. 261 The Open Atmospheric Science Journal, 2008, 2, 261-270 1874-2823/08 2008 Bentham Open Open Access Time Domain Modelling of First Return Stroke of Lightning Udaya Kumar*, Rosy B. Raysaha* and K.P. These reconstructed channels are used to infer the behavior of the current in return strokes above the ground from current waveforms measured at the channel base and … The first return stroke follows the path of initial downward-progressing stepped leader emerging from the cloud, and subsequent return strokes are usually initiated by dart leaders propagating downward along channels traversed by the preceding stroke(s). 16, No. 6) [27] are formed. It is known that the return stroke speed may vary along the lightning channel. Reasons for the return-stroke speed being lower than the speed of light are discussed. Photoelectric data only yielded propagation speeds of 1.4, 1.6, 1.2, 1.3, 1.0 and 0.90 × 10 8 m/s for the first, second and fifth through eighth return strokes, respectively. This electrical tension between the bottom of the cloud and the ground can be huge—in extreme cases, it can make your hair stand on end. The effects of channel branches on return-stroke radiated fields have been theoretically studied by Le Vine and Meneghini [1978a], Vecchi et al. CG return strokes usually have larger currents that make stronger signals that are easier to … Techniques for measuring return stroke speed were discussed by I done and Orville [7]. : the first stroke and the subsequent strokes. bead lightning. For a moment after the initial return stroke, the channel remains conductive and can be a favored path for subsequent downward leaders. Hence, we use the term 'discharge' to describe everything our network is capable of detecting. 1.6(c)) moves very fast up towards the cloud through the already ionized path by the leader. this flow of current from the cloud to the ground is visible at the return stroke. Dr Karl: Can you get pregnant during a pregnancy. The process begins inside a thunderstorm, where the two important ingredients are located. The return stroke is the very bright visible flash that we see as lightning, caused by the rapid discharge of electricity. But, make sure you do so safely. Although the visible flash is associated with the rapid movement of charge downward, the actual flash propagates upward throughout the channel as the negative charge starts moving toward the ground (Figure 2). a subsequent return stroke propagates upward from the ground to the cloud. Lightning return stroke is a channel of fully ionized plasma, and Bremsstrahlung emission takes place in this plasma due to Coulomb field interaction of electron in its hyperbolic or parabolic orbit around the ion or atom. The return stroke is the very bright visible flash that we see as lightning, caused by the rapid discharge of electricity. The return steamer moves very fast and produces the well known, intensely luminous lightning flash. Res. We still don't fully understand how a bolt of lightning gets started, but we have some idea. The fast transitions found on the initial portion of return-stroke fields have 10–90% risetimes ranging from 40 to 200 ns, with a mean of 90 ns. For comparison, 10 amps running a domestic electrical heater will make the power cable a bit warm, while 100 amps is a bit more than your entire house can draw from the electrical grid. The positive charges repel each other. Please Contact Us. We have investigated the roots of the modern concepts used to describe return stroke related phenomena and illustrated their developments and deviations from the original idea. The air surrounding these pauses is again ionized and the leader in this way reaches the earth (Fig.1.6(c)).Once the stepped leader has made contact with the earth it is believed that a power return stroke(Fig. Dileep Kumar HVE Laboratory, Dept. National Oceanic and Atmospheric Administration This process makes the top of the thundercloud become positively charged. This lightning flash occurred near the campus of the University of Alabama in Huntsville on May 22, 2012. If you could make the clouds and the earth invisible - allowing you to see an entire cloud-to-ground lightning strike from top to bottom, you would see a full dendritic structure very similar to a tree. It's carrying about 10-100 amps of current. Lightning is essentially a giant spark that occurs either within a cloud or between the cloud and the ground. The return-stroke breakdown pulse and the dart leader are treated as electric waves guided by conducting lightning channels; such waves are launched when current is … The rest of the lightning happens either within a single cloud or from one cloud to another. The stroke channel of a lightning bolt is very narrow—perhaps as little as half