Tie-Dyed Sky

The night sky can sometimes look like a tie-dyed T-shirt flapping on a clothesline. Ribbons and swirls of bright color ripple through the sky. They can change appearance in seconds – blown by the solar wind. The colorful display is an aurora – the northern and southern lights. An aurora flares to life as charged particles from the Sun run into Earth at high speed. Earth’s magnetic field funnels the particles toward the magnetic poles. When particles hit atoms and molecules high above the surface, they knock atoms out of their usual configuration. When they return to normal, the atoms emit light. The color of an aurora depends on what the charged particles hit, and where they hit it. Most auroras are green. They switch on when particles hit oxygen molecules at altitudes of about 60 to 200 miles. Red auroras are fed by oxygen that’s even higher. The lower fringes of a display can appear pink or dark red – the result of collisions with nitrogen at lower altitudes. Collisions with hydrogen and oxygen create blue and purple auroras. But they’re not very common, and they’re hard for the eye to take in. They’re easier to see in photographs. Most of the time, the northern lights stay close to the magnetic pole. When the Sun spews out more particles, though, they can spread outward, shining in regions where they’re seldom seen. And the colors can get more intense – dramatically “tie-dying” the night sky. Script by Damond Benningfield