Lightning intensity
August 14, 2009 6:10 AM   Subscribe

Why does lightning hitting the CN Tower give off brighter, more sustained strikes?

I was watching the lightning storm that rolled through Toronto last week and took a few pictures from my window at random intervals. Any time the CN Tower got struck (like this for example) the whole sky would light up and it would feel almost like it was daytime, but when other buildings got struck (like this for example) the strikes are not nearly as bright or sustained. So what's so special about the CN Tower? Obviously, it's the tallest thing in the area, so it might have higher odds of getting hit. But once it's hit, is there something intrinsic about its shape or material composition that allows it to sustain bright strikes for longer?
posted by reformedjerk to Science & Nature (5 answers total) 2 users marked this as a favorite
Perhaps because it is so extraordinarily tall, its lighting diversion system differs significantly from those on mere skyscrapers or other lesser structures.
posted by onshi at 6:32 AM on August 14, 2009

Well judging just from those pictures, it looks more like proximity to the bolt is your answer. Did you notice the same thing if it hit a building that was closer to you than the CN tower was?
posted by Grither at 6:33 AM on August 14, 2009

Best answer: After an initial lightning burst, the air that the current went through stays ionized for a short while before returning to normal. If there is enough charge in the area, this channel provides an easy conduit, so you can have multiple discrete strikes along the same route. Usually this is a very fast phenomenon, but it's easy enough to see fast multiple flashes with a good lightning storm. I would be extremely unsurprised if the height and shape of the CN tower makes it such a preferable target that these secondary strikes can continue for longer than with typical cloud to ground situations. I don't know if this is enough to explain all the brightness you see, but I think it's the cause of the sustained nature of the strikes.
posted by Schismatic at 6:58 AM on August 14, 2009

How far was your window from the CN tower, and how far from the other building that got struck? The correction for brightness goes like the square of the distance.
posted by fantabulous timewaster at 8:52 AM on August 14, 2009

Best answer: It looks to me from your pics that the CN Tower strike has multiple sources from many areas of the clouds (see thinner bolts running down to the main one). Building on Schismatic's answer, once an ionized (low impedance) path has been established, other nearby concentrated-charge areas of cloud may "piggy back" on that pathway to dump their own charge to the ground, resulting in a more sustained lightning bolt.
posted by rocket88 at 8:58 AM on August 14, 2009

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