12/1/2023 0 Comments Red lightning gifA featured high speed video that was captured by Thomas Ashcraft, Jacob L Harley, Matthew G McHarg, and Hans Nielsen in 2019 at about 100,000 frames per second is fast enough to provide better detailing of how sprites develop. Since the 1989 video capture, sprites have been imaged from the ground, from aircraft and from space, and have become the subject of intensive investigations. Several years after their discovery they were named sprites (air spirits) after their elusive nature. They were first documented photographically on July 6, 1989, when scientists from the University of Minnesota, using a low-light video camera, accidentally captured the first image of what would subsequently become known as a sprite. Wilson had suggested in 1925, on theoretical grounds, that electrical breakdown could occur in the upper atmosphere, and in 1956 he witnessed what possibly could have been a sprite. The earliest known report is by Toynbee and Mackenzie in 1886. Sprites are associated with various other upper-atmospheric optical phenomena including blue jets and ELVES. However, sprites are cold plasma phenomena that lack the hot channel temperatures of tropospheric lightning, so they are more akin to fluorescent tube discharges than to lightning discharges. Sprites are sometimes inaccurately called upper-atmospheric lightning. Sporadic visual reports of sprites go back at least to 1886 but they were first photographed on July 4, 1989, by scientists from the University of Minnesota and have subsequently been captured in video recordings many thousands of times. They often occur in clusters above the troposphere at an altitude range of 50–90 km (31–56 mi). Sprites appear as luminous red-orange flashes. They are usually triggered by the discharges of positive lightning between an underlying thundercloud and the ground. Sprites or red sprites are large-scale electric discharges that occur in the mesosphere, high above thunderstorm clouds, or cumulonimbus, giving rise to a varied range of visual shapes flickering in the night sky. Electrical discharges above thunderstorm clouds First color image of a sprite, taken from an aircraft A sprite over Laos, as seen from the ISS
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