thunderstorms occur. The north and south poles and the areas over the oceans have the fewest lightning strikes. The place where lightning occurs most often is near the small village of KifukaSony VAIO VPCF13Z0E/B battery
in the mountains of eastern Democratic Republic of the Congo,[25] where the elevation is around 975 metres (3,200 ft). On average this region receives 158 lightning strikes per 1 square kilometer (0.39 sq mi) a year.[26] Other hotspots includeCatatumbo lightning in Venezuela, Singapore[27]Sony VAIO VPCM13M1E/L battery
Teresina in northern Brazil[28] and "Lightning Alley" in CentralFlorida.
According to this cloud particle charging hypothesis, charges are separated when ice crystals rebound off graupel. Charge separation appears to require strong updrafts which carry water droplets upward, supercooling them to between -10 and -40 °C (14 and -40 °F). Sony VAIO VPCM13M1E/W battery
These water droplets collide with ice crystals to form a soft ice-water mixture called graupel. Collisions between ice crystals and graupel pellets usually result in positive charge being transferred to the ice crystals, and negative charge to the graupel.[20]
Updrafts drive the less heavy ice crystals upwards, causing the cloud top to accumulate increasing positive charge. Sony VAIO VPCF22M1E battery
Gravitycauses the heavier negatively charged graupel to fall toward the middle and lower portions of the cloud, building up an increasing negative charge. Charge separation and accumulation continue until the electrical potential becomes sufficient to initiate a lightning discharge, Sony VAIO VPCF11M1E/H battery
which occurs when the distribution of positive and negative charges forms a sufficiently strong electric field.
Even assuming an electric field has been established, the mechanism by which the lightning discharge begins is not well known.Sony VAIO VPCF13M0E/B battery
Electric field measurements in thunderclouds are typically not large enough to directly initiate a discharge.[35] Many hypotheses have been proposed, ranging from including runaway breakdownto locally enhanced electric fields near elongated water droplets or ice crystals.[36] Sony VAIO VPCYB2M1E battery
Percolation theory, especially for the case of biased percolation,[37]describe random connectivity phenomena, which produce an evolution of connected structures similar to that of lightning strikes.
As a thundercloud moves over the surface of the Earth, Sony VAIO VPCYB3V1E battery
an electric charge equal to but opposite the charge of the base of the thundercloud is induced in the Earth below the cloud. The induced ground charge follows the movement of the cloud, remaining underneath it.
An initial bipolar discharge, or path of ionized air, starts from a negatively charged region of mixed water and ice in the thundercloud. Sony VAIO VPCY11M1E battery
Ionized channels of the discharge are known as leaders. The positive and negative charged leaders, generally a "stepped leader", proceed in opposite directions. The negatively-charged one proceeds downward in a number of quick jumps (steps). About 90% of the leaders exceed 45 m (148 ft) in length, with most in the order of 50 to 100 m (164 to 328 ft).[38] Sony VAIO VPCS12L9E/B battery
As it continues to descend, the stepped leader may branch into a number of paths.[39] The progression of stepped leaders takes a comparatively long time (hundreds of milliseconds) to approach the ground. This initial phase involves a relatively small electric current (tens or hundreds of amperes), Sony VAIO VPCF11S1E/B battery
and the leader is almost invisible when compared with the subsequent lightning channel.
When a stepped leader approaches the ground, the presence of opposite charges on the ground enhances the strength of theelectric field. The electric field is strongest on ground-connected objects whose tops are closest to the base of the thundercloud, Sony VAIO VPCYB3V1E/R Battery
such as trees and tall buildings. If the electric field is strong enough, a conductive discharge (called apositive streamer) can develop from these points. This was first theorized by Heinz Kasemir.[40][41]
As the field increases, the positive streamer may evolve into a hotter, Sony VAIO VPCF23P1E Battery
higher current leader which eventually connects to the descending stepped leader from the cloud. It is also possible for many streamers to develop from many different objects simultaneously, with only one connecting with the leader and forming the main discharge path. Photographs have been taken on which non-connected streamers are clearly visible.[42] Sony VAIO VPCF23N1E Battery
Once a channel of ionized air is established between the cloud and ground this becomes a path of least resistance and allows for a much greater current to propagate from the Earth back up the leader into the cloud. This is the return stroke and it is the most luminous and noticeable part of the lightning discharge. Sony VAIO VPCY21S1E/L Battery
When the electric field becomes strong enough, an electrical discharge (the bolt of lightning) occurs within clouds or between clouds and the ground. During the strike, successive portions of air become a conductive discharge channel as the electrons and positive ions of air molecules are pulled away from each other and forced to flow in opposite directions. Sony VAIO VPCY21S1E/G battery
The electrical discharge rapidly superheats the discharge channel, causing the air to expand rapidly and produce a shock wave heard as thunder. The rolling and gradually dissipating rumble of thunder is caused by the time delay of sound coming from different portions of a long stroke.[43] Sony VAIO VPCF24M1E battery
High speed videos (examined frame-by-frame) show that most lightning strikes are made up of multiple individual strokes. A typical strike is made of 3 or 4 strokes, though there may be more.[44]
Each re-strike is separated by a relatively large amount of time, typically 40 to 50 milliseconds. Re-strikes can cause a noticeable "strobe light" effect.[43] HP Compaq HSTNN-IB16 Battery
Each successive stroke is preceded by intermediate dart leader strokes akin to, but weaker than, the initial stepped leader. The stroke usually re-uses the discharge channel taken by the previous stroke.[45]
The variations in successive discharges are the result of smaller regions of charge within the cloud being depleted by successive strokes. HP Compaq HSTNN-IB18 Battery
The sound of thunder from a lightning strike is prolonged by successive strokes.
Some lightning strikes exhibit particular characteristics; scientists and the general public have given names to these various types of lightning. The lightning that is most-commonly observed is streak lightning. HP Compaq HSTNN-IB28 Battery
This is nothing more than the return stroke, the visible part of the lightning stroke. The majority of strokes occur inside a cloud so we do not see most of the individual return strokes during a thunderstorm.
