Probing Ida's magnetic personality.When the Galileo spacecraft spacecraft Vehicle designed to operate, with or without a crew, in a controlled flight pattern above Earth's lower atmosphere. Since streamlining is not needed in the high vacuum of this environment, a spacecraft's shape is designed according to its mission (see passed by the asteroid Ida on Aug. 28, it did more than capture close-up images of the rocky body (SN: 10/2/93, p.215). The craft's magnetometer detected several shifts in the direction of the solar wind's magnetic field near the asteroid. The solar wind solar wind, stream of ionized hydrogen—protons and electrons—with an 8% component of helium ions and trace amounts of heavier ions that radiates outward from the sun at high speeds. consists of a stream of charged particles charged particle n. An elementary particle, such as a proton or electron, with a positive or negative electric charge. blowing outward from the sun. Because several types of interactions between Ida and the solar wind could account for the switches in field direction, the data don't prove the asteroid possesses a magnetic field, cautions physicist Margaret Kivelson of the University of California, Los Angeles UCLA comprises the College of Letters and Science (the primary undergraduate college), seven professional schools, and five professional Health Science schools. Since 2001, UCLA has enrolled over 33,000 total students, and that number is steadily rising. . For instance, if the asteroid had sufficient electrical conductivity Not to be confused with electrical conductance, a measure of an object's or circuit's ability to conduct an electric current between two points, which is dependent on the electrical conductivity and the geometric dimensions of the conducting object. , it could generate a current that might disturb the solar wind and alter its magnetic field. Kivelson says that one of the Galileo findings in particular suprised her. Galileo detected a shift in the winds's magnetic field just before the craft's closet approach to Ida. She and her colleagues had modeled the solar wind and its magnetic field as a river flowing swiftly through space. The team reasoned that when the river meets an obstacle such as Ida, it drapes drape v. draped, drap·ing, drapes v.tr. 1. To cover, dress, or hang with or as if with cloth in loose folds: draped the coffin with a flag; a robe that draped her figure. around it, creating a disturbance "downstream" from the rocky body. Indeed, Kivelson notes, Galileo detected a downstream disturbance in the solar wind's magnetic field when the craft passed near the asteroid Gaspra two years ago. Kivelson suggests that the solar wind's magnetic field near Ida was more closely alligned with the direction of the solar wind than the magnetic field near Gaspra was. She says this could account for the upstream change in the field, which Galileo detected for the five minutes preceding the craft's closet approach to Ida and for a shorter period just after. The nature of the disturbance suggests that it was carried through the solar wind by a so-called whistler whistler: see marmot. See Windows XP. wave, which transmits higher frequences at a faster speed. In the case of tiny Gaspra, adds Kivelson, analysis has revealed that the area over which the solar wind's magnetic field changed direction was much larger than the asteroid's 14-kilometer diameter. These changes imply that Gaspra may have its own magnetic field. |
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