An aurora is a natural geosolar phenomenon that occurs when the charged particles from the sun, known collectively as the solar wind, make contact with the Earth’s upper atmosphere.
Normally, the Earth’s magnetic field is strong enough to prevent the solar wind from passing through to the atmosphere, but when the wind becomes more intense during a solar flare, the charged particles (ions) collide with oxygen and nitrogen atoms in the Earth’s uppermost atmospheric level, the ionosphere. The solar wind can be especially intense when the sun ejects a large cloud of ions at high speeds towards Earth, an event known as a coronal mass ejection.
This collision transfers the kinetic energy of the ions to the atoms, which respond to their increase in energy by releasing light. Oxygen atoms usually produce a red or green light, while nitrogen atoms produce a blue or purple light, in accordance with their respective emission spectra. The produced light constitutes the aurora.
Due to Earth’s orbit and its rotation along its north-south polar axis, northern latitudes and southern latitudes experience auroras more often than more equatorial locations. Northern auroras are called aurora borealis and southern auroras, aurora australis.
It may seem as though auroras are an Earth-specific phenomenon, but auroras have been seen on other planets in the solar system as well; Mars, Venus, Jupiter, Saturn, Uranus, and Neptune all have auroras, mostly occurring in ultraviolet light that renders them unobservable to the human eye. By definition, any planet with both an atmosphere and a magnetic field has the potential to have auroras, meaning that there are likely many other planets yet to be discovered that experience this amazing display of nature’s beauty.
Sources: MTU, NASA, National Geographic, Aurora Zone, Webb Space Telescope