Last week, the National Science Foundation’s National Optical-Infrared Astronomy Research Laboratory (NOIRLab) released an incredible image – not of the cosmos, but of clouds around one of its observatories. The photograph shows not one but two rare lightning phenomena: blue jets and red sprites.
The red sprites are massive electrical discharges above thunderstorm clouds. Researchers believe that a particular combination of events has to occur for the formation of these phenomena. First of all, you have to have a thunderstorm – but that alone is not enough. Scientists believe that plasma irregularities in the ionosphere are also needed.
The ionosphere is the region around our planet, about 50 kilometers (31 miles) from the surface, where electrons and electrically charged atoms and molecules tend to reside. It is created by UV light hitting our atmosphere.
The research focus on the nature of these phenomena has now shifted to the origin of these irregularities. It is possible that such differences in the plasma are long-term features, although it is not clear how they stay that way. Alternatively, they could be caused by the motion of a meteor crossing the atmosphere. The region of the ionosphere where sprites form is also where meteors spend a fair bit of time before they are completely burned away by the denser air of the lower atmosphere.
Blue jets are closer in behavior to the regular lightning, but instead of going down into the ground, they go from the upper level of the clouds further up into the atmosphere. Their color is believed to be related to the ionization of nitrogen in the atmosphere which results in ultraviolet emission. They are also briefer than regular lightning, lasting only for a few milliseconds.
Sprites were first photographed in 1989, and since then there have been thousands of reported observations of these phenomena. Blue jets, on the other hand, are much rarer with only hundreds of reported sightings. However, they have even been seen from space!
And that's actually where most of our understanding comes from. As these phenomena happen above clouds, there's no better viewpoint than the International Space Station. The Atmosphere-Space Interactions Monitor (ASIM), a European instrument dedicated to studying storms, has documented several of these rare events.
It is clear, given the rarity of these, that this photograph is truly a gem. Taken back in August 2017 by the Cloud Cams of the Gemini North observatory, we can't help but be in awe at seeing these truly spectacular phenomena both getting snapped at once.