Satellite makes solar wind count.Like water from a spinning lawn sprinkler, electrically charged particles in the solar wind spiral outward from the sun's corona in continuous streams. Hydrogen and helium make up about 99.9 percent of the wind, with a medley of heavy elements filling in the rest. Now, measurements from the Solar and Heliospheric Observatory The Solar and Heliospheric Observatory (SOHO) is a spacecraft that was launched on an Atlas IIAS launch vehicle on 2 December 1995 to study the Sun, and began normal operations in May 1996. (SOHO Soho (sōhō`, sə–), district of Westminster, London, England, known for its continental restaurants. Once a fashionable quarter, it became popular among writers and artists in the 19th cent. ) satellite have provided the most detailed picture to date of these so-called minor elements, which carry major information about processes occurring in the sun's corona. Antoinette B. Galvin of the University of Maryland University of Maryland can refer to:
Scientists recognized some of the chemical isotopes from previous satellite observations of the solar wind, but CELIAS also detected many that had not been reported there before. These include isotopes of silicon Silicon (Si) has numerous known isotopes, with mass numbers ranging from 22 to 44. 28Si (the most abundant isotope, at 92.23%), 29Si (4.67%), and 30Si (3.1%) are stable; 32Si is a radioactive isotope produced by argon decay. , sulfur, calcium, chromium, iron, and nickel. Isotopes of neon Neon (Ne) Standard atomic mass: 20.1797(6) u Table nuclide symbol Z(p) N(n) isotopic mass (u) half-life nuclear spin representative isotopic composition (mole fraction) range of natural variation (mole fraction) and argon argon (är`gŏn) [Gr.,=inert], gaseous chemical element; symbol Ar; at. no. 18; at. wt. 39.948; m.p. −189.2°C;; b.p. −185.7°C;; density 1.784 grams per liter at STP; valence 0. were measured by SOHO but not by earlier satellites, although they had been detected in solar wind during the Apollo lunar landings more than 20 years ago, Galvin says. Compared to instruments on previous satellites, SOHO's mass spectrometer collects more particles and can distinguish more accurately between them. This power enables the scientists to see the detailed time distribution of isotopes. "Before, we'd just grossly average over days or months," Galvin says. "Now, we can do it on a time scale of hours, occasionally minutes, so we're getting structures we didn't see before. It's very new and exciting." The isotopes provide clues to where the solar wind originates, indicating how particles move to the corona from the sun's surface and the temperature in the corona, Galvin says. Right now, most of the solar wind is coming from coronal holes, or openings in the sun's magnetic field, but later in the year, the scientists expect coronal mass ejections (SN: 2/1/97, p. 68) to step up. "There will be a lot to show with time," Galvin says. |
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