Threedimensional MHD simulation of a flux rope driven CME

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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 Seminar Daikou Shiota
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1. Introduction Coronal Mass Ejection (CME)
LASCO/SOHO
typically mass 1015-16g energy 1031-32erg

• traditionally defined as large-scale expulsion of
  plasma

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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.
4
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)

5
Introduction

• 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)

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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)

7
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

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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
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Steady-state solar wind model (Groth et al. 2000)
bimodal solar wind model Volumetric heating
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Flux Rope of Gibson Low (GL)
self-similar flux rope
Gibson Low (1998)
Force-free solution
Roussev et al. (2003a)
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Flux rope
GL type flux rope is superimposed to the
steady-state solar wind solution
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Flux rope
density
density
plasma ß
B
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3D view of the CME
V
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Time evolution
V
velocity distribution in the meridional plane
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Time evolution
V
velocity distribution in the equatorial plane
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Time evolution and energetics
velocity
During the first hour the net change
The total energy increase is supplied from the
magnetic energy of the flux rope. The mass
1.41016g of plasma is ultimately accelerated by
the CME while the flux rope initially contained
11015g.
The CME is launched by initial force imbalance.
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Temperature of the shock behind plasma
temperature
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Deceleration
empirical relationship of CME deceleration
(Sheeley et al. 1999)
The deceleration is too large to be accounted for
by ballistic motion in the Suns gravitational
field but rather due to the mass of plasma swept
up
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Synthetic Thomson scattered images
Z
X
Z
X
Y
Y
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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. ? the
preevent structure is a dense helmet streamer
with three-part structure. ? the energy for the
eruption comes from preevent magnetic
configuration and yields 51031erg of kinetic
and gravitational energy to drive 1016g of
plasma from the corona. ? the shock in front of
the flux rope interacts with the bimodal solar
wind. ? synthetic Thomson-scattered images show
density structures that qualitatively represent a
loop-cavity structure.