Cloud-to-ground is the best known and second most common type of lightning. HP Compaq HSTNN-IB51 Battery
Of all the different types of lightning, it poses the greatest threat to life and property since it strikes the ground. Cloud-to-ground (CG) lightning is a lightning discharge between a cumulonimbus cloud and the ground. It is initiated by a leader stroke moving down from the cloud. HP Compaq HSTNN-IB52 Battery
Bead lightning is a type of cloud-to-ground lightning which appears to break up into a string of short, bright sections, which last longer than the usual discharge channel. It is relatively rare. Several theories have been proposed to explain it; one is that the observer sees portions of the lightning channel end on, and that these portions appear especially bright. HP Compaq HSTNN-IB55 Battery
Another is that, in bead lightning, the width of the lightning channel varies; as the lightning channel cools and fades, the wider sections cool more slowly and remain visible longer, appearing as a string of beads.
Ribbon lightning occurs in thunderstorms with high cross winds and multiple return strokes. HP Compaq HSTNN-IB62 Battery
The wind will blow each successive return stroke slightly to one side of the previous return stroke, causing a ribbon effect.
Staccato lightning is a cloud-to-ground lightning (CG) strike which is a short-duration stroke that (often but not always) appears as a single very bright flash and often has considerable branching.[48] HP Compaq HSTNN-LB05 Battery
These are often found in the visual vault area near the mesocyclone of rotating thunderstorms and coincides with intensification of thunderstorm updrafts. A similar cloud-to-cloud strike consisting of a brief flash over a small area, appearing like a blip, also occurs in a similar area of rotating updrafts. HP Compaq HSTNN-LB08 Battery
Forked lightning is a name, not in formal usage, for cloud-to-ground lightning that exhibits branching of its path.
Local variations in cloud formations can cause the bottom of a cloud to accumulate a positive charge which will induce a negative charge on the ground. HP Compaq HSTNN-LB0E Battery
Lightning can occur with both positive and negative polarity. An average bolt of negative lightning carries an electric current of 30,000 amperes (30 kA), and transfers 15 coulombs of electric charge and 500 megajoules of energy. Large bolts of lightning can carry up to 120 kA and 350 coulombs.[49] HP Compaq HSTNN-LB11 Battery
An average bolt of positive lightning carries an electric current of about 300 kA — about 10 times that of negative lightning.
Unlike the far more common "negative" lightning, positive lightning occurs when a positive charge is carried by the top of the clouds (generally anvil clouds) rather than the ground. HP Compaq HSTNN-LB51 Battery
Generally, this causes the leader arc to form in the anvil of the cumulonimbus and travel horizontally for several miles before veering down to meet the negatively charged streamer rising from the ground. The bolt can strike anywhere within several miles of the anvil of the thunderstorm, often in areas experiencing clear or only slightly cloudy skies; HP Compaq HSTNN-LB52 Battery
they are also known as "bolts from the blue" for this reason. Positive lightning makes up less than 5% of all lightning strikes.[51]
Because of the much greater distance they must travel before discharging, positive lightning strikes typically carry six to ten times the charge and voltage difference of a negative bolt and last around ten times longer.[52] HP Compaq HSTNN-MB05 Battery
During a positive lightning strike, huge quantities of ELF and VLF radio waves are generated.[53]
As a result of their greater power, as well as lack of warning, positive lightning strikes are considerably more dangerous. HP Compaq HSTNN-OB06 Battery
At the present time, aircraft are not designed to withstand such strikes, since their existence was unknown at the time standards were set, and the dangers unappreciated until the destruction of a glider in 1999.[54] The standard in force at the time of the crash, Advisory Circular AC 20-53A, HP Compaq HSTNN-OB52 Battery
was replaced by Advisory Circular AC 20-53B in 2006,[55] however it is unclear whether adequate protection against positive lightning was incorporated.[56][57]
Positive lightning is also now believed to have been responsible for the 1963 in-flight explosion and subsequent crash of Pan Am Flight 214, a Boeing 707.[58] HP Compaq HSTNN-OB62 Battery
Due to the dangers of lightning, aircraft operating in U.S. airspace have been required to have static discharge wicks to reduce the possibility of attracting a lightning strike, as well as to mitigate radio interference due to static buildup through friction with the air, but these measures may be insufficient for positive lightning.[59] HP Compaq HSTNN-UB05 Battery
Positive lightning has also been shown to trigger the occurrence of upper atmosphere lightning. It tends to occur more frequently in winter storms, as withthundersnow, and at the end of a thunderstorm.[20]
Dry lightning is a term in Canada and the United States for lightning that occurs with no precipitation at the surface. HP Compaq HSTNN-UB11 Battery
This type of lightning is the most common natural cause of wildfires.[60] Pyrocumulus clouds produce lightning for the same reason that it is produced by cumulonimbus clouds.
Rocket lightning is a form of cloud discharge, generally horizontal and at cloud base, HP Compaq HSTNN-UB18 Battery
with a luminous channel appearing to advance through the air with visually resolvable speed, often intermittently.[61]
Lightning discharges may occur between areas of cloud without contacting the ground. HP Compaq HSTNN-UB68 Battery
When it occurs between two separate clouds it is known as inter-cloud lightning, and when it occurs between areas of differing electric potential within a single cloud it is known as intra-cloud lightning. Intra-cloud lightning is the most frequently occurring type.[20] HP Compaq HSTNN-UB69 Battery
These are most common between the upper anvil portion and lower reaches of a given thunderstorm. This lightning can sometimes be observed at great distances at night as so-called "heat lightning". In such instances, the observer may see only a flash of light without hearing any thunder. HP Compaq HSTNN-W42C Battery
The "heat" portion of the term is a folk association between locally experienced warmth and the distant lightning flashes.
