The NSF Inouye Solar Telescope Delivers Record-Breaking Images of Solar Flare, Coronal Loops
On August 8, 2024, the U.S. National Science Foundation (NSF) Daniel K. Inouye Solar Telescope captured the sharpest-ever images of a solar flare at the H-alpha wavelength (656.28 nm), revealing dark coronal loop strands in unprecedented detail. The observations, made during the decay phase of an X1.3-class flare, measured loop widths averaging 48.2 km, with some even half as narrow. By using the Inouye Solar Telescope to isolate light at the H-alpha wavelength, emitted by hydrogen atoms, solar physicists can identify fine structures in the lower solar atmosphere too small to observe in the past—offering a potential breakthrough in determining the fundamental scale of coronal loops and advancing solar flare modeling. By improving researchers’ ability to model solar flares, these observations will also improve forecasting for space weather events that are hazardous to satellites, power grids, and communications on Earth.
Coronal loops are arches of plasma that follow the Sun’s magnetic field lines, often preceding solar flares that trigger sudden releases of energy associated with some of these magnetic field lines twisting and snapping. This burst of energy fuels solar storms that can impact Earth’s critical infrastructure. Astronomers at the Inouye observe sunlight at the H-alpha wavelength (656.28 nm) to view specific features of the Sun, revealing details not visible in other types of solar observations.
“This is the first time the Inouye Solar Telescope has ever observed an X-class flare,” says Cole Tamburri, the study’s lead author who is supported by the Inouye Solar Telescope Ambassador Program while completing his Ph.D. at the University of Colorado Boulder (CU). The program is funded by the NSF and is designed to support Ph.D. students as they create a well-networked cohort of early-career scientists at U.S. Universities, who will bring their expertise in Inouye data reduction and analysis to the broader solar community. “These flares are among the most energetic events our star produces, and we were fortunate to catch this one under perfect observing conditions.”
The team—which includes scientists from the NSO, the Laboratory for Atmospheric and Space Physics (LASP), the Cooperative Institute for Research in Environmental Sciences (CIRES), and CU—focused on the razor-thin magnetic field loops (hundreds of them) woven above the flare ribbons. On average, the loops measured about 48 km across, but some were right at the telescope’s resolution limit. “Before Inouye, we could only imagine what this scale looked like,” Tamburri explains. “Now we can see it directly. These are the smallest coronal loops ever imaged on the Sun.”