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View Full Version : Discussion: Sun's Flip is Letting the Dust In



Fraser
2003-Aug-20, 04:35 PM
SUMMARY: The European Space Agency's Ulysses spacecraft has confirmed that the Sun's 11-year cycle that causes it to switch magnetic poles allows interstellar dust to enter our Solar System in greater quantities. The Sun normally puts a protective magnetic bubble around the solar system to push dust around us, but during this pole-switch, the bubble disappears for a little while. Astronomers believe this will increase the amount of material that falls on the Earth to 40,000 tonnes of dust a day - it won't really cause a problem; however, we may be able to see some more faint falling stars.


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sky-high
2003-Aug-21, 02:05 PM
Interesting. That dust doesn't bother me much, frankly, I hope we are speaking in scientific terms and "dust" means almost microscopical particles. Our dear atmosphere, banged and full of ozone holes as it may be, still does a good job in burning out much larger meteors, and, sometimes, dramatically, even unfortunate spaceships.
What does bother me, is the perspective of getting more cosmic radiation (remeber those gamma sources recently discovered, alledgedly THE most powerfull in the Universe ?), since the magnetic field of the Sun is weaker, in this binge year of his. What I'd like to know (and please consider that a question) is: would Earth's magnetic field be strong enough to protect us from cosmic radiation? Would that result in just making Van Allen belts "shinier" ? Or this means we'll really gonna get it this time ?
And another question: the normally available detection devices (Geiger counters) are sensitive enough, or properly tuned to measure cosmic radiation too? Or are they good only for atomic radioactivity< period ?

Regards Sky-High

Markus Landgraf
2003-Aug-22, 09:11 AM
About the deflection of cosmic rays by the solar magnetic field: Yes, the Sun protects us from (at least a part) of galactic cosmic rays. That&#39; independent of the solar cycle. During solar max the field strength is equal the field strength during solar min. However, the *polarity* is highly disordered, which means that cosmic rays as well as dust grains "see" positive polarity for a couple of days and then negative polarity for another couple of days. Because dust grains, though light-wight from our point of view, are super massive compared to cosmic rays, they react only to an average magnetic field. If positive and negative polarity acts about equal time on the dust grains, they do not change their path at all. Cosmic rays react to the magnetic field within minutes, so they are kept at bay also by the disordered magnetic field of the Sun during solar max conditions. That&#39;s what we found with Ulysses.