Utilizing CISM MHD Results in SEP Modeling

S. A. Ledvina, D. Odstrcil, J. G. Luhmann, D. Krauss-Varban, and I. Roth

What the SEP simulations need from the MHD results

• The shock location

• The shock strength, MA,

• The shock normal angle Bn

• The MHD variables– Density– Temperature– Magnetic field– Velocity

The SEP code uses the guiding center approximation:

• We only need to store the MHD variable along the magnetic field lines that originates from the Earth and traces back to the Sun.

• Since this is the only field line we need we can save the MHD values along this line often (~5 minutes).

To meet these requirements we have added a field line tracing output routine to ENLIL

Finding the Shock

• Normalize the dynamic pressure by r2.

• Calculate the gradients in the normalized pressure.

Finding the Shock Cont.• Calculate the gradient of the

normalized pressure along the field line.

• Starting from the Earth find the largest magnitude of the gradient. That is the shock location.

• Find where the gradients change by some value (~20%) from the background. Use the values midway between these points to find:– Shock strength– Shock jump conditions

Gradient along field line

Finding the shock normal angle

• Minimum variance analysis?

Remaining Code Issues

• Adding a field line tracing output routine to MAS

• Tracing field lines across the MAS-ENLIL boundary

• Tracing field lines across processors in parallel computations

Model Interface