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Old August 2nd 07, 08:53 AM posted to sci.geo.meteorology
Martin Brown Martin Brown is offline
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First recorded activity by Weather-Banter: Nov 2003
Posts: 935
Default Does electrostatic charge keep a cloud up?

On Aug 2, 7:06 am, "dave" nospam wrote:

Sorry if I sound like a buffoon to you meteorologists. I'm simply a layman
that knows nothing about this but wants to learn. I did some searching and
it is said that warm rising air keeps clouds up. Is it possible the static
charge in the clouds could also have an effect? Something like anti-gravity
on a small scale? Thanks.


No. The tiny effect that a cloud with a static charge would feel from
electromagnetic forces would be an inverse square *attractive* force
towards the ground. The ground is a good enough conductor that forms
an equipotential surface with electric field lines coming out
perpendicular. Charge on the ground arranges itself to cancel out the
horizontal component of electric field. It also allows Faraday
screening cages to protect you from lightning bolts.

One way of matching these boundary conditions without solving the
maths explicitly is to imagine an equal and opposite image charge the
same distance under the ground. It would only really have an
appreciable effect if the cloud was very close to the ground.

The cloud behaves dynamically as if it feels the influence of this
other fictitious image charge cloud reflected in the ground. I
couldn't find a nice online demo of this well known electrostatic
principle that was light on the maths.

The closest I could find was for a test charge above a cylinder at
Berkley.

http://socrates.berkeley.edu/~fajans...iles/frame.htm

(choose unshielded and 100% shielding for an idea of how the Earth
affects the field from a very high cloud)

Regards,
Martin Brown