AAS 204th Meeting, June 2004
Session 67 Solar Input to the Heliosphere
SPD Topical Session, Wednesday, June 2, 2004, 2:30-4:00pm, 4:15-6:00pm, 704/706

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[67.04] A Numerical Model of CME Initiation and Shock Development for the 1998 May 2 Event: Implications for the Acceleration of GeV Protons

I. I. Roussev, I. V. Sokolov (CSEM, University of Michigan), T. G. Forbes (Department of Physics & Institute for the Study of Earth, Ocean, & Space, University of New Hampshire), T. I. Gombosi (CSEM, University of Michigan), M. A. Lee (Department of Physics & Institute for the Study of Earth, Ocean, & Space, University of New Hampshire)

We present modeling results on the initiation and evolution of the coronal mass ejection which occurred on 1998 May 2 in NOAA AR8210. This is done within the framework of a global model of the solar magnetic field as it was observed by the Wilcox Solar Observatory. Our calculations are fully three-dimensional and involve compressible magnetohydrodynamics. We begin by first producing a steady-state solar wind for Carrington Rotation 1935/6. The solar eruption is initiated by slowly evolving the boundary conditions until a critical point is reached where the configuration loses mechanical equilibrium. As this point, the field erupts, and a flux rope is ejected away from the Sun, reaching a maximum speed in excess of 1,000 km/s. The shock that forms in front of the rope reaches a fast-mode Mach number in excess of 4 and a compression ratio greater than 3 by the time it has traveled a distance of 5 solar radii from the surface. Thus, by constructing a fully three-dimensional numerical model, which incorporates magnetic field data and a loss-of-equilibrium mechanism, we have been able to demonstrate that a shock can develop close to the Sun sufficiently strong to account for the energization of solar particles. For this event, diffusive-shock-acceleration theory predicts a distribution of solar energetic protons with a cut-off energy of about 10 GeV.

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