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Eos, Transactions American Geophysical Union

Magnetospheric research and the history of the solar system

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Abstract

Instruments in space make it now possible to observe our cosmic environment not only in the visual and radio wavelengths but also in the infrared, ultraviolet X ray and γ ray parts of the electromagnetic spectrum. This reveals that quite a few of the generally accepted astrophysical concepts can no longer be valid. But, in order to understand what we see, it is essential to clarify what laws of physics govern the cosmic phenomena. As (at least by volume) more than 99.99% of the universe consists of plasma, plasma physics is essential. Another and at least as important a change in our basic astrophysical concepts is due to the in situ measurements in the magnetospheres of the planets. These have demonstrated that cosmic plasmas have properties drastically different from those that were rather generally accepted as late as 5 or 10 years ago. These latter were based on the classical theory of plasmas (by Chapman and Cowling and others) which was admirable from a mathematical point of view but unfortunately did not agree very well with experiments and observations. Measurements in the laboratory and in situ measurements by spacecraft have shown that plasma physics must be considered more as an empirical than a purely mathematical science [Alfven, 1981, chap. I and IV, 1982]. In the following we shall follow an essentially empirical approach to certain important astrophysical problems.

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