lalonde ha scritto:
Visto che siamo ripariti dall inizio cito ancora Hannes Alfvén e poi chiudo visto che non mi è rimasto più nulla da dire:

Citazione:

The results of our experiments lead to an entirely new way of looking at the behavior of stellar matter. It has always been assumed that the movement of gases in stars obeys the laws of hydrodynamics, as they apply to ordinary liquids and gases. But if a magnetic field drastically changes the properties of the dense stellar gases as it does in the mercury model, then they must behave very differently from ordinary fluids. Let us see whether the curious behavior of mercury in a magnetic field can shed any light on some of the great mysteries in astronomy.

Consider sunspots. Few astronomical phenomena have been more thoroughly studied. We have charted their paths across the sun's surface, discovered their cycle of activity and their effects on solar radiation, analyzed their light and learned from the splitting of their spectral lines (the so-called Zeeman effect) that they have strong magnetic fields. But what sunspots are, how they originate, how they can produce magnetic fields -- that seems more difficult to explain. It was once thought that sunspots were great eddies in the solar atmosphere, similar to cyclones on the earth. The motions of gas in sunspots, however, are not at all like those of the air in cyclones.

The pieces of the puzzle begin to fall into place if we think of the mercury model. We can assume that the energetic nuclear reactions in the interior of the sun cause violent motions of the matter there. This would correspond to the stirring of the mercury at the bottom of the vessel.In the sun's general magnetic field, whose lines of force apparently run from the center of the sun out to the surface, these motions would generate magnetohydrodynamic waves that would travel to the surface. The waves would account for the strong magnetic fields associated with sunspots .

As we have seen, magnetohydrodynamic waves also generate an electric field. This may well account for some of the other phenomena observed on the sun's surface. The very high voltages generated by the waves may discharge into the sun's atmosphere, very much as a discharge tube in the laboratory produces corona discharges into the air. Such discharges would explain the solar prominences. The marvelous motion pictures of solar prominences taken at Pic du Midi in the Pyrenees and at the High Altitude Observatory near Climax, Col., give a vivid impression that they are electrical discharges.

The sun's emission of radio noise, another great mystery, would also be accounted for by this method of generating electricity. As radio listeners know too well, all sorts of electric currents -- in transmission lines, household appliances and so on -- produce radio noise. The large electric currents generated in stars by magnetohydrodynamic forces would give rise to radio waves and broadcast them into space.

Finally, the magnetohydrodynamic process seems to offer a plausible explanation for the great energy of the cosmic rays. How these particles are driven to their fantastic energies, sometimes as high as a million billion electron volts, is one of the prime puzzles of astronomy. No known (or even unknown) nuclear reaction could account for the firing of particles with such energies; even the complete annihilation of a proton would not yield more than a billion electron volts.

But if we suppose that the cosmic-ray particles are driven by electric and magnetic fields in space, in the same way as we accelerate particles in our big laboratory accelerators, it is easy to see how they could reach very high energies indeed. We know that interstellar space is not absolutely void. Although the matter in it is very thin, certainly not more than an average of one atom per cubic centimeter, in the vastness of the universe it adds up to an enormous amount of material. In at least some regions the interstellar matter is ionized, so that it is a good electrical conductor. Furthermore, there are good arguments for assuming that a weak magnetic field (some millions of a gauss) pervades all of space. It is likely, therefore, that magnetohydrodynamic waves roam ceaselessly througlr space, generating weak but very extensive electric fields, especially near the stars. If so, we can picture charged atomic nuclei being propelled across electrified space, gathering speed as they go and crashing into the earth's atmosphere with energies far beyond any that could ever be generated within any star or planet.