Hannes Alfvén’s research while affiliated with KTH Royal Institute of Technology and other places

A theory of the origin and evolution of the Solar System (Alfvén and Arrhenius, 1975, 1976) which considered electromagnetic forces and plasma effects is revised in the light of new information supplied by space research. In situ measurements in the magnetospheres and solar wind have changed our views of basic properties of cosmic plasmas. These results can be extrapolated both outwards in space, to interstellar clouds, and backwards in time, to the formation of the solar system. The first extrapolation leads to a revision of some cloud properties which are essential for the early phases in the formation of stars and solar nebulae. The latter extrapolation makes possible to approach the cosmogonic processes by extrapolation of (rather) well-known magnetospheric phenomena. Pioneer-Voyager observations of the Saturnian rings indicate that essential parts of their structure are ‘fossils’ from cosmogonic times. By using detailed information from these space missions, it seems possible to reconstruct certain events 4–5 billion years ago with an accuracy of a few percent. This will cause a change in our views of the evolution of the solar system.

The use of in situ magnetospheric results in cosmology is discussed. Extrapolation of magnetospheric results makes it necessary to revise the evolutionary history of interstellar dust clouds and the formation of stars, including the Sun and the solar nebula, out of which our planetary system derived. The formation of planets and satellites can also be approached by an extrapolation backwards in time of magnetospheric results. A combination of these two methods makes it possible to reconstruct events 4 to 5 billion years ago with an accuracy of a few percent. This reconstruction is based on the Pioneer and Voyager measurements of the highly structurized Saturnian rings. These can be regarded as a time capsule which registered decisive processes leading to the formation of our solar system.

The paper is based on Holberg's analysis of the Voyager photographs in both reflected and transparent light, combined with occultation data of stars seen through the rings. Besides rapidly varying phenomena (spokes, braided ring, etc.), which according to Mendis are due to gravito-electromagnetic effects, the ring consists of abulk structure, a fine structure, and also ahyperfine structure, showing more than 10000 ringlets. The large number of ringlets can be explained by the Baxter-Thompson ‘negative diffusion’. This gives the ringlets a stability which makes it possible to interprete them as ‘fossils’, which originated at cosmogonic times. It is shown that thebulk structure can be explained by the combined ‘cosmogonic shadows’ of Mimas, the co-orbiting satellites, and the Shepherd satellites. This structure originated at the transition from the plasma phase to the planetesimal phase (which probably took place 4–5×109 y ago). Further, Holberg has discovered that the shadows are not simple void region but exhibit a certain characteristic ‘signature’. This is not yet understood theoretically. Parts of thefine structure are explained by Holberg as resonances with the satellites. Parts are here interpreted as cosmogonic shadow effects. However, there are a number of ringlets which can neither be explained by cosmogonic nor by resonance effects. The most important conclusion is that an analysis of the ring data is likely to lead to areconstruction of the plasma-planetesimal transition with an accuracy of a few percent.

Progress in laboratory studies of plasmas and in the methods of transferring the results to cosmic conditions, together within situ measurements in the magnetospheres, are now causing a ‘paradigm transition’ in cosmic plasma physics. This involves an introduction ofinhomogeneous models with double layers, filaments, ‘cell walls’, etc. Independently, it has been discovered that the mass distribution in the universe is highly inhomogeneous; indeed,hierarchical. According to de Vaucouleurs, the escape velocity of cosmic structures is 102–103 times below the Laplace-Schwarzschild limit, leaving avoid region which is identified as a key problem in cosmology. It is shown that a plasma instability in the dispersed medium of the structures may produce this void and, hence, explain the hierarchical structure. The energy which is necessary may derive either from gravitation or from annihilation caused by a breakdown of cell walls. The latter alternative is discussed in detail. It leads to a ‘Fireworks Model’ of the evolution of the metagalaxy. It is questioned whether the homogeneous four-dimensional big bang model can survive in an universe which is inhomogeneous and three-dimensional.

The Voyager 1 and 2 observations of the fine structure of the Saturnian ring system demonstrate the importance of electric forces in controlling the dynamics of fine (charged) dust in the rings. A new theory (“gravito-electrodynamics”) which combines the electric and the gravitational forces on these grains leads to natural explanations of a number of observed ring phenomena. If plasma processes play a significant role in the dynamics of the ring system at the present time, it is difficult to avoid the conclusion that they also played an important and perhaps crucial role at cosmogonic times during the emplacement and subsequent condensation of the initial dusty plasma. We believe that the Saturnian ring system represents a “time-capsule” containing vital clues about the physical processes operating during the early stages of its formation. We will show that both its overall structure as well as its fine structure, as determined by Voyagers 1 and 2, indicate the crucial importance of plasma processes in its formation and subsequent evolution.

