Sunday, August 20, 2006

I came across an article, which, after reading, I thought how little we know of our own atmosphere. Nature has so many hidden secrets, that I do not think man will know fully.
I reproduce the article as I find it worth sharing, © "The Discovery News" from their site dated 19th Aug.

Study: Dust Storms Are Electric
Larry O'Hanlon, Discovery News


Aug. 17, 2006 — It's not just wind that raises sands and dust devils, say physicists, powerful electrical fields created by wind, sand and dust also levitate more of the nose-tingling stuff into the air.
The first-of-its-kind discovery could have implications for global climate modeling and even help explain what makes Mars such a dusty world.
More than 100,000 volts per yard of natural, so called "static" electricity have been measured in desert dust storms and the mini-tornado-like dust devils. Now, under laboratory conditions, Jasper Kok, a graduate student at the University of Michigan in Ann Arbor, has reproduced the electrical fields found near the ground in desert wind storms and shown that they can also lift sand grains.
"We were very surprised," said Kok of the power of electrical fields to raise dust and sand. He and his faculty advisor, Nilton Renno, are publishing their results in a coming edition of Geophysical Research Letters.
The process starts with a little dry wind in a dusty, arid place that kicks up small dust grains so they collide with larger sand grains, Kok explained. When this happens the smaller grains steal electrons from the larger grains, giving the smaller grains a negative charge and the larger grains a positive charge.
"It’s very similar to rubbing your feet on a carpet to become charged," said Kok. In that case you are the smaller grain and the carpet is the larger grain.
Next, the negatively charged smaller grains are lofted above the ground by breeze, creating a negatively charged region in the air above the positively charged ground. That separation of charges is an electrical field.
Once that field is in place, as Kok has shown in the lab, more grains can be lifted up by the electrical forces, making for even dustier conditions than wind speed alone could create.
The phenomenon could have significant impacts on how much dust gets into the air worldwide, which means it’s a matter that global climate modelers need to study more closely, says Ron Miller of NASA’s Goddard Institute for Space Studies in New York. Dust is an "aerosol," which can reflect sunlight back into space and cool the Earth’s surface, as well as just influence the quality of the air.
"For a given wind that’s already kicking up dust, you’d get more dust," observed Miller. It could also affect areas downwind of a dust source, he said, by transporting the electrical fields to other areas and more readily mobilizing dust in those places as well.
That matters a lot in places like China, where dust from the northern deserts whips south across industrial regions, picking up a lot of pollutants that can then be blown east as far as the European Alps.
As for Mars, electrical fields may help explain how dust gets around there, says Renno.
"On Mars the wind required to lift dust from the surface is very large," said Reno. This is because the atmosphere of Mars is very thin. "Winds of the magnitude required have never been measured, but there’s dust everywhere."
Kok says he’s already working on a new laboratory experiment with Mars-like conditions to see if the electrical fields may be at work on the Red Planet.

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