Where Do We Go from Here?

We have made much progress in using observations from space to discover basic properties of the Sun, its magnetic field, and the Earth's magnetosphere. But we have only just begun to see the Sun as it really is, and many very important questions remain. For instance, we still have no adequate theory to explain why the period of the sunspot cycle is 11 years rather than, say, 2 years or 50 years. And we are far from being able to predict when (or even if) another long interval with few if any sunspots will occur. To answer such questions, we will need a program of systematic new space observations and much intensive theoretical work in the years to come.

New techniques of observation will enable us to probe the convective, oscillatory, and rotational motions that take place deep inside the Sun. These studies will be crucial for understanding how the solar magnetic field is generated. Telescopes, mounted on spacecraft, will give us detailed pictures of the fine structure of the Sun's surface. Currently anticipated instrumentation can reveal details a fifth as large as can be perceived (due to blurring by the Earth's atmosphere) from the ground. Spacecraft could be launched into trajectories that would carry them far out of the plane of the planetary orbits, so that they could look down over the poles of the Sun. Moving along these paths, the spacecraft could pass directly through the streams of solar wind that originate at the Sun's north and south poles. We would thus obtain our first information on the full three dimensional structure of the solar wind and the Sun's magnetic field.

To better study the Earth's magnetosphere and ionosphere, the next major advances will require measure ments made simultaneously by perhaps five different spacecraft located around the magnetosphere and in the solar wind just upstream from the Earth. With coordinated measurements like these we can accurately trace the changing motions of the magnetosphere and follow disturbances in the streams of solar particles as they travel through space around the Earth.

A basic new type of investigation will be possible with future large orbital laboratories such as Spacelab, which will be launched on the Space Shuttle. These laboratories will allow us to make active experiments in space, in contrast to the earlier passive measurements. By injecting known amounts of radio waves or atomic particles into space and observing how they travel away from the spacecraft, we can answer questions about space around the Earth in much the same way that Earthbound physicists determine physical conditions in laboratory vessels. The future missions will be logical extrapolation from previous space- and ground based studies of the Sun and the Earth's environment. We now know enough to frame the questions that we believe they will answer. These explorations will bring closer the day when our understanding of the phenomena around us is complete enough to tell how the entire Sun-Earth system works and how we can anticipate its future behavior.

Selected Readings

Akasofu, S.-I. 1979,
Aurora Borealis - The Amazing Northern Lights,
special issue of Alaska Geographic, 2, No. 6.

Eddy, J.A. 1979,
A New Sun - The Solar Resultsfrom Skylab
(Washington, D.C.: NASA), SP-404.

Eddy, J.A. (ed.) 1978,
The New Solar Physics
(Boulder, Colo.: Westview Press).

Fire ofLife: The Smithsonian Book of the Sun, 1981
(New York: W.W. Norton and Co.; Smithsonian Exposition Books).

Gibson, E. G. 1973,
The Quiet Sun
(Washington, D.C.: NASA), SP-303.

Herman, J. R. and R. A. Goldberg 1979,
Sun, Weather, and Climate
(Washington, D.C.: NASA), SP-426.