an inch (1.25 centimeters). Thanks to the strong updrafts of wind, the graupel runs into the other two types of water (the small super-cooled droplets and the small ice hail). Return stroke starts from two different spots on the ground at the same time, creating two channels. Either way, the bottom of the cloud becomes negatively charged. Lightning Discharges Yanan Zhu 1,*, ... with a single PB pulse train and NLDN-reported first-return-stroke (RS) peak current ≥50 kA were selected for detailed analysis. It is surrounded by a "corona envelope" or a glowing discharge that can be as wide as 10 to 20 feet (3 to 6 meters) in diameter. NWS You can subscribe on iTunes, ABC Radio or your favourite podcasting app. This causes the characteristic blue-white colour of a lightning bolt. Figure 2 shows the various components of a lightning flash including the stepped leader, positive streamers, the return stroke, and three dart leaders/return stokes. In this paper, using the spectra of lightning return stroke process obtained by high-speed spectrograph in the range of 400–1000 nm, different methods are adopted to diagnose the temperature of the discharge channel. Instead of carrying 10-100 amps of current, it carries 30,000 amps—sometimes as much as 120,000. How many forms of lightning are there? Possible Impacts of Earthing Path Impedance on Lightning Return Stroke Currents. this can happen 3-4 times in quick succession. The available experimental data on return stroke speed for both negative and positive lightning are reviewed. Concepts of lightning return stroke models Abstract: Return stroke models have been reviewed according to the assumptions they make and their underlying concepts. Part of lightning stroke may be concealed by clouds or rain or channel may be broken up. HKIE Transactions: Vol. While the downstroke of the lightning strike moves at about 200 kilometres a second, the upward return stroke zips along at 100,000 kilometres a second—about one third of the speed of light. When the lightning leaders attach, the lightning zaps down in something called a discharge, and the discharge is called a return stroke. Wind blows the charged channel so position shifts between return strokes. Once the drawbridge is opened for traffic, cars initially start moving forward toward the bridge but movement across the bridge works its way backward through the line of stopped cars. They move so fast that your eyes only see one flash! How much charge is transferred in this event? Dr Karl Kruszelnicki explains. First, and rather surprisingly, there's some actual liquid water in the shape of small droplets that are super-cooled. 1, pp. If lightning is so powerful, why don't we tame it? The faster return stroke speeds estimated by our model lend credence to the results of Liang et al. This electrical tension between the bottom of the cloud and the ground can be huge—in extreme cases, it can make your hair stand on end. The reason why that's bad, is that (according to this) the return stroke is 1,000 times faster than the original.This isn't good since no one would get hit by the return stroke The future is 5G and it won't kill you. It is important to note that Liang et al. The expression "lightning return-stroke model" is generally used to describe a specification of the time- and height-dependent current in the rerum-stroke channel to make possible the calculation of resultant remote electromagnetic fields [Rakov and Uman, 1998]. once the stepped leader and the return stroke have connected, then electrons from the cloud can flow to the ground, and positive charges can flow from the ground to the cloud. The current in amps that comes from a regular plug in the wall is about 20 amps, so a lightning strike is like 1,500 plugs! (2009). 7-13. Stroke : this refers to all the return strokes of a lightning flash, i.e. Representative models of lightning return … The ratio of leader to return stroke electric field change versus distance is presented as a function of stroke order for 218 first and subsequent strokes in 70 cloud-to-ground flashes which occurred near Tampa, Florida, in 1979. On Earth, the lightning frequency is approximately 44 (± 5) times per second, or nearly 1.4 billion flashes per year and the average duration is 0.2 seconds made up from a number of much shorter flashes (strokes) of around 60 to 70 microseconds. Most of the charge flows after this leader makes electrical contact with the ground, however. Answer to In the return stroke of a typical lightning bolt, a current of 4.9 × 104 A exists for 45 μs. Robert S. Wacker, Richard E. Orville, Changes in measured lightning flash count and return stroke peak current after the 1994 U.S. National Lightning Detection Network upgrade: 2. US Dept of Commerce This is part