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For decades, scientists have tried in vain to accurately predict solar flares - intense bursts of light on the Sun that can send a flurry of charged particles into the solar system. Now, using NASA's Solar Dynamics Observatory, one team has identified flickering loops in the solar atmosphere, or corona, that seem to signal when the Sun is about to unleash a large flare.
These warning signs could help NASA and other stakeholders protect astronauts as well as technology both in space and on the ground from hazardous space weather.
Led by heliophysicist Emily Mason of Predictive Sciences Inc. in San Diego, California, the team studied arch-like structures called coronal loops along the edge of the Sun. Coronal loops rise from magnetically driven active regions on the Sun, where solar flares also originate.
The team looked at coronal loops near 50 strong solar flares, analyzing how their brightness in extreme ultraviolet light varied in the hours before a flare compared to loops above non-flaring regions. Like flashing warning lights, the loops above flaring regions varied much more than those above non-flaring regions.
"We found that some of the extreme ultraviolet light above active regions flickers erratically for a few hours before a solar flare," Mason explained. "The results are really important for understanding flares and may improve our ability to predict dangerous space weather."
Published in the Astrophysical Journal Letters in December 2024 and presented on Jan. 15, 2025, at a press conference during the 245th meeting of the American Astronomical Society, the results also hint that the flickering reaches a peak earlier for stronger flares. However, the team says more observations are needed to confirm this link.
Other researchers have tried to predict solar flares by examining magnetic fields on the Sun, or by looking for consistent trends in other coronal loop features. However, Mason and her colleagues believe that measuring the brightness variations in coronal loops could provide more precise warnings than those methods - signaling oncoming flares 2 to 6 hours ahead of time with 60 to 80 percent accuracy.
"A lot of the predictive schemes that have been developed are still predicting the likelihood of flares in a given time period and not necessarily exact timing," said team member Seth Garland of the Air Force Institute of Technology at Wright-Patterson Air Force Base in Ohio.
