Tom Donaly wrote:


Hi Chuck,
Read "Meteorological Aspects of Precipitation Static" By
Lieutenant Robert C, Edwards, U.S.N.R., and Captain George W. Brock,
U.S.A.A.F. from the Journal of Meteorology, Vol. 1, Number 4,
December, 1945. If you Google "Precipitation Static" you can
find a pdf file of it. They actually went up in three different
airplanes, an RB-37, a B-25D, and a B-17G and did some measurements.
You might be interested in their methods and conclusions.
73,
Tom Donaly, KA6RUH

Hi Tom,

Thanks for the reference. Quite an interesting article.

My one problem with it after a quick reading is their
autogenous/exogenous electrification dichotomy. More particularly, their
notion of exogenous electrification, which " . . . occurs when an
aircraft flies through electric fields previously established by a
charge separation in the free atmosphere."

Not sure it is important to the physics exactly how the electric field
was established, but taking the airplane to be an isolated conductor in
an electric field, I wonder how "electrification" can take place.

Perhaps 60 years ago we used different terminology, but electrification
usually refers to contact charge separation. Since there is no assumed
contact with charged particles in the exogenous electrification mode,
electrification may be a misnomer today. As I suggested in an earlier
post, all an electric field can do to an isolated conductor is
redistribute the charges preexisting on the conductor. Of course if the
redistribution of charges leads to coronal discharges favoring either
the positive or negative "end" of the plane, then the plane could
acquire a non-zero net charge (i.e., be electrified). The authors don't
give a hint that this is what was envisioned, though.

I'd appreciate comments on whether such a thing as "exogenous
electrification" as described by the authors makes sense to anyone else.

73.

Chuck
NT3G


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On Sat, 23 Dec 2006 10:02:20 -0500, chuck wrote:

Since there is no assumed
contact with charged particles in the exogenous electrification mode,
electrification may be a misnomer today. As I suggested in an earlier
post, all an electric field can do to an isolated conductor is
redistribute the charges preexisting on the conductor. Of course if the
redistribution of charges leads to coronal discharges favoring either
the positive or negative "end" of the plane, then the plane could
acquire a non-zero net charge (i.e., be electrified). The authors don't
give a hint that this is what was envisioned, though.

Hi Chuck,

The author wasn't particularly interested in the electrification as he
was the conduction and subsequent discharge. In actuality, what is
described as exogenous electrification is no different from
autogenous. The air currents described simply convect smaller
particles as has been described in subsequent years in other aviation
material starting with "Atmospheric Electricity," Chalmers, J.A. -
1967; or earlier with "The Fair Weather Atmospheric Electric Potential
and its Gradient," Clark, J.F. 1958.

Normal convection builds up a charge stratification on the order of
190 V/m at ground level, but declines to half that a mile up. At that
same mile altitude (above ground level) charge density increases
1000%.

Needless to say, aircraft at different altitudes in identical, clement
weather are subject to vastly different fields.

73's
Richard Clark, KB7QHC

Richard Clark wrote:


Hi Chuck,

The author wasn't particularly interested in the electrification as he
was the conduction and subsequent discharge. In actuality, what is
described as exogenous electrification is no different from
autogenous. The air currents described simply convect smaller
particles as has been described in subsequent years in other aviation
material starting with "Atmospheric Electricity," Chalmers, J.A. -
1967; or earlier with "The Fair Weather Atmospheric Electric Potential
and its Gradient," Clark, J.F. 1958.

Normal convection builds up a charge stratification on the order of
190 V/m at ground level, but declines to half that a mile up. At that
same mile altitude (above ground level) charge density increases
1000%.

Needless to say, aircraft at different altitudes in identical, clement
weather are subject to vastly different fields.

73's
Richard Clark, KB7QHC

Hi Richard,

Thanks for the second opinion and additional information. I agree with
your interpretation.

73,

Chuck

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