Seen St Elmos fire many times. A purple sparking glow on the nose of the plane seen lighting upwards on the windscreen. From the cabin can be seen (more faintly) dancing on the leading edge. Probability and statistically you need to fly a good number of hours in your career to see the stuff. The chances are it'll be close to a TS, in very moist unstable air. Struck by lightning with no St Elmos fire beforehand though, and seen some really impressive SE fire without any lightning flashes too.