Average temperatures plunge to around -36℃ at the center of the Arctic Ocean and about -32℃ in Canada's Arctic Archipelago. The ocean from the Sea of Norway to the Barents Sea is warmed by the Gulf Stream, so the surface does not freeze even during the arctic nights. Temperatures in this region are a striking 30℃ warmer than at the center of the Arctic Ocean.
3.1.3 The Aurora Borealis and Magnetic Storms
The aurora was named after the Roman goddess of the dawn, who chased the darkness away and led humanity into the light. The aurora appears near each of the poles; the northern aurora is called the aurora borealis and the southern aurora is called the aurora australis.
The surface of the sun often sets off massive explosions called flares and emits a violent storm of ions from a zone at the surface called the corona. These emissions form a "solar wind" of particles that travel rapidly outward in all directions. The solar wind is a form of matter known as plasma: charged protons and electrons stripped from hydrogen atoms. This current traverses the 150 million kilometers from the sun to the earth in about three days, traveling at about 450km/h by the time it nears the earth. Because the earth has a magnetic field, the solar wind is deflected around the earth along magnetic field lines and is thus prevented from breaking through the magnetic field and reaching the earth's surface. The earth and its magnetic field together form a zone called the magnetosphere, which is bent away from the sun by the solar wind, forming a shape rather like the tail of a comet. The solar particles thus flow away around the earth's magnetic field. Through the interaction of the solar wind and the magnetosphere, a powerful electric generator is formed, generating more than 100 billion watts of electricity. This enormous current guides the plasma along lines of magnetic force from behind the earth to the Arctic and Antarctic zones.
The aurora is generated in the extreme upper reaches of the earth's atmosphere, 80km from the surface. The atmosphere at this level is as close to a vacuum as the space inside a neon tube. The plasma from the solar wind excites the oxygen and nitrogen atoms, creating a discharge illumination effect much like that used in neon tubes. The colors of the aurora differ according to the type of atoms struck by the plasma and the distance from the earth. The most commonly seen auroras, with their characteristic greens and blues, are generated by the illumination of oxygen atoms at a relatively near 110km from the earth's surface. At 400km, oxygen atoms emit light in the dark-red part of the spectrum, creating a "red aurora." Ionized nitrogen atoms emit a blue light at 90-150km, and at 90km neutral hydrogen molecules appear as a beguiling pink. The aurora thus appears as a multicolored curtain many miles high, colored red at the top, green and blue in the middle and reddish-purple and pink at the bottom.
