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

• non-uniform vertical mesh– 12km @ surface

– 70km @ bottom

• uniform horizontal mesh– 100km horizontal

resolution

48 Mm

48 M

m

20 M

m

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 StateTemperature, Density and Pressure

Mean Atmosphere StateIonization of H and He

QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.

-- 6.5 hr sequence (out of 50 hrs).-- 6.5 hr sequence (out of 50 hrs).

Velocity in vertical planeVelocity in vertical plane

l to r --> top to bottom

surface, 2, 4, 8, 12, 16 Mm

Continuous scale change: granulates -> supergranules

vertical velocity on horizontal planes

(48 Mm wide)

Velocity spectrumno 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 aYUV420 codec decompressor

are needed to see this picture.

Oscillation modes: k- diagram

How to calculate the spectrum?

Average power spectra(correct) or

Average time sequence(incorrect)

Artificial feature,

Noisy

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 Steinstein@pa.msu.edu

Solar Physics Post-Doc

Dr. Robert Stein

Michigan State University

• Simulate solar magneto-convection

• Apply to local helioseismology

solarpostdoc@pa.msu.edu