Jim Lux wrote:
breakdown? Is there some distinction to "full?")

One often makes a distinction between a corona discharge which exists as
a steady state sort of thing and the streamers which precede a "spark".
Both are air breakdown phenomena, but qualitatively different, and both
are different from a low pressure discharge like that found in a
fluorescent lamp or neon bulb, or from phenomena like St Elmo's Fire.
. . .

Most interesting. I've always thought that St. Elmo's fire was a corona
discharge, and a quick web search indicates that it's apparently a very
widely held misconception. What's the difference?

Roy Lewallen, W7EL