aurora

An aurora is a natural light display in Earth's sky, typically visible in high-latitude regions near the Arctic and Antarctic. The phenomenon results from charged particles emitted by the Sun colliding with atoms and molecules in Earth's upper atmosphere. The term aurora borealis refers to the northern lights, while aurora australis denotes the southern lights.

When solar wind interacts with the magnetosphere, particles are guided along magnetic field lines toward polar regions. Collisions with atmospheric oxygen and nitrogen excite atoms, which release photons as they return to ground state. Oxygen emissions produce green light around 100–150 km altitude, red at higher altitudes; nitrogen can yield purple, pink, or blue tints.

Auroras shimmer as curtains, arcs, or rays that move and shimmer with wavy motion. They occur at altitudes roughly 80–300 km, more intense during geomagnetic activity or substorms. They are most often seen during dark, clear nights in winter months at high latitudes, and are more frequent around the equinoxes due to ionospheric dynamics.

Scientific study began in earnest in the 18th and 19th centuries, with early hypotheses tying auroras to Earth's magnetism. Modern research uses ground-based observatories, all-sky cameras, spectrographs, and satellites to monitor space weather. Auroras can affect high-frequency radio propagation and satellite communications but are not harmful at ground level.