You might think there is just the one type of lightning you see during the summer. There are actually numerous types, from the familiar to lightning that flashes out the top of the thunderstorm, out into space.
Cloud-to-ground lightning is one type you normally see during a storm. Lightning is a giant electrical discharge between positive and negative electrons. As a storm moves over an area, the cloud can be charged with negative ions and the ground can be charged with the opposite positive ions. When it comes to electricity, opposites attract and when there is enough electrical difference between the cloud and the ground, you see this electrical discharge as lightning. The giant discharge is the lightning connecting with the oppositely polarized charge on the ground. This could be the ground itself, a tree, a house, a power pole or worse. Anything on the ground can build up a large and opposite electron charge, opposite of the cloud moving over. That is why you should get inside as soon as you hear thunder. Many times you will see lightning look like it is striking the same object many times. What you are seeing are the return strokes. The step leader which starts the bolt of lightning and the streamer coming off of the ground connecting to the step leader and return strokes. There can be as many as 20 return strokes. For a more in depth article, you can read Why Does Lightning Strike.
The video below is a slow motion shot that shows the many step leaders looking for a place to discharge (the path of least resistance) and then the streamer coming up from the ground to meet the step leader.
At night, cloud-to-cloud lightning is beautiful as it can light up the entire sky. Cloud-to-cloud lightning is the same principle as cloud-to-ground lightning. In this case, the positive and negative electrons are between clouds. When the positive and negative charges build up enough, they can discharge between clouds. Usually you can see the cracks of lightning inside the clouds and even coming out of the sides of a thunderstorm. Sheet lighting is another name for cloud-to-cloud lightning since it appears as sheets of light behind clouds or rain.
Is it lightning, a myth or some other electrical phenomena? No one knows exactly what ball lightning is, for centuries, people have reported seeing this and say that it starts right after a lightning strike. Those who have seen ball lightning say it is about the size of a baseball, maybe larger and makes a sizzling or the hissing sound of boiling water. Sometimes it floats through the air and other times it skitters along the ground. It glows at about the same brightness of a 100-watt light bulb. There have been reports that these balls have melted through glass, screens and walls as they float through the air. They last for an average of 25 seconds before fading away or sometimes dissipating with a small explosive sound.
In 2007, Dr. Pace VanDevender, a senior member of the IEEE and a Fellow of the American Physical Society and the American Association for the Advancement of Science wrote an interesting paper on ball lightning. Here are a few of the characteristics of ball lightning according to Dr. VanDevender.
- It originates from nothing visible.
- It is lethal or possibly lethal.
- It contains an estimated 100,000 to 1 billion joules of energy.
- Can penetrate walls, metal and glass without leaving a mark.
- It can excavate tons of earth.
Scientists think that ball lightning is made of plasma clouds, which are charged atoms. When lightning strikes some surface, vapor is formed. This vapor condenses and mixes with oxygen, which then burns. Another theory is that it is made up of electrically charged water molecules. Other theories include tiny black holes, antigravity, radio frequency excitation and neutrinos.
An actual National Weather Service report from July 1874 of ball lightning in Denver, Colorado.
Another beautiful and mysterious form of lightning is called sprites, gigantic jets and elves. A sprite is visible from the ground if a thunderstorm is far enough away and better visible when flying above the thunderstorms. In 1989, the Space Shuttle recorded sprites above thunderstorms in Australia.
Sprite lightning flashes from the top of the thunderstorm upwards into space and can travel as high as 50 miles (80 km) into the atmosphere. From the ground you can see this above the top of storms. Sprites are reddish pink in color and very fast, lasting from 3 to 10 milliseconds (.003 to .01 seconds). These sprites emit a strong electromagnetic pulse that could interact with the portion of the atmosphere called the ionosphere. The ionosphere is the area that bounces radio waves. Scientists are not sure if the sprite is a discharge that moves out from the top of a thunderstorm or is it an actual electrical discharge connecting the thunderstorm and the ionosphere.
Most scientists believe that sprites are associated with strong negatively charged lightning strikes. Other scientists think that conditions high in the atmosphere, like gravity waves or dust from meteors are the causes of sprites.
Sprite lightning. Walter Lyons, FMA Research, Fort Collins, Colorado
With more people and their video cameras trying to capture lightning, more people are being hit by lightning. Do not stand outside to record lightning. If you want to be a storm spotter, you have to learn safety.
© 2010 Sam Montana
References and Interesting Web Sites
NOAA National Severe Storms Laboratory
NASA Goddard Space Flight Center
The IEEE, Plasma Cosmology and Extreme Ball Lightning Wallace Thornhill, Holoscience.com