St Elmo's fire
As the others have said usually the appearance of the phenomenon was the trigger for "let's get away from it - asap". On a Nimrod it would appear on the AAR probe and on the wiper brackets and, oddly, as a slowly rotating "halo" on the intakes. It was also accompanied by rising static levels on HF and UHF radios as we tiptoed away wincing in anticipation of the lightning strike which often followed. Now THAT was a real attention getter. HTH.
The Ancient Mariner
PS. I seem to remember the explanation was that it concentrated on "conductors where the radius of curvature was smallest". (but I could be wrong)