Another terminology used for cloud–cloud or cloud–cloud–ground lightning is "Anvil Crawler",HP Compaq HSTNN-W42C-A Battery
due to the habit of the charge typically originating from beneath or within the anvil and scrambling through the upper cloud layers of a thunderstorm, normally generating multiple branch strokes which are dramatic to witness. These are usually seen as a thunderstorm passes over the observer or begins to decay. HP Compaq HSTNN-W42C-B Battery
The most vivid crawler behavior occurs in well developed thunderstorms that feature extensive rear anvil shearing.
Sheet lightning is an informal name for cloud-to-cloud lightning that exhibits a diffuse brightening of the surface of a cloud, HP Compaq HSTNN-XB0E Battery
caused by the actual discharge path being hidden or too far away. The lightning itself cannot be seen by the spectator, so it appears as only a flash, or a sheet of light. The lightning may be too far away to discern individual flashes.
Heat lightning is a common name for a lightning flash that appears to produce no discernable thunder because it occurs too far away for the thunder to be heard. HP Compaq HSTNN-XB11 Battery
The sound waves dissipate before they reach the observer.
Lightning has been triggered by launching lightning rockets carrying trailing spools of wire into thunderstorms. The wire unwinds as the rocket ascends, providing a path for lightning. These bolts are typically very straight due to the straight path created by the wire.[63] HP Compaq HSTNN-XB18 Battery
The International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, Florida typically uses rocket induced lightning in their research studies.
Lightning has also been triggered directly by other human activities: Flying aircraft can trigger lightning.[64] HP Compaq HSTNN-XB21 Battery
Furthermore, lightning struck Apollo 12 soon after takeoff, and has struck soon after thermonuclear explosions.
Since the 1970s,researchers have attempted to trigger lightning strikes by means of infrared or ultraviolet lasers, HP Compaq HSTNN-XB24 Battery
which create a channel of ionized gas through which the lightning would be conducted to ground. Such triggering of lightning is intended to protect rocket launching pads, electric power facilities, and other sensitive targets.
In New Mexico, U.S., scientists tested a new terawatt laser which provoked lightning. HP Compaq HSTNN-XB28 Battery
Scientists fired ultra-fast pulses from an extremely powerful laser thus sending several terawatts into the clouds to call down electrical discharges in storm clouds over the region. The laser beams sent from the laser make channels of ionized molecules known as "filaments". HP Compaq HSTNN-XB51 Battery
Before the lightning strikes earth, the filaments lead electricity through the clouds, playing the role of lightning rods. Researchers generated filaments that lived too short a period to trigger a real lightning strike. Nevertheless, a boost in electrical activity within the clouds was registered. HP Compaq HSTNN-XB52 Battery
According to the French and German scientists, who ran the experiment, the fast pulses sent from the laser will be able to provoke lightning strikes on demand.[79] Statistical analysis showed that their laser pulses indeed enhanced the electrical activity in the thundercloud where it was aimed—in effect they generated small local discharges located at the position of the plasma channels. HP Compaq HSTNN-XB59 Battery
Lightning has been observed within the atmospheres of other planets, such as Venus, Jupiter and Saturn. Lightning on Venus is still a controversial subject after decades of study. During the Soviet Venera and U.S. Pioneer missions of the 1970s and '80s, signals suggesting lightning may be present in the upper atmosphere were detected.[81] HP Compaq HSTNN-XB61 Battery
However, the Cassini–Huygens mission fly-by of Venus in 1999 detected no signs of lightning at all. Despite this, it has been suggested that radio pulses recorded by the spacecraft Venus Express (which began orbiting Venus in April 2006) may originate from lightning on Venus. HP Compaq HSTNN-XB62 Battery
Because the electrostatic discharge of terrestrial lightning superheats the air to plasma temperatures along the length of the discharge channel in a short duration, kinetic theory dictates gaseous molecules undergo a rapid increase in pressure and thus expand outward from the lightning creating a shock waveaudible as thunder. HP Compaq HSTNN-XB68 Battery
Since the sound waves propagate, not from a single point source, but along the length of the lightning's path, the sound origin's varying distances from the observer can generate a rolling or rumbling effect. Perception of the sonic characteristics is further complicated by factors such as the irregular and possibly branching geometry of the lightning channel, HP Compaq HSTNN-XB69 Battery
by acoustic echoing from terrain, and by the typically multiple-stroke characteristic of the lightning strike.
Light travels at about 300,000,000 m/s. Sound travels through air at about 340 m/s. An observer can approximate the distance to the strike by timing the interval between the visible lightning and the audible thunder it generates. HP Compaq HSTNN-XB85 Battery
A lightning flash preceding its thunder by five seconds would be about one mile (1.6 km) (5x340 m) distant. A flash preceding thunder by three seconds is about one kilometer (0.62 mi) (3x340 m) distant. Consequently, a lightning strike observed at a very close distance will be accompanied by a sudden clap of thunder, HP Compaq HSTNN-105C Battery
with almost no perceptible time lapse, and the smell of ozone (O3).
