Lightning Strikes Protection By Laser

Lightning strike is a sudden electric discharge between atmosphere and earth bound object. This discharge allows charged regions in the atmosphere to temporarily equalize themselves, when they strike an object on the ground. Lightning is always accompanied by the sound of thunder. Lightning can take three forms. One is intra-cloud lighting (IC), which takes places between electrically charged regions of a cloud; second is cloud-to-cloud (CC) lighting, where it occurs between one functional thundercloud and another; and third is cloud-to-ground (CG) lightning, which primarily originates in the thundercloud and terminates on an earth surface (but may also occur in the reverse direction). Many factors affect the frequency, distribution, strength and physical properties of lightning flash in a particular region of the earth. These include ground elevation, latitude, prevailing wind currents, relative humidity, proximity to warm and cold bodies of water, etc.

The first systematic and scientific study of lightning was performed by Benjamin Franklin during the second half of the 18th century. Prior to this, scientists had discerned how electricity could be separated into positive and negative charges and stored. They had also noted a connection between sparks produced in a laboratory and lightning. C.T.R. Wilson (1869-1959) was the first who used electric field measurements to estimate the structure of thunderstorm charges involved in lightning discharges. Wilson also won the Nobel Prize for the invention of the Cloud Chamber, a particle detector used to discern the presence of ionized radiation. 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 3rd, 1995 and the subsequent lightning Imaging Sensor (LIS) aboard TRMM, which was launched on November 28th, 1997. Although a great deal of research on lightning has been conducted, but nowadays lightning stands as a topic of considerable interest for investigation.

lightning strikes originates when wind updraft and downdrafts take place in the atmosphere, creating a charging mechanism that separates electric charges in clouds leaving negative charges (-) at the bottom and positive charges (+) at the top. As the charge at the bottom of the cloud keeps growing, the potential difference between cloud and ground, which is positively charged, grows as well. This process will continue until air breakdown occurs. When a breakdown at the bottom of the cloud creates a pocket of positive charge, an electrostatic discharge channel forms and begins traveling downwards in steps tens of meters in length. In the case of IC or CC lightning, this channel is then drawn to other pockets charged ground.

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. These severe injuries are not usually caused by thermal burns since 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. metallic objects in contact with the skin may "concentrate" the lightning's energy, resulting in more serious injuries, such as burns from molten or evaporating metal. However, during a flash, the current flowing through the channel and around the body will generate large electromagnetic field and EMPs within the nervous system or pacemaker of the heart, upsetting normal operations. Another effect of lightning on human is hearing problem. The resulting shock wave of thunder can damage the ears. Also, electrical interference to telephones or headphones may result in damaging acoustic noise.

Trees are frequent conductors of lightning to the ground. If the damage is severe, the tree may not be able to recover, and decaysets in, eventually killing the tree.

Telephones, modems, computers and other electronic devices can be damaged by lightning, as harmful over current can reach them through the phone jack, Ethernet cable, or electricity outlet. Close strikes can also generate electromagnetic pulses (EMPs) - especially during "positive" lightning discharges. Lightning currents have a very fast rise time, on the order of 40 kA per microsecond. Hence, conductors of such currents exhibit marked skin effect, causing most In addition to electrical wiring damage, the other types of possible damage to consider include structural, fire, and property damage.

Remain indoors (or inside a closed car), away from doors and windows, fireplaces and metal objects, to avoid side flashes. When outside and unable to find shelter, maintain distance from tall trees, hilltops, or other exposed areas. A person caught outside in the open without cover crouch on the ground with his or her limbs close together. Do not swim in a lightning storm.

A lightning rod (or lightning protector) is a metal strip or rod connected to earth through conductors and a grounding system, used to provide a preferred pathway to ground 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. Other names include "lightning conductor", "arrester", "surgitator agitator", and "discharger". These are an early form of a heavy duty surge protection device (SPD). Modern arresters, constructed with metal oxides, are capable a safely shunting abnormally high voltage surges to ground while preventing normal system voltage from being shorted to ground.

If thunder can be heard at all, then there is a risk of lightning. 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

David Aragon (2014) an optical scientists at the University of Arizona and the University of Central Florida have developed a technology capable of sending high-intensity laser beams through the atmosphere much farther than was possible before. The research is still in the laboratory phase. Currently, high-intensity lasers, produced with modern technology essentially disappear over distance greater than a few inches or several feet at best when focused tightly, due to diffraction - the same effect the makes a stick seem to "bend" when dipped into water. This makes them too short- ranged for applications such as diverting lightning. The breakthrough lies in embedding the primary, high-intensity laser beam inside a second beam of lower intensity. As the primary beam travels through the air, the second beam-called dress beam - refuels it with energy and sustains the primary beam over much greater distance than were previously achievable. The development of the new technology was supported by a five-year, $7.5 million U.S. Department of Defense grant - awarded to a group of researchers led by Jerome Moloney, a UA mathematics and optical sciences professor. Moloney is heading up the multidisciplinary, multi-institution research effort to investigate ultra-short laser pulses, focusing on their effects in the atmosphere and ways to improve their propagation over many kilometers. Laser beams that are more effective in overcoming scattering caused by atmospheric turbulence, water droplets in clouds, mist and rain, according to Moloney (2014). Such beams could be used in detection systems reaching over long distances. According to Aurlien Houard (France, 2012) Firing a laser would create an ionized channel in the atmosphere, which could conduct the lightning to the ground. Laser lightning rods could be an alternative to material, like some type of salts, towards the static layer of a thunderhead. But a laser would be easier to control than a rocket. A team of French researchers set out to test how well lasers can harness and control lightning. They sent a laser beam past a spherical electrode toward an oppositely charged flat electrode. The laser stripped away the outer electrons from the atoms in its way, ionizing the pathway between the electrodes and creating a plasma filament - like lab lightning - that channeled an electrical discharge from the flat electrode to the spherical one. Then the team added a longer, pointed electrode to their set of electrode shapes and watched what happened. Left to its own devices, lightning follows the path of least resistance, striking the first thing it comes across-in a thunderstorm, that's the tallest thing, and in this experiment, it's the nearest thing. With no laser lightning rod, the discharge predictably hit the tall pointed electrode first. But when the researchers used the laser filament to guide it, the electrical discharge followed the ionized path and hit the spherical electrode instead. The team found they could pull this off even after the discharge was already on its way, meaning they could divert the path of lightning. Although a great deal of research on lightning has been conducted, but nowadays lightning stands as a topic of considerable interest for investigation.

1. Krider, E.P. and Franklin, B. (2006): Lightning Rods. Physics Today: 42-48. 2. Aurlien H.; Forestier, B. and Durand, M. (2012): Triggering, guiding and deviation of 3. Malk Scheller, Matthew, S.; Mohammad. Ali Miri; Jerome V. Moloney, Miroslav Kolesik (2014): Externally refueled optical filaments. Nature Photonics 8, 297-301. 4. Martin, A.; Uman, D. and Kenneth, M. (1970): Lightning return stroke current from magnetic and radiation field measurements Journal of geophysical science: (75), 5143–5147.