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92-677: The Rice Ridge Fire was started by a lightning strike on July 24, 2017. By August 5, the fire had spread near Morrell Falls and made runs towards the Bob Marshall Wilderness . Aircraft focused on making water drops while crews worked on protective activities along Highway 83 and on the northside of Seeley Lake and Double Arrow Lodge . Evacuation warnings were put in place for residents of on both side of Highway 83 south of Rice Ridge Road to Morrell Creek and south of Cottonwood Lakes Road, east of Highway 83, including Seeley Lake and Double Arrow Lodge. The American Red Cross opened

184-508: A thundercloud moves over the surface of the Earth, an equal electric charge , but of opposite polarity, is induced on the Earth's surface underneath the cloud. The induced positive surface charge, when measured against a fixed point, will be small as the thundercloud approaches, increasing as the center of the storm arrives and dropping as the thundercloud passes. The referential value of the induced surface charge could be roughly represented as

276-422: A "termination". The primary conducting channel, the bright, coursing light that may be seen and is called a "strike", is only about one inch ( ca. 2.5 cm) in diameter, but because of its extreme brilliance, it often looks much larger to the human eye and in photographs. Lightning discharges are typically miles long, but certain types of horizontal discharges can be tens of miles in length. The entire flash lasts only

368-461: A base and carbon dioxide is an acidic gas, it is possible that charged water clouds in which the negative charge is in the form of the aqueous hydroxide ion, interact with atmospheric carbon dioxide to form aqueous carbonate ions and aqueous hydrogen carbonate ions. The typical cloud-to-ground lightning flash culminates in the formation of an electrically conducting plasma channel through the air in excess of 5 km (3.1 mi) tall, from within

460-523: A bell curve. The oppositely charged regions create an electric field within the air between them. This electric field varies in relation to the strength of the surface charge on the base of the thundercloud – the greater the accumulated charge, the higher the electrical field. The best-studied and understood form of lightning is cloud to ground (CG) lightning. Although more common, intra-cloud (IC) and cloud-to-cloud (CC) flashes are very difficult to study given there are no "physical" points to monitor inside

552-459: A bidirectional leader initiates between the main negative and lower positive charge regions in a thundercloud. The weaker positive charge region is filled quickly by the negative leader which then propagates toward the inductively-charged ground. The positively and negatively charged leaders proceed in opposite directions, positive upwards within the cloud and negative towards the earth. Both ionic channels proceed, in their respective directions, in

644-545: A brilliant, blue-white color. Once the electric current stops flowing, the channel cools and dissipates over tens or hundreds of milliseconds, often disappearing as fragmented patches of glowing gas. The nearly instantaneous heating during the return stroke causes the air to expand explosively, producing a powerful shock wave which is heard as thunder . High-speed videos (examined frame-by-frame) show that most negative CG lightning flashes are made up of 3 or 4 individual strokes, though there may be as many as 30. Each re-strike

736-421: A charge opposite of that of the leader tip. The negative end of the bidirectional leader fills a positive charge region, also called a well, inside the cloud while the positive end fills a negative charge well. Leaders often split, forming branches in a tree-like pattern. In addition, negative and some positive leaders travel in a discontinuous fashion, in a process called "stepping". The resulting jerky movement of

828-410: A conductive portion of the main leader network, a return stroke-like process occurs and a dart leader travels across all or a portion of the length of the original leader. The dart leaders making connections with the ground are what cause a majority of subsequent return strokes. Each successive stroke is preceded by intermediate dart leader strokes that have a faster rise time but lower amplitude than

920-470: A day that seems devoid of clouds. This occurrence is known as "a bolt from the blue [sky]"; lightning can strike up to 10 miles from a cloud. Lightning interferes with amplitude modulation (AM) radio signals much more than frequency modulation (FM) signals, providing an easy way to gauge local lightning strike intensity. To do so, one should tune a standard AM medium wave receiver to a frequency with no transmitting stations, and listen for crackles among

1012-418: A fraction of a second. Lightning strikes can injure humans in several different ways: Warning signs of an impending strike nearby can include a crackling sound, sensations of static electricity in the hair or skin, the pungent smell of ozone , or the appearance of a blue haze around persons or objects ( St. Elmo's fire ). People caught in such extreme situations – without having been able to flee to

