Lightning is a natural phenomena that occurs in almost every part of the world. It is the result of a large charge separation resulting from the friction between air masses sliding by one another. The lightning most people envision is between the ground and a cloud. Although the physics of ground to cloud lightning is the most understood, there are other more common types. And there are rare, fascinating examples, such as ball lightning. Ball lightning has a long written and oral history in sea folklore as the mysterious luminous glow that bounces about ships during unstable weather conditions. It is also one of the proposed explanations for the "spook light" that plagues my home area in southern Missouri.
If the weather is not too humid, you will be able to generate your own "safe" lightning bolts during this week's lab. You will use a Van der Graaff generator. Essentially, the Van der Graaff generator consists of a metal base, a fast moving rubber belt, and a metal sphere. Charge is transported between the base and the sphere by the belt. On a good day, our laboratory generator is capable of producing about 100,000 volts! But at worst, you will suffer only a mild pin-prick sensation. (Really, trust me!)
The Museum of Science in Boston has a very big generator that actually produces enough charge to be dangerous. The lightning link there shows how the initial lightning stroke is formed and why the visibility of the stroke usually moves upward. There are several links at this site worth exploring.
 Red Sprite |
Sprites (stratoshperic lightning) are another electrical discharge phenomena associated with thunder systems. They occur at the tops of thunder cells and extend into the stratosphere, reaching as high as 60 miles! The photograph to the left was taken by the
Langmuir Laboratory Weather Center. Although sprites are not well understood, there is evidence that they can effect chemistry in the stratosphere and create electrical disruptions in the ionosphere. Check out the sprites and elves site for more info and a few animated gifs. The Langmuir GHCC Lightning Research Team also has a Lightning and Atmospheric Research site with all the latest of the research efforts. The Lightning Primer link has the latest information on sprites and a decent lightning tutorial, as well.
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