Original poster: "Peter Terren" <pterren@xxxxxxxxxxxx> Hi AntonioThere are certainly differences between positive and negative coronas as you know. No doubt the streamers of a TC are the same, however they only stay of any one polarity for 10us before changing. They will tend to follow a previous channel developed up to a point. Perhaps the new streamer growth with each successive hit will be different depending on polarity. Both mine and Terry's equipment are not really good enough to be sure about which streamer channel goes how far. I will bear it in mind though particularly with a view to determining degree of branching with polarity. The whole discipline of streak cameras applied to Tesla coil sparks (by amateurs like me) is only 18 days old but is developing fast. I have observed though that the main current carrying strike can be positive or negative. I am not sure which is more common. Often there is some chaotic activity at that time and both polarities light up briefly, suggesting some higher frequency oscillation. This variability lasts for perhaps 10-15us before settling down to a regular ring down (often). I now have pictures of polarities at both ends. It is often quite variable as well with more activity at one end than the other. (I can feel a string theory coming on).
http://tesladownunder.com/HighVoltage.htm#High%20speed%20Tesla%20spark%20photography Peter
It would be interesting to see if there is some difference in the propagation of the streamer when the polarity is positive or negative. In the picture, I would say that the streamer that almost touches the target is positive, by the appearance of the tip with those branches. ... Antonio Carlos M. de Queiroz