HR: 08:00h
AN: SM51A-01    [PDF]
TI: Determining the Origin of Structures Observed in Cusp Ion Dispersions: A Case Study Using Global Simulations and Simultaneous CLUSTER and IMAGE Observations
AU: * Berchem, J
EM: jberchem@igpp.ucla.edu
AF: IGPP, UCLA, Los Angeles, CA 90095-1567 United States
AU: Peroomian, V
AF: IGPP, UCLA, Los Angeles, CA 90095-1567 United States
AU: Bosqued, J
AF: CESR, CNRS, Toulouse, 31000 France
AU: Frey, H
AF: SSL, UCB, Berkeley, CA 94720-7450 United States
AU: Escoubet, C
AF: ESTEC, ESA, Noordwijk, AG 2200 Netherlands
AB: Gaining an understanding of how structures in ion precipitation observed in the cusp are related to the complex topology of the dayside magnetosphere is an important step toward describing the merging processes occurring at the magnetospheric boundary. We report results from a study that employs three-dimensional magnetohydrodynamic and large-scale kinetic simulations in conjunction with simultaneous observations of proton auroras from the IMAGE FUV instrument and ion dispersions measured by CLUSTER CIS. The primary goal of the study is to determine the origin of the multiple structures in the ion dispersions observed in the cusp by CLUSTER on July 14, 2001. Using plasma and magnetic field parameters measured upstream of the bow shock by the ACE spacecraft as input to the simulations, we consider the IMAGE and CLUSTER observations in the context of topological changes and particle trajectories in the dayside magnetosphere, as inferred from the simulations. Results from the simulations indicate that, during periods of predominantly By IMF, merging occurs in two steps: first a merging of unconnected magnetosheath and closed-field lines sunward of the terminator, and then of northern and southern open field lines in the low latitude flanks, tailward of the terminator. The simulations suggest that this two-stage reconnection process could bring about the formation of the large-scale ion dispersion structures in the cusp observed during periods that appear uncorrelated to any obvious changes in IMF direction or dynamic pressure in the upstream solar wind.
DE: 2704 Auroral phenomena (2407)
DE: 2716 Energetic particles, precipitating
DE: 2724 Magnetopause, cusp, and boundary layers
DE: 2740 Magnetospheric configuration and dynamics
DE: 2753 Numerical modeling
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting