In Earth’s upper atmosphere, blue jets, red sprites, pixies, halos, trolls and elves streak toward space, rarely caught in the act by human eyes.
This mixed-bag of quasi-mythological terms are all names for transient luminous events, or, quite simply, forms of lightning that dance atop thunderstorm clouds. Airplane pilots have reported seeing them, but their elusive nature makes them hard to study. But ESA astronaut Andreas Morgensen, while aboard the International Space Station in Septemb