CISM Cone Model Approach to Interplanetary CME (ICME) Simulation
D. Odstrcil3,4, X-P. Zhao5, Y. Liu5, T.J. Hoeksema5, C.N. Arge6, S. Ledvina1, P.Riley2, J. Linker2
1University
of California, Berkeley, 2SAIC, 3University of Colorado, 4NOAA-SEC, 5Stanford, 6AFRL
This poster provides an update on the approach that CISM is taking to develop a simplified model of a CME’s effects on the solar wind, namely the transient disturbances known as ICMEs that are the major cause of large
geomagnetic storms. Case studies with the cone model include the halo CME in May 1997 that is also being simulated by CISM in a more detailed way starting at the Sun (see accompanying poster on the initiation of this
event in the coronal model). Other potential case studies are described here, including cases involving multiple CME disturbances that interact in ways that modify their individual effects. Overall the cone model allows us to
proceed in developing the heliospheric portions of the model, to explore the effects of interaction with the solar wind structure, and to develop model products necessary for SEP event simulations and geospace coupling.
Simulation of Interplanetary CMEs
Coronal Mass Ejections (CMEs) and the Cone Model
CME-1
When will disruptive CMEs impact Earth? Coronagraph
observations alone aren’t enough to make the forecast for the
most geoeffective halo CMEs. In 2002, Zhao et al. first devised
the Cone Inversion Model to estimate the ICME’s 3D geometric
and kinematic properties from the 2D LASCO images based on
the conical shell CME model of Howard et al. (1982).
The configuration of isolated CMEs and ICMEs is a magnetic flux
rope with two ends anchored on the solar surface. The outer
boundary of CME plasma structures can be geometrically
approximated by cones, i.e. hollow bodies that expand from an
apex located at the Sun’s center to a round or elliptical base that is
flat.
Halo CMEs, visible by Thompson scattering, can thus be
reproduced by projecting the cone base onto the plane of the sky;
then cone model parameters can be inverted using the
characteristics of the observed CME halos.
The first test of this idea was carried out using a circular cone
model for the 12 May 1997 front-side full-halo CME by Zhao et al.
(2002). Th inversion solution of the circular cone model has been
improved by Xie et al. (2004)
Multiple Transient Events
CME-2
CME-4
CME-3
CME-5
CME-3
First, background solar wind is computed using the output from either the WSA
.
empirical or MAS numerical coronal model. Then, an over-pressured plasma cloud
(with location, diameter, and speed from the cone model) is launched into heliosphere.
Resulting interplanetary disturbance has two-part structure (shock+ejecta) and
forward-reverse shock pair structure may form by cloud expansion.
 5 halo CMEs between April 27 and May 2, 1998
 total 18 CMEs between April 27 and May 2, 1998
http://cdaw.gsfc.nasa.gov/CME_list/
May 12, 1997
May 1, 1998
CME-1
CME-2
CME-3
CME-4
CME-5
Further study shows that there are three types of halo CMEs
and the circular cone model is only valid for about 10% of all
events. The Stanford group has just developed an elliptical
cone model that can determine the characteristics of any halo
CME from observed parameters (Zhao, 2007).
Since the number of halo parameters is generally one less
than the number of model parameters, two approaches are
used to estimate the ambiguous CME propagation direction.
April 21, 2002
August 24, 2002
The one-point method uses images
from a single vantage point with other
data about the CME (e.g. the origin).
These figures show inversions for all
types of halo CMEs using this approach.
The results are highly satisfactory!
The ejecta has no magnetic structure and so best represents an ICME’s leading shock,
sheath, and trailing rarefaction region. This may be useful for providing a global context,
predicting whether shocks and/or ejecta will hit geospace, and some SEP applications.
Coronagraph observations
from STEREO A & B will
enable the two-point
method that can
accurately determine the
CME propagation direction
and validate the one-point
approach.
Validation: the figure
at left shows the
apparent geometry of
a single CME
observed from various
vantage points that
can be tested with
STEREO data.
Weak (top left) and strong (top right) energetic particle events were
observed by GOES spacecraft. The IMF line traced from the geospace
to inner boundary of the heliospheric domain shows proximity of two
solar active regions and an interplanetary shock in the latter case.
High Resolution of Shocks at Geospace
ICMEs and IMF Connectivity
ICMEs (white shaded structures), IMF lines (colored by normalized density), during the
April/May 1998 events. Geospace is magnetically connected to stronger shock front
when a rarefaction region, caused by the preceding ICME, is present.
Nested grids with progressively finer resolution centered on geospace is used
to achieve high resolution of interplanetary shocks hitting the magnetosphere.
Global (left) and detail (right) view show an interplanetary transient with the
distorted shock front as it propagates through a moderate streamer. Upper
and lower half show solution on single and nested grids. L1-point and Earth
position is marked by white diamond and rectangle, respectively.