Proposed spacecraft would study effects of solar plasma. Scientists think `ubiquitous' gas may harm the ozone, affect the weather

When shuttle astronauts shot off electron beams and fired rocket engines into the atmosphere during their recent mission, they were experimenting with the most pervasive form of matter in the universe -- plasma. That's what physicists call a gas of electrically charged particles with equal numbers of positive and negative charges. As the National Academy of Sciences points out, because plasma is ubiquitous, the physics of this state of matter ``defines a basic language'' that connects laboratory research with phenomena as diverse as fluorescent lamps, Earth's aurora, and ejection of vast streams of material from distant galaxies.

So the Academy's Space Science Board is urging a beefed-up program of space research to learn more about the plasmas that permeate our solar system. It is especially interested in how streams of plasma coming from the sun affect Earth's environment, perhaps even the weather.

Here, then, is a field of science that most people probably find obscure, if they have heard of it at all. Yet the effects it discovers and the concepts and theories it develops have very practical consequences.

For example, there has been considerable concern that pollution by some spray-can propellants, refrigerants, and nitrogen oxide from fertilizer could damage Earth's ozone layer.

This layer, high in the atmosphere, filters out harmful solar ultraviolet rays. But the plasma linkage between sun and Earth also affects the chemistry of this atmospheric region. It, too, can create nitrogen oxide, which may harm the ozone layer. Here is an important environmental effect that needs investigating.

Commercial, military, and scientific satellites orbit in a plasma environment. Solar outbursts can disrupt this environment, interfering with or even damaging the spacecraft. Satellite designers and users need to understand these effects to operate effectively.

Back on Earth, one of the most intractable problems in applied physics has been the effort to harness hydrogen fusion to make electric power. Researchers are frustrated by their lack of knowledge of how plasmas behave, not by any ignorance of nuclear physics.

Again, research in the larger plasma laboratory of the solar system may shed useful light on this earthly problem.

In short, the Space Science Board thinks solar plasma physics has so much to offer, both in scientific and practical terms, that it wants to boost the National Aeronautics and Space Administration (NASA) budget in this field from roughly $300 million a year to $400 million a year. That would pay for the United States share of a diversified international research effort running through the end of the century.

The board's top-priority project illustrates what this enterprise would entail. Called the International Solar- Terrestrial Physics program, the United States has joined with the European Space Agency and Japan to lay out the project.

A squadron of spacecraft (see illustration), to be launched from 1989 through the early 1990s, would study the sun and its outflowing plasmas and their effect on Earth's space environment. Solar studies from the shuttle and the NASA space station, to be on orbit in 1992, would be included.

Physicists consider plasma so important they dignify it by calling it the fourth state of matter. Thus they rank it with the more familiar states of being a solid, a liquid, or an ordinary nonelectrified gas. Plasma is the substance of the sun and stars, of the interplanetary medium, and of the outer atmospheres of planets. Because matter in the plasma state carries electric charges, it responds to magnetic forces and can, itself, act on magnetic fields.

The outer atmosphere of the sun continually expands outward through the solar system. This is the solar wind (represented by arrows coming out from the sun in diagram), which flows past Earth at speeds typically of a million kilometers an hour (about 622,500 m.p.h.). Sometimes Earth's magnetic fields (solid and thin dotted lines surrounding Earth in illustration) guide this flow. Sometimes the solar wind blows so strongly it sweeps magnetic fields along with it.

However, the magnetic fields of Earth and other magnetically active planets control the immediate planetary environment.

Earth's fields act as an obstacle to the solar wind, which flows around what physicists call Earth's magnetosphere like a stream flowing around a rock.

Many other bodies in the universe, including some galaxies, also appear to have magnetospheres. Thus the study of the interaction of Earth's magnetospheric zone with the solar wind has far-reaching scientific implications.

Considered a developing set of ideas and theory, plasma physics is remarkable for its breadth of application. As the academy board observes, it deals ``with problems of true intellectual significance that may be studied effectively in space and whose importance extends to laboratory physics as well as large-scale astrophysics.'' No wonder the board wants an extra $100 million a year for this research.

A Tuesday column. Robert C. Cowen is the Monitor's natural science editor.

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