A General Cone Model Approach to Heliospheric CMEs and SEP Modeling

Magnetogram-based quiet corona and solar wind model

The SEPs are modeled as a passive test particle (ion) population in a post-process approach that uses the MHD model shock to characterize shock source “injections”, and the time-dependent modeled magnetic field lines between the Sun and a selected observer location to define the path of transport from the shock.

SOHO (LASCO, EIT, MDI) Images and magnetogram

Local Solar Wind parameters can drive the magnetosphere simulation; SEPs enter the magnetosphere along open field lines and at low latitudes on occasion. Our models can replace the data in both cases.

This poster provides an update on the approach that CISM is taking to develop a physics-based model of the coupled corona and solar wind, including the transient disturbances known as CMEs. As a first case study of a Coronal Mass Ejection (CME) event, CISM chose a relatively simple halo CME in May 1997 that was well-observed at the Sun and had geospace effects. Major progress on the initiation of that event is described in an acoompanying poster. A n approach known as the Cone Mode (of CMEs)l is being developed as a simpler alternative to modeling many events in the heliosphere, and to enable the addition of the solar energetic particle component of heliospheric space weather. The Cone Model is also highlighted in an accompanying poster. Comparisons of the models with observations are regularly used to guide their development and adjust strategies..

CISM’s Cone Inversion Model of CMEs uses 2D coronagraph images of halo CMEs to estimate the location, orientation, and properties of a 3D cone-shaped disturbance that may be used to simulate a CME injection in the solar wind simulation. This scheme, developed under MURI, is now a CORHEL option (see Cone Model poster)

Observer Shock-connected fieldlines in the Cone model give SEPsource location and strength.

IMP-8 data,Plot from A. Tylka

Selected Halo CMEEvent,

Selected Halo CMEEvent, May 12, 1997

Time-dependent corona and CME Initiation-A Case Study

SOHO MDI synoptic map for CR1913 (left)and (below) modeled magnetic field lines,and simulated SOHO EIT EUV images, Theseillustrate the ability of the coronal model toreproduce coronal holes-the solar wind sources.The coronal model couples to the solar windmodel (right) to produce CISM’s CORHEL.

Overview of CISM Solar/Heliosphere Research: From Solar Wind to SEP EventsJ.G. Luhmann, D. Krauss-Varban, Y. Li, S. Ledvina, C.O. Lee, W. Abbett, B. Lynch1, J.A. Linker, P. Riley, Z. Mikic, R, Lionello2, D. Odstrcil3,4, Y. Liu, X-P. Zhao5, C.N. Arge6

1 University of California, Berkeley, 2SAIC, 3 University of Colorado, 4NOAA-SEC, 5Stanford, 6AFRL

ENLIL boundary conditions from MAS, May 12 ’97 event showing cone model injection location.

(From D. Odstrcil and X-P. Zhao.)

(SOHO LASCO images)

Observed sites of other CMEs show two distinctive coronal magnetic field

settings involved in simple CMEs. These.show initial field geometries with both simple (parallel) active region and overlying coronal field

geometries and multipolar geometries with magnetic null points.

Both are being tested to determine if the resulting eruption properties

depend on the initial field geometry.

Major progress is being madein modeling the details of one specific well-observed event(See CME Initiation Poster).Other CMEs (right) from theregion can tell us if the sameinitiation mechanism repeats.

STEREO and ACE mission data will provideunique opportunities to test our model

of SEP events at several locations at once-to see if we reproduce this classical concept.

Shock strength from the May 12.’97event cone model (left, from

S. Ledvina) and modeled SEP proton event time profile (above)

The recent corona has been very quiet,dominated by several large low latitudecoronal holes. These have produced anideal period to see if the model can also

reproduce the solar wind stream structure.

Student C. Lee runs the coupled models at the CCMC to compare (above)

the measured and modeled solar wind

At left are plots of coronal magnetic field lines from a GONG Website that uses

one of our models. At right is a plot from the CCMC-

showing solar wind results.

Coupled Model Grids

(V. Pizzo)

SOHO and Yohkoh data plots from Y. Li (left) andmodeled pre-CME fieldgeometries of two types

from B. Lynch (right)

(D. Odstrcil)

(Images, fromJ. Linker, P. Riley,

Z. Mikic)