The auroral glow is triggered when the solar wind, which permeates the solar system, is enhanced by an influx of high-energy atomic particles emanating from sunspots. The electrons and protons penetrate the magnetosphere of the earth and enter the lower Van Allen radiation belt, overloading it. The excess electrons and protons are discharged into the atmosphere over an area centring on the north and south magnetic poles and extending about 20° from them. These particles then collide with gas molecules in the atmosphere, thereby exciting the molecules and causing luminescence, the emission of visible light.

The aurora assumes an endless variety of forms, including: the auroral arch, a luminous arc lying across the magnetic meridian; the auroral band, generally broader and much more irregular than the arch; filaments and streamers at right angles to the arch or band; the corona, a luminous circle near the zenith; auroral clouds, indistinct nebulous masses, that may occur in any part of the heavens; the auroral glow, a luminous appearance high in the sky, the filaments converging towards the zenith; and curtains, fans, flames, or streamers of various shapes.

Auroras have also been observed in the atmospheres of other planets, notably Jupiter.