[Towertalk] Explain this!

[Pete Smith]

At 06:44 AM 4/25/02 -0600, mcduffie@actcom.net wrote:
>On Thu, 25 Apr 2002 07:17:58 -0400, Scott Detloff K8DX wrote:
>
> > Inspection of the vertical this morning shows nothing out of the
> > ordinary.
> >
> > Any ideas?

I think K1MK may have been closest to the mark with the mention of St. 
Elmo's Fire.  I found the following explanation on the Scientific American 
web site.  Elsewhere, I think I have also read that it can be caused by 
wind on a conductor.  Either way, it seems to fit the facts...

"William Beaty is an electrical engineer who has designed numerous science 
exhibits for museums. He is the creator of the Science Hobbyist web page 
and is a member of the Mad Science Network.. He offers the following 
explanation:
St. Elmo's Fire is a type of continuous electric spark called a "glow 
discharge." You've seen it many times before, since it is almost exactly 
the same as the glows found inside fluorescent tubes, mercury vapor 
streetlights, old orange-display calculators and in "eye of the storm" 
plasma globes. When it occurs naturally, we call it St. Elmo's Fire, but 
when it occurs inside a glass tube, we call it a neon sign.
St. Elmo's Fire and normal sparks both can appear when high electrical 
voltage affects a gas. St. Elmo's fire is seen during thunderstorms when 
the ground below the storm is electrically charged, and there is high 
voltage in the air between the cloud and the ground. The voltage tears 
apart the air molecules and the gas begins to glow. It takes about 30,000 
volts per centimeter of space to start a St. Elmo's fire (although sharp 
points can trigger it at somewhat lower voltage levels.)
St. Elmo's Fire is plasma. A normal gas is composed of molecules. The 
molecules are composed of atoms, which in turn are composed of electrons 
and clusters of proton particles. If the electric force applied to each bit 
of gas is greater than a certain level of voltage, it causes the electrons 
and protons of the gas molecules to be pulled away from each other. High 
voltage transforms the gas into a glowing mixture of separate proton 
clusters and electrons. We call this mixture of particles by the name 
"plasma," and it is conductive. It also fluoresces with light.
The color of the glow depends on the type of gas involved. If we lived in 
an atmosphere of neon gas, then St. Elmo's fire would be red/orange, and 
lightning would be white with orange edges. Our atmosphere is nitrogen and 
oxygen, and this mixture glows blue/violet when exposed to high voltage 
fields. If a neon sign tube was filled with nitrogen/oxygen instead of 
neon, it would light up blue/violet rather than red/orange.
Is this phenomenon related to ball lightning? No one knows, because no one 
knows what ball lightning is, and it might not be a spark at all. St. 
Elmo's fire is sometimes mistaken for ball lightning. Among other 
differences, ball lightning can drift around like a soap bubble, while St. 
Elmo's Fire always remains attached to an object."

73, Pete N4ZR