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**Session 74 - The Quiet & Active Sun.**

*Display session, Friday, January 09*

*Exhibit Hall, *

## [74.03] Global-scale numerical simulation of solar turbulent convection and its coupling to rotation

*J. R. Elliott, M. Miesch, J. Toomre (JILA, U. Colorado), T. C. Clune (SGI/ Cray), G. A. Glatzmaier (Los Alamos Nat. Lab.)*
The larger scales of convection in the sun are influenced by rotation,
leading to a redistribution of angular momentum which is seen as
differential rotation. Previous numerical simulations of such global-scale
convection in rotating spherical shells of fluid have been restricted by
computational resources to deal with nearly laminar flow regimes for the
resolved scales of motion, though provisions were made for diffusive
transport by nominally turbulent unresolved scales. The disparities between
the differential rotation profiles that those models predict (angular
velocity nearly constant on cylinders) and those deduced from the frequency
splittings of p modes (nearly constant on radii in the convection zone),
coupled with recent advances in high performance computing, encouraged us
to begin pursuing numerical simulations of global-scale convection in
turbulent parameter regimes. We anticipate that rotationally-constrained
turbulence can possess inverse cascades that yield large-scale coherent
vorticity structures and strong mean flows which coexist with less
persistent smaller-scale turbulence, and yield angular velocity
profiles that may be quite different than those obtained with laminar
convection.

The dominant challenge to all turbulence simulations is to be able to
explicitly describe the dynamics over a broad enough range of length scales.
To this end, we have developed a new code for studying rotating anelastic
convection in spherical shells, employing expansions in spherical harmonics
to resolve horizontal structures and in Chebyshev polynomials to resolve
radial structures. Appropriate optimization techniques, including expedient
use of inter-processor tranposes and sophisticated load balancing, enable
the code to achieve high performance on massively parallel architectures,
and currently to reach a speed of around 100Mflop/s per node on the Cray T3E.
The new code is enabling us to perform simulations of convection at spatial
resolutions significantly higher than those of earlier studies, and thereby
to begin to investigate fully turbulent parameter regimes. We present the
results from such a simulation, which includes the important effects of
penetration into the stable interior, and discuss the corresponding
differential-rotation profile obtained.

**Program
listing for Friday**