The production of X-rays by a bolt of lightning was theoretically predicted as early as 1925[83] but no evidence was found until 2001/2002,[84] when researchers at the New Mexico Institute of Mining and Technology detected X-ray emissions from an induced lightning strike along a wire trailed behind a rocket shot into a storm cloud. HP Compaq HSTNN-C12C Battery
In the same year University of Florida and Florida Tech researchers used an array of electric field and X-ray detectors at a lightning research facility in North Florida to confirm that natural lightning makes X-rays in large quantities. The cause of the X-ray emissions is still a matter for research, as the temperature of lightning is too low to account for the X-rays observed.[85] HP Compaq HSTNN-C66C Battery
A number of observations by space-based telescopes have revealed even higher energy gamma ray emissions, the so-called terrestrial gamma-ray flashes (TGFs). These observations pose a challenge to current theories of lightning, especially with the discovery of the clear signatures of antimatter produced in lightning.[86] HP Compaq HSTNN-C66C-4 Battery
The movement of electrical charges produces a magnetic field (see electromagnetism). The intense currents of a lightning discharge create a fleeting but very strong magnetic field. Where the lightning current path passes through rock, soil, or metal these materials can become permanently magnetized. HP Compaq HSTNN-C66C-5 Battery
This effect is known as lightning-induced remanent magnetism, or LIRM. These currents follow the least resistive path, often horizontally near the surface[87][88] but sometimes vertically, where faults, ore bodies, or ground water offers a less resistive path.[89] HP Compaq HSTNN-C67C Battery
One theory suggests that lodestones, natural magnets encountered in ancient times, were created in this manner.[90]
Lightning-induced magnetic anomalies can be mapped in the ground, and analysis of magnetized materials can confirm lightning was the source of the magnetization and provide an estimate of the peak current of the lightning discharge. HP Compaq HSTNN-C67C-4 Battery
The earliest detector invented to warn of the approach of a thunder storm was the lightning bell. Benjamin Franklin installed one such device in his house.[95] The detector was based on an electrostatic device called the 'electric chimes' invented byAndrew Gordon in 1742. HP Compaq HSTNN-C67C-5 Battery
Lightning discharges generate a wide range of electromagnetic radiations, including radio-frequency pulses. The times at which a pulse from a given lightning discharge arrive at several receivers can be used to locate the source of the discharge. HP Compaq HSTNN-DB05 Battery
The United States federal government has constructed a nation-wide grid of such lightning detectors, allowing lightning discharges to be tracked in real time throughout the continental U.S.
The Earth-ionosphere waveguide traps electromagnetic VLF- and ELF waves. HP Compaq HSTNN-DB06 Battery
Electromagnetic pulses transmitted by lightning strikes propagate within that waveguide. The waveguide is dispersive, which means that their group velocity depends on frequency. The difference of the group time delay of a lightning pulse at adjacent frequencies is proportional to the distance between transmitter and receiver. HP Compaq HSTNN-DB0E Battery
Together with direction finding methods, this allows to locate lightning strikes up to distances of 10000 km from their origin. Moreover, the eigenfrequencies of the Earth-ionospheric waveguide, the Schumann resonances at about 7.5 Hz, are used to determine the global thunderstorm activity.[98] HP Compaq HSTNN-DB11 Battery
In addition to ground-based lightning detection, several instruments aboard satellites have been constructed to observe lightning distribution. These include the Optical Transient Detector (OTD), aboard the OrbView-1 satellite launched on April 3, 1995, and the subsequent Lightning Imaging Sensor (LIS) aboard TRMMlaunched on November 28, 1997. HP Compaq HSTNN-DB16 Battery
Since the late 1980s, there have been several attempts to investigate the possibility of harvesting energy from lightning. While a single bolt of lightning carries a relatively large amount of energy (approximately 5 billion joules[102]), this energy is concentrated in a small location and is passed during an extremely short period of time (milliseconds); HP Compaq HSTNN-DB28 Battery
therefore, extremely high electrical power is involved.[103] It has been proposed that the energy contained in lightning be used to generate hydrogen from water, or to harness the energy from rapid heating of water due to lightning.[104]
A technology capable of harvesting lightning energy would need to be able to rapidly capture the high power involved in a lightning bolt. HP Compaq HSTNN-DB29 Battery
The ever-changing energy involved in each lightning bolt is a problem. Additionally, lightning is sporadic, and therefore energy would have to be collected and stored; it is difficult to convert high-voltage electrical power to the lower-voltage power that can be stored. HP Compaq HSTNN-DB67 Battery
Another major challenge when attempting to harvest energy from lightning is the impossibility of predicting when and where thunderstorms will occur. Even during a storm, it is very difficult to tell where exactly lightning will strike.[102]
In many cultures, lightning has been viewed as part of a deity or a deity in of itself. HP Compaq HSTNN-FB05 Battery
These include the Greek god Zeus, the Aztec god Tlaloc, the Mayas' God K, Slavic mythology's Perun, the Baltic Pērkons/Perkūnas, Thor in Norse mythology, Ukko in Finnish mythology, the Hindu god Indra, and the Shinto god Raijin. In the traditional religion of the African Bantu tribes, lightning is a sign of the ire of the gods. HP Compaq HSTNN-FB18 Battery
Verses in the Jewish religion and in Islam also ascribe supernatural importance to lightning.
The expression "Lightning never strikes twice (in the same place)" is similar to "Opportunity never knocks twice" in the vein of a "once in a lifetime" opportunity, i.e., something that is generally considered improbable. Lightning occurs frequently and more so in specific areas. HP Compaq HSTNN-FB51 Battery
Since various factors alter theprobability of strikes at any given location, repeat lightning strikes have a very low probability (but are not impossible).[105][106] Similarly, "A bolt from the blue" refers to something totally unexpected.
Some political parties use lightning flashes as a symbol of power, such as the People's Action Party in Singapore and the British Union of Fascists during the 1930s. HP Compaq HSTNN-FB52 Battery
The Schutzstaffel, the secret police of the Nazi Party, used the Sig rune in their logo which symbolizes lightning. The German word Blitzkrieg, which means "lightning war", was a major offensive strategy of the German army during World War II.
In French and Italian, the expression for "Love at first sight" is Coup de foudre and Colpo di fulmine, respectively, which literally translated means "lightning strike". HP Compaq HSTNN-I04C Battery
Some European languages have a separate word for lightning which strikes the ground (as opposed to lightning in general); often it is acognate of the English word "rays". The name of New Zealand's most celebrated thoroughbred horse, Phar Lap, derives from the shared Zhuang and Thai word for lightning.[107] HP Compaq HSTNN-I12C Battery
The bolt of lightning in heraldry is called a thunderbolt and is shown as a zigzag with non-pointed ends. This symbol usually represents power and speed.
