AEROGRAPHER'S MATE 3 & 2 



1. CLOUD TO GROUND LIGHTNING (CG). Polar auroras are due to electrically charged 

 Lightning occurring between cloud and ground. particles, ejected from the sun, acting on the 



2. CLOUD DISCHARGES (IC). Lightning which rarefied gases of the higher atmosphere. The 

 takes place within the thunder cloud. particles are channeled by the earth's magnetic 



3. CLOUD TO CLOUD DISCHARGES (CC). field, so that auroras are mainly observed near 

 Streaks of lightning reaching from one cloud to the magnetic poles. In the Northern Hemisphere 

 another. they are known as aurora borealis; in the South- 



4. AIR DISCHARGES (CA). Streaks of lightning ern Hemisphere they are known as aurora aus- 

 which pass from a cloud to the air but do not tralis. 



strike the ground. 



AIRGLOW 

 AURORAS 



Airglow is similar in origin and nature to 



A luminous phenomenon which appears in the auroras; it, too, is an upper atmospheric elec- 



high atmosphere in the form of arcs, bands, trical phenomenon. The main differences between 



draperies or curtains. This phenomenon is us- airglow and aurora are that airglow is quasi- 



ually white but may have other colors. The steady (quasi means seemingly) in appearance, 



lower edges of the arcs or curtains are usually is much fainter than aurora, and appears in the 



well defined while the upper edges are not. middle and lower latitudes. 



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