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.
It was way back in 2011 that NASA was preparing for the final launch of the Space Shuttle Endeavor, which had to wait for clear weather to launch. Lightning strikes provide dangerous conditions for takeoff, and for electronics in general, as the exchange of large amounts of charge can disrupt modern computer systems easily. (Bill Ingalls/NASA via Getty Images)
Up to ~10 coulombs of charge — over 10²⁰ electrons — can be exchanged with each discharge.
While lightning strikes typically represent charge exchanges between the clouds and the ground, other pathways are possible and will occur under the right conditions. Here, charged particles in volcanic ash are exchanged both within the ash clouds and between the clouds and the ground, as captured here during the eruption of Taal volcano in January, 2020. (Rouelle Umali/Xinhua via Getty Images)
This is no optical illusion, but rather a lightning strike that travels upwards from the clouds. This results in a rare but very real phenomenon known as ‘blue jet’ lightning, which appears to rise straight up from the clouds. We now know that there is a higher, negatively charged upper layer to exchange electrons with the cloud, and that path is sometimes preferred over the one that would bring lightning to the ground. (THIJS BORS / NORTHERN TERRITORY, AUSTRALIA)
One such phenomenon is known as “blue jet” lightning, which rises upwards from the clouds.
This photograph was taken at the summit of Mauna Kea, and depicts blue jet lightning nearby. There is a thunderstorm occurring where the large bright cloud is, which is illuminated by lightning. At least some of this lightning is traveling upwards, as the path to the ground is not the only one along which charge can be exchanged. (GEMINI OBSERVATORY / AURA)
Instead of occurring between the charged clouds and the ground, charge exchange can proceed upwards.
This sequence of an upper atmospheric lightning event shows its various stages. Initially, there’s a leading jet that rises up to about the sodium layer in the atmosphere. Then, tendrils appear above it, and at last, charge is exchanged to about 90–100 km altitude. The entire process takes a little under one second. (O. A. VAN DER VELDE ET AL., NAT. COMMS 10, 4350 (2019))
A negatively charged layer above the clouds causes an upward propagation instead, with blue and ultraviolet light arising from nitrogen’s emission.
This photograph from NASA’s Juno spacecraft shows a transient lightning event on Jupiter. Shown here, this diagram represents photon counts in a specific wavelength of light, which would correspond to high-energy plasma discharges that arise from lightning strikes occurring well above the uppermost cloudtops of Jupiter. (R. S. GILES ET AL, (2020), ARXIV:2010.13740)
While anecdotal stories of ‘red sprites’ during thunderstorm conditions date back to 1886, we lacked any photographic evidence until a 1989 University of Minnesota study captured them, and the first color image was not acquired until this 1994 image. Red sprites and blue jets are still poorly understood phenomena. (NASA/UNIVERSITY OF ALASKA FAIRBANKS)
Blue jets may be bright, but their discovery was preceded by a longer-lasting, redder phenomenon: red sprites.
A variety of transient lightning phenomena, including red sprites and blue jets, which are the most commonly seen ones other than the normal, below-cloud lightning. These phenomena may be extremely common, but have only been revealed recently due to the difficulty of observing them under normal terrestrial conditions; they require dark, clear skies. (LUIS CALÇADA/ESO, BASED ON ORIGINAL BY FRANKIE LUCENA)
First reported way back in 1886, they weren’t photographed until 1989.
This photograph from the International Space Station shows a lightning strike with a red sprite over it. The zoomed-in portion shows a close-up view, where the upward-moving red tendrils can clearly be delineated. This faint but brilliant phenomenon can be seen by either naked eyes or through photographic capture only under the right viewing conditions. (IMAGE SCIENCE AND ANALYSIS LABORATORY, NASA-JOHNSON SPACE CENTER)
This photograph comes from the International Space Station as it flies over a populated area with a thunderstorm to the right. The bright blue spots are what lightning strikes look like, but the red phenomenon above the large blue spot is a brilliant ‘red sprite’ appearing briefly in the upper atmosphere. (NASA ISS EXPEDITION 44)
These aren’t from up-going lightning, but cold plasma discharges occurring above terrestrial lightning strikes.
This time-lapse photograph shows a series of successive red sprites all together. While the human eye would never see a sight like this, as each individual red sprite itself is very brief, a thunderstorm can produce many such sprites over just a few minutes, as lightning discharges can severely alter the distribution and currents of electrons in the upper atmosphere. (PAUL M. SMITH / HTTPS://TWITTER.COM/PAULMSMITHPHOTO/STATUS/1353404662012121088)
A multicolored aurora, shown with the Milky Way over New Zealand, is possible as incoming charged particles strike different layers and elements present in the atmosphere. The red color is due to a combination of de-exciting hydrogen and nitrogen atoms, where the red nitrogen signature also appears in the ‘red sprite’ phenomenon. (BEN (SEABIRDNZ) OF FLICKR)
Occurring above the cloud-tops, blue jets and red sprites are only visible if the skies are darkened and one has a clear line-of-sight to the optical phenomenon in question. As these are faint, short-lasting, and typically occur during foul weather, it’s no wonder that it took more than a century from when this phenomenon was first reported until it was photographically captured. (ABESTROBI / WIKIMEDIA COMMONS)
Ongoing research continues to investigate these optical/ultraviolet phenomena more deeply.
This series of two sprites, at upper left and lower center, were taken ~21 minutes apart and stitched together afterwards to reveal their proper locations in the sky. Sky phenomena like red sprites are faint and swift, but can be captured with the proper photographic technique or visually seen by a keen and lucky observer. (ESO / PETR HORÁLEK)
Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.
