2004年10月14日 太陽雑誌会(速報) 西田
Merging of coronal and heliospheric
numerical two-dimensional MHD models
D. Odstrcil, et al., J. Geophys. Res., 107, 2002.
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
staggered values
• Heliospheric Model
– 2-D axisymmetric ideal MHD equations
– Explicit finite difference total-variationdiminishing high-resolution Lax-Friendrichs
(TVDLF) scheme using cell-centered values
• Merged numerical
grid
• Coronal Model
– 200x300 grid points
– Nonuniform mesh for
the streamer
• Heliospheric Model
– 340x240 grid points
Fig. 1
• The output from the
coronal model is used
as a boundary
condition for the
heliospheric solutions
Ambient State in the corona
Fig. 2
Ambient State in the heliosphere
Fig. 3
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 geoeffectivity models.
Fig. A1

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