Messengers from the Sun
Auroras are natural colored light displays in the sky, particularly in the polar zone. In northern latitudes, the effect is known as the aurora borealis, named after the Roman goddess of dawn, Aurora, and the Greek name for north wind, Boreas. Aurorae are produced by the collision of charged particles from Earth’s magnetosphere, mostly electrons but also protons and heavier particles, with atoms and molecules of Earth’s upper atmosphere (at altitudes above 80 km). The particles originate from the Sun and reach the Earth in the stream of solar wind. By their collision they excite atoms and molecules in the upper atmosphere which result in the colorful glow of aurora. As noted by the photographer “Auroras, standing atop the atmosphere about 100km overhead, can often reach up into the heavens another 1000 kilometers. The lower portion of the auroral wall, the first 400km of aurora height, the light is green, but once the wall grows in height and pushes above the 400km point, anything above that turns a beautiful red. So a full blown 1000km aurora wall will have 400km of green light on the lower part of the wall, and will have about 600km of red light standing above that. And when you end up looking through both the green light and some distant red, the color of the two mixed will give the look of yellow light, as red and green light make yellow. Hence some of the colors you can see here”.