Shop Windows to the Universe

The Universe at Your Fingertips 2.0 DVD from the Astronomical Society of the Pacific is in our online store, filled with Earth and space science resources.
This image is a summary of the main features of the plasmasphere: the plasmapause, main body of the plasmasphere, dusk-bulge region and detached plasma regions outside the main body of the plasmasphere
Click on image for full size

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 of 4-6 Earth radii. The plasmapause, where densities drop by a factor of 10-100 in a relatively short distance, was discovered in 1963.

The plasmasphere is essentially an extension of the ionosphere to high altitudes. Inside of the plasmapause, geomagnetic field lines rotate with the Earth. Plasma, flowing up from the ionosphere, is trapped on these corotating field lines and builds up to high densities. Outside the plasmapause, magnetic field lines are unable to corotate because they are influenced strongly by electric fields of solar wind origin. They convect to the magnetopause boundary on the day side of the Earth, sweeping the ionospheric plasma out of the magnetosphere and forming the sharp plasmasphere boundary. The plasmasphere bulges out to greater distances on the dusk side of the Earth.

The plasmasphere is composed mostly of hydrogen ions. The plasma density ranges from 104 cm-3 just above the topside ionosphere to 102 cm-3 within and 10 cm-3 just exterior to the plasmapause. The base of the plasmasphere is taken as the altitude (~ 1000 kilometers) at which protons replace oxygen as the dominant species in the ionospheric plasma. The ion temperature in the plasmasphere is generally between 0.5 eV and several eV (1 eV = 11,700 K).

Shop Windows to the Universe Science Store!

Our online store includes fun classroom activities for you and your students. Issues of NESTA's quarterly journal, The Earth Scientist are also full of classroom activities on different topics in Earth and space science!

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 Plasma State

Plasma is known as the fourth state of matter (the first three states being solid, liquid and gas).Matter in ordinary conditions on Earth has electrons that orbit around the atomic nucleus. The electrons...more

The Magnetic Field

The force of magnetism causes material to point along the direction the magnetic force points. This property implies that the force of magnetism has a direction. As shown in the diagram to the left, the...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

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...more

Space Missions to study Earth's Atmosphere & Climate

Television weather forecasts in the space age routinely feature satellite views of cloud cover. Cameras and other instruments on spacecraft provide many types of valuable data about Earth's atmosphere...more

Magnetosphere

A magnetosphere has many parts, such as the bow shock, magnetosheath, magnetotail, plasmasheet, lobes, plasmasphere, radiation belts and many electric currents. It is composed of charged particles and...more

AU

AU stands for Astronomical Units. Distances in space are too large to measure in Earth standards like miles or kilometers. For distances too large to measue in AU, we use light years. A light year is the...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF