Astronomy Picture of the Day

    Discover the cosmos! Each day a different image or photograph of our
      fascinating universe is featured, along with a brief explanation
                    written by a professional astronomer.

                               2021 January 4

                Sprite Lightning at 100,000 Frames Per Second
     Video Credit & Copyright: Matthew G McHarg, Jacob L Harley, Thomas
                           Ashcraft, Hans Nielsen

   Explanation: What causes sprite lightning? Mysterious bursts of light
   in the sky that momentarily resemble gigantic jellyfish have been
   recorded for over 30 years, but apart from a general association with
   positive cloud-to-ground lightning, their root cause remains unknown.
   Some thunderstorms have them -- most don't. Recently, however, high
   speed videos are better detailing how sprites actually develop. The
   featured video, captured in mid-2019, is fast enough -- at about
   100,000 frames per second -- to time-resolve several sprite "bombs"
   dropping and developing into the multi-pronged streamers that appear on
   still images. Unfortunately, the visual clues provided by videos like
   these do not fully resolve the sprite origins mystery. High speed
   vidoes do indicate to some researchers, though, that sprites are more
   likely to occur when plasma irregularities exist in the upper
   atmosphere.

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