Determining the Plasmapause boundary with ULF Pulsations using High to Low
Latitude Ground-based Magnetometers

Weygand, J. M., M. B. Moldwin, D. Berube, M. J. Engebretson, H. K. Rassoul

A number of ULF pulsation events were identified during 2000. These events
occurred on the dayside and nightside of the magnetosphere and have
frequencies consistent with previous IMF correlations. We have performed a
comparison of the phase difference of ULF pulsations with the CANOPUS as
well as the MEASURE and MACCS magnetometer arrays, both of which employ GPS
timing. The results suggest that most the pulsations first arrive at low L
values (L of approximately 1.7) except at the boundary of the plasmasphere.
However, some cases appear to show no phase difference within the one
second precision of the measurements. This study will focus on the Chi et
al. [2000] model of the magnetosphere, magnetoseismology,  and the theory
that magnetic upstream waves cross the magnetopause directly into the
magnetosphere. The results from this study will be compared to IMAGE EUV
estimated plasmapause locations.

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To be presented at the Magnetospheric Imaging Workshop, 
Yosemite National Park, California, U.S.A., Feb. 5-8, 2002.