This is a 3-part blog on lighting. The first will be general information, the second on what creates lightning and the third on lightning protection.
Florida is the lighting capital of the United States and second to equatorial
Africa in the world, with four times as much lightening than any other state. Although lightning is a year-around event, the number of strikes peaks during the summer months with the summer sea-breeze induced annual (life sustaining) rains. Of the approximately100 annual deaths due to lighting about 10 are from Florida. But what is lighting and what causes it and how can you do to protect yourself?
Of course lightning occurs in thunderstorms, but it also occurs in volcanic eruptions, nuclear bomb denotations, and forest fires. Lightening, as we most commonly know it, comes from thunderstorms. In fact, it is not a thunderstorm if it doesn’t have lightening. Lightning can be from cloud-to-ground (CG), in-cloud, cloud-to-cloud (IC and CC), and from cloud-to-space). Heat (or sheet) lighting is usually observed in the evening and is from a storm that is about 30 miles away. It is called heat lightning because it is usually clear and hot and in the evening when you see it.
The earth is like a giant spherical capacitor, with the surface containing a surfeit of negative charge and the ionosphere (30 - 50 miles up), having a net positive charge. If it weren’t for lightning, the stream of electrons going up (the fair weather current) would discharge this capacitor in about 45 minutes. This layer of positive charge is very important as it allows for long range communication, and also protects us from damaging radiation from solar eruptions.
Each second there or about 75 CG strokes or about 1.4 billion flashes per year. A single storm could produce tens of thousands of flashes. Actually each flash could contain multiple flashes. Usually there are 3 to 5 but as many as 40 have been recorded.
Most lightning channels are at least 2 miles long, but one CC was 100 km or 62 miles long.
The temperature of a lightening bolt is 5 times hotter (54,000 degrees F) than the surface of the sun. The bolt has a diameter of about and inch and a half. The thunder arises because of the nearly instantaneous expansion of the air because it is so hot. It produced a shock wave, just as a chemical explosion (firecracker) does by producing a large quantity of gas very quickly.
You can tell the distance by counting the seconds between the flash and when you hear the thunder and diving by 5. (Sound travels at a rate of about 5 sec per mile).
When lightening strikes the desert, fulgurites are formed. The lightening bold melts the sand and it forms a hollow glass tube that is the replica of the flow of the dissipating lightening strike. The longest one found was more than 16 feet long.
Other forms of lightening, such as “ball lightening” are rare and amazing but are not well understood.