The Rotational Influence on Solar Convection

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• Keith Julien (University of Colorado Boulder)
• Thursday 19 May 2022, 16:00-17:00
• Seminar Room 1, Newton Institute.

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TURW05 - Advances in geophysical and astrophysical turbulence

The observational absence of giant convection cells near the Sun’s outer surface is a long- standing conundrum for solar modelers. We herein propose an explanation. Rotation strongly influences the internal dynamics, leading to suppressed convective velocities, enhanced thermal-transport efficiency, and (most significantly) relatively smaller dominant length scales. We specifically predict a characteristic convection length scale of roughly 30 Mm throughout much of the convection zone, implying weak ow amplitudes at 100- 200 Mm giant cells scales, representative of the total envelope depth. Our reasoning is such that: Coriolis forces primarily balance pressure gradients (geostrophy). Background vortex stretching balances baroclinic torques. Both together balance nonlinear advection. Turbulent fluxes convey the excess part of the solar luminosity that radiative diffusion cannot. We show that these four relations determine estimates for the dominant length scales and dynamical amplitudes strictly in terms of known physical quantities. We predict that the dynamical Rossby number for convection is less than unity below the near-surface shear layer, indicating rotational constraint.

This talk is part of the Isaac Newton Institute Seminar Series series.

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