Lightning

GEOGRAPHY/ SCIENCE

Topic:

• GS-2: Important Geophysical phenomena such as earthquakes, Tsunami etc
• GS-3: General Science

Lightning

Context: Recently, thirty people were killed in separate incidents of lightning in various parts of India. Lightning is the biggest contributor to accidental deaths due to natural causes.

What is lightning?

• It is the process of occurrence of a natural ‘electrical discharge of very short duration and high voltage between a cloud and the ground or within a cloud’, accompanied by a bright flash and sound, and sometimes thunderstorms.

How does lightning occur?

• It is a result of the difference in electrical charge between the top and bottom of a cloud.
• As water vapour moves upwards in the cloud, it condenses into water due to decreasing temperatures. A huge amount of heat is generated in the process, pushing the water molecules further up.
• As they move to temperatures below zero, droplets change into small ice crystals. As they continue upwards, they gather mass, until they become so heavy that they start descending.
• It leads to a system where smaller ice crystals move upwards while larger ones come down. The resulting collisions trigger release of electrons, in a process very similar to the generation of electric sparks. 
• The moving free electrons cause more collisions and more electrons leading to a chain reaction.
• The process results in a situation in which the top layer of the cloud gets positively charged while the middle layer is negatively charged.

• In little time, a huge current, of the order of lakhs to millions of amperes, starts to flow between the layers.
  • It produces heat, leading to the heating of the air column between the two layers of cloud. It is because of this heat that the air column looks red during lightning. 
  • The heated air column expands and produces shock waves that result in thunder sounds.

• The Earth is a good conductor of electricity. While electrically neutral, it is relatively positively charged compared to the middle layer of the cloud. As a result, an estimated 20-25% of the current flow is directed towards the Earth. It is this current flow that results in damage to life and property.

Do you know?

• Lightning has a greater probability of striking raised objects on the ground, such as trees or buildings.
• Lightning Conductor is a device used to protect buildings from the effect of lightning.
  • If lightning hits the structure, it will preferentially strike the rod and be conducted to ground through a wire, instead of passing through the structure, where it could start a fire or cause electrocution.
• The most lightning activity on Earth is seen on the shore of Lake Maracaibo in Venezuela.
• Lightning incidents is directly related to the climate crisis, and the availability of more moisture over land due to global warming.
  • An increase of one degree Celsius would increase the frequency of lightning strikes by 12%, warned California University in a study published 2015.

Connecting the dots:

• Forest Fires
• Thunderstorms & Tornadoes