amdx fired this volley in news:lrj1nc$kch$1@dont-
email.me:

No, I'm ignorant on that subject. I am looking for an answer.
I have some 15kv neon transformers, I could connect one to my variac
and test it myself, but I'm getting lazier as I get older.
My thinking is the plasma is a conductor so it will sustain an arc at
lower voltages, but if there is not enough current to keep it hot, the
arc will extinguish. But that one big speculation on my part
Mikek

Well, you answered yourself quite well.
Actually, with most HV devices, the arc does stop -- at twice whatever
the frequency of the output transformer; 60Hz, 120KHz, whatever.

But the column of ionized air takes a while to cool, and remains more
conductive than air for a period of time.

I don't know how much current is necessary to keep it hot, but it is true
that even with an intermittent arc, the arc path will maintain a lower
resistance long enough to wait for the next half-cycle.

It's why lightning can strike multiple times in exactly the same spot and
air path.

Lloyd