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Convection Simulations

Convection Simulations. Robert Stein Ake Nordlund Dali Georgobiani David Benson Werner Schafenberger. Objectives. Understand supergranulation & the magnetic network Find signatures of emerging magnetic flux Validate and refine local helioseismic methods. Competed Simulations.

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Convection Simulations

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  1. Convection Simulations Robert Stein Ake Nordlund Dali Georgobiani David Benson Werner Schafenberger

  2. Objectives • Understand supergranulation & the magnetic network • Find signatures of emerging magnetic flux • Validate and refine local helioseismic methods

  3. Competed Simulations • Hydrodynamic solar surface convection 96 Mm wide x 20 Mm deepDuration: 20.9 hours (bootstrapped from 48 Mm wide)Resolution: 100 km horizontal, 12-75 km vertical • 48 Mm wide x 20 Mm deepDuration: 60 hours (boostrapped from 24 Mm wide)Resolution: 100 km horizontal, 12-75 km vertical

  4. 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

  5. 20 Mm Computational Domain 96 Mm 96 Mm Computational Domain for the CFD Simulations of Solar Convection

  6. Mean Atmosphere Temperature, Density and Pressure (K) (105 dynes/cm2) (10-7 gm/cm2)

  7. Mean Atmosphere Ionization of He, He I and He II

  8. Energy Fluxes

  9. Entropy Histogram

  10. rms Velocity

  11. rms Velocity, O-burning convection Courtesy Dave Arnett Vertical Horizontal

  12. Fractional area in Upflows

  13. Fractional area in Upflows, O burning Courtesy Dave Arnett

  14. Surface shear layerf-plane rotation

  15. Vertical velocity:scan from temperature minimum to 20 Mm depthsize of cellular structures increases with depth

  16. Streamlines: red down, blue up;15 hours; 48 x 20 Mm, vertical scale is depthsome downflows are halted, others merge into larger structures

  17. Tracer particles: 48 x 20 Mm, 15 hours,vertical scale is grid not depth(white is fastest, dark is slowest)

  18. Velocity spectrum

  19. Horizontal Velocity Spectrum -200 km 0 Mm 2 Mm 4 Mm 8 Mm 16 Mm

  20. Upflows at surface come from small area at bottom (left)Downflows at surface converge to supergranule boundaries (right)

  21. Upflows at surface come from small area at bottom (left)Downflows at surface converge to supergranule boundaries (right)

  22. Streamlinesseededat bottom

  23. Streamlines:red=downblue=up.Seededin themiddle

  24. Mass Conservation Rising fluidmust turn over and descend within about ascale height to conserve mass. The actualmixing(entrainment) length in the simulation is1.8 HP.

  25. Vorticity:11.75 hours,Finite Time Lyapunov Exponent Field, subdomain 21 Mm wide x 19 Mm high x 0.5 Mm thick, (from 48x 20 Mm simulation)

  26. Energy balancebuoyancy work ~ dissipation(~ div FKE @ surface)

  27. Buoyancy work, O-burning driven convectioncourtesyD. Arnett

  28. Dissipation length ~ 4 HP

  29. KE, FKE, div FKE

  30. Wave generation & propagation Courtesy Junwei Zhao

  31. k-w Diagram simulation MDI

  32. Horizontal velocity (2-3 Mm depth):simulation (left), travel time inversion (right)

  33. 6x6x3 Mmstreamlines seeded near bottom

  34. 6x6x3 Mmfieldines seeded near bottom

  35. Vertical velocity (image) (km/s) & Velocity vectors in slice

  36. Vertical velocity (image) (km/s) & Magnetic field linesin slice

  37. Temperature (image) &Velocity vectorsin slice

  38. The End

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