Has anyone seen St. Elmo's fire, also known as corona discharge in everyday life? I've seen in it a lab demonstration but I'm curious what it actually looks like in the real world and how common it is. If you model a ship's spar as a long perfectly conducting cylinder then by solving poisson's equation you can show that at the top and bottom sides of the cylinder (long dimension is horizontal) the electric field is twice that of the applied field. So whenever the electric potential from cloud to sky is more than 1/2 the breakdown voltage you should see the discharge. I guess I'm not very lucky since I've never seen it.