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1104-482: A great distance but not heard; dry lightning , which can cause forest fires ; and ball lightning , which is rarely observed scientifically. Humans have deified lightning for millennia. Idiomatic expressions derived from lightning, such as the English expression "bolt from the blue", are common across languages. At all times people have been fascinated by the sight and difference of lightning. The fear of lightning

1196-446: A high-resistance medium must obstruct the free, unimpeded equalization of the opposite charges. The atmosphere provides the electrical insulation, or barrier, that prevents free equalization between charged regions of opposite polarity. It is well understood that during a thunderstorm there is charge separation and aggregation in certain regions of the cloud; however, the exact processes by which this occurs are not fully understood. As

1288-601: A lifetime probability of about 1 in 60,000. However, due to increased awareness and improved lightning conductors and protection, the number of annual lightning deaths has been decreasing steadily year by year. According to the National Oceanic and Atmospheric Administration in 2012, over the twenty years to 2012 the United States averaged 51 annual lightning strike fatalities, making it the second-most frequent cause of weather-related death after floods . In

1380-417: A lightning strike that produced no external injuries. It may also point to the victim not being directly struck at all, but just being very close to the strike termination. Another effect of lightning on bystanders is to their hearing . The resulting shock wave of thunder can damage the ears. Also, electrical interference to telephones or headphones may result in damaging acoustic noise . According to

1472-500: A lightning-related injury, let alone particulars, which a medical examiner , police investigator , or on the rare occasion a trained lightning expert may have difficulty identifying to record accurately. As of 2013, direct-strike casualties could be much higher than reported numbers. In 2015 it was reported that between five and ten deaths from lightning occur in Australia every year with over 100 injuries occurring. In 2018, it

1564-412: A negative charge. Updrafts within a storm cloud separate the lighter ice crystals from the heavier graupel, causing the top region of the cloud to accumulate a positive space charge while the lower level accumulates a negative space charge. Because the concentrated charge within the cloud must exceed the insulating properties of air, and this increases proportionally to the distance between the cloud and

1656-601: A number of much shorter flashes (strokes) of around 60 to 70 microseconds . Many factors affect the frequency, distribution, strength and physical properties of a typical lightning flash in a particular region of the world. These factors include ground elevation, latitude , prevailing wind currents, relative humidity , and proximity to warm and cold bodies of water. To a certain degree, the proportions of intra-cloud, cloud-to-cloud, and cloud-to-ground lightning may also vary by season in middle latitudes . Because human beings are terrestrial and most of their possessions are on

1748-466: A number of successive spurts. Each leader "pools" ions at the leading tips, shooting out one or more new leaders, momentarily pooling again to concentrate charged ions, then shooting out another leader. The negative leader continues to propagate and split as it heads downward, often speeding up as it gets closer to the Earth's surface. About 90% of ionic channel lengths between "pools" are approximately 45 m (148 ft) in length. The establishment of

1840-549: A preferred pathway to ground if lightning terminates on a structure. The class of these products is often called a "finial" or "air terminal". A lightning rod or "Franklin rod" in honor of its famous inventor, Benjamin Franklin , is simply a metal rod, and without being connected to the lightning protection system, as was sometimes the case in the past, will provide no added protection to a structure. Other names include "lightning conductor", "arrester", and "discharger"; however, over

1932-544: A safer, fully enclosed space – are advised to assume the "lightning position", which involves "sitting or crouching with knees and feet close together to create only one point of contact with the ground" (with the feet off the ground if sitting; if a standing position is needed, the feet must be touching). Lightning strikes can produce severe injuries in humans, and are lethal in between 10 and 30% of cases, with up to 80% of survivors sustaining long-term injuries. These severe injuries are not usually caused by thermal burns, since

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2024-552: A shelter at the Potomac Community Center. On September 6, a drone flew into the restricted fire area, causing fire protection work to stop temporarily. As of August 7, Seeley Lake itself was closed so that aerial crews could draw water from the lake, but the homes and businesses around the lake were open. The fire burned on the east side of Rice Ridge and in Swamp Creek. Crews shifted to focus on containing