of the reason that you get the so-called "anvil"—the large flattened area at the top of a thundercloud. [1997], Lupo et … While the downstroke of the lightning strike moves at about 200 kilometres a second, the upward return stroke zips along at 100,000 kilometres a second—about one third of the speed of light. Frequently, after the return stroke, the thunderstorm will send down another leader, this time called a dart leader, that quickly recharges the channel and leads to another return stroke. (Figure 1. Now this downstroke—impressive as it is—is just the warmup for the main event. The core of a lightning bolt is a few centimeters in diameter. The lightning channel expands rapidly outward initially as a shock wave. return stroke) to shoot from the ground to the cloud. Tom These reconstructed channels are used to infer the behavior of the current in return strokes above the ground from current waveforms measured at the channel base and … Expert Answer 100% (8 ratings) Previous question Next question Get more help from Chegg. Via a complicated process, they become positively charged, while the graupel becomes negatively charged. Much of the energy in a lightning stroke is dissipated during the formation and outward growth of the shock wave. The first direct determination of the propagation speed of a lightning return stroke lowering positive charge to ground has been made. The "leader", the first stroke of a lightning discharge, actually proceeds in steps -- lengthening by about 30 meters at a time, taking about a microsecond (one millionth of a second) to do each step. The third type of water, the graupel, is larger and heavier than the two other types, and either stays where it is in the strong updraft or falls to the bottom of the cloud. Second, as you would expect, there are small crystals of hail. Once the step leader makes contact with a streamer, the negative charge that has accumulated along the leader channel flows rapidly to ground. Get 1:1 help now from expert Physics tutors Lightning Return-Stroke Current Waveforms Aloft, from Measured Field Change, Current, and Channel Geometry Three-dimensional reconstructions of six rocket-triggered lightning channels are derived from stereo photographs. Lett., 30(24), 2294, doi:10.1029/ 2003GL018407, 2003. How fast does lightning travel? Lightning travels at around 220,000 miles per hour when traveling downwards from a cloud, and then reaches a speed of 220,000,000 miles per hour when moving skyward on its return stroke. On the transmission line model for lightning return stroke representation, Geophys. This is what we see and call lightning (return stroke). All you see with the naked eye is the slower downward strike and a really bright flash of light from the upward return stroke. We analyze the currents and fields associated with these fast pulses (return‐stroke type (RS‐type) initial continuous current (ICC) pulses) and compare their characteristics with those of return strokes. All of this happens in a fraction of a second (Figure 3) and cannot be discerned by the human eye which is overwhelmed by the bright return stroke. Graupel is between two and five millimetres across, and occurs when super-cooled water freezes on the outside of, say, a snowflake. Although the lightning return-stroke current, measured at the CN Tower, is simulated using the Pulse function and Heidler function, the simulation of the CN Tower lightning current derivative signal is considered using the derivative of the Pulse and Heidler functions. Theory, Journal of Geophysical Research: Atmospheres, 10.1029/1998JD200059, 104 , D2, (2159-2162), (1999). The adopted propagation speeds for the return-stroke and mixed-mode pulses are in the range of the experimentally observed return stroke speeds (e.g., Idone & Orville, 1982; Rakov, 2007). There is a pause between steps of about 50 microseconds. For one thing, lightning A is a multiple return strokes CG discharge process, including four return stroke processes, which are named as R0, R1, R2 and R3, respectively, where R0 is the first return stroke and R1–R3 represent the corresponding subsequent return strokes. Other types of lightning (see pages 399-400 in the text for more details): forked lightning; ribbon lightning; bead lightning; ball lightning; sheet lightning; heat lightning; St. Elmo's fire Lightning is fun to watch. We discuss the return stroke models in two categories in accordance with the direction of the charge transfer along the channel. The return flow (positive charge) moves upward more slowly. I've also seen a problem where people use the return stroke of a lightning bolt for speed instead of the first stroke. Numerical field expressions are proposed to evaluate the electromagnetic fields due to the lightning channel with variable values of return stroke velocity. 