Charged Particle Motion in Earth's Magnetosphere

Precipitation of Magnetospheric Charged Particles

Magnetospheric charged particles on closed magnetic field lines (both ends of which penetrate the earth’s atmosphere) find themselves in a magnetic mirror geometry. Unless they are traveling nearly parallel to the magnetic field, they bounce back and forth between the Northern and Southern Hemispheres on paths high above the dense regions of the earth’s upper atmosphere.

Animation courtesy the COMET and HAO programs at UCAR/NCAR.

If, however, their paths are nearly parallel to the field lines, they can reach atmospheric regions where they collide with neutrals. By this process, charged particles precipitate from the magnetosphere into the atmosphere. The range of small pitch angles through which particles are precipitated is called the loss cone.

Pitch angles

As plasma sheet field lines approach the earth, the loss cone expands. In addition, charged particles can be scattered into the loss cone by magnetic and electrical disturbances in the magnetosphere. Particles precipitated via the loss cone from the magnetosphere into the upper atmosphere produce the aurora.

Animation courtesy the COMET and HAO programs at UCAR/NCAR.

Last modified May 17, 2005 by Randy Russell.

You might also be interested in:

Cool It! Game

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

Earth's Magnetic Poles

Earth has a magnetic field. If you imagine a gigantic bar magnet inside of Earth, you'll have a pretty good idea what Earth's magnetic field is shaped like. Of course, Earth DOESN'T have a giant bar magnet...more

Earth's North Magnetic Pole

Earth has a magnetic field with a north pole and a south pole. Earth's magnetic field is pretty much like the magnetic field around a bar magnet. Earth's North Magnetic Pole (NMP) is not in the same place...more

Charged Particle Motion in Earth's Magnetosphere

Motions within Earth's metallic core generate the planet's global magnetic field. This magnetic field extends beyond Earth's surface and atmosphere into the space surrounding our home planet. The interaction...more


Altocumulus clouds are part of the Middle Cloud group. They are grayish-white with one part of the cloud darker than the other. Altocumulus clouds usually form in groups. Altocumulus clouds are about...more


Altostratus clouds belong to the Middle Cloud group. An altostratus cloud usually covers the whole sky. The cloud looks gray or blue-gray. The sun or moon may shine through an altostratus cloud, but will...more


Cirrocumulus clouds belong to the High Cloud group. They are small rounded puffs that usually appear in long rows. Cirrocumulus are usually white, but sometimes appear gray. Cirrocumulus clouds are the...more


Cirrostratus clouds belong to the High Cloud group. They are sheetlike thin clouds that usually cover the entire sky. The sun or moon can shine through cirrostratus clouds. When looking at the sun through...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