In situ measurements in the magnetospheres together with general advancement in plasma physics are now necessitating introduction of a number of effects that have been recently discovered or earlier neglected. Examples are: ? Electric double layers (like in the lower magnetosphere); ? Thin current layer (like in the magnetopause) giving space a cellular structure; ? Current produced filaments (e.g., in prominences, solar corona and interstellar clouds). ? Further it is important to use the electric current (particle) description and to study the whole circuit in which the current flows. ? The pinch effect cannot be neglected as is now usually done. ? The critical velocity phenomenon is essential, for example for the band structure of solar system. ? Theory of dusty plasmas is important. The result is a change in so many theories in cosmic plasma physics that it is appropriate to speak of an introduction of a new paradigm. This should be based on empirical knowledge from magnetospheric and laboratory investigations. Its application to astrophysics in general, including cosmology, will necessarily lead to a revision of, e.g., the present theories of the formation of stars, planets and satellites. It is doubtful whether the big bang cosmology will survive.

In situ measurements in the magnetospheres together with general advancement in plasma physics are now necessitating introduction of a number of effects that have been recently discovered or earlier neglected. Examples are: Electric double layers (like in the lower magnetosphere); Thin current layer (like in the magnetopause) giving space a cellular structure; Current produced filaments (e.g., in prominences, solar corona and interstellar clouds). Further it is important to use the electric current (particle) description and to study the whole circuit in which the current flows. The pinch effect cannot be neglected as is now usually done. The critical velocity phenomenon is essential, for example for the band structure of solar system. Theory of dusty plasmas is important. The result is a change in so many theories in cosmic plasma physics that it is appropriate to speak of an introduction of a new paradigm. This should be based on empirical knowledge from magnetospheric and laboratory investigations. Its application to astrophysics in general, including cosmology, will necessarily lead to a revision of, e.g., the present theories of the formation of stars, planets and satellites. It is doubtful whether the big bang cosmology will survive.

As the theory of the origin and evolution of the solar system should constitute the general background for the science of planetary interiors, I give a summary of some of the main problems in this field of research.Space research, especially measurements in the magnetospheres (including helisophere) and ionospheres, has drastically changed our understanding of the properties of space plasmas in the density region 105–1020 particles/m3 and magnetization region 10−10–10−5wb/m2. This gives us a better understanding of the early processes leading to the formation of the solar system in the following respects. Electromagnetic forces were of decisive importance. The clouds may have been formed out of diffuse interstellar matter by (“pinch effect”). Their evolution is treated by the theory of highly inhomogeneous dusty plasmas, penetrated by a network of electric currents. Contrast-enhanced pictures of interstellar clouds support this scenario. From observations of particle ejection from the sun, we know that in plasmas of comparable densities a takes place, resulting in regions with He or the CNO elements or the heavy elements dominating (or strongly enhanced). Similar processes should take place in interstellar clouds and give similar results. This is basic for our understanding of chemical differences between the celestial bodies in the solar system. Next phase in the evolution is the falling in of chemically differentiated gas clouds and dust towards the primeval sun. (This process is later reproduced in a smaller scale around the giant planets). This leads to the accumulation of matter in certain bands, which explains the of the solar system. Laboratory experiments and the theory of the critical velocity are now giving increased understanding of this process. These fall within the bands where matter should be accumulated, thus confirming the importance of the band structure. The Uranus ring was explicitly predicted. measurements of the auroral current system and the Io-Jupiter circuit makes it possible to base the theory of transfer of angular momentum on present-day phenomena, which can be extrapolated to cosmogonic conditions. The two-third fall down law at the condensation is supported. The study of the Io torus provides information on the dynamics of particles, which is important for the understanding of the jet stream formation and evolution. Objections against the jet stream concept are partially correct, but can be removed if the early azimuth independent jet stream model is changed into an inhomogeneous model, similar to the observed Io torus. The resulting differences in planetary structure and composition (which are the subject of this workshop) are discussed. The terrestrial planets should be formed largely from the dust content of the primeval cloud captured in the innermost cloud.

The agreement to within a few percent between the theoretically predicted cosmogonic shadow effect and observations of large scale structures of the Saturnian rings and the asteroidal region is discussed. Although the theory has to be modified, its observationally confirmed core remains valid. A transformation from the fixed coordinate system to a system which corotates with the plasma shows that in the latter system the orbits of the condensed particles contain a number of cusps where the condensed material is focused and stays for a comparatively long time. As a result, radiative cooling decreases the temperature, possibly by one or several orders of magnitude. This makes the cusps form small cold high density regions in a plasma, the major part of which is hot and dilute.

The cosmogonic shadow effect is described, considering charged particles (electrons, ions, charged dust) in an axisymmetric dipole field around a gravitating, rotating body. The medium is two-thirds supported by centrifugal force and one-third by electromagnetic forces under the condition that the magnetic field is strong enough to control the motion. If the electromagnetic forces disappear, e.g., by deionization of the dusty plasma, the medium contracts to two-thirds its original central distance. The Voyager 1 Saturn results demonstrate that the macrostructure of the Saturnian ring system can be explained as a result of this effect at the formation of the system. A similar analysis of the asteroidal belt shows that its macrostructure can also be explained by the cosmogonic shadow effect. The observational results show that during their formation both the Saturnian rings and the asteroidal belt passed a plasma state dominated by electromagnetic effects.