Maui, Hawai'i; June 3, 2025 – A team of solar physicists has released a new study shedding light on the fine-scale structure of the Sun's surface. Using the unparalleled power of the U.S. National Science Foundation (NSF) Daniel K. Inouye Solar Telescope, built and operated by the NSF National Solar Observatory (NSO) on Maui, scientists have observed, for the first time ever in such high detail, ultra-narrow bright and dark stripes on the solar photosphere, offering unprecedented insight into how magnetic fields shape solar surface dynamics at scales as small as 20 kilometers (or 12.4 miles). The level of detail achieved allows us to clearly link these stripes to the ones we see in state-of-the-art simulations—so we can better understand their nature.
These stripes, called striations and seen against the walls of solar convection cells known as granules, are the result of curtain-like sheets of magnetic fields that ripple and shift like fabric blowing in the wind. As light from the hot granule walls passes through these magnetic "curtains," the interaction produces a pattern of alternating brightness and darkness that traces variations in the underlying magnetic field. If the field is weaker in the curtain than in its surroundings it appears dark, if it is relatively stronger it appears bright.
"In this work, we investigate the fine-scale structure of the solar surface for the first time with an unprecedented spatial resolution of just about 20 kilometers, or the length of Manhattan Island," says NSO scientist Dr. David Kuridze, the study's lead author. "These striations are the fingerprints of fine-scale magnetic field variations."
The findings were not anticipated, and only possible because of the Inouye Solar Telescope's unprecedented abilities. The team used the Inouye's Visible Broadband Imager (VBI) instrument operating in the G-band, a specific range of visible light especially useful for studying the Sun because it highlights areas with strong magnetic activity, making features like sunspots and fine-scale structures like the ones in the study easier to see. The setup allows researchers to observe the solar photosphere at an impressive spatial resolution better than 0.03 arcseconds (i.e., about 20 kilometers on the Sun). This is the sharpest ever achieved in solar astronomy. To interpret their observations, the team compared the images with cutting-edge simulations that recreate the physics of the Sun's surface.
The study confirms that these striations are signatures of subtle but powerful magnetic fluctuations—variations of only a hundred gauss, comparable to a typical refrigerator magnet's strength—that alter the density and opacity of the plasma, shifting the visible surface by mere kilometers. These shifts, known as Wilson depressions, are detectable thanks only to the unique resolving power of the 4-meter primary mirror of the NSF Inouye Solar Telescope, the largest in the world.
"Magnetism is a fundamental phenomenon in the universe, and similar magnetically induced stripes have also been observed in more distant astrophysical objects, such as molecular clouds," shares NSO scientist and co-author of the study Dr. Han Uitenbroek. "Inouye's high resolution, in combination with simulations, allows us to better characterize the behavior of magnetic fields in a broad astrophysical context."
Studying the magnetic architecture of the solar surface is essential for understanding the most energetic events in the Sun's outer atmosphere—such as flares, eruptions, and coronal mass ejections—and, consequently, improving space weather predictions. This discovery not only enhances our understanding of this architecture but also opens the door to studying magnetic structures in other astrophysical contexts—and at small scales once thought unachievable from Earth.
"This is just one of many firsts for the Inouye, demonstrating how it continues to push the frontier of solar research," says NSO Associate Director for the NSF Inouye Solar Telescope, Dr. David Boboltz. "It also underscores Inouye's vital role in understanding the small-scale physics that drive space weather events that impact our increasingly technological society here on Earth."
The paper describing this study, titled "The striated solar photosphere observed at 0.03'' resolution," is now available in The Astrophysical Journal Letters.
