Energy produced by nuclear fusion in the sun's core travels to the surface, where it is released as sunlight. In the paper "Supergranular-scale solar convection not explained by mixing-length theory" published in Nature Astronomy, the researchers describe using data from NASA's Solar Dynamics Observatory (SDO) to study around 23,000 supergranules. Because the sun's surface blocks light, the scientists used sound waves to explore the supergranules' internal structure, employing a method known as Helioseismology.

The analysis of this vast dataset revealed that the supergranules, extending about 20,000 km below the sun's surface, exhibit distinct up and down heat flows. The researchers found that downflows are approximately 40 percent weaker than upflows, suggesting the presence of unseen components in the downflows.

Through rigorous testing, the researchers proposed that these missing elements might be small-scale plumes (~100 km) transporting cooler plasma downward. The large sound waves in the sun are too coarse to detect these plumes, resulting in weaker observed downflows. These results contradict the widely accepted mixing-length theory of solar convection.

"Supergranules are a significant component of the heat transport mechanisms of the sun, but they present a serious challenge for scientists to understand," said Shravan Hanasoge, Ph.D., research professor and co-author of the paper. "Our findings counter assumptions that are central to the current understanding of solar convection, and should inspire further investigation of the sun's supergranules."

This research, carried out at CASS in collaboration with Tata Institute of Fundamental Research, Princeton University, and New York University, utilized NYUAD's high-performance computing resources.

Research Report:Supergranular-scale solar convection not explained by mixing-length theory

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NYU Abu Dhabi Center for Astrophysics and Space Science
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