| BLUE JETS, which are restricted to the part of the
atmosphere below about 40 kilometers altitude, are comparatively difficult
to observe. A color image (right) shows that the jets give off a deep-blue
light, which does not penetrate the atmosphere readily--quite unlike the
reddish hues that dominate sprites
and elves.
So observation requires going above the dense lower atmosphere. Sentman
and Wescott recorded such eerie cones of blue light for the first time
while flying over an intense storm in Arkansas in 1994. This sequence of
video images from a sensitive monochromatic camera (A-D) reveals how these
lights jet upward from the top of thunderclouds at speeds of about 120
kilometers per second. Researchers are still trying to reconcile competing
theories to explain exactly how blue jets come about. |
Image: Daniel L. Osborne, University of Alaska-Fairbanks |