2116-453: A storm being overhead, contrary to popular belief . If thunder can be heard at all, then a risk of lightning exists. The National Lightning Safety Institute also recommends using the F-B (flash to boom) method to gauge distance to a lightning strike. The flash of a lightning strike and resulting thunder occur at roughly the same time. But light travels 300,000 km/sec, almost a million times

2208-503: A strike increases above a set level determined by a risk assessment for the location's conditions and circumstances. One significant improvement has been in the area of detection of flashes through both ground- and satellite-based observation devices. The strikes and atmospheric flashes are not predicted, but the level of detail recorded by these technologies has vastly improved in the past 20 years. Although commonly associated with thunderstorms at close range, lightning strikes can occur on

2300-434: A strike victim wearing an iPod suffered more serious injuries as a result. During a flash, though, the current flowing through the channel and around the body can generate large electromagnetic fields and EMPs, which may induce electrical transients (surges) within the nervous system or pacemaker of the heart, upsetting normal operations . This effect might explain cases where cardiac arrest or seizures followed

2392-451: A threshold and form upward streamers. Once a downward leader connects to an available upward leader, a process referred to as attachment, a low-resistance path is formed and discharge may occur. Photographs have been taken in which unattached streamers are clearly visible. The unattached downward leaders are also visible in branched lightning, none of which are connected to the earth, although it may appear they are. High-speed videos can show

2484-516: 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 . The smoke and mist expelled by a very large forest fire can cause secondary lightning strikes, starting additional fires many kilometers downwind. When water in fractured rock

2576-519: A wide range of electromagnetic radiation , from heat created by the rapid movement of electrons , to brilliant flashes of visible light in the form of black-body radiation . Lightning causes thunder , a sound from the shock wave which develops as gases in the vicinity of the discharge experience a sudden increase in pressure. Lightning occurs commonly during thunderstorms as well as other types of energetic weather systems, but volcanic lightning can also occur during volcanic eruptions . Lightning

2668-399: Is a natural phenomenon formed by electrostatic discharges through the atmosphere between two electrically charged regions, either both in the atmosphere or one in the atmosphere and one on the ground , temporarily neutralizing these in a near-instantaneous release of an average of between 200 megajoules and 7 gigajoules of energy , depending on the type. This discharge may produce

2760-487: Is an atmospheric electrical phenomenon and contributes to the global atmospheric electrical circuit . The three main kinds of lightning are distinguished by where they occur: either inside a single thundercloud (intra-cloud), between two clouds (cloud-to-cloud), or between a cloud and the ground (cloud-to-ground), in which case it is referred to as a lightning strike . Many other observational variants are recognized, including " heat lightning ", which can be seen from

2852-568: Is called astraphobia . The first known photograph of lightning is from 1847, by Thomas Martin Easterly . The first surviving photograph is from 1882, by William Nicholson Jennings ,  a photographer who spent half his life capturing pictures of lightning and proving its diversity. There is growing evidence that lightning activity is increased by particulate emissions (a form of air pollution). However, lightning may also improve air quality and clean greenhouse gases such as methane from

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2944-443: Is rapidly heated by a lightning strike, the resulting steam explosion can cause rock disintegration and shift boulders. It may be a significant factor in erosion of tropical and subtropical mountains that have never been glaciated. Evidence of lightning strikes includes erratic magnetic fields. Telephones , modems , computers , and other electronic devices can be damaged by lightning, as harmful overcurrent can reach them through

3036-418: Is separated by a relatively large amount of time, typically 40 to 50 milliseconds, as other charged regions in the cloud are discharged in subsequent strokes. Re-strikes often cause a noticeable " strobe light " effect. To understand why multiple return strokes utilize the same lightning channel, one needs to understand the behavior of positive leaders, which a typical ground flash effectively becomes following

3128-477: Is strongest on grounded objects whose tops are closest to the base of the thundercloud, such as trees and tall buildings. If the electric field is strong enough, a positively charged ionic channel, called a positive or upward streamer , can develop from these points. This was first theorized by Heinz Kasemir. As negatively charged leaders approach, increasing the localized electric field strength, grounded objects already experiencing corona discharge will exceed