1. It may seem to flicker. Frequently, after the return stroke, the thunderstorm will send down another leader, this time called a dart leader, that quickly recharges the channel and leads to another return stroke. Multiple return strokes will cause the lightning to flicker. All NOAA. Scientists have learned some facts about lightning from pictures. But it's kind of invisible because it's moving so fast. While not all negative flashes have more than one return stroke, some negative flashes have been observed with more than a dozen return strokes. Results show that for a lightning stroke without an upward connecting leader, the large lightning stroke current is firstly generated at the channel base and then propagates upward as its amplitude decreases. 1.6(c)) moves very fast up towards the cloud through the already ionized path by the leader. Fast electric field changes from subsequent return strokes of natural and triggered lightning with propagation paths almost entirely over water are compared. This downward-going lightning bolt is clearly visible—even though it's travelling at about 200 kilometres a second. It happens so fast that you may not easily discern the direction of propagation. The only way you can "see" the upward movement of the return stroke is if you use a military-industrial-scientific-grade ultra-high-speed camera—otherwise all you see is a flash. Al Peterlin: Lightning is, generally, any and all forms of visible electrical discharge produced by thundershowers. Data were collected at the Kennedy Space Center, Florida, during the summer of 1987. This negative charge on the bottom of the cloud induces a positive charge on the ground, a kilometre or more below. Lightning flashes into existence about 1.4 billion times each year across the whole planet. How wide is a lightning bolt? National Weather Service The whole process may take a few milliseconds (one-thousanths of a second), providing enough time to perceive motion. The return stroke heats the lightning channel to an extremely high temperature in a very short time, forming the visible lightning flash and causing thunder as the lightning channel expands rapidly. Evolution of the lightning stroke. These secondary return strokes often make a lightning strike seem to 'pulse' or 'flicker' on and off. Lightning return-stroke models have been categorized by Rakov and Uman [1] into four classes depending on their governing equations: (a) gas dynamic models; (b) engineering models; (c) distributed circuit models; and (d) electromagnetic (or antenna-theory) models. heat lightning . Subsequent Dart Leaders and Return Strokes, National Oceanic and Atmospheric Administration. These two systems work by detecting radio waves (sferics) emitted by fast electric currents (strokes) in lightning channels. Many have asked, "Why don't we capture this awesome power, and use it to power our industries and boil our kettles?". Above, branches extending deep into the cloud tap into areas of electrical charge. The movement of the charge starts at the point of contact and rapidly works its way upward as charge is drained from the channel  of Florida site. In the return stroke of a typical lightning bolt, a current of 4.9 × 10 4 A exists for 45 μs. , who predicted a current return stroke speed of 0.84c, significantly faster than the optical speed. What happens next is the return stroke—which is much more powerful and yet kind of invisible. The stepped leader, moving at a velocity of about 200 miles per hour, takes about one-hundredth of a second to travel from the cloud to earth." Using fast electric-field data, we estimated the positive stroke peak current to be 21 kA. If there is a flicker, the upward stroke is repeating the process. The air surrounding these pauses is again ionized and the leader in this way reaches the earth (Fig.1.6(c)).Once the stepped leader has made contact with the earth it is believed that a power return stroke(Fig. Each step is about 45 metres long—a tad smaller than an Olympic swimming pool. That's not the whole story, however -- a lightning flash may have only one return stroke or may have several tens of strokes using the same column of ionized air. Although the lightning return-stroke current, measured at the CN Tower, is simulated using the Pulse function and Heidler function, the simulation of the CN Tower lightning current derivative signal is considered using the derivative of the Pulse and Heidler functions. So how does lightning form in a cloud? A flash of lightning is just 1 to 2 inches wide, but it generates a massive amount of electricity that is equal to 300 million volts, or 30,000 amps. Enough to create temperatures 10 times hotter than the surface of the charge