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From: Rolf Sinclair/Nsf Physics Division <rsinclai_at_NSF.GOV>
To: HASTRO-L_at_WVNVM.WVNET.EDU <HASTRO-L_at_WVNVM.WVNET.EDU>
Date: 30 September 1998 03:55
Subject: Red Sprites
>Hi HASTRO --
>
>Two recently-discovered forms of lightning could be of interest to
>historians of astronomy. Although they are not astronomical phenomena per
>se, but occur in the upper atmosphere, this distinction would not have
>been recognized in the past. (The aurora was recognized only in the 18th
>century as an atmospheric effect.) Called "red sprites" and "blue jets",
>they go upward from the cloud tops into the region (ca. 100 km altitude)
>between the troposphere and the stratosphere. They are visible with the
>naked eye as flashes traveling upward from the tops of clouds of a
distant
>lightning storm. It would be interesting to know if there are any
sightings
>of these phenomena prior to 1900, or records of them in tradition or
>mythology. Were there such sightings, they might not have been
>distinguished from "astronomical" or auroral phenomena.
>
>In brief, red sprites are a dull red color and often occur multiply. They
>can extend perhaps 15 degrees above a lighting storm 150 km distant. Blue
>jets are fainter and do not extend as high. One good observing place
could
>be on a mountain top, looking out across plains at the tops of distant
>storm clouds (or in the direction of a below-the-horizon lightning
storm).
>It would be interesting to see if there are any traditions of observing
>such phenomena at particular places or seasons.
>
>Interestingly, C. T. R. Wilson had predicted these phenomena in 1956, and
>although there were a few recorded naked-eye sightings over the last
>century, the first instrument recording was made by accident in 1989.
Since
>that time, sprites and jets have been the subject of an intensive study,
>and it has been found they are a reasonably common occurrence. These
>phenomena are well described by Davis Sentman (Geophysical Institute,
Univ.
>of Alaska) at http://elf.gi.alaska.edu/, with a number of pictures and
>instructions on how to observe them and descriptions of what to look for.
>Dr. Sentman is interested in collecting information on contemporary or
>historic naked-eye sightings. He estimates that under the right
conditions
>there is a greater likelihood of seeing a red sprite than of seeing a
>meteor. [See also Sentman et al., Scientific American 277, No. 2 (August
>1997), pp. 56-59.]
>
>Rolf Sinclair
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