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Space Plasmas
| Article
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14564 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
3 / 1988 |
2,791 Words |
| Author
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Anthony L. Peratt
Anthony L. Peratt conducts plasma research at the Los Alamos
National Laboratory. He was previously with the Maz Planck
Institute for Plasma Physics in West Germany. |
Ionized matter--plasma--is overwhelmingly the dominant constituent of the universe as a whole. Yet most people are ignorant of plasmas. In daily life on the surface of planet Earth, perhaps the plasma to which people are most commonly exposed is the one that produces the cool efficient glow from fluorescent lights. Neither solid, nor liquid, nor gas, a plasma most closely resembles the latter, but unlike gases whose components are electrically neutral, plasmas are composed of electrically charged particles.
Plasmas are so hot, or energetic, that the atoms or molecules composing them have been ionized; they have lost one or more of their electrons to become electrically charged. In a fluorescent bulb, this gaseous mixture of ions and electrons remains charged only so long as the light is turned on; when the voltage is removed, the plasma reverts to an ordinary gas. In space, however, this "fourth state of matter," composed of ions and free electrons, remains electrically charged due to its high energy. Thus plasmas carry electric currents and are more influenced by electromagnetic forces than by gravitational forces. Outside the Earth's atmosphere, the dominant form of matter is plasma, and "empty" space has been found to be quite "alive" with a constant flow of plasma matter.
Given its nature, the plasma state is characterized by a complexity that vastly exceeds that exhibited in the solid, liquid, and gaseous states. Correspondingly, the study of the physical and especially the electrodynamical properties of plasma forms one of the most far-ranging and difficult research areas in physics today. From spiral galaxies to controlled fusion and laser beam generators, this little-known state of matter is proving to be of ever greater significance in explaining the dynamics of the universe and in harnessing the material world for the greatest technological result.
With the advent of planetary space probes, the solar system has come to be regarded as the primary laboratory in which plasma processes of great generality can be studied. The discovery in the 1960s of the Van Allen radiation belts and the solar wind gave clear signs that the dynamic relations between the Earth and the Sun would have to be expressed in terms of plasma science. Today, plasma science is recognized as the key to understanding the generation of magnetic fields in planets, stars, and galaxies; phenomena occurring in interstellar and intergalactic media; and phenomena occurring in stellar atmospheres, including that of the Sun.
In the laboratory, the last
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