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, A01102

2004 May 12 Plasma SeminarDaikou Shiota

1. Introduction Coronal Mass Ejection (CME)

traditionally defined as large-scale expulsion of plasma

typically

mass 1015-16g

energy 1031-32erg

LASCO/SOHO

IntroductionThe 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.

IntroductionHelmet streamer･ closed bipolar configuration ･･･ X-ray arcade･ magnetic shear ･･･ X-ray sigmoidThe 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 re

present a significant restructuring of the global coronal magnetic field. (Low 1996)

CME modelssheared magnetic arcade

Wolfson (1982), Mikic et al. (1988), Steinolfson (1991), Choe & Lee (1996), Mikic & Linker (1994), Linker & Mikic (1994)

magnetic flux ropesMouschovias & Poland (1978), Chen (1996), Wu & Guo (1997), Wu et al. (1999) , Wu et al. (2000)

reconnection-driven CME modelForbes & Priest (1995), Lin & Forbes (2000), Chen & Shibata (2000) Antiochos et al. (1999)

Introduction

Recent 3D modelGibson & 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

Introduction

In this paper• numerically forming a steady-state model of

the 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

Q)1(

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

bimodal solar wind model

Volumetric heating

20

2

00 exp sunRrpTqQ

0

2

2

0 sin

sin25.4),(r

Flux Rope of Gibson & Low (GL)

Roussev et al. (2003a)

Gibson & Low (1998) self-similar flux rope

Force-free solution

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

Flux rope

plasma β|B|

density 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

erg100.4~ 31 kEerg104.3~ 31 thE

erg100.6~ 30 gE

The total energy increase is supplied from the magnetic energy of the flux rope.

The mass 1.4×1016g of plasma is ultimately accelerated by the CME while the flux rope initially contained ~1×1015g.

Temperature of the shock behind plasma

temperature

Decelerationempirical 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

SummaryThe 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 ~5×1031erg of kinetic and gravitational energy to drive ~1016g 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.