An aurora is a natural light display—commonly known as the Northern Lights (aurora borealis) or Southern Lights (aurora australis)—that occurs near polar regions when charged particles from the Sun interact with Earth's magnetosphere and upper atmosphere.
These particles, primarily electrons and protons, are carried by the solar wind or released during events like coronal mass ejections. They are funneled by Earth's magnetic field toward the polar regions, where they collide with atoms of oxygen and nitrogen in the upper atmosphere, causing those atoms to emit visible light.
The specific colors of an aurora depend on which gas is excited and at what altitude. Green, the most common auroral color, results from oxygen at about 100–300 km altitude. Red auroras come from oxygen higher up, while nitrogen can produce blue or purple hues.
Auroras appear in many forms, including arcs, curtains, rays, and coronas. Their dynamic shapes are influenced by fluctuations in the magnetosphere, which are often driven by variations in solar activity.
While auroras are visually captivating, they also signal space weather conditions. Strong geomagnetic storms that intensify auroras can interfere with satellite electronics, GPS signals, radio communications, and even power grids on Earth.
Auroral displays are not unique to Earth. Other planets with magnetic fields and atmospheres, such as Jupiter and Saturn, also exhibit auroras. Observations from ESA's Cluster mission and various NASA spacecraft continue to advance our understanding of how auroras form and behave.