Stable auroral structures which only show very slow changes in position or shape.
Active aurora is normally bright.
Particularly strong displays can produce multiple forms. For instance, homogeneous arcs can appear in pairs, one lying above the other. At times, auroral arcs, bands and other forms may not fully develop. Arcs may not join in the middle or only occupy the eastern or western half of the sky. Fragmentary aurora is often seen during the declining stages of a display, described by some observers as 'break-up'.