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Lightning: # 1 Cause Of Natural Fire In North America.

The reason that a metal top car is a reasonably safe place to be in a severe lightning storm is NOT the rubber tires. Hopefully the lightning will pass safely through the outer metal shell of your vehicle and into the ground. However, there are cases where the electrons remain in the metal body and don't travel to the ground until you make the fatal connection by stepping out.   See:  Faraday Cage

A leader of a bolt of lightning can travel at speeds pf 60,000 meters per second (13,670 miles per hour), and can reach a temperature approaching 30,000 degrees Celsius (54,000 degrees Fahrenheit), hot enough to convert silica into glass. Large bolts of negative lightning from the clouds carry an electric current of up to 100,000 amps. Lightning rapidly heats the air in its immediate vicinity to about 20,000 degrees Celsius (36,000 degrees Fahrenheit), about three times the temperature of the surface of the sun. This compresses the surrounding air and creates an acoustic wave that is heard as thunder.

An Explanation of Lightning by Tom Chester, 2009

A negative charge (excess of electrons) builds up at the base of a cloud, creating a strong electric field relative to the ground (a massive positive reservoir that can accept excess electrons). This causes electrons to start moving down from the cloud through the air, which is a good insulator. The electrons have to struggle to get through the air, usually in a jagged line with several leaders. It also causes positive charges to go up toward the cloud from the ground. The positive charges move more slowly, since they are thousands of times more massive. There are many leaders coming up from the ground, from many points. This process continues until a positive leader hits a negative leader, typically much closer to the ground than to the cloud. At that point, the electrons at the bottom of the leader zip to the ground, followed by the electrons that were stacked up in the negative leader, like cars in a traffic jam. Although the electrons go from the cloud to the ground, the visible flash begins at the bottom of the lightning bolt, and travels up, as the electron "gridlock" gets resolved. This is called the return stroke and it is the most luminous and noticeable part of the lightning discharge. You can now see why it isn't always the highest point on the ground that gets struck. Maybe its positive leader didn't make as much progress as a positive leader from a nearby shorter object.

In the following image, you can see many "failed leaders" that were false starts for the negative charges on their way down. Note that there were several negative leaders close to the ground; one of them matched up with a positive leader and became the major lightning bolt (return stroke), leaving several smaller failed ones. You see the failed negative leaders since electrons still take all paths downward in the previously ionized channel. You don't see the failed positive leaders since they aren't connected to any electrons from the clouds.

Frequently Asked Questions From National Weather Service
Lightning Safety Tips From The National Weather Service

Lightning Over North Twin Oaks Valley, San Marcos
Fujichrome Transparency Taken by W.P. Armstrong, Summer 2005

More Images Of Lightning Bolts and a Lightning-Struck Pine
See A Hollow High Voltage Overhead Transmission Line

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