[TowerTalk] Lightning: LEC, Inc

[Eric Gustafson]

>Date: Thu, 23 Jul 1998 22:35:09 -0400
>From: "Bill Fisher, W4AN" <w4an@contesting.com>
>
>http://www.lightningeliminators.com/
>
>Very interesting concepts on lightning elimination.  
>
>73
>
>Bill, W4AN
>
>Bill Fisher, W4AN (EX KM9P)
>http://www.contesting.com 
>



Hi Bill,

I also stumbled on this site a few weeks ago.  I asked a local
ham (and PhD Physicist) to review the claims on that site and
comment on his opinion of the probability of its basis in
reality.

Here is what he emailed back to me about the dissipation array
theories.

		       ------------------

I think they would have a valid physical basis for function if
lightning didn't work the way it does.

The reference to Poisson's equation refers to a space charge
calculation called Debye Huckel theory.  It is based on there
being a freely moving low-density plasma consisting of mobile
charge carriers and fixed (or slowly moving) opposite charges
filling the space between two electrodes of some geometry.
Usually the geometry is concentric spheres or parallel plates.

In the spherical electrode case, the charges congregate near the
smallest radii or curvature and screen the field present near
that point.  Thus, if you move away from the point, instead of
the field dropping like 1/R^2 it drops exponentially.  This is
called space charge screening.

The problem is that lightning doesn't operate that way, even when
there are a number of sharp points present.  It operates by
generating a down-plunging "dart leader" which is relatively
uninterested in the details of the field near such points.  It
has actually been following a photo-ionization track, and only in
the vicinity of the point is its direction affected by local
space charge.

The gross effect of a set of points like that is to provide a
sort of low-probability-of-strike volume _under_ it, within which
there is a reduced probability of a strike.  This is because the
probability of a strike to the structure with all the points on
it has gone up.

		      ---------------------

I tend to put a lot of stock in his assessment since it agrees
with my field experience with the "porcupine ball" protectors.

My family lives near one of the plants that they calim is a
success story for their dissipation arrays.  The next time I get
back east for a visit, I think I'll mosey across the road and ask
their engineering department what they think about the
technology.

73, Eric  N7CL

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