And after years of mystery, we finally know where they come from.
Here on Earth, thunderstorms and accompanying lightning strikes represent tremendous releases of energy.
Up to ~10 coulombs of charge — over 10²⁰ electrons — can be exchanged with each discharge.
Rather than transporting electrons between clouds and the ground, however, nature sometimes prefers alternative pathways.
One such phenomenon is known as “blue jet” lightning, which rises upwards from the clouds.
Instead of occurring between the charged clouds and the ground, charge exchange can proceed upwards.
A negatively charged layer above the clouds causes an upward propagation instead, with blue and ultraviolet light arising from nitrogen’s emission.
Similar examples of these transient luminous events occur above the clouds on Jupiter, too.
Blue jets may be bright, but their discovery was preceded by a longer-lasting, redder phenomenon: red sprites.
First reported way back in 1886, they weren’t photographed until 1989.
Since then, they’ve been witnessed many times, including from space.
These aren’t from up-going lightning, but cold plasma discharges occurring above terrestrial lightning strikes.
The color arises from fluorescent emissions: similar to auroral reds.
Red sprites may occur wherever thunderstorms do, but are typically obscured by clouds and/or daylight.
Ongoing research continues to investigate these optical/ultraviolet phenomena more deeply.
Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.
Starts With A Bang is written by Ethan Siegel, Ph.D., author of Beyond The Galaxy, and Treknology: The Science of Star Trek from Tricorders to Warp Drive.