The aurora borealis can be seen in the northern night sky as patterns of light in either w]hite or in colors that continuously change shape and position. They appear phosphorescent. The Latin term “aurora borealis” means northern lights.
Aurorae are sun explosions that travel into earth’s atmosphere. The explosions can be solar flares, solar winds or coronal mass ejections. It is the latter that most often causes the northern lights. These ejections are caused when a solar wind breaks through the sun’s outer atmosphere (the corona). The wind begins like this: The sun's surface is much cooler than its inside, which is several million degrees. In the sun's corona, the temperature rises again to several million degrees. This heat causes such violent collisions between gas particles that atoms disintegrate into electrons and nuclei. What was once hydrogen becomes a gas of free electrons and protons called plasma. This plasma escapes the sun's corona through a hole in the sun's magnetic field. As the plasma escapes, they are swirled by the rotation of the sun, like the swirls in a bowl of batter beaten with an electric mixer. After 2-5 days', the plasma reaches the earth's magnetic field , traveling at about 5 million miles per hour. Most of the proton and electron debris stays outside our atmosphere, but a few penetrate and are magnetically attracted to the North and South poles (where they are called the southern lights) where they collide with the atoms and molecules in our atmosphere. This collision charges the particles in our atmosphere with greater energy. Then those particles revert back to their original energy levels and emit the supercharge they received from the sun particles.
In more detail, the process is like this: Most of the northern lights form from the electrons that accelerate into the atmosphere. Their kinetic energy changes to visible light as follows: A hydrogen atom in our atmosphere is made up of a single positive proton nucleus around which spins a single electron, usually in close orbit. The hydrogen atom a minimum of energy. When a free electron from the plasma collides with the hydrogen electron at high speed, it releases energy. This results in the spinning electron moving into farther out energy orbit further out and it now contains more potential energy, but is unstable and unable to retain this energy. It returns to its original orbit, releasing the extra energy as a photon of light. Billions of such collisions, called quantum leaps, occurring at once, creating the northern lights.Paper Masters