3220-460: Is usually negatively charged, this is where most CG lightning originates. This region is typically at the elevation where freezing occurs within the cloud. Freezing, combined with collisions between ice and water, appears to be a critical part of the initial charge development and separation process. During wind-driven collisions, ice crystals tend to develop a positive charge, while a heavier, slushy mixture of ice and water (called graupel ) develops

3312-458: The Kelvin water dropper . The most likely charge-carrying species were considered to be the aqueous hydrogen ion and the aqueous hydroxide ion. The electrical charging of solid water ice has also been considered. The charged species were again considered to be the hydrogen ion and the hydroxide ion. An electron is not stable in liquid water concerning a hydroxide ion plus dissolved hydrogen for

3404-411: The phone jack , Ethernet cable , or electricity outlet . Close strikes can also generate EMPs, especially during "positive" lightning discharges. Lightning currents have a very fast rise time , on the order of 40 kA per microsecond. Hence, although lightning is a form of direct current , conductors of such currents exhibit marked skin effect as with an alternating current , causing most of

3496-605: The static . Stronger or nearby lightning strikes will also cause cracking if the receiver is tuned to a station. 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. Lightning-detection 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

3588-476: The triboelectric effect leading to electron or ion transfer between colliding bodies. Uncharged, colliding water-drops can become charged because of charge transfer between them (as aqueous ions) in an electric field as would exist in a thunder cloud. The main charging area in a thunderstorm occurs in the central part of the storm where air is moving upward rapidly (updraft) and temperatures range from −15 to −25 °C (5 to −13 °F); see Figure 1. In that area,

3680-584: The tropics where atmospheric convection is the greatest. This occurs from both the mixture of warmer and colder air masses , as well as differences in moisture concentrations, and it generally happens at the boundaries between them . The flow of warm ocean currents past drier land masses, such as the Gulf Stream , partially explains the elevated frequency of lightning in the Southeast United States . Because large bodies of water lack

3772-417: The 1840s as has the electrification of pure liquid water by the triboelectric effect. William Thomson (Lord Kelvin) demonstrated that charge separation in water occurs in the usual electric fields at the Earth's surface and developed a continuous electric field measuring device using that knowledge. The physical separation of charge into different regions using liquid water was demonstrated by Kelvin with

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3864-508: The 27th, the fire had expanded to 22,427 acres (91 km) and threatened 1,060 homes. The next day, Seeley Lake was once more closed for recreational use. A third drone flight through the fire zone caused the crew activities to stop that evening. Mandatory evacuations were put in place due to the fire threatening 580 homes in the Seeley Lake area and schools were closed. As of September 1, the fire had burned 37,032 acres (150 km) and

3956-462: The CDC there are about 6,000 lightning strikes per minute, or more than 8 million strikes every day. As of 2008 there were about 240,000 "lightning strikes incidents" around the world each year. According to National Geographic in 2009, about 2,000 people were killed annually worldwide by lightning. If all eight billion humans have an equal chance of being killed over a 70-year lifespan, this gives

4048-607: The Congo , where the elevation is around 975 m (3,200 ft). On average, this region receives 158 lightning strikes per square kilometre per year (410/sq mi/yr). Other lightning hotspots include Singapore and Lightning Alley in Central Florida . According to the World Meteorological Organization , on April 29, 2020, a bolt 768 km (477.2 mi) long was observed in

4140-424: The Earth where lightning can damage or destroy them, cloud-to-ground (CG) lightning is the most studied and best understood of the three types, even though in-cloud (IC) and cloud-to-cloud (CC) are more common types of lightning. Lightning's relative unpredictability limits a complete explanation of how or why it occurs, even after hundreds of years of scientific investigation. About 70% of lightning occurs over land in

4232-613: The F-B time is 25 seconds or less, that is, if the lightning is closer than 8 km or 5 miles. A 2014 report suggested that whether a person was standing up, squatting , or lying down when outside during a thunderstorm does not matter, because lightning can travel along the ground; this report suggested being inside a solid structure or vehicle was safest. The riskiest activities include fishing, boating, camping, and golf. 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

