Veil is the most bland and very common form of aurora. It usually covers its homogeneous dim glow over a wide area of the sky at once. Most often, the veil is seen in the calmer and quiet phase of the night after the aurora maximum as a background for other forms. The veil can also occur alone and in that case it will be quite difficult to reliably identify as an aurora, especially at a observation site which has a lot of light pollution.
A similar glow of light can also be caused by airborne moisture, smoke, or a very thin layer of clouds that reflects the light that hits them. However, clouds can also be used to identify veil, especially if the middle or upper cloud appears dark against a lighter background, then it is very likely to be aurora veil if the brightness of the background sky is not due to the rising or falling Moon or Sun. When photographing, very long exposure times usually reveal the green colour of the veil auroras.
Veil and rays. Photo by Esa Palmi.
Red aurora veil. Photo by Marko Mikkilä.
Veil. Photo by Milla Myllymaa.
Aurora veil that changes color from green at the lower edge through purple to blue at the top. Photo by Jaakko Hatanpää.
Dim green veil. Photo by Jarmo Leskinen.
Radial aurora band surrounded by veil. Photo by Jussi Alanenpää.