Ask A Scientist Weather Archive

 
name         Jason
status       student
location     NH

Question -   Is lightning stroke DC current or AC current?
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Lightning is DC -- well almost. There are several "kinds" of lightning.
Cloud -- Earth = Cloud -- Earth -- Cloud; Cloud -- Cloud; Earth -- Cloud.
In order of  decreasing frequency. At least for most studies. Usually the
charge carrier is negative (presumably electrons) but apparently some
discharges appear to be positive! Often there is a "leader" stroke that on
high speed photos approach the surface of the Earth, but "do not quite make
it" and then there is a Earth -- Cloud return stroke (presumably the path
is "set up" by the leader stroke. So this would be AC but with a single
cycle. Make no mistake lightning is a difficult and complex phenomenon to
study. It happens fast, and is difficult to track. Some studies "listen"
to the thunder clap, which also provides interesting information, if not
always well understood. The book "The Lightning Discharge" by Martin A.
Uman is devoted to the subject. Interesting reading, thoroughly
referenced. But after reading it there are more interesting questions than
definitive answers.

Vince Calder
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