National Geographic : 1947 Nov
C.W.Gartlein This Aurora Display Presents a Homogeneous Arc Below and a Homogeneous Band Above The band is more irregular than the arc. It is not unusual for two different types of auroras to appear together (pages 701,702,704). C.W.Gartlein Aurora with Two Homogeneous Arcs, One above the Other; Some Displays Have Several Such Arcs Often the arcs gradually climb up the sky and break up into rays, forming a rayed arc aurora (Plate III and page 703). This occurs after the lower border becomes sharp.