Over the past few decades, scientists have painted a more complete picture of aurora formation. The drama begins on the fiery, tumultuous surface of the sun, which continuously ejects plasma , a hot, gaseous mixture of electrons, protons and ions. Gusting past Mercury and Venus, these solar winds take about two or three days to reach Earth. Fortunately, the hot plasma doesn t come slamming into the planet with a cataclysmic blow. The field deflects the winds like a giant shield.
Auroras form over the polar openings in Earth's magnetic field.
Here, the energized electrons from the plasma collide with individual air molecules in Earth s upper atmosphere. Each type of atom or molecule produces its own color palette. A similar process is at work in computer and TV screens, where an electron gun fires a beam onto various phosphors embedded in the screen, which together produce a color picture. In our atmosphere, when a high-energy electron bumps into an atom of oxygen, the oxygen becomes excited. If the oxygen atom can hold onto that energy for a fraction of a second, it will give off green or red light.