12. The Phenomenon of Sprites and Other Upper Atmospheric Lightning
Although most of us are aware with the lightning occurring in the lower atmosphere, high above the clouds there is an entire world of electrical events occurring. Among the most aesthetically beautiful and scientifically fascinating aspects of lightning studies are these upper atmospheric lightning phenomena, which bear names like sprites, elves, and blue jets.
Usually between 50 and 90 km, sprites are large-scale electrical discharges occurring high above thunderstorm clouds. Usually started by strong positive cloud-to- ground lightning strikes, they show as large, red, jellyfish-shaped flashes. Though they are quite large—they may be tens of kilometres tall— sprites are difficult to see with the unaided eye since they just last a few milliseconds.
Another kind of higher atmospheric lightning are elves (Emission of Light and Very Low Frequency disturbances owing to Electromagnetic Pulse Sources). Usually found at altitudes around 100 km, they show as fast expanding circles of light. Less than a moment, elves are even more ephemeral than sprites.
Rising-propagating discharges from the top of thunder clouds, blue jets reach altitudes ranging from roughly 40 to 50 km. Their name signifies that molecular nitrogen emissions give them blue hue.
Just discovered in the late 20th century, these upper atmospheric events have transformed our knowledge of the electrical character of Earth’s atmosphere. They show that with complicated interactions between several layers of the atmosphere, the environment is an electrically active medium extending far above the clouds we can observe.
Scientists are still researching these events by means of high-altitude balloons, aeroplanes, and even space-based observations. Understanding the worldwide electrical circuit and its possible effects on atmospheric chemistry and temperature depends on an awareness of these upper atmospheric electrical events.