stepped leader
Quick Summary
Lightning is a powerful electrical discharge that occurs during thunderstorms. It happens when the accumulated electric charges within a thundercloud become large enough to overcome the insulating capacity of the air.12
Cloud-to-Ground Lightning
This type of lightning begins with a "stepped leader," a faint, downward-moving channel of ionized air that descends from the cloud in distinct steps, typically about 30 meters long. The stepped leader moves at a relatively slow speed, about one two-thousandth the speed of light.1
As the stepped leader nears the ground, it induces an opposite charge on the surface. An upward discharge then rises from the ground to meet the leader, creating a connection. This junction triggers a bright, rapid "return stroke" that is perceived as lightning. This return stroke carries a massive current and heats the channel to extremely high temperatures, making it much brighter than the stepped leader.2
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