4324-629: The US, as of 1999, between 9 and 10% of those struck died, with an annual average of 25 deaths in the 2010s decade (16 in 2017). In the United States in the period 2009 to 2018 an average of 27 lightning fatalities occurred per year. In the United States an average of 23 people died from lightning per year from 2012 to 2021. Some people suffer from lifelong brain injuries. As of 2005, in Kisii, Kenya , some 30 people die each year from lightning strikes. Kisii's high rate of lightning fatalities occurs because of

4416-510: The USAF placed protective lightning strike-diversion tower arrays at all of the Italian and Turkish Jupiter MRBM nuclear armed missiles sites after two strikes partially arming the missiles. The exact location of a lightning strike and when it will occur are still impossible to predict. However, products and systems have been designed of varying complexities to alert people as the probability of

4508-437: The atmosphere, while creating nitrogen oxide and ozone at the same time. Lightning is also the major cause of wildfire, and wildfire can contribute to climate change as well. More studies are warranted to clarify their relationship. The details of the charging process are still being studied by scientists, but there is general agreement on some of the basic concepts of thunderstorm electrification. Electrification can be by

4600-425: The atmosphere. Lightning strikes the average commercial aircraft at least once a year, but modern engineering and design means this is rarely a problem. The movement of aircraft through clouds can even cause lightning strikes. A single lightning event is a "flash", which is a complex, multistage process, some parts of which are not fully understood. Most CG flashes only "strike" one physical location, referred to as

4692-402: The attachment process in progress. Once a conductive channel bridges the air gap between the negative charge excess in the cloud and the positive surface charge excess below, there is a large drop in resistance across the lightning channel. Electrons accelerate rapidly as a result in a zone beginning at the point of attachment, which expands across the entire leader network at up to one third of

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4784-664: The brainstem, which controls breathing. Several studies conducted in South Asia and Africa suggest that the dangers of lightning are not taken sufficiently seriously there. A research team from the University of Colombo found that even in neighborhoods that had experienced deaths from lightning, no precautions were taken against future storms. An expert forum convened in 2007 to address how to raise awareness of lightning and improve lightning-protection standards, and expressed concern that many countries had no official standards for

4876-432: The case of biased percolation, describes random connectivity phenomena, which produce an evolution of connected structures similar to that of lightning strikes. A streamer avalanche model has recently been favored by observational data taken by LOFAR during storms. When a stepped leader approaches the ground, the presence of opposite charges on the ground enhances the strength of the electric field . The electric field

4968-519: The cloud to the ground's surface. The actual discharge is the final stage of a very complex process. At its peak, a typical thunderstorm produces three or more strikes to the Earth per minute. Lightning primarily occurs when warm air is mixed with colder air masses, resulting in atmospheric disturbances necessary for polarizing the atmosphere. Lightning can also occur during dust storms , forest fires , tornadoes , volcanic eruptions , and even in

5060-476: The clouds. Also, given the very low probability of lightning striking the same point repeatedly and consistently, scientific inquiry is difficult even in areas of high CG frequency. In a process not well understood, a bidirectional channel of ionized air, called a " leader ", is initiated between oppositely-charged regions in a thundercloud. Leaders are electrically conductive channels of ionized gas that propagate through, or are otherwise attracted to, regions with

5152-424: The cold of winter, where the lightning is known as thundersnow . Hurricanes typically generate some lightning, mainly in the rainbands as much as 160 km (99 mi) from the center. Lightning is not distributed evenly around Earth . On Earth, the lightning frequency is approximately 44 (± 5) times per second, or nearly 1.4 billion flashes per year and the median duration is 0.52 seconds made up from

5244-431: The combination of temperature and rapid upward air movement produces a mixture of super-cooled cloud droplets (small water droplets below freezing), small ice crystals, and graupel (soft hail). The updraft carries the super-cooled cloud droplets and very small ice crystals upward. At the same time, the graupel, which is considerably larger and denser, tends to fall or be suspended in the rising air. The differences in