The lightning bolt is used to represent the instantaneous communication capabilities of electrically-powered telegraphs and radios, HP Compaq HSTNN-I39C Battery
and is a common insignia formilitary communications units throughout the world. A lightning bolt is also the NATO symbol for a signal asset.
Ball lightning may be an atmospheric electrical phenomenon, the physical nature of which is still controversial. HP Compaq HSTNN-I40C Battery
The term refers to reports of luminous, usuallyspherical objects which vary from pea-sized to several metres in diameter.[108] It is sometimes associated with thunderstorms, but unlike lightning flashes, which last only a fraction of a second, ball lightning reportedly lasts many seconds. HP Compaq HSTNN-I44C Battery
Ball lightning has been described by eyewitnesses but rarely recorded bymeteorologists.[109] Scientific data on natural ball lightning is scarce owing to its infrequency and unpredictability. The presumption of its existence is based on reported public sightings, and has therefore produced somewhat inconsistent findings. HP Compaq HSTNN-I44C-A Battery
Laboratory experiments have produced effects that are visually similar to reports of ball lightning, but at present, it is unknown whether these are actually related to any naturally occurring phenomenon. One theory is that ball lightning may be created when lightning strikes silicon in soil, HP Compaq HSTNN-I44C-B Battery
a phenomenon which has been duplicated in laboratory testing.[110] Given inconsistencies and the lack of reliable data and completely contradicting and unpredictable behavior, the true nature of ball lightning is still unknown[111] and was often regarded as a fantasy or a hoax.[112] HP Compaq HSTNN-I45C Battery
Reports of the phenomenon were dismissed for lack of physical evidence, and were often regarded the same way as UFO sightings.[111] Severely contradicting descriptions of ball lightning makes it impossible even to create a plausible hypothesis that will take into account described behavior. HP Compaq HSTNN-I45C-A Battery
Natural ball lightning appears infrequently and unpredictably, and is therefore rarely (if ever truly) photographed. However, several purported photos and videos exist. Perhaps the most famous story of ball lightning unfolded when 18th-century physicist Georg Wilhelm Richmann installed a lightning rod in his home and was struck in the head – and killed – by a "pale blue ball of fire." HP Compaq HSTNN-I45C-B Battery
Sprites are large-scale electrical discharges that occur high above a thunderstorm cloud, giving rise to a range of visual shapes. They are triggered by the discharges of positive lightning between the thundercloud and the ground.[53] The phenomena were named after the mischievous sprite (air spirit) Puck in Shakespeare's A Midsummer Night's DreamHP Compaq HSTNN-I48C-A Battery
They often occur in clusters, lying 50 to 90 kilometres (31 to 56 mi) above the Earth's surface. Sprites have been mentioned as a possible cause in otherwise unexplained accidents involving high altitude vehicular operations above thunderstorms.[114]
Blue jets differ from sprites in that they project from the top of the cumulonimbus above a thunderstorm, HP Compaq HSTNN-I48C-B Battery
typically in a narrow cone, to the lowest levels of the ionosphere 25 miles (40 km) to 50 miles (80 km) above the earth.[115] They are also brighter than sprites and, as implied by their name, are blue in colour.
ELVES often appear as dim, flattened, circular in the horizontal plane, expanding glows around 250 miles (400 km) in diameter that last for, typically, just one millisecond. HP Compaq HSTNN-I49C Battery
They occur in the ionosphere 60 miles (97 km) above the ground over thunderstorms. Their color was a puzzle for some time, but is now believed to be a red hue. Elves is an acronym for Emissions of Light and Very Low Frequency Perturbations from Electromagnetic PulseSources. HP Compaq HSTNN-I50C-B Battery
This refers to the process by which the light is generated; the excitation of nitrogen molecules due to electron collisions (the electrons possibly having been energized by the electromagnetic pulse caused by a discharge from the Ionosphere).
Lightning strikes are electrical discharges caused by lightning, typically during thunderstorms. HP Compaq HSTNN-I54C Battery
Humans can be hit by lightning directly when outdoors. Contrary to popular notion, there is no "safe" location outdoors. People have been struck in sheds and makeshift shelters. However, shelter is possible within an enclosure of conductive material such as an automobile, which is an example[1] of a crude type of Faraday cage. HP Compaq HSTNN-I64C-5 Battery
Lightning strikes can produce severe injuries, and have a mortality rate of between 10% and 30%, with up to 80% of survivors sustaining long-term injuries.[2] These severe injuries are not usually caused by thermal burns, since the current is too brief to greatly heat up tissues, HP Compaq HSTNN-I65C-5 Battery
instead nerves and muscles may be directly damaged by the high voltage producing holes in their cell membranes, a process called electroporation.
In a direct hit the electrical charge strikes the victim first. If the victim's skin resistance is high enough, much of the current will flash around the skin or clothing to the ground, resulting in a surprisingly benign outcome. HP Compaq HSTNN-IB05 Battery
Metallic objects in contact with the skin may concentrate the lightning strike, preventing the flashover effect and resulting in more serious injuries. At least two cases have been reported where a lightning strike victim wearing an iPod suffered more serious injuries as a result. HP Compaq HSTNN-IB08 Battery
However, during a flash the current flowing around the body will generate large magnetic fields, which may induce electrical currents within organs such as the heart. This effect might explain the cases where cardiac arrest followed a lightning strike that produced no external injuries.[2] HP Compaq HSTNNIB12 Battery
Splash hits occur when lightning prefers a victim (with lower resistance) over a nearby object that has more resistance, and strikes the victim on its way to ground. Ground strikes, in which the bolt lands near the victim and is conducted through the victim and his or her connection to the ground HP Compaq GJ655AA Battery
(such as through the feet, due to the voltage gradient in the earth, as discussed above), can cause great damage.
