Supergranulation-Scale Solar Convection Simulations

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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

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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

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Significance and Questions

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

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Computational Domain

• 50Mm x 50Mm x 20Mm
• 5003 grid points
• Grid clustering near visible surface

Computational Domain for the CFD Simulations of
Solar Convection
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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

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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

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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 -- 20 Mm deep
• Create 24 Mm wide box - and relax the following
• 12 Mm stretched to 24Mm
• generates large scale structure
• 12 Mm doubled to 24 Mm

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Initialization Methods

• Construction of 50 Mm Initial State

• Stretch 12 Mm x 20 Mm to 50 Mm
• Generates large scale structure
• Breaks symmetry
• Stretch 24 Mm x 20 Mm to 50 Mm
• Generates intermediate level structure
• Quadruple 12 Mm x 20 Mm to 50 Mm
• Produces small scale structure
• Combine Relax

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Initialization Snapshots

• Components Composite Uz at 0.25 Mm

Snapshots of methods composite (?)
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Initialization Snapshots

• Components Composite Uz at 17.3 Mm

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Mean Atmosphere State

• Temperature, Density and Pressure

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Mean Atmosphere State

• Ionization of H and He

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Energy Fluctuation

• Need for Relaxation

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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