What event is caused by radiation hitting the Earth's atmosphere?

The Northern Lights are an atmospheric light display caused by solar radiation and charged particles interacting with Earth's upper atmosphere. Scientifically, this phenomenon is called an aurora borealis.

Streams of particles carried by the solar wind are guided toward the polar regions by Earth's magnetic field. When those particles collide with oxygen and nitrogen high above the surface, they transfer energy to the atmospheric atoms. As the atoms return to their normal energy state, they release light.

The most familiar aurora color is green, usually produced by excited oxygen. Oxygen can also create red light at higher altitudes, while nitrogen contributes blue and purple shades. Solar storms, including those associated with coronal mass ejections, can make auroras brighter and allow them to appear farther from the poles than usual.

The southern counterpart is called the Southern Lights, or aurora australis. “Northern Lights” is therefore a regional name rather than the general scientific term: the broader phenomenon is an aurora, and it can occur in both hemispheres.