Best of the Web: Interesting Facts About Lightning

Posted on December 22, 2008

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Really interesting things you probably did not know about thunder and lightning.

1. Stepped Leaders

Step Leaders

The different “forks” of a lightning bolt are called stepped leaders, and they are, essentially, failed paths of lightning bolts searching for a place to hit the ground.

These leaders are not the lightning strikes. They only map out the course that the strike will follow.  It only becomes a lightning bolt when a stepped leader makes contact with a streamer, which is a path coming from earth reaching out to touch a stepped leader. The leader that reaches the streamer first reaps the rewards of the journey by providing a conductive path between the cloud and the earth (AKA the lightning bolt).

Here is a great example of step leaders in slow motion:

Reference

2. Streamers

Streamers

As the step leaders approach the earth, objects on the surface begin responding to the strong electric field. The objects reach out to the cloud by “growing” positive streamers. These streamers also have a purplish color and appear to be more prominent on sharp edges.  In actuality, anything on the surface of the earth has the potential to send a streamer. Once produced, the streamers do not continue to grow toward the clouds; bridging the gap is the job of the step leaders as they stage their way down. The streamers wait patiently, stretching upward as the step leaders approach.

After the step leader and the streamer meet, the ionized air (plasma) has completed its journey to the earth, leaving a conductive path from the cloud to the earth. With this path complete, current flows between the earth and the cloud. This discharge of current is nature’s way of trying to neutralize the charge separation. The flash we see when this discharge occurs is not the strike — it is the local effects of the strike.

Here is a great picture catching a streamer coming from the ground near a strike:

Reference

3. Thunder

Thunder

When a leader and a streamer meet and the current flows (the strike), the air around the strike becomes extremely hot. So hot that it actually explodes because the heat causes the air to expand so rapidly. The explosion is soon followed by what we all know as thunder.

Thunder is the shockwave radiating away from the strike path. When the air heats up, it expands rapidly, creating a compression wave that propagates through the surrounding air. This compression wave manifests itself in the form of a sound wave.

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4. Lightning Can Get Up To 5x Hotter Than the Surface of the Sun

Lightning is hotter than the sun

The temperature of a lightning bolt can reach 30,000°C – five times hotter than the surface of the sun.

Reference

5. Lightning Can Travel Up To 60 Miles

Lightning

A single bolt of lightning can travel up to 60 miles and the longest ones are found at the squall line of a storm.

Reference

6. A Lightning Bolt is Typically the Width of a Quarter

Lightning Bolt

About the size of a Quarter to Half-Dollar! Lightning looks so much wider than it really is just because its light is so bright!

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7. Lightning is Not Confined To Just Thunderstorms

Volcano Lightning

It’s been seen in volcanic eruptions, extremely intense forest fires, surface nuclear detonations, heavy snowstorms, and in large hurricanes.

Reference

8. Airplanes Frequently Get Struck by Lightning

Airplanes get struck by lightning frequently

On average, each airplane in the US commercial fleet is struck by lightning at least once a year.

But lightning has not caused an airliner crash in the USA or of a U.S. airline plane anywhere in more than 40 years.

Protection begins with the fact that airliners, and the majority of other airplanes, are made of aluminum, which is a very good electrical conductor. A lightning bolt’s electricity flows along the airplane’s skin and into the air.

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9. There is No Such Thing as “Heat Lightning”

Heat lightning

The term heat lightning, that is rumored to form because of hot weather, is just lightning that is too far away for thunder to be heard.

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10. Upper-atmospheric Lightning (Blue Jets & Red Sprites)

Red Sprites

Only recently have we documented the existence of Lightning that is above clouds, and shoots up!

The first images of a sprite were accidentally obtained in 1989. Now there are thousands of pictures and videos documenting this mysterious phenomena.

Sprites are massive but weak luminous flashes that appear directly above an active thunderstorm system and are coincident with cloud-to-ground or intracloud lightning strokes. Along with sprites, blue jets take place above thunderstorms as well.

Blue jets are a second high altitude optical phenomenon, distinct from sprites, observed above thunderstorms using low light television systems. As their name implies, blue jets are optical ejections from the top of the electrically active core regions of thunderstorms.

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