how fast is lightning return stroke

a subsequent return stroke propagates upward from the ground to the cloud. 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. The electrons all come zapping down from the cloud, and it has about 30,000 amps! 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. HKIE Transactions: Vol. There is a pause between steps of about 50 microseconds. Via a complicated process, they become positively charged, while the graupel becomes negatively charged. Concepts of lightning return stroke models Abstract: Return stroke models have been reviewed according to the assumptions they make and their underlying concepts. The stroke channel of a lightning bolt is very narrow—perhaps as little as half an inch (1.25 centimeters). The effects of channel branches on return-stroke radiated fields have been theoretically studied by Le Vine and Meneghini [1978a], Vecchi et al. It is known that the return stroke speed may vary along the lightning channel. The return stroke is the very bright visible flash that we see as lightning, caused by the rapid discharge of electricity. 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. Lightning return stroke speed is one of the main parameters in lightning modeling, so as in evaluating lightning-induced effects [6]. Expert Answer 100% (8 ratings) Previous question Next question Get more help from Chegg. 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. 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. Lightning is so impressive that when it happens it stops you in your tracks. The process begins inside a thunderstorm, where the two important ingredients are located. return stroke) to shoot from the ground to the cloud. The results show that the peak time derivative of the currents in lightning strokes terminating on poorly conducting ground is significantly lower than the case of highly conducting ground. This lightning flash occurred near the campus of the University of Alabama in Huntsville on May 22, 2012. We still don't fully understand how a bolt of lightning gets started, but we have some idea. 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. 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. EMC, 33, 351-357, 1991). This process makes the top of the thundercloud become positively charged. A return stroke explodes "up" the pathway or channel and this is what we actually see as the lightning stroke. this can happen 3-4 times in quick succession. Eventually, over about a 20,000th of a second, a lightning strike stutters its way towards the ground in a series of steps. Dr Karl Kruszelnicki explains. 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. Evolution of the lightning stroke. Did you know Great Moments In Science is a podcast? How much charge is transferred in this event? 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 … 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). Numerical field expressions are proposed to evaluate the electromagnetic fields due to the lightning channel with variable values of return stroke velocity. This is what we see and call lightning (return stroke). I've also seen a problem where people use the return stroke of a lightning bolt for speed instead of the first stroke. Representative models of lightning return … 1.6(c)) moves very fast up towards the cloud through the already ionized path by the leader. If lightning is so powerful, why don't we tame it? What happens next is the return stroke—which is much more powerful and yet kind of invisible. This causes the characteristic blue-white colour of a lightning bolt. 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). this flow of current from the cloud to the ground is visible at the return stroke. Hence, we use the term 'discharge' to describe everything our network is capable of detecting. Instead of carrying 10-100 amps of current, it carries 30,000 amps—sometimes as much as 120,000. A schematic illustration from one of the triggered lightning experiments in Florida (at the northern edge of the Kennedy Space Center in this case, not at the Univ. ribbon lightning. Stroke : this refers to all the return strokes of a lightning flash, i.e. A powerful "return stroke" releases much more energy. All you see with the naked eye is the slower downward strike and a really bright flash … 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. 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 Get 1:1 help now from expert Physics tutors The return stroke is the very bright visible flash that we see as lightning, caused by the rapid discharge of electricity. 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. What would happen if lightning struck a bullet in midair? bead lightning. of Electrical Engineering, Indian Institute of … 16, No. This is similar to cars that have been stopped by an open drawbridge. Techniques for measuring return stroke speed were discussed by I done and Orville [7]. They move so fast that your eyes only see one flash! [1997], Lupo et … NWS 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 … These rather perverse conditions produce three types of water. National Weather Service The super-cooled water droplets and hail are much smaller and lighter, so the strong up-currents of wind inside the thundercloud carry them upwards. Hamelin, A. Eybert-Berard, "Submicrosecond Characteristics of Lightning Return-Stroke Currents," IEEE Trans. This stupendous amount of current is enough to create temperatures 10 times hotter than the surface of the Sun—50,000 degrees. 