A secondary effect of lightning on bystanders or users of telephone equipment can be hearing damage, as the strike may cause bursts of extremely loud acoustic noise. HP Compaq GJ655AA#ABH Battery
An estimated 24,000 people are killed by lightning strikes around the world each year and about 240,000 are injured. [4] In the United States, it is the #2 weather killer (second only to floods).[5] In the US, between 9% and 10% of those struck die,[6] for an average of 40 to 50 deaths per year (28 in 2008).HP Compaq Business Notebook NX6115 Battery
The odds of an average person living in the US being struck by lightning in a given year is 1/1,000,000, while the odds of being struck by lightning in a lifetime is 1/10,000 (estimated lifespan of 80 years).[8]
US National Park Ranger Roy Sullivan has the record for being struck by lightning the most times. HP Compaq Business Notebook NX6120 Battery
Sullivan was struck seven times during his 35-year career. He lost the nail on one of his big toes, and suffered multiple injuries to the rest of his body.
Trees are frequent conductors of lightning to the ground.[10] Since sap is a poor conductor, its electrical resistance causes it to be heated explosively into steam, HP Compaq Business Notebook NX6125 Battery
which blows off the bark outside the lightning's path. In following seasons trees overgrow the damaged area and may cover it completely, leaving only a vertical scar. If the damage is severe, the tree may not be able to recover, and decay sets in, eventually killing the tree.
In sparsely populated areas such as the Russian Far East and Siberia, lightning strikes are one of the major causes of forest fires.[11] HP Compaq Business Notebook NX6140 Battery
The smoke and mist expelled by a forest fire can cause electric charges, multiplying the intensity of a forest fire.[11] It is commonly thought that a tree standing alone is more frequently struck, though in some forested areas, lightning scars can be seen on almost every tree. HP Compaq Business Notebook NX6300 Series Battery
The two most frequently struck tree types are the oak and the elm.[12] Pine trees are also quite often hit by lightning. Unlike the oak, which has a relatively shallow root structure, pine trees have a deep central tap root system that goes down into the water table.[13] Pine trees usually stand taller than other species, which also makes them a likely target. HP Compaq Business Notebook NX6310 Battery
Factors which lead to pines being targeted are a high resin content, loftiness, and their sharp needles which lend themselves to a high electrical discharge during a thunderstorm.
Trees are natural lightning conductors and are known to provide protection against lightning damage to nearby buildings by diverting lightning strikes away from structures. HP Compaq Business Notebook NX6310/CT Battery
Tall trees with high biomass for the root system provide good lightning protection. An example is the teak tree (Tectona grandis). When planted near a building, its height helps to capture the oncoming lightning leader, and the high biomass of the root system helps in dissipation of the lightning's charge. HP Compaq Business Notebook NX6315 Battery
Telephones, modems, computers and other electronic devices can be damaged by lightning, as harmful overcurrent can reach them through the phone jack, Ethernet cable, or electricity outlet.[15] Close strikes can also generate electromagnetic pulses (EMPs) – especially during "positive" lightning discharges. HP Compaq Business Notebook NX6320 Battery
Lightning currents have a very fast risetime, on the order of 40 kA per microsecond. Hence, conductors of such currents exhibit marked skin effect, causing most of the currents to flow through the outer surface of the conductor.[16]
In addition to electrical wiring damage, the other types of possible damage to consider include structural, fire, and property damage. HP Compaq Business Notebook NX6320/CT Battery
The field of lightning protection is almost totally void of systems or concepts designed to deal with the general problem area as a whole. Chaff and silver iodide crystals concepts were devised to deal directly with the cloud cells and were dispensed directly into the clouds from an overflying aircraft. HP Compaq Business Notebook NX6325 Battery
The chaff was devised to deal with the electrical manifestations of the storm from within, while the silver iodide salting technique was devised to deal with the mechanical forces of the storm.
Several different types of devices, including lightning rods and electrical charge dissipators, are used to prevent lightning damage and safely redirect lightning strikes. HP Compaq Business Notebook NX7000 Battery
A lightning rod (or lightning protector) is a metal strip or rod, usually of copper or similar conductive material, used as part of lightning safety to protect tall or isolated structures (such as the roof of a building or the mast of a vessel) from lightning damage. Its formal name is lightning finial or air terminalHP Compaq Business Notebook NX7010 Battery
Sometimes, the system is informally referred to as a lightning conductor, arrester, or discharger; however, these terms actually refer to lightning protection systems in general, or specific components within them. Lightning protection systems alter lightning streamer behavior. HP Compaq Business Notebook NX7100 Battery
Although commonly associated with thunderstorms at close range, lightning strikes can occur on a day that seems devoid of clouds. This occurrence is known as "A Bolt From the Blue";[17] lightning can strike up to 10 miles from a cloud.
Lightning interferes with AM (amplitude modulation) radio signals much more than FM (frequency modulation) signals, HP Compaq Business Notebook NX7400 Battery
providing an easy way to gauge local lightning strike intensity.[18] To do so, one should tune a standard AM medium wave receiver to a frequency with no transmitting stations, and listen for crackles amongst the static. Stronger or nearby lightning strikes will also cause cracking if the receiver is tuned to a station. HP Compaq Business Notebook NX8200 Battery
As lower frequencies propagate further along the ground than higher ones, the lower medium wave (MW) band frequencies (in the 500-600 kHz range) can detect lightning strikes at longer distances; if the longwave band (153-279 kHz) is available, using it can increase this range even further. HP Compaq Business Notebook NX8220 Battery
Lightning prediction systems have been developed and may be deployed in locations where lightning strikes present special risks, such as public parks. Such systems are designed to detect the conditions which are believed to favor lightning strikes and provide a warning to those in the vicinity to allow them to take appropriate cover. HP Compaq Business Notebook NX8420 Battery
The U.S. National Lightning Safety Institute[19] advises everyone to have a plan for their safety when a thunderstorm occurs and to commence it as soon as the first lightning or thunder is observed. This is important, since lightning can strike without rain actually falling. If thunder can be heard at all, then there is a risk of lightning. HP Compaq Business Notebook NX9000 Battery
The safest place is inside a building or a vehicle. Risk remains for up to 30 minutes after the last observed lightning or thunder.
