An auroral form (see aurora) consisting of narrow lines of light that extend up into the sky, approximately vertical to the horizon. They follow the lines of force of the Earth's magnetic field, and their appearance is normally a sign that the display is becoming more active. They may be seen in isolation or, more commonly, associated with auroral arcs and bands. When folded, rayed bands pass overhead they may produce a spectacular corona (3).
Subjects: Meteorology and Climatology.