A moving ion has a mean free path which can be calculated with a formula which considers pressure or density, as well as velocity producing voltage. This free path is the distance an ion can move before it's likely to hit some other molecule. If this collision does occur, maximum efficiency lies with the lowest usable voltage. However, ion sparks don't seem to collide with anything on an extremely short distance. Instead, they travel along a hair line spark that's thin enough that the ions just wriggle through and past air molecules they encounter.
I've been looking at a regular spark plug and it seems to have a resonant chamber at the end, around the tapering ceramic insulator surrounding the central rod electrode. With my setup, I can hear a buzzing noise from the spark plug's arc, and there's also some random clicking sounds. Now and then, one of the clicks will be just right to hit the resonance of the end chamber. This causes ions to form. And these ions develop a normal coulomb force which limits the number of ions which can be present in the resonant chamber. As a result, a certain number of ions immediately shoot out, traveling along a hair line spark. This ion spark has a different color than a regular electrical spark, and that's what convinces me the spark contains ions. These ions travel out a good half inch, forming a mesh like pattern in the air. They're certainly not encountering a mean free path restriction. AND these sparks are longitudinal - they move straight out for a distance, then stop. Or then move in a perpendicular direction due to the negative magnetic rotation, when it appears during each of the cycles.
