Scientists create 'MRI' of sun's interior

US and German scientists say an "MRI" of the sun's interior plasma motions is yielding clues to how it transfers heat from its deep interior to its surface. Researchers at New York University with colleagues from NASA and the Max Planck Institute in Germany say the findings upend our understanding of how heat is transported outward by the sun, and challenges existing explanations of the formation of sunspots and magnetic field generation. The sun's heat, generated by nuclear fusion in its core, is transported to the surface by convection in the outer third, but that convection cannot be directly observed, the researchers said. To create the equivalent of an MRI, or magnetic resonance imaging, of the plasma flows, researchers examined high-resolution images of the sun's surface taken by NASA's Solar Dynamics Observatory showing motions on the sun's surface caused by convection. Analyzing the precise movement waves on the sun's surface, the researchers were able to calculate its unseen plasma motions below. "These convective motions are currently believed to prop up large-scale circulations in the outer third of the sun that generate magnetic fields," NYU researcher Shravan Hanasoge said. "However, our results suggest that convective motions in the sun are nearly 100 times smaller than these current theoretical expectations. "If these motions are indeed that slow in the sun, then the most widely accepted theory concerning the generation of solar magnetic field is broken, leaving us with no compelling theory to explain its generation of magnetic fields and the need to overhaul our understanding of the physics of the sun's interior." The study has been published in the Proceedings of the National Academy of Sciences.