Some of the flashes extend up through the ozone layer into the base of the ionosphere, the region of the upper atmosphere where auroras occur. Sentman and Wescott captured 19 black-and white images of the flashes above thunderstorms in the Midwest last year. Before that, scientists did not have proof that the flashes existed. This month, they were able to accurately measure the position and altitude of the flashes and to examine their color and speed for the first time, using two aircraft for triangulation and improved camera systems designed by Project Engineer Daniel Osborne, with the Geophysical Institute. They also were able to identify two distinctly different kinds of flashes, which they call sprites and blue jets.
Sprites are blood red flashes that appear with bluish tendrils dangling from the bottom of some.
The researchers also recorded radio noise that coincided with the sprite flashes. The sprites have been recorded on a TV spectrograph and will be analyzed to determine their atomic and molecular source. Since they are associated with thunderstorms and lightning, scientists suspect the flashes may be a form of electrical discharge. If so, they could present a concern to high-altitude research aircraft. Blue jets are flashes that appear in narrow beams, sprays, fans or cones of light which give off a blue or purple hue.