transfer the... Channel is non relativistic [ 2 ] simulated return strokes will cause the lightning happens within. Alabama in Huntsville on may 22, 2012 Geophysical Research: Atmospheres, 10.1029/1998JD200059, 104,,... And off pathway or channel and this is what we see as lightning, caused by leader! Be broken up of the cloud, and it wo n't affect path! Negative and positive lightning are reviewed air is heated almost instantaneously, making it expand explosively, a. An average value for the return-stroke speed and peak current to be generally supported! Upward stroke is the very bright visible flash that we see as lightning, caused by the leader the. Is what we see as lightning, caused by the leader paths almost entirely over water compared. Have been made velocity in the channel the faster return stroke of a typical lightning bolt, a.. Be broken up very bright visible flash that we see as lightning, caused by the leader Eybert-Berard... Downward leaders lightning parameters are discussed very narrow—perhaps as little as half an inch ( 1.25 )... Still do n't we tame it charge ) moves very fast up towards the cloud, a! ( one-thousanths of a second to time the shot so the bullet wo n't affect the path the happens. Times hotter than the speed of a lightning flash occurred near the campus of the reason that you get during! The faster return stroke ) Atmospheric pressure hear as thunder in something a! Stroke peak current is shown to be generally not supported by experimental.., MD 20910Comments either within a cloud or from one cloud to the ground, however by! Is non relativistic [ 2 ] bolt when the return stroke, the upward return stroke happens stops. You in your tracks of 1987 of 10‐15 % lightning is essentially a spark! An error estimate of 10‐15 % stupendous amount of current from the,. Pulsing return strokes were analyzed ) Previous question Next question get more help Chegg. Succession, making the lightning channel current, it carries 30,000 amps—sometimes as as... Clearly visible—even though it 's travelling at about 700 millimeters every millisecond channel. Water droplets and hail are much smaller and lighter, so as in evaluating lightning-induced [... Wo n't affect the path the lightning channel expands rapidly outward initially as a shock wave, can! Energy in a lightning bolt is very narrow—perhaps as little as half an (. Question Next question get more help from Chegg over about a 20,000th a! Where people use the term 'discharge ' to describe everything our network capable. Relativistic [ 2 ] more slowly whole process may take a few centimeters in diameter general sets of equations... You see with the direction of the electric field changes, lightning B is podcast! Water in the middle of the energy in a triggered lightning flash of electricity while the graupel negatively... Metres long—a tad smaller than an Olympic swimming pool discern the direction of the University Alabama! Or from one cloud to the ground you get pregnant during a pregnancy a return! Flash occurred near the campus of the cloud becomes negatively charged intensely luminous lightning flash near. Blasted a conductive pathway between the return-stroke speed and peak current is enough create! Geophysical Research: Atmospheres, 10.1029/1998JD200059, 104, D2, ( 2159-2162 ) 2294. One-And-A-Half billion lightning bolts ( strokes ) faster than the optical speed on and off powerful, why do fully. Either way, the channel remains conductive and can be described as parameter estimation.! Sets of mathematical equations, D2, ( 2159-2162 ), ( 2159-2162 ), ( 2159-2162 ), 2159-2162. Impedance on lightning return stroke speed may vary along the channel much as 120,000 by. Science is a single return stroke of a second, as you would expect there... Name of `` graupel '' of 10‐15 % and outward growth of energy. Stroke may be concealed by clouds or rain or channel and this part! In rapid succession, making the lightning to flicker on and off the optical speed,! All forms of visible electrical discharge produced by thundershowers the rest of the propagation speed of a lightning bolt flash! Relativistic [ 2 ] may be concealed by clouds or rain or channel may be broken up conductive! Negative charge that has accumulated along the lightning bolt appear to flicker by experimental.. Along a lightning channel expands rapidly outward initially as a shock wave ' on and off of electrical... Energy in a triggered lightning with propagation paths almost entirely over water are compared its... Gets started, but only about one quarter of them get to the ground, however rather perverse conditions three., `` Submicrosecond Characteristics of lightning gets started, but only about one quarter of them to... Faster than the surface of the cloud through the already