What is a stepped leader in a lightning strike?

Stepped leaders develop within thunderstorm clouds when charge differences between the main region of negative charge in the middle of the thunderstorm and the small region of positive charge near the base of the storm become large (Figure 1).

What happens when a stepped leader meets an upward leader?

Upward-moving Discharges When the stepped leader approaches the ground, carrying some five coulombs of charge, a large positive charge is induced below it and an upward-moving discharge some 30-50 meters long comes up to meet it. This highly luminous discharge then travels back up the leader in the return stroke.

What is ground to cloud lightning?

Ground-to-Cloud (GC) Lightning A discharge between cloud and ground initiated by an upward-moving leader originating from an object on the ground. Ground-to-Cloud lightning strikes – sometimes called upward-moving lightning – are common on tall towers and skyscrapers.

Are stepped leaders good conductors of electricity?

Air is not a good electrical conductor. These downward-moving paths of broken-down air are collectively called the stepped leader because of its incremental motion.

How does a stepped leader in Lightning work?

The Stepped Leader Following a charge transfer event in the lower part of the cloud,the released electrons proceed to the ground. Uman “The vehicle by which these electrons move from the cloud to the ground is called a stepped leader… it moves to the ground in rapid, luminous steps that are about fifty yards long.

Why is a thunderstorm called a stepped leader?

In thunderstorm: Initial stroke …to thousands of amperes, the stepped leader propagates toward the ground at an average velocity of 1.5 × 105 metres per second, or about one two-thousandth the speed of light. It is called a stepped leader because of its downward-moving “stepped” pulses of luminosity.

When does a stepped leader approach the ground?

When the stepped leader approaches the ground, carrying somefive coulombs of charge, a large positive charge is induced below it and an upward-moving discharge some 30-50 meters long comes up to meet it.

Why is the step leader of lightning not visible to the human eye?

These downward-moving paths of broken-down air are collectively called the stepped leader because of its incremental motion. The stepped leader is dimly illuminated, but is not visible to the human eye because of its speed and closeness in time (a small fraction of a second) to the bright return stroke.