What Is Earth’s Magnetic Field?

Earth has an invisible force field around it called a magnetic field. You cannot see it or feel it, but it surrounds our entire planet like a giant protective bubble. This magnetic field stretches far out into space, forming a region called the magnetosphere. It acts like a shield that protects all living things on Earth from harmful particles that fly through space.

What Creates the Magnetic Field?

Deep inside Earth, there is a core made mostly of iron and nickel. The outer core is so hot that these metals are liquid, and they are constantly moving and swirling around. As these liquid metals flow, they create electrical currents, and those currents generate Earth’s magnetic field. Scientists call this process the geodynamo, and it has been working for billions of years.

Earth’s Magnetic Poles

Earth’s magnetic field has two poles, a north magnetic pole and a south magnetic pole, just like a bar magnet. The magnetic poles are close to the geographic North and South Poles, but they are not in exactly the same spot. In fact, the magnetic poles slowly move over time, shifting a few miles each year. Right now, the north magnetic pole is located in the Arctic region of Canada, slowly drifting toward Siberia.

How Compasses Work

A compass is a simple tool that uses Earth’s magnetic field to help people find their way. Inside a compass, there is a small magnetized needle that can spin freely. The needle always points toward the north magnetic pole because it is pulled by Earth’s magnetic field. People have been using compasses for navigation for over a thousand years, long before GPS was invented.

The Magnetosphere: Earth’s Shield

The magnetosphere is the huge region of space around Earth that is controlled by the magnetic field. It protects us from the solar wind, which is a stream of charged particles constantly flowing from the Sun. Without the magnetosphere, the solar wind could strip away Earth’s atmosphere over time, making our planet unable to support life. Mars lost most of its atmosphere because it does not have a strong magnetic field like Earth does.

The Northern and Southern Lights

One of the most beautiful effects of Earth’s magnetic field is the aurora, also called the Northern Lights (aurora borealis) and Southern Lights (aurora australis). Auroras happen when charged particles from the Sun follow the magnetic field lines toward the poles and crash into gases in Earth’s atmosphere. These collisions make the gases glow in spectacular colors like green, purple, pink, and blue. Auroras are most often seen in places near the Arctic and Antarctic, like Alaska, Norway, and southern New Zealand.

What Makes Auroras Different Colors?

The colors of an aurora depend on which gases the solar particles hit and how high up the collision happens. Green auroras, the most common color, are caused by oxygen molecules about 60 to 150 miles above Earth’s surface. Red auroras come from oxygen at even higher altitudes, above 150 miles up. Purple and blue auroras are created when the particles collide with nitrogen molecules in the atmosphere.

Animals and the Magnetic Field

Many animals can sense Earth’s magnetic field and use it to find their way during long migrations. Sea turtles travel thousands of miles across the ocean and use the magnetic field like a built-in map to return to the same beach where they were born. Birds such as Arctic terns and homing pigeons also rely on magnetic navigation during their long migrations. Even some bacteria contain tiny magnetic crystals that help them orient themselves in the water.