1. Taiyou Zasshikai on May 17, 2004
A Numerical Model of a Coronal Mass Ejection: Shock Development with Implications for the Acceleration of GeV Protons
Roussev, I.I., Sokolov, I.V., Forbes, T.G., Gombosi, T.I., Lee, M.A. and Sakai J.I.
ApJ, 2004, 605, 73L
Taiyou Zasshikai on May 17, 2004
Daikou Shiota

2. Introduction Coronal mass ejection (CME)
Solar energetic particle (SEP) events
High energy protons (100MeV) are particularly important
Major hazard for spacecraft
It has been proposed (e.g., Lee 1997; Reames 1999) these particles are produced by a Fermi process (type A) at a shock in front of the CME (close to the Sun ~10Rsun).
However, whether or not such a process is actually feasible has remained uncertain (Tsurutani 2003), because of the lack of knowledge about strength and location of the shock.

3. Initial configuration
Magnetogram data of AR8210 (Wilcox Solar Observatory)
Composite synoptic map (Carrington maps for rotation 1935 & 1936)
during the period from April through May of 1998
the potential field source surface method (PFSSM; Altschuler et al. 1977)
3D magnetic field
+ empirical model (Roussev et al. 2003)
↓ time evolution
a steady state solar wind

4. Magnetic configuration and flow pattern

5. Initiation of CME (Amari et al. 1999, 2000, 2003)
converging motions
shear motions
horizontal boundary motions

6. Movie

7. Fast-wave speed
Because of this sharp decrease so close to the Sun, the velocity of the ejecta quickly becomes supersonic.

8. Speed & Trajectories of the flux rope and the shock
pure shear motions t=
rapid deceleration due to the formation of the current sheet t=
converging motions t=
rapid acceleration due to loss of equilibrium

9. 3D view

10. Compression ratio of the shock & Proton cut-off energy
a high-energy cutoff for SEPs predicted on the basis of diffusive shock acceleration

11. Conclusion
There has been some controversy in recent years about whether or not diffusive shock acceleration theory can account for the GeV particles observed early in SEP events.
By constructing a fully three-dimensional numerical model, which incorporates solar magnetic data and a loss-of-equilibrium mechanism, they have been able to determine that a shock can develop close to the Sun sufficiently strong to account for energetic particles up to 10 GeV.