HR: 1340h
AN: SH33A-1188    [Abstracts]
TI: CME Shock and Sheath Structures Relevant to Particle Acceleration
AU: * Manchester, W B
EM: chipm@umich.edu
AF: Center for Space Environment Modeling, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109 United States
AU: Kota, J
EM: kota@lpl.arizona.edu
AF: Lunar and Planetary Laboratory, 1629 E. University Blvd., Tucson, Az 85721 United States
AU: Gombosi, T
EM: tamas@umich.edu
AF: Center for Space Environment Modeling, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109 United States
AU: Igor, S V
EM: igorsok@umich.edu
AF: Center for Space Environment Modeling, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109 United States
AU: Roussev, I
EM: iroussev@umich.edu
AF: Center for Space Environment Modeling, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109 United States
AU: De Zeeuw, D
EM: darrens@umich.edu
AF: Center for Space Environment Modeling, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109 United States
AU: Powell, K
EM: powell@engin.umich.edu
AF: Center for Space Environment Modeling, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109 United States
AU: Toth, G
EM: gtoth@grid.engin.umich.edu
AF: Center for Space Environment Modeling, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109 United States
AU: Toth, G
EM: gtoth@grid.engin.umich.edu
AF: Dept. of Atomic Physics, Eotvos University, Pazmany setany 1/A, Budapest, 1117 Hungary
AU: Zurbuchen, T
EM: thomasz@umich.eduj
AF: Dept. of Atmospheric Oceanic and Space Sciences, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109 United States
AB: Most high-energy solar energetic particles (SEPs) are believed to be accelerated at shock waves driven by coronal mass ejections (CMEs). The acceleration process strongly depends on the shock geometry, and the structure of the sheath that forms behind the shock. In an effort to understand the structure and time evolution of such CME-driven shocks and their relevance to particle acceleration, we investigate the interaction of a fast CME with the ambient solar wind by means of a three-dimensional (3-D) numerical ideal magnetohydrodynamics (MHD) model. Our global steady-state coronal model possesses high-latitude coronal holes and a helmet streamer structure with a current sheet near the equator, reminiscent of near solar minimum conditions. Fast and slow speed solar wind flow at high and low latitude respectively and the Archimedian spiral geometry of the interplanetary magnetic field is reproduced by solar rotation. Within this model system, we drive a CME to erupt by the introduction of a Gibson-Low magnetic flux rope that is embedded in the helmet streamer in an initial state of force imbalance. The flux rope rapidly expands and is ejected from the corona with maximum speeds in excess of 1000 km/s driving a fast-mode shock from the inner corona to a distance of 1 astronomical unit (AU). We find that the ambient solar wind structure strongly affects the evolution of the CME-driven shocks causing deviations of the of the fast-mode shocks from their expected global configuration. These deflections lead to substantial compressions of the plasma and magnetic field in their associated sheath region. The sudden post-shock increase in magnetic field strength on low latitude field lines is found to be effective for accelerating particles to the GeV range.
DE: 7513 Coronal mass ejections
DE: 7514 Energetic particles (2114)
DE: 7839 Nonlinear phenomena
DE: 7843 Numerical simulation studies
DE: 7851 Shock waves
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2004 AGU Fall Meeting