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'Blue jets' get a charge out of atmosphere

A blue tone was added to this photo of the "blue jet" to illustrate what the human eye would see. The camera was only able to capture images in monochrome green because of the low lighting conditions.  

By Marsha Walton
CNN Sci-Tech

UNIVERSITY PARK, Pennsylvania (CNN) -- Pilots, stargazers and scientists have talked about the phenomenon known as "blue jets" for nearly a century. Now some new images are helping shed light on these upper atmospheric flashes.

In September 2001, led by electrical engineering professor Victor Pasko from Pennsylvania State University, researchers used high-speed, low-light video cameras to document the optical flash as it extended from the top of a thunderstorm up towards the ionosphere, some 40-50 miles (70-80 kilometers) above ground.

"It was like a column of blue light, overwhelming, gigantic," said Pasko, who observed the blue jet from a research area near the Arecibo Observatory in Puerto Rico.

How are "blue jets" formed? Click here to find out more 

The data they collected, detailed in this week's Nature magazine, indicates that these blue jets establish a direct path of electrical contact between a thundercloud and the lower ionosphere.

While their video system captured the images in black and white, Pasko and the other observers all say the flash they saw was blue. The electrical current ionizes molecules and makes them glow; the blue emission comes from nitrogen.

Blue jets usually last from just a few milliseconds up to a full second.

Because of the distribution of the electrical charge, the jets are always cone shaped, about a mile or two at the base and six miles across the top.

Mistaken for UFOs

Pasko says they are related to strong hail activity in thunderstorms.

What do scientists hope to learn from monitoring these flashes? Perhaps more about the electrical circuitry of the earth; ozone, also possible dangers to aircraft or spacecraft.

"We've looked at these through many different instruments," said Pasko. "With video, radar, electromagnetic measurements."

Pasko says the research is intriguing because images have only been captured for about a dozen years; from the ground, from aircraft, even from the space shuttle.

Some researchers say over the years these blue jets may have been reported as UFOs, because of their color and the mystery of the phenomenon.

Additional research on blue jets, and a related phenomenon known as a "red sprite" is underway in Japan, South America and Australia.


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