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Detailed Reference Information |
Cahill, L.J., Sugiura, M., Lin, N.G., Arnoldy, R.L., Shawhan, S.D., Engebretson, M.J. and Ledley, B.G. (1984). Observation of an oscillating magnetic field shell at three locations. Journal of Geophysical Research 89: doi: 10.1029/JA089iA05p02735. issn: 0148-0227. |
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On July 14, 1982, 1830--1930 UT, a complex magnetic pulsation event was observed near the magnetic shell L~4.5 in the local afternoon. A large magnetic storm was in progress and had proceeded to the early recovery phase. The event began, at 1832 UT, with a sudden decrease in ‖B‖ and a brief, 120-s compressional pulsation. A transverse pulsation then developed with period near 180-s and amplitude about 5 nT. Near 1850 UT this pulsation decreased abruptly and was replaced by a 44-s transverse pulsation. By 1858 UT the 44-s pulsation was fading and a 240-s azimuthal pulsation developed rapidly. It slowly decreased in amplitude after 1910 UT and was gone by 1930 UT. The event was observed at the DE-1 satellite near the equator in both electric and magnetic field components and at the ground magnetic observatories Siple. Antarctica, and Roberval, Quebec, 15 to 30 west of DE-1 and at opposite ends of an L=4.2 field line. The 180-s and 240-s pulsations were fundamental, toroidal, resonant oscillations of a magnetic field shell. Since the first 180-s pulsation started and stopped simultaneously at all three locations and the corresponding magnetic pulsations remained in phase at all three locations, this is interpreted to be a large-scale toroidal oscillation of one resonant field shell. In the 240-s pulsation, DE-1 was on one resonant shell and the ground stations, oscillating at 220 a period, were on another lower L value shell. The 44 a pulsation, also transverse at DE-1, was weaker on the ground and poorly correlated with the DE-1 measurements, suggesting that it was more localized in azimuth. |
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Publisher
American Geophysical Union 2000 Florida Avenue N.W. Washington, D.C. 20009-1277 USA 1-202-462-6900 1-202-328-0566 service@agu.org |
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