This spectacular signal from the Sun alerts us to solar flares hours ahead of eruption

SAN DIEGO — A new study reveals that the Sun may give us advance notice before unleashing powerful solar flares, potentially providing crucial hours of warning before these massive eruptions disturb Earth’s technology and communications systems. Looking at data from over 50 major solar flares, researchers discovered telltale changes in the Sun’s outer atmosphere that begin ramping up 2-3 hours before a flare occurs.

Solar flares are intense bursts of radiation that erupt from the Sun’s surface, sending waves of energy and particles hurtling through space. When aimed at Earth, these cosmic tempests can disrupt satellite operations, interfere with radio communications, force airlines to reroute flights, and even cause widespread power grid issues. Currently, our ability to predict exactly when and where flares will occur remains limited, often giving us little time to prepare for their impacts.

“We found that some of the extreme ultraviolet light above active regions flickers erratically for a few hours before a solar flare,” explains Emily Mason, a heliophysicist at Predictive Sciences Inc. in San Diego, California, who helped lead the study, in a statement. “The results are really important for understanding flares and may improve our ability to predict dangerous space weather.”

Research published in The Astrophysical Journal Letters used data from NASA’s Solar Dynamics Observatory, a spacecraft that continuously monitors the Sun in different wavelengths of light. The team examined massive arches of super-heated gas called coronal loops that rise above the Sun’s surface. These loops, which can be millions of miles long, are anchored in magnetically active regions where solar flares tend to originate.

Magnetic field lines in the Sun’s atmosphere can become twisted and tangled, building up enormous amounts of energy, like a rubber band being wound tighter and tighter. When these magnetic fields suddenly reconnect and release their pent-up energy, a solar flare erupts. While scientists have long studied the magnetic conditions that lead to flares, this research took a different approach by examining how the temperature and brightness of coronal loops change during the build-up to an eruption.

The research team analyzed 53 significant flares that occurred between 2011-2022, focusing specifically on flares that happened near the edge of the Sun’s disk, where the arching loops of plasma are clearly visible against the dark background of space. “The Sun’s corona is a dynamic environment, and each solar flare is like a snowflake — every single flare is unique,” says lead author Kara Kniezewski, a graduate student at the Air Force Institute of Technology. “We find that searching for periods of ‘chaotic’ behavior in the coronal loop emission, rather than specific trends, provide a much more consistent metric and may also correlate with how strong a flare will be.”

What emerged was a clear pattern: in the 2-3 hours before a flare, the coronal loops showed significantly more variable and chaotic behavior compared to quiet periods, particularly in two specific wavelengths of light — 131 and 304 Angstroms — which reveal plasma at different temperatures. This enhanced variability suggests that the magnetic field is becoming increasingly unstable as it approaches the breaking point.

The team’s approach differs from previous prediction methods. “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,” notes study co-author Seth Garland, of the Air Force Institute of Technology. Their method showed 60-80% accuracy in identifying flare conditions 2-6 hours before an event.

Intriguingly, the team also noticed that certain types of flares gave even stronger advance warning signals than others. Flares that remained confined to the Sun’s atmosphere, rather than ejecting material into space, were three times more likely to be preceded by distinct spikes in 131 Angstrom emissions from compact groups of loops near the center of the active region.

The findings, presented at the 245th meeting of the American Astronomical Society, suggest this new approach could help develop more reliable flare prediction methods. “Previous work by other researchers reports some interesting prediction metrics,” notes co-author Vadim Uritsky of NASA’s Goddard Space Flight Center and the Catholic University of Washington, D.C. “We could build on this and come up with a well-tested and, ideally, simpler indicator ready for the leap from research to operations.”