The National Lightning Safety Institute recommends using the F-B (flash to boom) method to gauge distance to a lightning strike.HP Compaq Business Notebook NX9100 Battery
The flash of a lightning strike and resulting thunder occur at roughly the same time. But light travels at 300,000 kilometers in a second, almost a million times the speed of sound. Sound travels at the slower speed of 344 m/s, so the flash of lightning is seen before thunder is heard. HP Compaq Business Notebook NX9110 Battery
To use the method, count the seconds between the lightning flash and thunder. Divide by 3 to determine the distance in kilometers, or by 5 for miles. Immediate precautions against lightning should be taken if the F-B time is 25 seconds or less, that is, the lightning is closer than 8 km (5.0 mi). HP Compaq Business Notebook NX9420 Battery
Do not rely on the F-B method for determining when to relax the safety measures, because lightning typically occurs in multiple locations, and just because some strikes are far away does not prevent another strike nearby. Precautions should not be relaxed until thunder cannot be heard for 30 minutes, at any distance. HP Compaq Business Notebook TC4200 Battery
A person injured by lightning does not carry an electrical charge, and can be safely handled to apply first aid before emergency services arrive. Lightning can affect the brainstem, which controls breathing. If a victim appears lifeless, it is important to begin artificial resuscitation immediately to prevent death by suffocation.[20] HP Compaq Business Notebook TC4400 Battery
Some lightning strikes have caused either numerous fatalities or great damage. The following is a partial list:
In 1660, lightning struck the gunpowder magazine at Osaka Castle, Japan; the resultant explosion set the castle on fire. HP Compaq Business Notebook 8510P Battery
In 1665, lightning struck the main tower of the castle and it burned down to the foundation.
A particularly deadly lightning incident occurred in Brescia, Italy in 1769. Lightning struck the Church of St. Nazaire, igniting the 90 tonnes of gunpowder in its vaults; the resulting explosion killed 3000 people and destroyed a sixth of the city.[21] HP Compaq Business Notebook 8510W Battery
1902: A lightning strike damaged the upper section of the Eiffel Tower, requiring the reconstruction of its top[22]
November 14, 1969: Apollo 12 Thirty-six-and-a-half seconds after lift-off, the vehicle triggered a lightning discharge through itself and down to the earth through the Saturn V's ionized plume. HP Compaq Business Notebook 8710P Battery
However, the Saturn V continued to fly correctly; the strikes had not affected the Saturn V's Instrument Unit.
July 12, 1970, the central mast of the Orlunda radio transmitter collapsed after a lightning strike destroyed its foundation insulator. HP Compaq Business Notebook 8710W Battery
November 2, 1994, lightning struck fuel tanks in Dronka, Egypt and caused 469 fatalities.[23]
Roy Sullivan held a Guinness World Record after surviving 7 different lightning strikes over 35 years.[24]
In July 2007, lightning killed up to 30 people when it struck a remote mountain village Ushari Dara in northwestern Pakistan.[25]HP Compaq Business Notebook 9400 Battery
On 31 October 2005, sixty-eight dairy cows, all full of milk, died on a farm at Fernbrook on the Waterfall Way near Dorrigo, New South Wales after being struck by lightning. Three others were paralysed for several hours but they later made a full recovery. HP Compaq Business Notebook NC2400 Battery
The cows were sheltering under a tree when it was struck by lightning and the electricity spread onto the surrounding soil killing the animals.[26]
On December 8, 1963, Pan Am Flight 214 crashed outside Elkton, Maryland during a severe electrical storm, with a loss of all 81 passengers and crew. HP Compaq Business Notebook NC4000 Battery
The Boeing 707–121, registered as N709PA, was on the final leg of a San Juan — Baltimore — Philadelphia flight.
On December 24, 1971 LANSA Flight 508 was a Lockheed L-188A Electra turboprop, registered OB-R-941, HP Compaq Business Notebook NC4010 Battery
operated as a scheduled domestic passenger flight by Lineas Aéreas Nacionales Sociedad Anonima (LANSA), that crashed in a thunderstorm en route from Lima, Peru to Pucallpa, Peru, killing 91 people – all of its 6 crew and 85 of its 86 passengers.The sole survivor was Juliane Koepcke, HP Compaq Business Notebook NC4200 Battery
who fell 2 miles (3.2 km) down into the Amazon rainforest strapped to her seat and remarkably survived the fall, and was then able to walk through the jungle for 10 days until she was rescued by local lumbermen. HP Compaq Business Notebook NC4400 Battery
Upper-atmospheric lightning or upper-atmospheric discharge are terms sometimes used by researchers to refer to a family of short-lived electrical-breakdown phenomena that occur well above the altitudes of normal lightning and storm clouds.Upper-atmospheric lightning is believed to be electrically induced forms of optical fluorescence. HP Compaq Business Notebook NC6000 Battery
The preferred usage is transient luminous event, because the various types of electrical-discharge phenomena in the upper atmosphere lack several characteristics of the more familiar tropospheric lightning. TLEs include red sprites, sprite halos, blue jets, gigantic jets, and ELVES. HP Compaq Business Notebook NC6100 Series Battery
There are several types of TLEs, the most common being sprites. Sprites are flashes of bright red light that occur above storm systems. C-sprites (short for "columniform sprites") is the name given to vertical columns of red light. C-sprites exhibiting tendrils are sometimes called carrot sprites. HP Compaq Business Notebook NC6105 Series Battery
Other types of TLEs include gnomes, blue jets, gigantic jets, blue starters, and ELVES. ELVES (Emission of Light and Very Low Frequency perturbations due to Electromagnetic Pulse Sources) refers to a singular event which is commonly thought of as being plural. TLEs are secondarHP Compaq Business Notebook NC6110 Battery
y phenomena that occur in the upper atmosphere in association with underlying thunderstorm lightning.
