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Coronal and Heliospheric Modeling of the May 12, 1997 MURI Event
MURI Project Review, NASA/GSFC, MD, August 5-6, 2003
Dusan Odstrcil
University of Colorado/CIRES & NOAA/Space Environment Center,Boulder, CO
Solar Wind Parameters
Large variations in plasma parameters between the Sun and Earth
Different regions involve different processes and phenomena
We distinguish between the coronal and heliospheric regions with an
interface located in the super-critical flow region (usually 18-30 Rs)
Modeling of Heliospheric Events
Heliospheric model(ENLIL, 3-D MHD solar wind)
Coronal model(SAIC, semi-empirical)
Halo-CME(SOHO/LASCO)
Photospheric magnetic field(NSO Kitt Peak)
Time-dependent boundary values(N, T, V, B)
Source-surface maps at 30 Rs
CME cone model(Zhao et al.)
Geometrical and kinematical data
Global Solar and Coronal Observations
Remote solar observations of the photospheric magnetic field Remote coronal observations of
the white-light scattered on density structures
Ambient Solar Wind Models
SAIC 3-D MHD steady state coronal
model based on photospheric field
maps
[Linker, Mikic, Riley]
CU/CIRES-NOAA/SEC 3-D solar wind model
based on potential and current-sheet source
surface empirical models
[Arge, Mayer, Pizzo]
UCB 3-D MHD steady state coronal model
based on photospheric field maps
[Ledvina, Luhmann]
CME Cone Model
[ Zhao et al., 2001 ]
Best fitting for May 12, 1997 halo CME
• latitude: N3.0• longitude: W1.0• angular width: 50 deg
• velocity:650 km/s at 24 Rs
(14:15 UT)• acceleration: 18.5 m/s2
Boundary Conditions
Ambient Solar Wind
Ambient Solar Wind +
Plasma Cloud
CASE - 1 CASE - 2
Evolution of Parameters at Earth
Ambient Solar Wind
Ambient Solar Wind +
Plasma Cloud
CASE - 1 CASE - 2
Latitudinal Distortion of ICME Shape
ICME propagates into bi-modal solar wind
Radial Compression of ICME Structure
Fast stream follows the ICME
Radial Compression of ICME Structure
ICME propagates into the enhanced density of a streamer belt flow
Synthetic White-Light Imaging
ICME transforms its appearance from a halo-like shell to a distorted one
with two bright spots (see right panel)
Larger time-interval between two images are needed to capture
expanding interplanetary transients
Total Brightness Running Difference
Appearance of Transient Density Structure
IPS observations detect interplanetary transients that sometime show two
enhanced spots instead of a halo ring[Tokumaru et al., 2003]
MHD simulation shows a dynamic interaction between the ICME and ambient solar wind that:
(1) forms an arc-like density structure; and
(2) results in two brighter spots in synthetic images
Propagation of Energetic Particles
IMF line connected to Earth by-passes the shock structure
=>Interplanetary CME-driven shock
cannot generate energetic particles observed at Earth
IMF line connected to Earth passes through the shock structure
=>Quasi-perpendicular shock can
generate energetic particles under certain circumstances
Early time Later time
Energetic Particles & Radio Emission
Important effect occurs away from the Sun-Earth line
Enhanced shock interaction together with quasi-perpendicular propagation relative to IMF lines favors particle acceleration and generation of radio emission
Global view Detailed view
Near-Earth Observations
Internal magnetic structure (flux rope) is not included
Interplanetary magnetic field is distorted by: shock compression, field line draping around ejecta, and stretching in rarefaction region
Examples of Ongoing WorkAnalytic flux-rope models (Vandas) Event-driven coronal models (Ledvina)
Graphical user-interface tools (Markel) Coupling with SEP, IPS, & SMEI(Jackson, Ledvina, Lee, Vandas)
Conclusions:Modeling of Interplanetary Events
• It is now possible to: - simulate ambient solar wind structure; - estimate arrival of shock and ejecta; - provide a global context.
• It is not yet possible to: - reproduce the internal magnetic structure of interplanetary CMEs
(due to lack of coronal magnetic field observations).
• Next steps: - initialization from photospheric observations; - multi-point, multi-perspective advanced observations; - framework for modeling, visualization, and analysis; - validation studies.