The Relationship Between Plasma Density Structure and ULF Waves at
Geosynchronous Orbit

B.J. Fraser (On leave from CRC for Satellite Systems, University of Newcastle,
NSW 2308, Australia, NOAA/SEC, Boulder, CO 80305), H.J. Singer, M.L. Adrian,
and D. L. Gallagher

Recent IMAGE satellite EUV observations by Adrian et al (2003) have shown
bifurcated plasmaspheric density features that are possibly signatures of ULF
standing waves in the magnetosphere. Coincidentally, Pc5 ULF waves in the
1-5mHz band were observed on the ground by the IMAGE magnetometer array in
Scandinavia.  In order to further investigate this relationship high resolution
GOES geosynchronous orbit magnetometer data have been analysed for the presence
of ULF waves associated with 20 observed EUV radial He+ enhanced plasma
structures seen by the IMAGE satellite over 2001.  Two satellites are used,
GOES-8 at 75 degrees W and GOES-10 at 135 degrees W.  Pc5 waves seen have 
azimuthal wave numbers typically <10, indicating a wide azimuthal extent, and 
Pc3-5 harmonic structure is also seen on some occasions.  Not all EUV 
structures have associated ULF waves at synchronous orbit.  Event studies 
illustrating the various wave types seen in association with a variety of EUV 
plasma structures, including bifurcations, fingers and plumes, will be 
presented and placed in the context of  field line, compressional cavity or 
waveguide mode resonances.

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Presentation at the Yosemite Conference of Inner Magnetospheric Interactions,
3 - 6 February 2004, Yosemite, California, USA