Supergranulation-Scale Solar Convection Simulations David Benson, Michigan State University, USA Robert Stein, Michigan State University, USA Aake Nordlund, Astronomical Observatory, NBIfAFG, Denmark AGU - SPD Conference May, 2005 New Orleans, LA

Overview Purpose Computational Methodology (brief) Methods for Initializing Simulations Preliminary Results: Simulations In-Progress  50Mm x 50Mm x 20Mm (deep) simulations  Relaxing thermally and dynamically Future Directions

Significance and Questions 1.Second Helium Ionization Zone Separate the role of second helium ionization zone from the effect of the increasing scale height with depth 2.Helioseismology Simulations serve as a tool for analyzing local helioseismic inversion techniques 3.Nature of the Surface Shear Layer 4.Development and Maintenance of the Magnetic Network

Computational Domain 50Mm x 50Mm x 20Mm grid points Grid clustering near visible surface 50 Mm 20 Mm Computational Domain for the CFD Simulations of Solar Convection

Numerical Method Spatial differencing –6th-order centered f.d. –staggered Time advancement –3rd order Runga-Kutta Equation of state –tabular –including ionization –H, He + abundant elements Radiative transfer –3D, LTE –4 bin opacity distrib. fxn Quenching

Computational Information Fortran 90 Parallelized - OpenMP –single parallel region Michigan State University –64 processor Altix NCSA –IBM P690 NASA Ames –Altix (128 processors) Objective: layer MPI on top of the OpenMP

Initialization Methods 24 Mm and 12 Mm Simulations 12 Mm simulation (9 Mm deep) well-relaxed extended adiabatically to 20 Mm Relax dynamics 12 Mm Mm deep Create 24 Mm wide box - and relax the following 1.12 Mm stretched to 24Mm generates large scale structure 2.12 Mm doubled to 24 Mm

Initialization Methods Construction of 50 Mm Initial State 1.Stretch 12 Mm x 20 Mm to 50 Mm Generates large scale structure Breaks symmetry 2.Stretch 24 Mm x 20 Mm to 50 Mm Generates intermediate level structure 3.Quadruple 12 Mm x 20 Mm to 50 Mm Produces small scale structure Combine & Relax Combine & Relax

Initialization Snapshots Components + Composite : Uz at 0.25 Mm Snapshots of methods + composite (?)

Initialization Snapshots Components + Composite : Uz at 17.3 Mm

Mean Atmosphere State Temperature, Density and Pressure

Mean Atmosphere State Ionization of H and He

Energy Fluctuation Need for Relaxation

Future Research Direction Relax hydrodynamic simulations (further) Implement magnetic field boundary conditions and add Coriolis force terms Results will be available to help in answering questions about... Maintenance of magnetic network f-plane rotation -- Coriolis force Local helioseismic inversion techniques