aurora

A diffused glow, bright patches, streamers, arches, or dancing color patterns that are frequently seen at high geographic latitudes mostly above 60°north or south latitude. The aurora seen in the Northern Hemisphere is referred to as aurora borealis, or the northern lights, and that in the Southern Hemisphere is known as aurora australis, or the southern lights. The phenomenon is associated with sunspot activity. The auroras are important in radio communications, because they affect the propagation of electromagnetic waves in high-frequency and very high frequency ranges. Signals may be returned to earth at much higher frequencies than usual when the aurora are active. The unusual solar activity that causes aurora, however, also can degrade normal ionospheric propagation. Sometimes, the disturbance is so pronounced that even wire circuits are disrupted by fluctuating magnetic fields.