Evolution of the
- once the stepped leader and the
return stroke have connected, then electrons from
the cloud can flow to the ground, and positive
charges can flow from the ground to the cloud.
- this flow of current from the
cloud to the ground is visible at the return stroke.
- the return stroke is
several cm in diameter
- after the first discharge, it is
possible for another leader to propagate down the
channel created by the first stepped leader.
- This new leader is called a dart leader.
- a subsequent return stroke
propagates upward from the ground to the cloud.
- this can happen 3-4 times in quick
Other types of
lightning (see pages
399-400 in the text for more details):
- forked lightning
- ribbon lightning
- bead lightning
- ball lightning
- sheet lightning
- heat lightning
- St. Elmo's fire
brief movie shows cloud-to-ground lightning, bolts of
cloud-to-cloud lightning, and sheet lightning.