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Artist's Concept of the Sun-Earth Space Plasma Environment
Copyright 1999. Space Science Institute, Boulder, Colorado, all rights reserved.

Many people believe the space in between the the Sun and its planets is empty, a vacuum devoid of energy or matter. But space is not empty. Our Sun constantly emits plasma, a superheated state of matter, which moves out in all directions at very high speeds to fill the entire solar system and beyond.

By studying processes that occur in the earth's magnetosphere (where earth's magnetic field has a greater influence than the Sun's interplanetary field), in interplanetary space, and around other planets, we are better able to appreciate the important role of plasmas throughout our plasma universe. This space plasma laboratory is truly our window to the stars.

The earth's magnetosphere is normally invisible because the dominant hydrogen and helium ions coming in the solar wind do not scatter light in visible wavelengths. However, comets emit heavier ions that are visible and which result in spectacular neutral and ion (plasma) tails. Images of earth's magnetosphere would show it to be a very large comet-like interaction region.

Sun Earth Connections program, NASA

The Sun is a variable star, especially in its output of ultraviolet radiation, X-rays, particles and magnetic fields. Corresponding large variations occur throughout the region of the Sun's influence, which is called the heliosphere and which includes the solar wind and all solar system magnetospheres. Space weather is the study of how the space environment affects astronauts, satellite operations, communication systems and ground-based power grids. In the long term, space weather could contribute to global climate change primarily through slow changes in solar radiation.

University of Alaska
Geophysical Institute

As the solar wind flows past earth's magnetosphere, it interacts with the geomagnetic field and acts as a cosmic generator producing millions of amps of electric current. Some of this electric current flows into earth's upper atmosphere which lights up like a neon tube to create the beautiful aurora. The aurora are always present because the solar wind source is always present, and they form a ring of emissions within the ionosphere centered on both magnetic poles at high latitude. However, they are normally sub-visual except at nighttime and during geomagnetic storms. In midwinter, residents of Fairbanks, Alaska enjoy auroral display two out of every three nights!


Magnetic energy burst on the solar surface hurls plasmas outward from the Sun.  Clear magnetic field
structures appear in light blue.
(Dr. Alan Title, Stanford Lockheed Institute for Space Research and NASA)

Plasmas pervade the heliosphere and local interstellar medium. The shape of the heliosphere results from a comet-like interaction with the surrounding plasma (from T. Eastman, IEEE Trans. Plasma Science, 18, 1990, p. 20).


Detail of Helix nebula showing stellar magnetospheres created by an interstellar plasma flow coming from the lower left region of image (NASA, Rice University)


Cygnus Loop nebula showing the interaction of multiple shock waves and
other highly structured plasma regions
(NASA Space Telescope Science Institute)

Intense regions of star birth are evident here near the boundaries of the dark pillars of the Eagle nebula. Electrodynamic effects of plasmas become important with only a few percent ionization as illustrated by earth's ionosphere. All visible regions here and most of the low-density regions in between are dominated by plasmas containing neutral particles, ions, electrons and electric and magnetic fields. Within the dark columns plasmas might be present only within and near stars, with the surrounding gas in these columns being cold and neutralized.
(NASA and Arizona State University)