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ULF Waves in the Low-Latitude Boundary LAyer and Their Relationship to Magnetospheric Pulsations: A Multisatellite Observation
AEROSPACE CORP EL SEGUNDO CA ENGINEERING AND TECHNOLOGY GROUP
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On April 30 day 120, 1985, the magnetosphere was compressed at 0923 UT and the subsolar magnetopause remained near 7 RE geocentric for approx. 2 hours, during which the four spacecraft Spacecraft Charging At High Altitude SCATHA, GOES 5, GOES 6, and Active Magnetospheric Particle Tracer Explorers AMPTE CCE were all in the magnetosphere on the morning side. SCATHA was in the low-latitude boundary layer LLBL in the second half of this period. The interplanetary magnetic field was inferred to be northward from the characteristics of precipitating particle fluxes as observed by the low-altitude satellite Defense Meteorological Satellite Program DMSP F7 and also from absence of substorms. We used magnetic field and particle data from this unique interval to study ULF waves in the LLBL and their relationship to magnetic pulsations in the magnetosphere. The LLBL was identified from the properties of particles, including bidirectional field-aligned electron beams at approx. 200 eV. In the boundary layer the magnetic field exhibited both a 5-10 min irregular compressional oscillation and a broadband Deltaff approx. 1 primarily transverse oscillations with a mean period of approx. 50 s and a left-hand sense of polarization about the mean field. The former can be observed by other satellites and is likely due to pressure variations in the solar wind, while the latter is likely due to a Kelvin-Helmoltz K.-H. instability occurring in the LLBL or on the magnetopause.
APPROVED FOR PUBLIC RELEASE