Three-dimensional MHD simulation of a flux rope driven CME Manchester IV, W.B., Gombosi, T.I., Roussev, I., De Zeeuw, D.L., Sokolov, I.V., Powell, K.G., Toth, G., and Opher M. Journal of Geophysical Research, 2004, 109, A May 12 Plasma Seminar Daikou Shiota

1. Introduction Coronal Mass Ejection (CME) traditionally defined as large-scale expulsion of plasma typically mass g energy erg LASCO/SOHO

Introduction The majority of CMEs originate from the disruption of large-scale coronal structure (helmet streamer) (Hundhausen 1988, 1993) A helmet streamer possesses a three-part structure (a high- density shell, a low density cavity, and a filament) → three-part structure of CMEs It is believed that the breakup of helmet streamers may result from a loss of equilibrium foollowing a slow, nearly quasi-static evolution.

Introduction Helmet streamer ･ closed bipolar configuration ･･･ X-ray arcade ･ magnetic shear ･･･ X-ray sigmoid The magnetic configuration of pre-event streamers possibly containing a flux rope coinciding with the plasma cavity (Low 1994, Low and Hundhausen 1995) CMEs are the result of a global MHD process and represent a significant restructuring of the global coronal magnetic field. (Low 1996)

CME models sheared magnetic arcade Wolfson (1982), Mikic et al. (1988), Steinolfson (1991), Choe & Lee (1996), Mikic & Linker (1994), Linker & Mikic (1994) magnetic flux ropes Mouschovias & Poland (1978), Chen (1996), Wu & Guo (1997), Wu et al. (1999), Wu et al. (2000) reconnection-driven CME model Forbes & Priest (1995), Lin & Forbes (2000), Chen & Shibata (2000) Antiochos et al. (1999) Introduction

Recent 3D model Gibson & Low (1998) analytic description of expansion of a flux rope Amari et al. (2000) formation of a flux rope within an arcade and its subsequent eruption Tokman & Bellan (2002) Introduction

In this paper numerically forming a steady-state model ofthe corona along with a bimodal solar wind they superimpose a 3-D magnetic flux rope with in the streamer belt (the solution of Gibson & Low 1998) time evolution

MHD model the block-adaptive tree solar wind Roe-type upwind scheme (BATS-R-US) code (Powell et al. 1999, Groth et al 2000) MHD equations

Steady-state solar wind model (Groth et al. 2000) bimodal solar wind model Volumetric heating

Flux Rope of Gibson & Low (GL) Roussev et al. (2003a) Gibson & Low (1998) self-similar flux rope Force-free solution

Flux rope GL type flux rope is superimposed to the steady-state solar wind solution

Flux rope plasma β |B| density

3D view of the CME |V|

Time evolution |V| velocity distribution in the meridional plane

Time evolution |V| velocity distribution in the equatorial plane

Time evolution and energetics velocity The CME is launched by initial force imbalance. During the first hour the net change The total energy increase is supplied from the magnetic energy of the flux rope. The mass 1.4×10 16 g of plasma is ultimately accelerated by the CME while the flux rope initially contained ~1×10 15 g.

Temperature of the shock behind plasma temperature

Deceleration empirical relationship of CME deceleration (Sheeley et al. 1999) The deceleration is too large to be accounted for by ballistic motion in the Sun’s gravitational field but rather due to the mass of plasma swept up

Synthetic Thomson scattered images X X Z YY Z

Summary The authors investigated the time evolution of 3D MHD model of a CME driven by magnetic pressure and buoyancy of a flux rope in an initial state of force imbalance. The model eruption possesses many features associated fast CME. ① the preevent structure is a dense helmet streamer with three-part structure. ② the energy for the eruption comes from preevent magnetic configuration and yields ~5×10 31 erg of kinetic and gravitational energy to drive ~10 16 g of plasma from the corona. ③ the shock in front of the flux rope interacts with the bimodal solar wind. ④ synthetic Thomson-scattered images show density structures that qualitatively represent a loop-cavity structure.