Coherent structures in granulation convection and their importance for higher order closure models

Kupka, F.; Robinson, Franklin

doi:10.1017/s1743921307000154

Cited by 3 publications

(1 citation statement)

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“…))w 2 2 (see also Kupka & Robinson 2007b). Away from the upper and lower boundaries the GH model differs by about 20% from unity while the QN approximation underestimates the fourth order moment by up to 200% (see Robinson 2007a andRobinson 2007b for more details).…”

Section: Applications Of 3d Solar Simulationsmentioning

confidence: 96%

Comparing convection in the Sun with Procyon A

Robinson

Demarque

2006

Proc. IAU

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Abstract. As well as reproducing observable features like solar granulation, 3D simulations can provide useful information for local or non-local stellar modeling. Examples include testing out the mixing length theory in the surface layers, providing the turbulent correction for stellar models of p-mode frequencies, testing eddy viscocity prescriptions used in tidal dissipation models and comparing different closures of higher order moments. Having validated the 3D code with the sun we applied it to other stars. For Procyon A the turbulence is about twice as strong as it is in the Sun (estimated by the peak root mean square vertical velocity which is about 6.5 km/s) and the granules are nearly an order of magnitude larger, with plumes regularly extending down 2-3 pressure scale heights below the surface of Procyon A. An interesting feature of the Procyon simulation is that the horizontal layers in the vicinity of the granules appear to radially pulsate in a quasi-periodic manner. This makes the superadiabatic layer move in and out over a distance of about half a pressure scale height in a time of about 20-30 minutes. This motion appears to be tied to the granulation but there may be other phenomena involved such as some kind of local kappa-mechanism confined to the granulation surface layers. We find similar behaviour in a simulation of an 11 Gyr subgiant sun. As the velocities are more like the sun (about 3km/s), the time period of the pulsation in the subgiant is 2-3 times longer than in Procyon A.

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Section: Applications Of 3d Solar Simulationsmentioning

confidence: 96%