The earth’s magnetic field is somewhat like a simple bar magnet. It has two poles on the surface of the earth, the northern magnetic pole and the southern magnetic pole. Away from the surface of the earth, the magnetic field becomes distorted. Just as the earth is tipped on its axis, the magnetic field is also tipped in respect to the rotation of the earth on its axis. Therefore magnetic north and true north are not the same thing. The earth’s magnetic field is weaker or more intense in different areas on the earth’s surface. Since the earth’s magnetic field is responsible for how a compass works, these variations in intensity mean that a compass must be fixed by specific amounts at certain points on the earth’s surface in order to give true directions. If there were no magnetic field, compasses would not work. Without it, the great feats of exploration that have been accomplished over the centuries would not have been possible.
Scientists use the dynamo theory to explain how the magnetic field works. According to this theory, there is a source of energy in the core of the earth that causes a self-sustaining magnetic field. Scientists believe that there is fluid motion in the earth’s core, and that this fluid motion involves movement of conductive material. When this movement occurs, a current is created that causes the earth’s magnetic field to become self-enforcing.
In the late 1950s, as man began to explore space, they discovered two bands or regions around the earth. These bands, called the Van Allen Radiation Belts, contain high concentrations of electrically charged particles. Most of these particles come from solar wind, which sends a stream of charged particles out from the sun. Also around the earth is a portion of space which is dominated by the earth’s magnetic field. This region of space is called the magnetosphere. The purpose of the magnetosphere is to deflect the solar wind and keep it from entering. However, during solar storms, some of the charged particles do get into the magnetosphere and become trapped in the earth’s magnetic field. This, in turn, creates a geomagnetic storm, producing the beautiful phenomenon called the Aurora Borealis.
The earth’s magnetic field helps to keep people safe while they travel by allowing them to use a compass to get good directions. It protects the earth’s atmosphere from solar wind and dangerous particles that could damage the earth. And it is involved in the geomagnetic storms that produce the fantastic Aurora Borealis.