A faint pulse of blue light that arises from the top of a thunderstorm and propagates upwards in the form of a narrow cone to altitudes of 40–50 km (at about 100 km s−1). Blue jets therefore extend approximately from bottom to top of the stratosphere. They were first observed scientifically in the early 1990s, but the mechanism by which they are formed is currently unknown. They are much rarer than the higher sprites and elves, to which they are apparently unrelated. They are not detectable from the ground, because of strong scattering of their blue light by the lower atmosphere. See also gigantic jet.
Subjects: Meteorology and Climatology.