Merging of coronal and heliospheric numerical two-dimensional MHD models

D. Odstrcil, et al., J. Geophys. Res., 107, 2002.

2004 年 10 月 14 日 太陽雑誌会 ( 速報 ) 西田

Introduction

• Space weather research involves a chain of various phenomena occurring simultaneously on different spatial and temporal scales.

• An integrated modeling approach is necessary for space weather research.

• This paper presents a demonstration of merged coronal and heliospheric 2-D MHD models.

Numerical Models

• Coronal Model– 2-D axisymmetric resistive MHD equations– Semi-implicit finite difference scheme using st

aggered values

• Heliospheric Model– 2-D axisymmetric ideal MHD equations– Explicit finite difference total-variation-diminis

hing high-resolution Lax-Friendrichs (TVDLF) scheme using cell-centered values

• Merged numerical grid

Fig. 1

• Coronal Model– 200x300 grid points– Nonuniform mesh for th

e streamer

• Heliospheric Model– 340x240 grid points

• The output from the coronal model is used as a boundary condition for the heliospheric solutions

Fig. 2

Ambient State in the corona

Fig. 3

Ambient State in the heliosphere

Fig. 4. Blue: 70°, Red: 80°, Black: 90°

Transient Disturbances

• The streamer products strongly sheared field lines that are nearly aligned with the neutral line; it is just a convenient mechanism.

• The sharing phase lasts 5.2 days.

• We reduce the magnetic flux at the photosphere to create a flux rope.

• After ~18 hours the arcade erupts.

http://sprg.ssl.berkeley.edu/cism/

Fig. 5

Fig. 6. Blue: 70°, Red: 80°, Black: 90°

Fig. 7

Fig. 8

Fig. 9

Fig. 10 . Blue: 70°, Red: 80°, Black: 90°

Conclusions (1/2)

• The merging of coronal and heliospheric MHD models has been successfully implemented for a 2-D ambient state and a transient disturbance.

• Different mathematical models, numerical methods, and computational grids were used in this work, and thus the merging of the numerical models was demonstrated for a quote general case.

Conclusions (2/2)

• Merged coronal and heliospheric models have enabled the simulation of transient disturbances.

• The solar wind and magnetic parameters at 1 AU resulting from the coupled computations can provide input for geo-effectivity models.

Fig. A1