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An update on convection zone modeling with the ASH code

An update on convection zone modeling with the ASH code. Mark Miesch HAO/NCAR Sacha Brun, Juri Toomre, Matt Browning, Marc DeRosa, Ben Brown, Nick Featherstone, Kyle Augustson. Oct, 2006. Outline. Convective patterns Mean Flows (DR & MC) Dynamo processes. Achievements Challenges

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An update on convection zone modeling with the ASH code

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  1. An update on convection zone modeling with the ASH code Mark Miesch HAO/NCAR Sacha Brun, Juri Toomre, Matt Browning, Marc DeRosa, Ben Brown, Nick Featherstone, Kyle Augustson Oct, 2006

  2. Outline • Convective patterns • Mean Flows (DR & MC) • Dynamo processes • Achievements • Challenges • Helioseismic implications

  3. What might giant cells look like? The ASH Code Radial velocity r=0.98R

  4. Look for Vorticity and Divergence in SSW maps?

  5. dvj/dj at r = 0.98R (d = 14.6 Mm) A better way to find NS downflow lanes?

  6. Summary: Convection StructureWhat might we look for in SSW maps? • Coherent Structures • Downflow network • Persistent NS lanes (Lisle et al 2004) • Correlations & Statistics • Cyclonic vorticity/horizontal convergence (Gizon 2006, Komm et al 2006) • Cool, vortical downflows • Reynolds stresses <vqvj>? • Spectra, pdfs, etc • Evolution • Correlation timescales of days to weeks • Prograde propagation of NS lanes • Shearing and fragmentation of cellular flows Miesch Oct, 2006

  7. Differential Rotation W (nhz) r/R

  8. Meridional Circulation vq(m s-1) equatorward vq (m s-1) 60o latitude 30o poleward r/R

  9. Maintenance of Mean Flows: Dynamical balances Statistically steady Neglect LF, VD Rapid rotation CF >> RS Ideal gas Hydrostatic, adiabatic background (1) Meridional circulation = Reynolds stresses • (2) Thermal Wind balance • (Taylor-Proudman theorem) Coriolis-induced tilting of convective structures DR, MC, RS, S are tied together by (1), (2)

  10. Thermal wind balance and coupling to the tachocline S=constant Lower BC S=S(q) Lower BC Warm poles!

  11. Summary: Mean FlowsGuidance for helioseismology, dynamo modeling • Differential rotation • Reynolds stresses • Latitudinal entropy/temperature variations • Tachocline may play an important role in maintaining global profile • Meridional Circulation • Delicate balance between large forces • Large fluctuations in space and time • Poleward circulation in the Sun may be a surface effect - we need deeper inversions! DR, MC, RS, S are tied together by dynamical balances Miesch Oct, 2006

  12. Dynamo Action in Global Convection Simulations Sustained Toroidal/Poloidal field generation Complex spatial and temporal dependence

  13. Tachocline promotes more organized fields W Magnetic Energy density

  14. Pumping, amplification, and organization of toroidal fields Mid-CZ Overshoot region/tachocline

  15. Summary: Dynamo ProcessesWhere do global convection simulations stand? • Achievements • Sustained field generation by turbulent convection (0-1) • Pumping downward into a tachocline (2) • Amplification by rotational shear (3) • Challenges • Formation of toroidal bands (4) • Flux destabilization and emergence (4-7) • Activity cycle (8) • Tachocline dynamics • Instabilities • Penetrative Convection • Waves & Oscillations • Confinement Miesch Oct, 2006

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