auroral

Auroral, in the context of atmospheric phenomena, refers to the aurorae, natural light displays in Earth's polar skies. They occur when charged particles emitted by the Sun travel through space and interact with the Earth's magnetosphere, following magnetic field lines toward the polar regions. When these particles collide with atoms and molecules in the upper atmosphere, they transfer energy and cause the atoms to emit light, producing shimmering curtains, bands, or diffuse glows.

The colors observed most commonly are green from excited atomic oxygen around 100-300 km altitude; red from higher-altitude oxygen above 200 km; and blue or purple from molecular nitrogen. The particular colors and shapes depend on particle energy, atmospheric composition, and altitude.

Auroral activity is more frequent and intense near the auroral ovals encircling the magnetic poles and increases during heightened solar activity, such as solar flares or coronal mass ejections. The activity is a key component of space weather and is studied to understand the magnetosphere and its interaction with the solar wind.

Historically observed by many cultures, aurorae were explained scientifically in the late 19th and early 20th centuries, with theoretical contributions from Kristian Birkeland and later space-based observations confirming the role of solar particles.