OFFICIAL NASA PRESS RELEASE: Sprites
Donald L. Savage
Headquarters, Washington, D.C.
July 26, 1994
Geophysical Institute, University of Alaska, Fairbanks
SPECTACULAR COLOR FLASHES RECORDED ABOVE ELECTRICAL
Hundreds of spectacular red and blue flashes of
light that extend upward from electrical thunderstorms
to altitudes as high as 60 miles (97 km)recently were
recorded on video for the first time.
The unusual flashes occurred over thunderstorms in
the Midwest between June 28 and July 12 during a
NASA-sponsored investigation into the phenomenon. To
capture the images, Principal Investigators Davis
Sentman and Eugene Wescott, professors at the
Geophysical Institute with the University
of Alaska, Fairbanks, (UAF) and co-directors of the
research project, used special low-light-level cameras
aboard two jet aircraft flown out of Oklahoma City.
"The flashes look like the Fourth of July, like
Roman candles with fountains," said Sentman. "The
video footage we received far exceeded our
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
flashes, which last only a few thousandths of a second,
extend from above storm clouds up to about 60 miles (97
km) high, reaching the bottom of the ionosphere. The
researchers also recorded radio noise that coincided
with the sprite flashes. When the recorded signals are
played through a speaker, they "pop," a sound that
differs from normal lightning discharge signals.
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
Blue jets are flashes that appear in narrow beams,
sprays, fans or cones of light which give off a blue or
purple hue. "To the eye, they resemble material
ejected from a high explosive source, the tracks of
atomic particles, or rays in a cloud chamber," Wescott
Pilots and others have reported seeing blue or
green columns of light above thunderstorms for years,
but Sentman and Wescott were the first to capture them
on video. They recorded about a dozen blue jets over
an intense storm in Arkansas on June 30.
The jets appeared to originate at the top of storm
clouds and then to travel upward to an altitude of
about 20 miles (32 km). They occurred at various
angles at speeds ranging from 20 to 60 miles a second
(32 to 97km/s), which is well above the speed of sound,
but far below that of light or radio waves.
The scientists coordinated their observations with
other groups in Fort Collins, Colorado, Pennsylvania
State University and Stanford University, where
researchers made video and radio wave observations from
the ground. The aircraft were leased by UAF from Aero
Air, Inc., Hillsboro, Oregon.
- end -
NOTE TO EDITORS: To illustrate this story, one color
and two black and white
images and a two minute, 46 second videotape are
available to news media by
faxing your request to NASA Headquarters Broadcasting
and Imaging Branch on 202/358-4333. Photo numbers are:
Color: B & W:
94-HC-186 94-H-200(B&W image of 94-HC-186)
Additional information on observations of the
phenomenon can be obtained by faxing NASA Headquarters
News and Information Branch on 202/358-4210,
requesting Release Number 93-167.