Simulations run on the world's most powerful supercomputer, Summit at the Oak Ridge Leadership Computing Facility, uncovered dramatic changes in the Sun's magnetic field strength at a rate 10 times faster than previously observed. The findings improve scientists' ability to predict space weather events, such as coronal mass ejections—eruptions of plasma and charged particles from the Sun that can lead to geomagnetic storms on Earth and harm astronauts and satellites.

Researchers at the University of Chicago’s Center for Computational Astrophysics simulated activity on the Sun’s surface—known as the photosphere—and in its outer layer—called the corona. Their goal was to understand how magnetic fields are generated and stored in both regions.

“To probe these phenomena, we’ve zoomed in on the Sun like never before, modeling an unprecedented number of tiny structures in the photosphere and the corona and their interactions,” said Juanyi Cao, a postdoctoral researcher at the University of Chicago and the first author of a study published in the Astrophysical Journal Letters. “Summit allowed us to perform the highest-resolution simulation ever done of these small-scale events to find the most compelling evidence of magnetic reconnection in action.”

The simulation reveals the presence of magnetic reconnection all over the Sun’s surface, indicating how the magnetic fields continuously break and reconnect throughout the Sun’s atmosphere. This process leads to the development of larger-scale structures such as sunspots and coronal loops that shape the Sun’s magnetism and drive space weather events.

"Simulating the Sun at this level of detail used to take several months. Running it on Summit, we did the same calculations in only 10 days,” said Congedo.

The scientists validated the simulation by comparing their results with observations made by the Interface Region Imaging Spectrograph on NASA's Solar Dynamics Observatory. The close match demonstrates that the simulation produces realistic physics and provides a valuable tool to study the generation of the solar magnetic field.

The computational demands of the simulation push present-day supercomputers to their limits. Each of the five simulations performed required thousands of computing nodes on the highly parallel Summit supercomputer for multiple weeks. The entire data set amounts to more than 200 terabytes.

“Our simulations demonstrate that the current generation of supercomputers is allowing us to solve previously intractable problems in astrophysics. We are entering an exciting era where we can routinely probe the Sun’s atmosphere at unprecedented spatial and temporal scales, setting the stage for revolutionary advances in our understanding of solar activity,” said Congedo.