Supergranulation-Scale Simulations of
Solar Convection
Robert Stein, Michigan State University, USA
Aake Nordlund, Astronomical Observatory, NBIfAFG, Denmark
David Benson, Michigan State University, USA
Computational Domain
• 48Mm x 48Mm x 20Mm
• 5003 grid points
20 Mm
• non-uniform vertical mesh
– 12km @ surface
– 70km @ bottom
• uniform horizontal mesh
– 100km horizontal
resolution
48 Mm
Computational Domain for the CFD
Simulations of Solar Convection
Numerical Method
•
Spatial differencing
– 6th-order 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
Mean Atmosphere State
Temperature, Density and Pressure
Mean Atmosphere State
Ionization of H and He
Velocity in vertical plane
-- 6.5 hr sequence (out of 50 hrs).
QuickTime™ and a
YUV420 codec decompressor
are needed to see this picture.
vertical velocity on
horizontal planes
(48 Mm wide)
l to r --> top to bottom
surface, 2, 4, 8, 12, 16 Mm
Continuous scale
change: granulates ->
supergranules
Velocity spectrum
no features besides granulation
Upflows at surface come from small area at bottom (left)
Downflows at surface converge to supergranule boundaries (right)
Upflows at surface come from small area at bottom (left)
Downflows at surface converge to supergranule boundaries (right)
QuickTime™ and a
YUV420 codec decompressor
are needed to see this picture.
Oscillation modes: k-w diagram
How to calculate the spectrum?
Noisy
Artificial feature,
Average
power
spectra
(correct)
or
Average
time
sequence
(incorrect)
Simulation Data
• Is available
– Full data sets ~ 200 Gb per hour solar time
– Slices of Vxyz & T at selected depths
~ 2 Gb per hour solar time
• Contact: Bob Stein
[email protected]
Solar Physics Post-Doc
Dr. Robert Stein
Michigan State University
• Simulate solar magneto-convection
• Apply to local helioseismology
[email protected]