What causes the northern lights to appear in the sky?

The northern lights, or aurora borealis, are caused by charged particles from the sun colliding with gases in Earth's atmosphere. The sun constantly emits a stream of charged particles called the solar wind. When these particles reach Earth, most are deflected by the planet's magnetic field, but some get funneled toward the polar regions where the magnetic field lines converge and dip toward Earth. As these particles collide with oxygen and nitrogen atoms in the upper atmosphere, they excite the atoms, causing them to release energy as light. Different gases produce different colors: oxygen typically produces green and red hues, while nitrogen creates blue and purple tones. The result is the shimmering, dancing light display visible at high latitudes.