Shop Windows to the Universe

With Explore the Planets, investigate the planets, their moons, and understand the processes that shape them. By G. Jeffrey Taylor, Ph.D. See our DVD collection.
This is an artist's conception of the Earth and the inner and outer radiation belts that surround it.
Click on image for full size
Windows to the Universe

Radiation Belts

The Earth's radiation belts are one component of the larger and more complex system called the magnetosphere. The radiation belts of the Earth are made up of energetic, electrically charged particles or electrons, protons and heavier atomic ions. These particles essentially get trapped in the magnetic field of the Earth. The kinetic energy of these particles is greater than or equal to 30 keV.

The radiation belts, like the plasmasphere, are toroidally shaped. These toroids encircle the planet. The inner radiation belt extends from about 400 km above the Earth to 12,000 km. The outer radiation belt extends from about 12,000 km to 60,000 km above the Earth. At times, the two belts overlap each other.

The belts of trapped radiation near the Earth were first detected by James Van Allen in 1958. Therefore these belts are also known as Van Allen Belts.

Dr. Van Allen has also found that the principal sources of particles for the outer radiation belt are the solar wind and the ionosphere. The main sources for the inner belts are solar energetic particles and reactions with galactic cosmic rays. The eventual fate of particles in the radiation belts is to become part of the atmosphere, to collide with satellites or to escape into space.

It is extremely important that we have a good understanding of the radiation belts because the energetic particles in these toroids affect in situ measurements and may have an effect on the survival of electronic and optical equipment, human and animal life forms. "The particle population of the Earth's radiation belts makes it dangerous for humans without massive shielding to do more than quickly pass through them," reports Dr. James Van Allen.

Last modified May 27, 2003 by Lisa Gardiner.

Shop Windows to the Universe Science Store!

Learn about Earth and space science, and have fun while doing it! The games section of our online store includes a climate change card game and the Traveling Nitrogen game!

Windows to the Universe Community

News

Opportunities

You might also be interested in:

Cool It! Game

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

The Earth's Magnetosphere

The Earth has a magnetic field with north and south poles. The magnetic field of the Earth is enclosed in a region surrounding the Earth called the magnetosphere. As the Earth rotates, its hot core generates...more

The Earth's Plasmasphere

The plasmasphere is a torus-shaped region within the Earth's magnetosphere. The Earth's plasmasphere is made of just that - plasma. It has a very sharp edge called the plasmapause at equatorial distances...more

The Discovery of the Radiation Belts

The belts of trapped radiation above the Earth's atmosphere, but within the magnetosphere, were first detected by James Van Allen in 1958. Therefore these belts are also known as Van Allen Belts. When...more

How Does the Earth's Magnetic Field Protect Us From Space Radiation?

Dangerous particles are not able to penetrate to the Earth's surface but are forced by the magnetic field to move around the Earth. Particles gain entry through the cusps that are shaped like funnels over...more

The Plasma Sheet

The plasma sheet is simply that, a sheet of plasma that extends down the magnetotail dividing the two lobes of the Earth's magnetic field. The particle density here is about 0.5 cm-3 for both electrons...more

Jupiter's Plasmasphere

Jupiter's magnetosphere is practically all plasmasphere. Jupiter's magnetosphere is filled with plasma. Most of the plasma comes from the donut-shaped cloud (torus) of material from Io. Besides ions and...more

Saturn's Plasmasphere

Saturn's plasmasphere is pretty big. Most of the plasma comes from the donut-shaped cloud (torus) of material from Titan and the other icy moons. Besides ions and electrons, the plasmasphere also contains...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA