Recently a discussion came up about this gif: http://i.imgur.com/r9Q8M4G.gifv
This lead to a few questions about electrical breakdown of insulators. The disagreement we're having is whether or not a current is present before a lightning strike occurs. I personally don't think there is any measurable current between the clouds and the ground prior to the electrical breakdown of the air, but other disagree with me. Others went as far as to say that there needs to be a current for lightning to happen. Considering that you don't need a current to polarize a dielectric, that sounds totally wrong to me, although the amount of disagreement I'm receiving has caused me to second guess myself.
Unfortunately I can't give any more context to this without posting individual comments, so to sum about the question:
- Is there a current between the air and ground prior to a lightning strike, or is the potential difference solely responsible for the electrical breakdown and discharge?