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.