Lightning storms are pretty impressive on the ground, but up in the air, they can be even more astonishing. In 1989, people noticed that sudden blue lines erupted from the top of thunderstorms. They would also see what looked like bright red jellyfish hanging over the clouds. These two optical phenomena were called red sprites and blue jets. They weren't spotted before because they're dim. Seeing them requires being in clear air and almost no light very close to a thunder storm, which is a place that very few people wanted to be.
For some time, sprites and jets were thought to have contributed to bad-weather airplane crashes. Now they're considered to be harmless. They are the upward component of lightning. Scientists think that the electrical discharge of lightning travels mainly downward, giving us the lightning bolt that we see from the ground. Meanwhile, some streams upwards and lights the sky. It's thought that the color comes from the nitrogen in the atmosphere glowing.
Along with sprites and jets there are all kinds of other dim atmospheric phenomena. Emission of Light and Very Low Frequency perturbations due to Electromagnetic Pulse Sources, or Elves, are expanding rings of light first photographed from a space shuttle. There are rounded lights called gnomes, and pinpoints called pixies. Because of the difficulty studying them, they're still not well understood. If you want to see them, they're best viewed from above the clouds about 200 to 300 miles away - either from a plane or a mountaintop. It needs to be night, and very dark, to see them, and the eyes have to be adjusted to the dark. Look above the clouds and don't let yourself be distracted by the lightning below. Some thing that they're part of every terrestrial storm, so keep your eyes peeled.
Top Image: NASA/University of Alaska, Fairbanks