Researchers Kinfe Teweldebirhan, Rituparna Curt, and Nicholas A. Featherstone from the University of California, Berkeley, have delved into the complex dynamics of rotating stellar convection, with implications for our understanding of the Sun’s behavior and, by extension, the energy industry’s reliance on solar power.
The team investigated how rotating convection responds to a latitudinally-varying heat flux at the base of the convective layer. This study was motivated by the solar near-surface shear layer, where flows transition from a buoyancy-dominated regime near the photosphere to a rotation-dominated regime at depth. Using spherical 3-D, nonlinear simulations, the researchers explored both high-Rossby-number (high-Ro) and low-Rossby-number (low-Ro) regimes, which represent buoyancy-dominated and rotation-dominated convection, respectively.
In both regimes, the researchers found that a strong thermal wind balance is sustained without external forcing. However, when a larger flux variation was imposed, this balance became stronger at high latitudes and weaker at low latitudes. Consequently, the differential rotation weakened, and at sufficiently high forcing, its latitudinal variation reversed for both low- and high-Ro systems.
The study also revealed that at fixed forcing, there exists a Rossby number above which convective flows efficiently mix heat laterally, preventing the imposed flux variation from imprinting on the surface. At sufficiently high Rossby numbers, thermal wind balance is no longer satisfied.
For the energy industry, particularly solar power, understanding these dynamics is crucial. The Sun’s near-surface region, which possesses weakened differential rotation compared to deep convection, has little to no variation of photospheric emissivity in latitude. This research helps to elucidate these phenomena, which can impact solar forecasting and energy production. The findings were published in the Astrophysical Journal.
This article is based on research available at arXiv.