The Solar Dynamics Observatory caught a record-setting solar flare on October 3, 2024.
Like a toddler about to throw a tantrum, the sun might change its face just before it erupts.
Observations of the lead-up to a massive solar flare revealed changes near the solar surface starting three hours before the flash, scientists report in a paper submitted May 8 to arXiv.org. The results could help experts develop methods to predict future solar flares, potentially giving us time to protect Earth’s power grid, orbiting satellites and astronauts in space.
“That’s always kind of the goal when we talk about pre-flaring,” says solar physicist Louis Seyfritz of the New Jersey Institute of Technology in Newark. “If we can predict when a huge solar flare … is going to happen, that means we can protect [astronauts] from any harmful radiation.”
Seyfritz and colleagues examined space-based observations of an active region on the sun that emitted an X-class solar flare, the most intense type of flare, on October 3, 2024.
“Pre-flaring is not very well documented because people like to see the stuff blow up,” Seyfritz says. But flares do come in groups. He and his colleagues knew that the same region had already emitted a strong flare a few days earlier. On October 3, other scientists trained NASA’s Interface Region Imaging Spectrograph space telescope on a single point in the active region to see if they could catch a flare in the act.
The telescope tracked changes in light emitted by the silicon IV ion, which traces plasma in the transition region between the sun’s surface and corona.
“One of the biggest questions about flares is what triggers them. In nature, most systems like to remain stable, so what makes the magnetic field on the sun destabilize to the point that runaway energy release is the next step?” asks solar physicist Emily Mason of Predictive Science Inc. in San Diego, who was not involved in the new work. “Observations like this one, that show what happens before that huge release of energy, are critical to tease out that trigger.”
Seyfritz and colleagues analyzed features of the light that probe the plasma’s temperature, turbulence and movement toward or away from the sun’s surface. They found all three parameters gradually increased beginning three hours before the flare, as the region accumulated energy. About 20 minutes before the flare, the temperature and turbulence jumped, as did the plasma’s speed away from the sun.
The team found that the parameters varied periodically over the three hours preceding the flare, with consistent ups and downs every 8 minutes and 20 minutes. Over the last hour before the flare, tracers of temperature and turbulence changed in sync.
The two oscillations seemed to vary with the measured light wavelength, with shorter wavelengths showing the 8-minute period and longer wavelengths showing the 15-minute period, Mason notes. That hints that there could be two different physical mechanisms happening in the plasma, she says.
The work is interesting and important, she says, but there are many steps between here and solar flare predictions that could be useful. It would be good to check if similar oscillations show up in an active region that isn’t about to erupt, for one thing.
And there are practical hurdles as well.
“I am confident that the oscillations reported here have the ability to predict major flares, but we would need a mission that could observe the whole sun at once (and probably be able to conduct the analysis onboard) in order to be useful in a predictive capacity,” she says. “The technology exists. It’s a matter of funding.”
