Ulysses finds surprise at sun's south pole.A funny thing happened to the Ulysses spacecraft during its recent sojourn below the sun's south pole South Pole, southern end of the earth's axis, lat. 90° S. It is distinguished from the south magnetic pole. The South Pole was reached by Roald Amundsen, a Norwegian explorer, in 1911. See Antarctica. . Contrary to expectations, the craft saw no signs of a magnetic south pole. Instead, it found that the magnetic field high above the solar surface has about the same intensity at the poles as at the equator. That finding puzzles scientists, who liken lik·en tr.v. lik·ened, lik·en·ing, lik·ens To see, mention, or show as similar; compare. [Middle English liknen, from like, similar; see like2 the sun's magnetic field to that of a bar magnet. Iron filings Iron filings are very small pieces of iron that look like a dark powder. They are very often used in magnetism demonstrations, to show magnetic lines. Since iron is a magnetic material, it will align itself with the magnetic lines of a magnet in the same way a compass will align sprinkled around a bar magnet reveal that the magnetic lines of force magnetic lines of force pl.n. Curved lines used to represent a magnetic field, drawn such that the number of lines is related to the strength of the magnetic field at a given point and the tangent of any curve at a particular point is along the loop from one end of the bar to the other and are densest, or strongest, at each end. Researchers believe that, in a similar fashion, the looping magnetic field lines of the sun have the highest intensity at the poles. In fact, observations from Earth indicate that at the solar surface, the outward, or radial component of the magnetic field is strongest in the polar regions polar regions: see Antarctica; Arctic, the. . But Ulysses, the first craft to pass over the sun's poles, never ventures closer than about twice the Earthsun distance (SN: 8/6/94, p.93). Flying through the solar wind, the stream of charged particles blowing out from the sun, the craft found that the intensity of the radial component of the magnetic field remains the same regardless of latitude. At the craft's distance from the solar surface, "the solar wind no longer retains memory of the magnetic field rooted at the surface of the sun," says Richard G. Marsden, Ulysses project scientist for the European Space Agency European Space Agency (ESA), multinational agency dedicated to the promotion, for exclusively peaceful purposes, of cooperation among European states in space research and technology. in Noordwijk, the Netherlands. He suggests that the corona, or hot outer atmosphere of the sun, somehow redistributes the magnetic field. As a result, Ulysses finds a much more diffuse field at the south pole. Researchers now expect to see a similar pattern above the sun's north pole, which Ulysses will explore for 4 months, beginning next June. |
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