An aurora (plural: auroras or aurorae), also known as polar lights, aurora polaris, northern lights, aurora borealis, or southern lights, aurora australis, is a natural light display in Earth's sky, predominantly seen in high-latitude regions (around the Arctic and Antarctic). Auroras display dynamic patterns of brilliant lights that appear as curtains, rays, spirals or dynamic flickers covering the entire sky.

Auroras are the result of disturbances in the magnetosphere caused by solar wind. These disturbances alter the trajectories of charged particles in the magnetospheric plasma. These particles, mainly electrons and protons, precipitate into the upper atmosphere (thermosphere/exosphere). The resulting ionization and excitation of atmospheric constituents emit light of varying colour and complexity. The form of the aurora, occurring within bands around both polar regions, is also dependent on the amount of acceleration imparted to the precipitating particles.

Most of the planets in the Solar System, some natural satellites, brown dwarfs, and even comets also host auroras.

 

Note:   The above text is excerpted from the Wikipedia article Aurora, which has been released under the GNU Free Documentation License.