Sprite (lightning) - Characteristics

Characteristics

Sprites have been observed over North America, Central America, South America, Europe, Southern Africa (Zaire), Australia, the Sea of Japan and Asia and are believed to occur during most large thunderstorm systems.

Three types of sprites have been categorized by Matthew 'Geoff' McHarg Ph.D. (UAsk) of the US Airforce Research Academy (and NASA). Using an image intensifier on the front of super slow motion camera Mcgarg and his researchers have named the sprites based on their visual appearance.

• Jellyfish sprite - very large, up to 30 miles by 30 miles.
• Carrot sprite
• C or Column sprite. These are large scale electrical discharges above the earth that are still not totally understood.

Sprites are colored reddish-orange in their upper regions, with bluish hanging tendrils below, and can be preceded by a reddish halo. They last longer than normal lower stratospheric discharges, which last typically a few milliseconds, and are triggered by the discharges of positive lightning between the thundercloud and the ground. They often occur in clusters of two or more, and typically span the altitude range 50 kilometres (31 mi) to 90 kilometres (56 mi), with what appear to be tendrils hanging below, and branches reaching above.

Optical imaging using a 10,000 frames per second high speed camera shows that sprites are actually clusters of small, decameter-sized (10–100 m, 30–300 ft) balls of ionization that are launched at an altitude of about 80 km and then move downward at speeds of up to ten percent the speed of light, followed a few milliseconds later by a separate set of upward moving balls of ionization. Sprites may be horizontally displaced by up to 50 km from the location of the underlying lightning strike, with a time delay following the lightning that is typically a few milliseconds, but on rare occasions may be up to 100 milliseconds.

In order to film sprites from Earth, special conditions must be present : 150-500 km of clear view to a powerful thunderstorm with positive lightning between cloud and ground, red-sensitive recording equipment, and a black unlit sky.