An aurora is a natural light display in the sky (from the Latin word aurora, “sunrise” or the Roman goddess of dawn), predominantly seen in the high latitude (Arctic and Antarctic) regions. Auroras are caused by charged particles, mainly electrons and protons, entering the atmosphere from above causing ionisation and excitation of atmospheric constituents, and consequent optical emissions. A geomagnetic storm causes the auroral ovals (north and south) to expand, and bring the aurora to lower latitudes. In northern latitudes, the effect is known as the aurora borealis (or the northern lights). Auroras seen within the auroral oval may be directly overhead, but from farther away they illuminate the poleward horizon as a greenish glow, or sometimes a faint red, as if the Sun were rising from an unusual direction. Its southern counterpart, the aurora australis (or the southern lights), has features that are almost identical to the aurora borealis and changes simultaneously with changes in the northern auroral zone. It is visible from high southern latitudes in Antarctica, South America, New Zealand, and Australia. Auroras also occur on other planets. Similar to the Earth’s aurora, they are also visible close to the planets’ magnetic poles.