Long-Period Oscillation Activity in the Morning Sector during Northward IMF

Chao-Song HUANG, George SOFKO, Sasha KOUSTOV, John MacDOUGALL*, Dieter ANDRE
Univ. of Saskatchewan, Canada, *On sabbatical leave from University of Western Ontario, Canada
W. J. HUGHES
Boston University, USA
V. O. PAPITASHVILI
University of Michigan, USA

During extended periods of northward IMF when the magnetosphere is expected to be very quiet, radar and magnetometer measurements have revealed ionospheric disturbances with a period in the range of about 40 - 55 minutes, at latitudes from 70 - 80 degrees. Two examples will be discussed. In the first, on Dec.08/97, the high-latitude magnetometer oscillations were followed by lower-latitude gravity wave oscillations of the same period. In the second, on Nov. 11/98, the long-period pulsations were seen most clearly in the Iceland West range-time velocity plots, and the large-scale convection pattern in the post-midnight/dawn sector showed the periodic changes. The oscillations will be discussed in terms of recent MHD models of the closed magnetosphere during such extended Bz+ conditions.

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