| 1. |
- Alfvén, Hannes
(författare)
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On hierarchical cosmology
- 1983
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Ingår i: Astrophysics and Space Science. - : Kluwer Academic Publishers. - 0004-640X .- 1572-946X. ; 89:2, s. 313-324
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Alfvén, Hannes
(författare)
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Solar-system history as recorded in the Saturnian ring structure
- 1983
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Ingår i: Astrophysics and Space Science. - : Kluwer Academic Publishers. - 0004-640X .- 1572-946X. ; 97:1, s. 79-94
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 3. |
- Alfvén, Hannes
(författare)
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The Voyager-1 - Saturn encounter and the cosmogonic shadow effect
- 1981
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Ingår i: Astrophysics and Space Science. - : Kluwer Academic Publishers. - 0004-640X .- 1572-946X. ; 79:2, s. 491-505
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Tidskriftsartikel (refereegranskat)abstract
- If an electrically conducting medium (e.g. a dusty plasma) rotates around a gravitating central body, which possesses an axisymmetric dipole field, the medium is supported to two-thirds by the centrifugal force and to one-third by electromagnetic forces under the condition that the magnetic field is strong enough to controll the motion. If the electromagnetic forces disappear — e.g. by a de-ionisation of the dusty plasma — the medium will fall down to two-thirds of its original central distance. The result of this process will be a ‘cosmogonic shadow effect’ which is described in some detail.The Voyager 1/Saturn results demonstrate that the macro-structure of the Saturnian ring system can be explained as a result of this effect working at the formation of the system. The agreement between the theoretical results and the observations is better than a few percent.A similar analysis of the asteroidal belt shows that its macro-structure can also be explained by the cosmogonic shadow effect. The agreement between theory and observations is perhaps even better than in the Saturnian ring system.The observational results demonstrate that during their formation both the Saturnian ring and the asteroidal belt passed a plasma state dominated by electromagnetic effects.
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| 4. |
- Carlqvist, Per, et al.
(författare)
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Energy source of the solar wind
- 1980
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Ingår i: Astrophysics and Space Science. - : D. Reidel Publishing Co. - 0004-640X .- 1572-946X. ; 71:1, s. 203-209
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Tidskriftsartikel (refereegranskat)abstract
- A direct transfer of energy from photospheric activity to the solar wind by means of electric currents is discussed. Currents are assumed to flow in quiescent prominences which occasionally erupt and give rise to expanding loop-like structures in the corona, as observed from Skylab. Due to expansion, the legs of the loops are transformed into coronal rays which carry currents from the photosphere to the outer parts of the corona or interplanetary medium and then back again to the photosphere. It is proposed that energy is transferred from photospheric activity to the solar wind in the following ways: (1) as kinetic energy of the ejected loop matter; (2) as electric power directly fed into the extended loops; and (3) as torsional waves produced by fluctuations in the loop currents.
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| 5. |
- Whipple Jr., E. C., et al.
(författare)
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A 3-ring circuit model of the magnetosphere
- 1981
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Ingår i: Astrophysics and Space Science. - : D. Reidel Publishing Co. - 0004-640X .- 1572-946X. ; 76:1, s. 35-47
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Tidskriftsartikel (refereegranskat)abstract
- We have modeled the magnetosphere by superimposing a dipole field, a uniform field and a perturbation field due to a simple current system. This current system consists of a ring current in the neutral line of the dipole plus uniform fields, together with vertical currents representing field-aligned currents to the neutral line. The current circuit is closed by two additional ring currents above and below the equatorial plane representing distributed adiabatic perpendicular currents. This system produces many magnetospheric features including a magnetopause, bending of magnetic field lines in the anti-solar direction, a magnetotail, and cusps on the day-side of the Earth. Our aim is to demonstrate that it is not necessary to think of the magnetic field topology as being caused by the flowing plasma carrying field lines. The fundamental physical problem is to derive the current system from the self-consistent interaction of the solar-wind and magnetospheric plasmas and fields.
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