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. The numerous pulsing return strokes occur in rapid succession, making the lightning bolt appear to flicker on and off. Al Peterlin: Lightning is, generally, any and all forms of visible electrical discharge produced by thundershowers. Now this downstroke—impressive as it is—is just the warmup for the main event. Dr Karl explains why, Dr Karl explains the difference between A1 and A2 milk. Definition: Lightning stroke is the direct discharge of an electrical charge between the atmosphere and the object of earth. The movement of the charge starts at the point of contact and rapidly works its way upward as charge is drained from the channel  Electron velocity in the partially ionized channel is non relativistic [2]. 1. Many have asked, "Why don't we capture this awesome power, and use it to power our industries and boil our kettles?". How fast does lightning travel? 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. Above, branches extending deep into the cloud tap into areas of electrical charge. A complete lightning discharge event can contain anywhere from a single return stroke to more than twenty, depending on the electrical structure of the storm. lightning return-stroke speed within the bottom 100 m or so of the channel. Lightning is fun to watch. It is important to note that Liang et al. Third, and again a bit unexpected, there are quite large blobs of soft hail with the unusual name of "graupel". Please Contact Us. We discuss the return stroke models in two categories in accordance with the direction of the charge transfer along the channel. 7-13. Safety1325 East West HighwaySilver Spring, MD 20910Comments? 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. Data were collected at the Kennedy Space Center, Florida, during the summer of 1987. 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. One-and-a-half billion lightning bolts sounds like a lot, but only about one quarter of them get to the ground. 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! For another, lightning B is a single return stroke CG discharge process. 1, pp. The whole process may take a few milliseconds (one-thousanths of a second), providing enough time to perceive motion. Wind blows the charged channel so position shifts between return strokes. When the lightning leaders attach, the lightning zaps down in something called a discharge, and the discharge is called a return stroke. This is part of the reason that you get the so-called "anvil"—the large flattened area at the top of a thundercloud. These two systems work by detecting radio waves (sferics) emitted by fast electric currents (strokes) in lightning channels. 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. 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. Scientists have learned some facts about lightning from pictures. 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. , who predicted a current return stroke speed of 0.84c, significantly faster than the optical speed. 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 future is 5G and it won't kill you. It happens so fast that you may not easily discern the direction of propagation. We show that all the models that we have considered can be described by two general sets of mathematical equations. This negative charge on the bottom of the cloud induces a positive charge on the ground, a kilometre or more below. 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. The faster return stroke speeds estimated by our model lend credence to the results of Liang et al. The bullet won't affect the path the lightning takes. iv First, we build a modeling environment for each function, which can be described as parameter estimation system. 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. 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). 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. Source: Leteinturier, C., J.H. Using fast electric-field data, we estimated the positive stroke peak current to be 21 kA. 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. 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. . Dr Karl: Can you get pregnant during a pregnancy. The return steamer moves very fast and produces the well known, intensely luminous lightning flash. 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. (2009). 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 … Theory, Journal of Geophysical Research: Atmospheres, 10.1029/1998JD200059, 104 , D2, (2159-2162), (1999). The lightning return stroke current is an important parameter for the evaluation of the efiect of lightning on power lines as the lightning can in°uence a power network both directly and indirectly. Return stroke starts from two different spots on the ground at the same time, creating two channels. Impressive that when it happens it stops you in your tracks makes contact with a streamer, negative. May be concealed by clouds or rain or channel and this is similar cars... Times ) Atmospheric pressure the leader channel flows rapidly to ground so position shifts between return strokes National... Between how fast is lightning return stroke atmosphere and the spectrum of the reason that you get the so-called anvil. 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Stroke speed for both negative and positive lightning are reviewed ( 8 ratings ) Previous question Next question more! A modeling environment for each function, which we hear as thunder estimated the positive stroke peak to...

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