The raysare parallel to the lines of force of the magnetic field, i.e. quite vertical, usually less than one degree thick light streaks. The rays can occur alone or in connection with other shapes, mainly with arcs and bands. Short rays are usually brightest at the bottom but dim quickly. The longest rays, even extending almost from the horizon to the zenith, are usually uniformly bright and quite calm, and unlike the shorter rays, most often occur in groups of a few rays or alone. Rays, like bands, are a very typical form of aurora.
Artificial light pillars, which are a halo phenomenon visible in ice mist, can sometimes be very similar to the rays of aurora. Confusion is possible especially when the lamps that cause the artificial light pillars are far away and not visible behind buildings or the forest. The nature of the phenomenon is clear at least from the photographs.
Rays. Picture of Tom Eklund.
Rays. Photo by Mika Puurula.
Two beams rise from the aurora veil. Photo by Anssi Mäntylä.
Two radial bands. Show Jani Lauanne.
Radial band and veil. Photo by Jussi Alanenpää.
Two rays. Photo by Aki Taavitsainen.
It may be possible to confuse such rays with artificial light columns. Compare the image below. Picture of Tom Eklund.
There is no aurora in this image, but all the light poles - including the wide and diffuse bar seen at the top left - are artificial light pillars born of ice mist. Photo by Sami Jumppanen.
Aurora and artificial light pillars. All the radial shapes in the picture above are probably artificial light pillars that coincide appropriately with the aurora band. In the image below, the aurora band has shifted and does not overlap with the pillars produced by the orange bulbs. There is no orange in auroras. Photo by Katariina Roiha
Oikein mukava joululahja :)