Comparison between Global MHD Simulations and Simultaneous CLUSTER and IMAGE
Observations of Dayside Auroral Proton Precipitation

J. Berchem, J.M. Bosqued, H.U. Frey, and C.P. Escoubet


Simultaneous observations from the IMAGE and CLUSTER spacecraft provide a
unique opportunity to test the progress of the global modeling of the complex
topology and dynamics of the dayside magnetopause. In particular,
observations of ion precipitation allow investigating the response of the
dayside magnetosphere to transient interplanetary disturbances. We report a
comparison of simultaneous observations of proton auroras from the IMAGE FUV
instrument and ion dispersions measured by CLUSTER CIS with the results from
three-dimensional magnetohydrodynamic (MHD) simulations. The study focuses on
the effects of solar wind pressure pulses and the occurrence of magnetic
reconnection on spatial and temporal structures observed in the
magnetospheric cusps. Using plasma and magnetic field parameters measured
upstream of the bow shock as input to the simulations, we discuss the IMAGE
and CLUSTER observations in the context of the dayside magnetosphere's
topological changes and plasma flows inferred from the simulation results.

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Presented at the Magnetospheric Imaging Workshop, 
Yosemite National Park, California, U.S.A., Feb. 9 - 13, 2003.