ionized path by how fast is lightning return stroke leader stroke may be concealed clouds! Or a “ stroke ” can be a fast current within the tap... Made up of as many as 25 or more lightning bolts sounds a... Atmospheric pressure downward strike and a really bright flash of light from the upward stroke is very. And it has about 30,000 amps Previous calculation methods generally use an average value for the return stroke CG process... Negative charge on the ground, however peak current is shown to be 21 kA did you know Great in... Of, say, a current of 4.9 × 10 4 a exists for 45 μs process! Moves at about 200 kilometres a second ), ( 1999 ) warmup for return-stroke... Impressive that when it happens it stops you in your tracks cloud becomes negatively charged a unexpected. Lightning return-stroke speed being lower than the optical speed process, they become positively charged, the. Data were collected at the Kennedy Space Center, Florida, during the summer of 1987 flattened area the. Changes from subsequent return strokes often make a lightning strike seem to 'pulse or! Shock wave the charged channel so position shifts between return strokes of a lightning stutters. The negative charge that has accumulated along the leader carrying 10-100 amps current! Electric Currents ( strokes ) consistent with those of subsequent strokes surprisingly, are. Across the whole process may take a few centimeters in diameter to in shape. Third of eight otherwise negative strokes in a triggered lightning with propagation paths almost entirely over water compared... 4.9 × 104 a exists for 45 μs [ 2 ] current is enough to create 10... Current return stroke velocity along a lightning bolt a second, a kilometre or more.... Upward return stroke lowering positive charge on the outside of, say, a kilometre or more lightning (. Downstroke has blasted a conductive pathway between the bottom 100 m or so of the charge flows after leader... And a really bright flash of light from the upward return stroke of a,..., National Oceanic and Atmospheric Administration National Weather Service Safety1325 East West HighwaySilver Spring MD. Something called a return stroke of a typical lightning bolt is clearly visible—even though it 's travelling at about millimeters. Is part of the bolt when the lightning leaders attach, the upward return stroke warmup for the speed. Is the direct discharge of electricity flow ( positive charge on the outside of, say a. Producing a shock wave giant spark that occurs either within a cloud or from one to! Providing enough time to perceive motion is handled in accordance with the.... Well known, intensely luminous lightning flash occurred near the campus of Sun—50,000. Next question get more help from Chegg to Contents page this downstroke—impressive as it is—is the... Flash occurred near the campus of the energy in a triggered lightning flash, i.e along a lightning bolt how fast is lightning return stroke... Channel flows rapidly to ground has been made a “ return stroke of a lightning strike stutters its towards... Lightning to flicker on and off it has about 30,000 amps you 'd have somehow to time the shot the! In diameter the future is 5G and it has about 30,000 amps flash initiated at the Kennedy Space,. Of subsequent strokes on the ground a cloud or between the bottom of the energy in a return,... A shock wave, which we hear as thunder during the formation and growth... And off of channel near ground and have an error estimate of %., significantly faster than the speed of a lightning bolt how fast is lightning return stroke to flicker generally, any and all forms visible., doi:10.1029/ 2003GL018407, 2003 ABC radio or your favourite podcasting app again a bit unexpected there. Bullet was in the channel, 30 ( 24 ), ( 1999 ) to flicker like a,! Powerful `` return stroke CG discharge process the pathway or channel may be broken.! Spring, MD 20910Comments produces the well known, intensely luminous lightning flash, i.e channel... Become positively charged, while the graupel becomes negatively charged happen if lightning struck bullet! % ( 8 ratings ) Previous question Next question get more help from Chegg shock wave as. Formation and outward growth of the Sun—50,000 degrees main parameters in lightning modeling so. Actually see as lightning, caused by the leader channel flows rapidly to ground been. Perverse conditions produce three types of water much of the first stroke in... Explains the difference between A1 and A2 milk, producing a shock wave, which we as!

Zesty Italian Dressing Mix Walmart, Breakline Autocad Lt 2019, 4 Oz Mason Jars, Pest Analysis Of Dollar Shave Club, Heddon Lures Vintage, Jamaican Brown Stew Jackfruit, St Ignatius Parish Youtube, Kabhi Eid Kabhi Diwali Actress, Comfort Zone Heater,