Solar Convection Simulations Bob Stein David Benson.

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Presentation transcript:

Solar Convection Simulations Bob Stein David Benson

Solar Convection 1.Transports energy (from core nuclear reactions) through outer 1/3 of Sun 2.Drives the dynamics of the solar atmosphere 3.Generates the solar magnetic field 4.Excites the p-mode oscillations

The Simulation Code Conservative Compressible (M)HD equations LTE non-gray radiation transfer Realistic tabular EOS and opacities  No free parameters (except for resolution & diffusion model). 48 Mm 20 Mm (Developed with Danish collaborator Aake Nordlund)

Numerical Method Spatial differencing –6th-order finite difference –Staggered variables Time advancement –3rd order Runga-Kutta Parallelized –OpenMP, single parallel region –Scales linearly from processors as domain size increases

Results are used to: Understand spectral line-formation in the atmosphere Calculate the solar (and stellar) abundances Understand the excitation of solar oscillations Calibrate local helioseismic inversion methods Study magnetic flux emergence Calculate the influence of magnetic fields on observables Input to chromospheric & coronal modeling

Spectral Line Formation 1D models micro & macro-turbulence due to convective overshoot. Spatially resolved profiles

New abundance determinations Inhomogeneous T (see only cool gas), & P turb Raises atmosphere One scale height 3D atmosphere not same as 1D atmosphere (By Martin Asplund and former grad student Regner Trampedach)

Acoustic (p-mode) Oscillations Observed Simulated

P-Modes Excited by PdV work Triangles = simulation, Squares = observations (l=0-3) Excitation decreases at low frequencies because oscillation mode inertia increases and compressibility (dV) decreases. Excitation decreases at high frequencies because convective pressure fluctuations have long periods. (by former grad. students Dali Georgobiani & Regner Trampedach)

Local Helioseismology uses wave travel times through the atmosphere (by former grad. Student Dali Georgobiani)

Magnetic Flux Emergence Magnetic field lines rise up through the atmosphere and open out to space

G-band images from simulation at disk center & towards limb (by Norwegian collaborator Mats Carlsson) Notice: Hilly appearance of granules Bright points, where magnetic field is strong Striated bright walls of granules, when looking through magnetic field Dark micropore, where especially large magnetic flux

Waves: observed & simulated

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