Magnetosphere and Atmosphere
Charged particles constantly spread out of the outer Van Allen radiation belt and fall into the auroral latitudes of the earth's atmosphere. There they collide with atoms of oxygen and nitrogen and stimulate these gases to radiate pale greens and occasional bright reds in patches or across the whole sky. These are the auroras, called the northern lights in our hemisphere. They are most often seen in zones between 65° and 70° north and south magnetic latitudes. Because the subatomic particles enter the atmosphere easily when the solar wind is more intense, more auroras color our night skies during the height of the 11-year sunspot cycle, when the sun is emitting more subatomic particles.