5336-493: The complete destruction of a facility or process or simply cause the failure of a remote electronic sensor; it can result in outdoor activities being halted for safety concerns to employees as a thunderstorm nears an area and until it has sufficiently passed; it can ignite volatile commodities stored in large quantities or interfere with the normal operation of a piece of equipment at critical periods of time. Most lightning-protection devices and systems protect physical structures on

5428-434: 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. The U.S. National Lightning Safety Institute advises American citizens to have a plan for their safety when a thunderstorm occurs and to commence it as soon as the first lightning is seen or thunder heard. This is important, as lightning can strike without rain actually falling and

5520-408: The current is too brief to greatly heat up tissues; 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 strike, the electrical currents in the flash channel pass directly through the victim. The relatively high voltage drop around poorer electrical conductors (such as a human being), causes

5612-508: The currents to flow through the outer surface of the conductor. In addition to electrical wiring damage, the other types of possible damage to consider include structural, fire, and property damage. The field of lightning-protection systems is an enormous industry worldwide due to the impacts lightning can have on the constructs and activities of humankind. Lightning, as varied in properties measured across orders of magnitude as it is, can cause direct effects or have secondary impacts; lead to

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5704-431: The earth, aircraft in flight being the notable exception. While some attention has been paid to attempting to control lightning in the atmosphere, all attempts proved extremely limited in success. Chaff and silver iodide crystal concepts were devised to deal directly with the cloud cells, and were dispensed directly into the clouds from an overflying aircraft. The chaff was devised to deal with the electrical manifestations of

5796-520: The fire line. Evacuation orders were revoked on September 15 and the Blackfoot-Clearwater Wildlife Management Area and lands owned by The Nature Conservancy were re-opened. Lightning strike A lightning strike or lightning bolt is a lightning event in which the electric discharge takes place between the atmosphere and the ground. Most originate in a cumulonimbus cloud and terminate on

5888-568: The fire on Morrell Mountain, also protecting the Morrell Mountain Lookout. Seeley Lake re-opened for recreational use on August 18. The next day, one campground remained closed and the fire had grown in Cottonwood Creek, causing Lolo National Forest to expand closures. On August 24, a forest service road, running north along Cottonwood Canyon, was evacuated due to threats to two cabins. Two trails were also closed. By

5980-457: The frequency of thunderstorms and because many of the area's structures have metal roofs. These statistics do not reflect the difference between direct strikes, where the victim was part of the lightning pathway, indirect effects of being close to the termination point, such as ground currents, and resultant, where the casualty arose from subsequent events, such as fires or explosions. Even the most knowledgeable first responders may not recognize

6072-456: The ground and tops up to 15 km (9.3 mi) in height. The place on Earth where lightning occurs most often is over Lake Maracaibo , wherein the Catatumbo lightning phenomenon produces 250 bolts of lightning a day. This activity occurs on average, 297 days a year. The second most lightning density is near the village of Kifuka in the mountains of the eastern Democratic Republic of

6164-412: The ground, called cloud-to-ground (CG) lightning. A less common type of strike, ground-to-cloud (GC) lightning, is upward-propagating lightning initiated from a tall grounded object and reaching into the clouds. About 25% of all lightning events worldwide are strikes between the atmosphere and earth-bound objects. Most are intracloud (IC) lightning and cloud-to-cloud (CC), where discharges only occur high in

6256-495: The ground, the proportion of CG strikes (versus CC or IC discharges) becomes greater when the cloud is closer to the ground. In the tropics, where the freezing level is generally higher in the atmosphere, only 10% of lightning flashes are CG. At the latitude of Norway (around 60° North latitude), where the freezing elevation is lower, 50% of lightning is CG. Lightning is usually produced by cumulonimbus clouds, which have bases that are typically 1–2 km (0.62–1.24 mi) above

6348-405: The ground. Called step potentials, they are responsible for more injuries and deaths in groups of people or of other animals than the strike itself. Electricity takes every path available to it. Such step potentials will often cause current to flow through one leg and out another, electrocuting an unlucky human or animal standing near the point where the lightning strikes. The electric current of

6440-400: The installation of lightning rods . Safety measures All events associated or suspected of causing damage are called "lightning incidents" due to four important factors. As such it is often inconclusive, albeit highly probable a lightning flash was involved, hence categorizing it as a "lightning incident" covers all bases. Airplanes are commonly struck by lightning without damage, with

