[TowerTalk] Rain static
Jim Lux
jimlux at earthlink.net
Thu Sep 1 10:08:42 EDT 2005
At 05:44 AM 9/1/2005, Tom Rauch wrote:
> > The charging rate is strongly affected by how many
>particles hit the object
> > in a unit of time. The higher antenna is subjected to more
>wind, so more
> > particles hit in a given unit of time (because the antenna
>"sweeps" a
> > larger volume of the air containing the particles).
>
>That doesn't fit in with the very common observation that
>lower antennas, all other things equal, are nearly immune to
>this effect or that the rate of noise gradually builds to a
>strong peak in pitch and intensity (despite no moisture or
>steady moisture rate) and the when a lightning hit pops
>someplace in the relative area the noise stops and rebuilds.
Sure it does... the charge on individual raindrops is very very strongly
affected by the local earth's E field. That rises just before a lightning
stroke. I'm not sure (I'll find out today), but I think that as the Efield
rises, the charge per drop increases, which would increase the
precipitation charging current, which, in a relaxation oscillator type
thing would increase the frequency. (cranking up the current on the
capacitor/neon bulb circuit)
>The "capacitor" being charged to abnormal potential is the
>earth and everything connected to the earth and the cloud or
>clouds over the earth. The only way to discharge it is to
>have a path from the cloud to the earth. The earth is a huge
>charge sink, so the cloud is the narrow area thing
>concentrating charges in the earth.
There are free ions that provide an alternate charge path, as well as the
continual path provided by the raindrops themselves. I can't recall the
number off hand, but there's an overall all clear air current flow from
high in the atmosphere to the earth's surface (I might have the sign
wrong.. the current might be up).
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