blue jet

:  a rare form of electrical discharge that is emitted from the top of a cumulonimbus cloud during a thunderstorm as a large upward jet of blue light Wescott and Sentman discovered that sprites are salmon-colored, and as they flew with Tobolski over the Arkansas storm that summer, they discovered that sprites were not alone above the clouds: fountains of blue light emerged directly from the clouds as well. These they named blue jets. — Elwood Norris, Discover, July 1997 Blue jets, by far the rarest member of the menagerie, shoot up from cloudtops at speeds of more than 60 miles a second to heights of 30 miles. — Karen Wright, Scientific American, Spring 2000