6532-438: The ionic channel takes a comparatively long amount of time (hundreds of milliseconds ) in comparison to the resulting discharge, which occurs within a few dozen microseconds. The electric current needed to establish the channel, measured in the tens or hundreds of amperes , is dwarfed by subsequent currents during the actual discharge. Initiation of the lightning leader is not well understood. The electric field strength within

6624-408: The leaders can be readily observed in slow-motion videos of lightning flashes. It is possible for one end of the leader to fill the oppositely-charged well entirely while the other end is still active. When this happens, the leader end which filled the well may propagate outside of the thundercloud and result in either a cloud-to-air flash or a cloud-to-ground flash. In a typical cloud-to-ground flash,

6716-436: The lower part of the storm. The result is that the upper part of the thunderstorm cloud becomes positively charged while the middle to lower part of the thunderstorm cloud becomes negatively charged. The upward motions within the storm and winds at higher levels in the atmosphere tend to cause the small ice crystals (and positive charge) in the upper part of the thunderstorm cloud to spread out horizontally some distance from

6808-416: The movement of the precipitation cause collisions to occur. When the rising ice crystals collide with graupel, the ice crystals become positively charged and the graupel becomes negatively charged; see Figure 2. The updraft carries the positively charged ice crystals upward toward the top of the storm cloud. The larger and denser graupel is either suspended in the middle of the thunderstorm cloud or falls toward

6900-426: The negative leader's connection with the ground. Positive leaders decay more rapidly than negative leaders do. For reasons not well understood, bidirectional leaders tend to initiate on the tips of the decayed positive leaders in which the negative end attempts to re-ionize the leader network. These leaders, also called recoil leaders , usually decay shortly after their formation. When they do manage to make contact with

6992-567: The next two days. By the morning of September 5, the Reef Fire merged into the Rice Ridge Fire. That evening, mandatory evacuation orders were lifted for Seeley Lake. On September 7, Seeley Lake reopened for recreational use. By the end of the next day, structure protections were completed for 25 homes on the north side of Placid Lake and on cabins around Coopers Lake. A strategic, aerial burnout took place over three days to help secure

7084-470: The return stroke averages 30 kiloamperes for a typical negative CG flash, often referred to as "negative CG" lightning. In some cases, a ground-to-cloud (GC) lightning flash may originate from a positively charged region on the ground below a storm. These discharges normally originate from the tops of very tall structures, such as communications antennas. The rate at which the return stroke current travels has been found to be around 100,000 km/s (one-third of

7176-545: The southern U.S.—sixty km (37 mi) longer than the previous distance record (southern Brazil, October 31, 2018). A single flash in Uruguay and northern Argentina on June 18, 2020, lasted for 17.1 seconds—0.37 seconds longer than the previous record (March 4, 2019, also in northern Argentina). In order for an electrostatic discharge to occur, two preconditions are necessary: first, a sufficiently high potential difference between two regions of space must exist, and second,

7268-404: The speed of light). The massive flow of electric current occurring during the return stroke combined with the rate at which it occurs (measured in microseconds) rapidly superheats the completed leader channel, forming a highly electrically conductive plasma channel. The core temperature of the plasma during the return stroke may exceed 27,800 °C (50,000 °F), causing it to radiate with

7360-413: The speed of light. This is the "return stroke" and it is the most luminous and noticeable part of the lightning discharge. A large electric charge flows along the plasma channel, from the cloud to the ground, neutralising the positive ground charge as electrons flow away from the strike point to the surrounding area. This huge surge of current creates large radial voltage differences along the surface of

7452-458: The speed of sound. Sound travels at the slower speed of about 340 m/sec (depending on the temperature), so the flash of lightning is seen before thunder is heard. A method to determine the distance between lightning strike and viewer involves counting the seconds between the lightning flash and thunder. Then, dividing by three to determine the distance in kilometers, or by five for miles. Immediate precautions against lightning should be taken if

