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How lightning strikes? 

Topics Covered: Important Geophysical phenomena such as earthquakes, Tsunami, Volcanic activity, cyclone etc. 

How lightning strikes? 


Context: 

At least 30 people were killed in separate incidents of lightning in various parts of the country in the past 24 hours. This includes Rajasthan, UP and MP. 

 

How common are deaths by lightning? 

Deaths due to lightning have become frequent in the country. In July last year, 40 people were killed by lightning in Bihar in two separate incidents. 

  • As a whole, India sees 2,000-2,500 lightning deaths every year on average. 
  • Also, lightning is the biggest contributor to accidental deaths due to natural causes. 

 

Challenges and concerns: 

  • Occurrences of lightning are not tracked in India, and there is simply not enough data for scientists to work with. 
  • Often, safety measures and precautions against lightning strikes do not receive as much publicity as other natural disasters such as earthquakes. 

 

What is lightning? 

Lightning is a very rapid — and massive — discharge of electricity in the atmosphere, some of which is directed towards the Earth’s surface. 

 

How does it strike? 

  1. Electrical discharges are generated in giant moisture-bearing clouds that are 10-12 km tall. The base of these clouds typically lies within 1-2 km of the Earth’s surface. Temperatures towards the top of these clouds are in the range of minus 35 to minus 45 degrees Celsius. 
  2. As water vapour moves upward in the cloud, the falling temperature causes it to condense. Heat is generated in the process, which pushes the molecules of water further up. 
  3. As they move to temperatures below zero degrees celsius, the water droplets change into small ice crystals. They continue to move up, gathering mass — until they are so heavy that they start to fall to Earth. 
  4. This leads to a system in which, simultaneously, smaller ice crystals are moving up and bigger crystals are coming down. 
  5. Collisions follow, and trigger the release of electrons — a process that is very similar to the generation of sparks of electricity. As the moving free electrons cause more collisions and more electrons, a chain reaction ensues. 
  6. This process results in a situation in which the top layer of the cloud gets positively charged, while the middle layer is negatively charged. 
  7. An enormous amount of heat is produced, and this leads to the heating of the air column between the two layers of the cloud. This heat gives the air column a reddish appearance during lightning. As the heated air column expands, it produces shock waves that result in thunder. 

 

How does this current reach the Earth from the cloud? 

  1. While the Earth is a good conductor of electricity, it is electrically neutral. However, in comparison to the middle layer of the cloud, it becomes positively charged. As a result, about 15%-20% of the current gets directed towards the Earth as well. It is this flow of current that results in damage to life and property on Earth. 

 

Insta Curious: 

Do you think lightning only strikes the tallest object? 

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InstaLinks: 

Prelims Link: 

  1. How lightning strikes? 
  2. What are megaflashes? 
  3. Is earth a good conductor of electricity? 
  4. Types of clouds. 
  5. Lightning strikes in India. 

Mains Link: 

Write a note on how lightning phenomenon. 

Sources: Indian Express.