No. 103: Jan-Feb 1996
Geophysicists have recently recognized that something very strange transpires above thunderclouds. First, there is the phenomenon we have called "rocket lightning" in our books and newsletters. Scientists now call these upwardly directed discharges "sprites." (SF#84) The sprites are short-duration red flashes in the ionosphere, sometimes with bluish tendrils extending down into the thunderclouds. Second, there are the newly recognized "blue jets," a new class of upward discharges. This phenomenon is detailed in a paper by E.M. Wescott et al. Here is their abstract:
"Initial observations of as newly documented type of optical emission above thunderstorms are reported. "Blue jets," or narrowly collimated beams of blue light that appear to propagate upwards from the tops of thunderstorms, were recorded on B/W and color video cameras for the first time during the Sprites94 aircraft campaign, June-July 1994. The jets appear to propagate upward at speeds of about 100 km/s and reach terminal altitudes of 40-50 km. Fifty-six examples were recorded during a 22-minute interval during a storm over Arkansas. We examine some possible mechanisms. but have no satisfactory theory of this phenomenon."
(Wescott, E.M., et al; "Preliminary Results from the Sprites94 Aircraft Campaign: 2. Blue Jets," Geophysical Research Letters, 22:1209, 1995.)
Comment. The blue jets may be related to other controversial phenomena that suggest surface-to-ionosphere electrical discharges, such as mountain-top glows and low-level auroras, as presented in our catalog Lightning, Auroras. A description of this book is located here.