| 11. |
- Alfvén, Hannes
(författare)
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Hubble expansion in a Euclidean framework
- 1979
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Ingår i: Astrophysics and Space Science. - : Kluwer Academic Publishers. - 0004-640X .- 1572-946X. ; 66:1, s. 23-37
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Tidskriftsartikel (refereegranskat)abstract
- There now seems to be strong evidence for a non-cosmological interpretation of the QSO redshift — in any case, so strong that it is of interest to investigate the consequences. The purpose of this paper is to construct a model of the Hubble expansion which is as far as possible from the conventional Big Bang model without coming in conflict with any well-established observational results (while introducing no new laws of physics). This leads to an essentially Euclidean metagalactic model (see Table I) with very little mass outside one-third or half of the Hubble radius. The total kinetic energy of the Hubble expansion need only to be about 5% of the rest mass energy.Present observations support backwards in time extrapolation of the Hubble expansion to a ‘minimum size galaxy’R m , which may have any value in 0Some of the conclusions based on the Big Bang hypothesis are criticized and in several cases alternative interpretations are suggested. A comparison between the Euclidean and the conventional models is given in Table III.
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| 12. |
- Alfvén, Hannes, et al.
(författare)
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Inter-stellar clouds and formation of stars
- 1978
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Ingår i: Astrophysics and Space Science. - : Springer Nature. - 0004-640X .- 1572-946X. ; 55:2, s. 487-509
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Tidskriftsartikel (refereegranskat)abstract
- Part I gives a survey of the drastic revision of cosmic plasma physics which is precipitated by the exploration of the magnetosphere throughin situ measurements. The ‘pseudo-plasma formalism’, which until now has almost completely dominated theoretical astrophysics, must be replaced by an experimentally based approach involving the introduction of a number of neglected plasma phenomena, such as electric double layers, critical velocity, and pinch effect. The general belief that star light is the main ionizer is shown to be doubtful; hydromagnetic conversion of gravitational and kinetic energy may often be much more important.In Part II the revised plasma physics is applied to dark clouds and star formation. Magnetic fields do not necessarily counteract the contraction of a cloud; they may just as well ‘pinch’ the cloud. Magnetic compression may be the main mechanism for forming interstellar clouds and keeping them together.Part III treats the formation of stars in a dusty cosmic plasma cloud. Star formation is due to an instability, but it is very unlikely that it has anything to do with the Jeans instability. A reasonable mechanism is that the sedimentation of ‘dust’ (including solid bodies of different size) is triggering off a gravitationally assisted accretion. A ‘stellesimal’ accretion analogous to the planetesimal accretion leads to the formation of a star surrounded by a very low density hollow in the cloud. Matter falling in from the cloud towards the star is the raw material for the formation of planets and satellites.The study of the evolution of a dark cloud leads to a scenario of planet formation which is reconcilable with the results obtained from studies based on solar system data. This means that the new approach to cosmical plasma physics discussed in Part I logically leads to a consistent picture of the evolution of dark clouds and the formation of solar systems.
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| 13. |
- Alfvén, Hannes
(författare)
-
Observations and cosmology
- 1979
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Ingår i: Chemiker-Zeitung. - : Dr. Alfred Hüthig Verlag, GMBH, Heidelberg. - 0009-2894. ; 103:10, s. 334-336
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 14. |
- Alfvén, Hannes
(författare)
-
Origin of cosmic magnetic-fields
- 1979
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Ingår i: Physics of the Earth and Planetary Interiors. - : Elsevier BV. - 0031-9201 .- 1872-7395. ; 20:2-4, s. 185-191
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Tidskriftsartikel (refereegranskat)abstract
- A summary is given of the reasons why an understanding of cosmic hydromagnetic phenomena is impossible without describing them explicitly by electric currents. This applies also to the production of cosmic magnetic fields. The purpose of the paper is to demonstrate that a simple translation from the traditional magnetic field description to a current description gives important new aspects of cosmical electrodynamics, including a new approach to the production of magnetic fields.One of the results is that the kink-instability of electric currents is found to be the basic physical phenomenon responsible for magnetic flux generation in cosmical physics. Laboratory plasma experiments demonstrate the existence of a simple mechanism for flux amplification, and it seems obvious that the same mechanism should work also under cosmical conditions.A simple model is discussed. We start from a poloidal magnetic field (which may be extremely weak). Differential motions change the field configuration which means that kinetic energy is transferred into magnetic energy of induced toroidal fields. The currents associated with these get unstable when the toroidal energy exceeds the poloidal energy resulting in an amplification of the original poloidal field.This simple process of transfer of kinetic energy into poloidal magnetic energy is probably the main mechanism for magnetic flux generation in low density cosmic plasmas. In view of the serious difficulties of planetary dynamo theories, attempts should be made to develop it into a theory of the magnetization of celestial bodies.
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| 15. |
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| 16. |
- Booth, R. S., et al.
(författare)
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High-resolution observations of quasars from the Parkes +/- 4 deg. sample
- 1979
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Ingår i: Monthly notices of the Royal Astronomical Society. - Oxford : Oxford University Press. - 0035-8711 .- 1365-2966. ; 188, s. 159-163
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Tidskriftsartikel (refereegranskat)abstract
- VLBI observations of 20 compact quasars have been made between Jodrell Bank and Onsala at a frequency of 1666 MHz. Twelve of the quasars have inverted or peaked spectra at centimetre wavelengths and these are all unresolved, having angular diameters of less than 0.015 arcsec. Two out of five quasars with overall flat spectra are partially resolved on this scale size, as are three steep-spectrum quasars.
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| 17. |
- Bååth, L.B. 1948-
(författare)
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Radiospår i galaxhopar
- 1973
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Ingår i: Astronomisk tidsskrift. - København/Oslo/Saltsjöbaden : Astronomisk Selskab/Norsk astronomisk selskap/Svenska astronomiska sällskapet. - 0004-6345. ; 6:1, s. 18-24
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 18. |
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| 19. |
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| 20. |
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