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: http://www.iki.rssi.ru/mirrors/stern/Education/wcosray.html
Дата изменения: Unknown Дата индексирования: Fri Dec 21 22:01:07 2007 Кодировка: |
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(Files in red–history) Index 28. Aurora Origin 28a. Plus and Minus 29. Low Polar Orbit 30. Magnetic Storms 30.a Chicago Aurora 31. Space Weather 32. Magnetic planets 33. Cosmic Rays 34. Energetic Particles 35. Solar fast Particles |
The Sun's plasma is much hotter, and that of the magnetosphere is hotter still. Auroral electrons typically have 1000 to 10,000 ev, as do protons in the magnetotail. Ring current protons have more, around 20,000 to 100,000 ev, while inner belt protons go higher still, typically 10,000,000 to 100,000,000 ev. In a nutshell, the magnetosphere is a high-energy environment, where speeds amounting to 1/10 the speed of light are not uncommon. How unusual is such an environment? How does the rest of the universe compare? Are the high-energy ions and electrons of the magnetosphere an exceptional and rare population? The unexpected answer is that even higher energies seem quite commonplace in the universe. One piece of evidence is a rain of fast ions constantly bombarding Earth, coming from distant space and much more energetic than any found in the magnetosphere. They are known as cosmic rays or cosmic radiation.
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Cosmic Rays and StarlightIndividually the cosmic ray ions are much faster and more energetic than those trapped in the Earth's field, though their overall density is rather small. The radiation is therefore not intense, giving us about as much energy as starlight. That does not sound like much, until one remembers what the stars are--distant suns, about a hundred billion of them traveling together in our galaxy, and untold billions in more distant galaxies. "As intense as starlight" seems to say that our galaxy gives about as much energy to exotic particles moving close to the speed of light, as it gives to the visible light of its billions of stars.Actually, the source of cosmic rays is probably not quite as intense, because cosmic ray particles can stay around the galaxy much longer than starlight. Starlight moves in straight lines, one pass through our galaxy and it is gone, into the great emptiness between galaxies. This may require (say) 5000- 50,000 years, going through a thickness of as many light years. Cosmic ray ions, on the other hand, may be trapped by weak magnetic fields in the galaxy--trapped not forever, because sooner or later they hit an atom of the rarefied gas which fills the void between stars, but for a period of the order of 10 million years. If cosmic ray ions stay around (on the average) 1000 times longer than starlight, their source only needs 1/1000 of the energy output of the stars to match the intensity of starlight. But even 1/1000 of the energy of starlight is still an enormous amount! If the Sun had invested 1/1000 of its energy input in cosmic radiation, the radiation level around it would have been sufficient to snuff out any life emerging on Earth.
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