7544-434: The storm from within, while the silver iodide salting technique was devised to deal with the mechanical forces of the storm. Hundreds of devices, including lightning rods and charge transfer systems, are used to mitigate lightning damage and influence the path of a lightning flash. A lightning rod (or lightning protector) is a metal strip or rod connected to earth through conductors and a grounding system, used to provide

7636-450: The surrounding air to ionize and break down, and the external flashover diverts most of the main discharge current so that it passes "around" the body, reducing injury. Metallic objects in contact with the skin may "concentrate" the lightning's energy, given it is a better natural conductor and the preferred pathway, resulting in more serious injuries, such as burns from molten or evaporating metal. At least two cases have been reported where

7728-566: The thundercloud is not typically large enough to initiate this process by itself. Many hypotheses have been proposed. One hypothesis postulates that showers of relativistic electrons are created by cosmic rays and are then accelerated to higher velocities via a process called runaway breakdown . As these relativistic electrons collide and ionize neutral air molecules, they initiate leader formation. Another hypothesis involves locally enhanced electric fields being formed near elongated water droplets or ice crystals. Percolation theory , especially for

7820-495: The thunderstorm cloud base. This part of the thunderstorm cloud is called the anvil. While this is the main charging process for the thunderstorm cloud, some of these charges can be redistributed by air movements within the storm (updrafts and downdrafts). In addition, there is a small but important positive charge buildup near the bottom of the thunderstorm cloud due to the precipitation and warmer temperatures. The induced separation of charge in pure liquid water has been known since

7912-435: The time scales involved in thunderstorms. The charge carrier in lightning is mainly electrons in a plasma. The process of going from charge as ions (positive hydrogen ion and negative hydroxide ion) associated with liquid water or solid water to charge as electrons associated with lightning must involve some form of electro-chemistry, that is, the oxidation and/or the reduction of chemical species. As hydroxide functions as

8004-406: The topographic variation that would result in atmospheric mixing, lightning is notably less frequent over the world's oceans than over land. The North and South Poles are limited in their coverage of thunderstorms and therefore result in areas with the least lightning. In general, CG lightning flashes account for only 25% of all total lightning flashes worldwide. Since the base of a thunderstorm

8096-570: The typical commercial aircraft hit at least once a year. Sometimes, though, the effects of a strike are serious. A 2020 lightning bolt across the southern United States set the record for the longest lightning bolt ever detected. The bolt stretched for 477 miles (768 kilometers) over Mississippi, Louisiana, and Texas, although it was between clouds and did not strike the ground. The World Meteorological Organization confirmed its record-breaking status in January 2022. Lightning Lightning

8188-606: The years these names have been incorporated into other products or industries with a stake in lightning protection. Lightning arrester, for example, often refers to fused links that explode when a strike occurs to a high-voltage overhead power line to protect the more expensive transformers down the line by opening the circuit. In reality, it was an early form of a heavy duty surge-protection device. Modern arresters, constructed with metal oxides, are capable of safely shunting abnormally high voltage surges to ground while preventing normal system voltages from being shorted to ground. In 1962,

8280-467: Was 18% contained. The fire continued to burn on Morrell Mountain and towards Cottonwood Lakes Road. Seeley Swan High School classes moved to a local resort due to fire threats. The Blackfoot-Clearwater Wildlife Management Area was closed, too. By Sunday night, September 3, the fire grew into a megafire after mapping flights reported it had burned 101,419 acres (410 km), nearly doubling in size within 24 hours. Additional evacuations were put in place over

8372-429: Was estimated that "...one in four people struck by lightning were sheltering under trees." Trees are frequent conductors of lightning to the ground. Since sap is a relatively poor conductor, its electrical resistance causes it to be heated explosively into steam, 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

8464-630: Was reported that "a direct strike accounts for only 3 to 5 per cent of all injuries and death, while ground currents, which spread out over the ground after lightning strikes, account for up to 50 per cent... ...Where the lightning strikes the ground, the ground becomes highly electrified and if you're within that area of ground electrification..." you can receive an electrical shock from the lightning. As of 2021, it has been reported that "30-60 people are struck by lightning each year in Britain, and on average, 3 (5-10%) of these strikes are fatal." In 2021, it

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