Nothern Lights

2 Pages 494 Words

Aurora a luminous atmospheric phenomenon occurring frequently above 60° North or South latitude, but also sometimes in other parts of the world. It is named according to its location, aurora borealis (northern lights) or aurora australis (southern lights). The term aurora polaris, polar lights, is a general name used for both of them. (1)
The aurora consists of rapidly shifting patches and dancing columns of light of various hues. (2) Extensive auroral displays are accompanied by disturbances in terrestrial magnetism and interference with radio, telephone, and telegraph transmission. (1) The period of maximum and minimum intensity of normal auroras seems to be almost exactly opposite that of the sunspot cycle, which is an 11-year cycle, so the intensity of the auroras is normally low while the sun is very active. (2) Huge displays that occur farther from the earth’s poles than normal, however, occur more often while the sun is very active. (2)
Studies made during and after the 1957 and 1958 International Geophysical Year indicate that the auroral glow is triggered when the solar wind carries high-energy atomic particles from sunspots. (1) The electrons and protons penetrate the magnetosphere of the earth and enter the lower Van Allen radiation belt, overloading it. The extra electrons and protons are distributed into the atmosphere over an area on the north and south magnetic poles and extending about 20° away from them. (1) These particles then collide with gas molecules in the atmosphere, thereby exciting the molecules and causing them to emit electromagnetic radiation in the visible portion of the spectrum. (2)
The auroras are, on average, less intense when the sun is most active. When the sunspot cycle is at its maximum, the sun emits much more ultraviolet radiation than it normally does. The ultraviolet radiation changes the earth’s magnetosphere, making it better able to handle the particles from the sunspots. (1...