HR: 15:10h
AN: SM53C-07    [Abstracts]
TI: Using global MHD simulations in conjunction with spacecraft observations to determine the large-scale topology of dayside merging
AU: * Berchem, J
EM: jberchem@igpp.ucla.edu
AF: IGPP, UCLA, Los Angeles, CA 90095 United States
AU: Bosqued, J M
EM: jean-michel.bosqued@cesr.fr
AF: CESR, CNRS, Toulouse, 31028 France
AU: Frey, H U
EM: hfrey@ssl.berkeley.edu
AF: SSL, UCB, Berkeley, CA 94720 United States
AU: Fuselier, S A
EM: stephen.a.fuselier@lmco.com
AF: Lockheed, Martin, Palo Alto, CA 94304 United States
AU: Escoubet, C P
EM: philippe.Escoubet@esa.int
AF: ESTEC, ESA, Noordwijk, 2200 AG Netherlands
AB: We report results from a study that employs three-dimensional magnetohydrodynamic (MHD) in conjunction with ion measurements from POLAR TIMAS and CLUSTER CIS experiments, and images of proton auroras from the IMAGE FUV instrument. Using plasma and magnetic field parameters measured upstream of the bow shock by the ACE spacecraft as input to the simulations, we consider the spacecraft observations in the context of the global topology of the merging as inferred from the simulations. Results indicate that the locations of the merging sites, though distorted, are mostly consistent with merging patterns predicted by the antiparallel merging model. The simulations also indicate that merging occurring at locations inconsistent with the model's predictions can often be explained by multiple merging processes. Such situations occur predominantly when the IMF is northward and has a significant By component. The simulations suggest that during these conditions, merging of the IMF with the Earth field can occur in several steps: first the merging of unconnected magnetosheath with closed field lines in regions expected from the model and then the merging of newly open field lines with either closed field lines or older open field lines in regions depending on the dynamics of the magnetosheath field. The results of the study emphasize the importance of the time evolution of the draping of the magnetosheath field in the global merging process.
DE: 7835 Magnetic reconnection
DE: 7843 Numerical simulation studies
DE: 2724 Magnetopause, cusp, and boundary layers
DE: 2753 Numerical modeling
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting