A lightning strike is a powerful, naturally occurring electrical discharge between an electrically active area in the atmosphere and the ground, or between two clouds. It begins when charges build up in storm clouds, causing a step leader to descend from the cloud.
When this leader meets an upward-rising streamer from the ground, a conductive path forms, and electrons surge along it, creating the bright flash and loud thunder we know. While most lightning occurs in the sky, cloud-to-ground strikes are the most dangerous, leading to injuries and fires.
How lightning forms
1. Charge separation:
Within a cumulonimbus storm cloud, colliding ice crystals and water droplets generate static electricity, causing charges to separate.
- Leader development:
A stepped leader, a negatively charged channel of ionized air, descends from the cloud towards the ground. - Upward streamer:
As the leader gets closer, positive charges on the ground, especially on tall objects like trees and buildings, migrate upward, creating an upward streamer. - Connection and discharge:
When the downward leader and upward streamer meet, a conductive path is completed, and electrons rush along this path, creating the bright flash of the lightning bolt. - Thunder:
The lightning bolt rapidly heats the surrounding air, causing it to expand explosively and create the sound of thunder.
Types of lightning strikes
Cloud-to-ground (CG) lightning: The most dangerous type, where the electrical discharge travels from a cloud to the ground or an object on the ground.
Intra-cloud (IC) lightning: An electrical discharge within a single cloud.
Cloud-to-cloud (CC) lightning: An electrical discharge between two different clouds.
Ground-to-cloud (GC) lightning: Less common, this is lightning that travels upward from a grounded object to the clouds.
Effects of a lightning strike
Heat:
The intense heat of the lightning bolt can cause severe burns, fires, and explosions.
Electrical damage:
The high-voltage current can damage structures, trees, and equipment.
Thunder:
The explosive expansion of air due to the heat creates the shockwave we hear as thunder.
Danger to life:
Cloud-to-ground strikes are particularly hazardous to people and can be fatal.