TLEs generally last anywhere from less than a millisecond to more than 2 seconds. The first TLE was captured accidentally in a video recording in 1989. HP Compaq Business Notebook NC6115 Battery
University of Minnesota researchers were waiting to record a rocket launch and pointed the camera at a distant thunderstorm. A TLE was later identified, appearing in only two frames of the film. TLEs have been captured by a variety of optical recording systems, with the total number of recorded events currently (early 2009) estimated at many tens-of-thousands. HP Compaq Business Notebook NC6120 Battery
The global rate of TLE occurrence has been estimated from satellite (FORMOSAT-2) observations to be several million events per year.
In the 1920s, the Scottish physicist C.T.R. Wilson predicted that electrical breakdown should occur in the atmosphere high above large thunderstorms. HP Compaq Business Notebook NC6200 Battery
In ensuing decades, high altitude electrical discharges were reported by aircraft pilots and discounted by meteorologists until the first direct visual evidence was documented on July 6, 1989 by scientists from the University of Minnesota. HP Compaq Business Notebook NC6220 Battery
Several years later, the optical signatures of these events were named 'sprites' by researchers at the University of Alaska to avoid inadvertently implying physical properties that were, at the time, still unknown. The terms red sprites andblue jets gained popularity after a video clip was circulated following an aircraft research campaign to study sprites in 1994. HP Compaq Business Notebook NC6230 Battery
Sprites are large-scale electrical discharges which occur high above a thunderstorm cloud, or cumulonimbus, giving rise to a quite varied range of visual shapes. They are triggered by the discharges of positive lightning between the thundercloud and the ground. HP Compaq Business Notebook NC6400 Battery
The phenomena were named after the mischievous sprite (air spirit) Puck in William Shakespeare's A Midsummer Night's Dream. They normally are colored reddish-orange or greenish-blue, with hanging tendrils below and arcing branches above. They can also be preceded by a reddish halo. HP Compaq Business Notebook NC8000 Battery
They often occur in clusters, lying 50 kilometres (31 mi) to 90 kilometres (56 mi) above the Earth's surface. Sprites were first photographed on July 6, 1989 by scientists from the University of Minnesota and have since been witnessed tens of thousands of times. HP Compaq Business Notebook NC8200 Battery
Sprites have been held responsible for otherwise unexplained accidents involving high altitude vehicular operations above thunderstorms.
Blue jets differ from sprites in that they project from the top of the cumulonimbus above a thunderstorm, typically in a narrow cone, HP Compaq Business Notebook NC8230 Battery
to the lowest levels of the ionosphere 40 to 50 km (25 to 30 miles) above the earth. In addition, whereas red sprites tend to be associated with significant lightning strikes, blue jets do not appear to be directly triggered by lightning (they do, however, appear to relate to strong hail activity in thunderstorms). HP Compaq Business Notebook NC8430 Battery
They are also brighter than sprites and, as implied by their name, are blue in color. The color is believed to be due to a set of blue and near-ultraviolet emission lines from neutral and ionized molecular nitrogen. They were first recorded on October 21, 1989, on a monochrome video of a thunderstorm on tHP Compaq Business Notebook NW8200 Battery
he horizon taken from the Space Shuttle as it passed over Australia. Blue jets occur much less frequently than sprites. By 2007, fewer than a hundred images had been obtained. The majority of these images, which include the first color imagery, are associated with HP Compaq Business Notebook NW8240 Battery
a single thunderstorm studied by researchers from the University of Alaska. These were taken in a series of 1994 aircraft flights to study sprites.[7]
Blue starters were discovered on video from a night time research flight around thunderstorms [8] and appear to be "an upward moving luminous phenomenon closely related to blue jets."[9] HP Compaq Business Notebook NW8440 Battery
They appear to be shorter and brighter than blue jets, reaching altitudes of only up to 20 km.[10] "Blue starters appear to be blue jets that never quite make it," according to Dr. Victor P. Pasko, associate professor of electrical engineering.[11] HP Compaq Business Notebook NW9440 Battery
On September 14, 2001, scientists at the Arecibo Observatory photographed a gigantic jet—double the height of those previously observed—reaching around 70 km (43 mi) into the atmosphere.[12] The jet was located above a thunderstorm over an ocean, and lasted under a second. HP Compaq Business Notebook NX4300 Battery
The jet was initially observed to be traveling up at around 50,000 m/s at a speed similar to typical lightning, increased to 160,000 and then 270,000 m/s, but then split in two and sped upward with speeds of at least 2,000,000 m/s to the ionosphere whence they spread out in a bright burst of light. HP Compaq Business Notebook NX4800 Battery
On July 22, 2002, five gigantic jets between 60 and 70 km (35 to 45 miles) in length were observed over the South China Sea from Taiwan, reported inNature.[13][14] The jets lasted under a second, with shapes likened by the researchers to giant trees and carrots. HP Compaq Business Notebook NX5100 Battery
ELVES often appear as a dim, flattened, expanding glow around 400 km (250 mi) in diameter that lasts for, typically, just one millisecond.[15] They occur in the ionosphere 100 km (62 mi) above the ground over thunderstorms. Their color was a puzzle for some time, but is now believed to be a red hue. HP Compaq Business Notebook NX6100 Series Battery
ELVES were first recorded on another shuttle mission, this time recorded off French Guiana on October 7, 1990.
ELVES is a whimsical acronym for Emissions of Light and Very Low Frequency Perturbations from Electromagnetic Pulse Sources.[16] HP Compaq Business Notebook NX6110 Battery
This refers to the process by which the light is generated; the excitation of nitrogen molecules due to electron collisions (the electrons possibly having been energized by the electromagnetic pulse caused by a discharge from an underlying thunderstorm).HP Compaq Business Notebook NX6110/CT Battery,HP Compaq Business Notebook 8200 Battery,HP Compaq Business Notebook 8400 Battery

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