The Magnetic Earth

Here you will earn about Earth's magnetic field, and how it shields us from solar storms!!

If you have any questions about Earth's magnetism, visit Ask the Space Scientist!

Magnetism: Have you ever played with a magnet? Surrounding every magnet is an invisible area that scientists call a 'field'. The Earth is also a giant magnet. You can use it to find your direction by using a compass. Scientists have studied Earth's magnetic field for hundreds of years. They keep track of its different parts by naming them. Look at the figure below to see what the different parts of this field in space are called. Scientists have to give the different parts names to keep track of which area they are discussing when talking to other scientists.

  Watch a Magnetosphere Movie

  Look at an Enlarged Picture

The Magnetosphere: Earth's invisible magnetic field is shaped like a comet. It has a long tail that stretches millions of miles behind Earth in the opposite direction from the Sun. When a Coronal Mass Ejection from the Sun reaches Earth, it makes Earth's magnetic field shake and become very disturbed. The stormy clouds and winds from the Sun pull at this tail and make it flap and shake. Like pulling taffy, pieces of this magnetic tail break off and flow out into distant parts of the solar system. The rest of the magnetic tail snaps back towards Earth. Gases that are trapped in this invisible, magnetic 'taffy' flow towards Earth too where they can cause other phenomena to happen.

 Watch a Magnetotail Movie

 Look at an Enlarged Picture

Ring Current: Some of the trapped particles will take a detour and join other invisible gases that flow around Earth. One of these collections of gas is called the Ring Current. It's a gigantic river of electrified particles. Like a current of electricity flowing in a wire, it also creates its own magnetism. A battle between the Ring Current magnetism and Earth's magnetism causes many changes to take place. Because everything in space is connected, changes in one place, cause changes to take place in another place. This happens because the particles in Earth's magnetic field are charged. This means that when they flow from place to place they form a n electrical current. As you know from experimenting with an electromagnet (a nail wrapped with wire attached to a battery), when currents flow they produce their own magnetic fields. In space, these currents of charged particles create magnetic fields that then interact with Earth's main field to produce complex, and vast, changes. When the ring current flows, its magnetic field actually cancels part of Earth's field over the equator. Scientists can detect these changes on the ground, and it can amount to nearly a 1% change in Earth's field. Fortunately, this isn't enough to cause any problems for humans or living things!

 Watch a Ring Current Movie

 Look at an Enlarged Picture

Van Allen Belts Earth is surrounded by clouds of invisible particles, which some artist probably has colored purple and blue. Textbooks will then tell you that these are called the van Allen Radiation Belts. The 'Belts' are an example of particles that are trapped in Earth's magnetic field much like fireflies trapped in a bottle. Although artists like to draw them as though they look like dense clouds of gas, they are so dilute that astronauts don't even see them, or feel them, when they are outside in their space suits. They are so dilute, in fact, that scientists didn't know they existed until they could put sensitive instruments inside satellites and study these clouds directly. This was one of the very first experiments conducted at the dawn of the Space Age in the late 1950's. Back then, scientists such as Prof. James van Allen at Iowa State University were very interested in particles called cosmic rays, which other physicists had detected from the ground as far back as the 1930's. There are actually three distinct belts caused by the flows of two kinds of charged particles: electrons and protons.

The Inner Belt region between 600 and 3,000 miles (1,000 and 5,000 km) contains high-energy protons carrying energies of about 100 million volts, and electrons with energies of about 1-3 million volts.

The Outer Belt region between 9,000 and 15,000 miles (16,000 and 24,000 km) consists of mostly electrons with energies of 5 to 20 million volts.

Where do the particles in the belts come from? One source of these particles is probably the Sun, which is a powerful and abundant source for particles like the ones found in the belts. A second source is cosmic rays from outside the solar system. A third source may be atoms and nuclei from Earth's atmosphere that have been fantastically boosted in energy to millions of volts by some series of processes we don't quite understand yet. Because the particles are not 'labeled' with their place of origin, it is very difficult for scientists to sort out how each of these sources actually contributes to the belts themselves.

 Watch a Ring Current Movie

 Look at an Enlarged Picture

 An Artificial Van Allen Belt

 Model of the electron belts.

 Model of the proton belt.

  Earth orbit belt Close up

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