A Numerical Study of the Breakout Model for Coronal Mass Ejection Initiation P. MacNeice, S.K. Antiochos, A. Phillips, D.S. Spicer, C.R. DeVore, and K. Olson ApJ, 2004, 614, Solar Seminar Daikou Shiota Introduction Coronal Mass Ejection (CME): the giant disruption of magnetic field and plasma Two CME Models which demonstrate exprosive eruption with full MHD numerical simulation. 1. Flux cancellation (Amari et al. 2000) 2. Magnetic breakout (Antiochos et al. 1999) Neither model can be considered to have been either definitively verifird or refuted by observations. However, there are anumber of studies that support a breakout interpretation. (e.g. Aulanier et al. 2000; Sterling & Moore 2001) This study They developed the previous numerical studies of breakout (Antiochos et al. 1999) and calculated the complete evolution of the breakout eruption, including the formation and escape of the plasmoid. (they used modified code and extend the computational domain to r ~ R sun ) The main issues they focus on are the speed of the eruption and the evolution of the magnetic helicity. Numarical model They solve 2.5-D ideal MHD equations Numerical grid Scheme multidimensional flux-corrected transport (FCT) (DeVore 1991) Results (Magnetic Field) Results (density) Results (radial velocity) Results (helicity) Evolution of velocity and energy Rapid acceleration Loss of equilibrium energyheight of X point Solid line: azimuthal magnetic energy Dash-dot line: azimuthal magnetic energy r < 1.5R sun Dash line: the change of non-azimuthal magnetic energy Dot line: kinetic energy Dependence of numerical resolution Helicity Helicity is represented as In this simulation, relative helicity is conserved. (B p is potnetial field) ~80% ejected as plasmoid Summary They simulate the complete evolution of the breakout eruption. The results show that the ejection occurs at a speed on the order of the coronal Alfven speed and hence that the breakout model can produce fast CMEs. Another key result is that the ejection speed is not sensitive to the refinement level of the grid used in the calculations, which implies that, at least for the numerical resistivity of these simulations, the speed is not sensitive to the Lundquist number. They calculate the helicity of the system and show that the helicity is well conserved during the breakout process. Most of the helicity is ejected from the Sun with the escaping plasmoid, but a significant fraction (of order 10%) remains in the corona. Observable Proerties of the Breakout Model for Coronal Mass Ejections B.J. Lynch, S.K. Antiochos, P. MacNeice, T.H. Zurbuchen, and L.A. Fisk ApJ, 2004, 617, Abstract We compare the magnetic breakout model for coronal mass ejections (CMEs) with observed general properties of CMEs by analyzing in detail the result of MacNeice et al. (2004). The model produces an eruption with a three-part plasma density structure that shows a bright circular rim outlining a dark central cavity in synthetic coronagraphic images of total brightness. The model also yields height-time profiles similar to most three-part CMEs, but the eruption speed by 2.5 R is of order the Alfven speed, indicative of a fast CME. We show that the evolution of the posteruptive flare loop and chromospheric ribbons determined from the model are in agreement with observations of long-duration flares, and we propose an explanation for the long-standing observation that flares have an impulsive and gradual phase. A helical magnetic flux rope is generated during eruption and is consistent with a large class of interplanetary CME observations. The magnetic fields in this flux rope are well approximated by the Lundquist solution when the ejecta are at 15 R and beyond. Furthermore, the interior density structure of the magnetic flux rope appears to have some of the basic features of an average magnetic cloud profile at 1 AU. Density synthetic coronagraphic images Three-part structure Running difference image Flare ribbon separation Close-up image beneath the erupting flux rope (density and field lines) In Situ Comparison