Earth's magnetic field is similar to a giant bar magnet. There is a north and south pole with magnetic lines of force surrounding the planet. The field lines indicate the direction and strength of the field at any point and run from north to south.
The magnetic north pole is currently in northern Canada at about 80 degrees north laatitude above the center of North America. The magnetic south pole is at about 60 degrees south latitude, off the coast of Antartica, south of Adelaide Australia.
Spaacecraft have shown there are two doughnut shaped zones of high energy particles about 3000 and 20,000 km above the Earth's surface. They are called the Van Allen belts, named after the physicist who designed the instruments that discovered them. They are referred to as belts because they are most obvious neaar the equator and because they surround the planet. The Van Allen belts would be a very dangerous place to be without protection. These areas are under heavy bombardment of high-velocity charged particles.
It is believed that the magnetic field of the Earth is generated by the liquid outer core. The spin of electrically conductive metals iduces magnetism. Other planets have magnetic fields as well. The Van Allen belts are created when charged particles headed in the direction of Earth are trapped by the Earth's magnetic field and forced into the areas that form the Van Allen belts.
Sometimes these charged particles escape the magnetosphere near the north and south poles. Here, the magnetic field lines intersect with the atmosphere. These particles collide with molecules in the atmosphere and can strip them of their charges. The atmospheric molecules are temporarily charged but soon drop back down to their ground states, releasing visible light as they do. We see this effect as the aurora borealis in the north, and aurora australis in the south.
Earth's magnetic field is importaant to us because it controls many of the potentially destructive charged particles that come near Earth. Without the magnetosphere, our atmosphere, and probably our ground, would be bombarded with harmful particles that could endanger life. Some scientist believe that life would not even have formed if Earth had not had a magnetosphere.
Copyright © 1997 Kathy A. Miles and Charles F. Peters II