NASA Supercomputer Reveals Unexpected Link Between Sun‘s Magnetic Field and Internal structure
SANTA CRUZ, CA – September 26, 2025 – A team of researchers at UC Santa Cruz has, using NASA’s Pleiades supercomputer, achieved a breakthrough in understanding the sun’s magnetic field and its connection to a mysterious internal layer called the tachocline.The findings, published in The Astrophysical Journal Letters, challenge previous models and offer a new foundation for predicting solar activity and studying stellar magnetism throughout the universe.
For years,scientists have struggled to accurately model the tachocline – a transition zone between the sun’s differentially rotating outer layers and its rigidly rotating interior. Previous simulations overemphasized the role of viscosity, the fluid’s resistance to flow. However, the UC Santa cruz team’s “hero” calculations, consuming tens of millions of computing hours over 15 months on Pleiades, revealed that viscosity plays a negligible role. Instead, radiative spreading – the natural broadening of energy transport within the radiative zone – is key.
Surprisingly, the model spontaneously generated a tachocline when run under these revised conditions. Further, the simulations demonstrated that magnetic fields originating in the convective zone actually help maintain the tachocline’s narrowness, a reversal of previously held assumptions.
“There’s a synergy here as the tachocline is believed to play a basic role in causing the dynamo process. It now seems that the reverse may also be true,in the sense that the magnetic field from the dynamo may cause the tachocline to exist in the first place,” explained Loren Matilsky,lead study author and a postdoctoral researcher.
This discovery establishes a feedback loop where the dynamo – the process by which the sun generates its magnetic field – not onyl relies on the tachocline but also actively creates and sustains it.
The implications extend beyond understanding our own star.Accurate modeling of the tachocline is crucial for predicting violent solar storms that can disrupt satellites and global power grids. Moreover, the findings offer insights into the magnetic properties of other stars, which are vital in understanding the formation of planetary systems and the potential for life on exoplanets.
“We’re learning a lot about our sun’s dynamics, and in the process, I think we’re also learning about how this works on other stars. The questions of the tachocline become all the more vital in light of other stellar systems and exoplanets,” Matilsky said.
While the simulations represent a significant advance, the team acknowledges that even NASA’s second most powerful supercomputer cannot capture every detail of the sun’s complex layers. Future research will focus on refining the models and applying them to other stars.
