Even lightning doesn't move around as much as this thread.
> I have heard these sorts of anecdotal accounts (including John's) from
> time-to-time. I wonder if all the tall towers are somehow increasing
> the capacitance between the cloud and the ground. Based on the
> relationship Q = CV, the earth-to-ground potential V would drop given
> a fixed charge in the cloud, if the cloud to ground capacitance were
> suddenly increased. Perhaps this is too much of an oversimplification,
> but it does seem to me like a plausible explanation for these
> anecodotal observations. What say folks?
Since the cloud is the primary concentration point of charge, there
is very little you can do about it except to have something discharge
The other "plate" is the entire earth, and the little bit of corona
you get just leaks off into the air around the points...it never
makes it back to the cloud.
The capacitance change would be about zero, because in the scheme of
things you are adding a tiny tiny point on a big blunt surface.
The problem is better thought of as voltage gradient. Corona and
perhaps an eventual arc forms when the voltage gradient is high.
Gradient increases with concentration of an electric field. That is
why two capacitor plates will have a much lower voltage breakdown
when they have microscopic points on the plates than when they are
finely polished. That's also why spark plugs and other intentional
spark gaps have the lowest voltage breakdown when they have sharp
Many points spread out over a large area can form a cloud of ionized
air, and that cloud of ions can decrease the voltage gradient at each
tower. That could increase the voltage required to have a breakdown.
> I wonder if this could be measured by current sensors placed around
> the various towers in big installations like these?
I've tried to measure current into my insulated 300 foot tower, and
it is microamperes unless a bolt flashes in the distance. Then it
ruins the meter, and knocks me on my rump. The very small leakage
current simply goes to replenish the ion cloud formed at points
near the top of the tower, it never really makes it back to the
clouds. Even if it did (without causing a lightning bolt), the amount
of charge change would be insignificant.
It seems reasonable to me that dozens of towers with big pointy
antennas and wires spread all around would look somewhat "blunt" as
an overall picture to the electric field, compared to a single tall
sharp structure all by itself. That could reduce the voltage gradient
around the towers, but not between cloud and earth.73, Tom W8JI