The phenomenon of the electromagnetic energy being returned to the earth as a result of unusual solar activity causing aurora. The aurora occur in the ionosphere. Theoretically, auroral propagation is possible, when the aurora are active, between any two points on the ground from which the same part of the aurora can be seen. Auroral propagation is characterized by rapid flutter, which makes voice signals such as AM (amplitude modulation), FM (frequency modulation), or SSB (single sideband) unreadable most of the time. This propagation method is highly unreliable.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved