Many observations of solar flares suffer from saturation and blooming, causing crucial information to be lost. Researchers recently validated a technique for retrieving information from saturated flare images, unlocking a treasure trove of powerful solar flares for examination.

Solutions for Saturation

Since 2010, the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) has been capturing nearly continuous extreme-ultraviolet images of the Sun’s disk, revealing our star’s dramatic high-energy behavior. Though SDO/AIA’s observations have transformed our understanding of the Sun’s activity, they have limitations: powerful solar flares can saturate the detector, spilling charge into nearby pixels.

This saturation and overflow compromises our ability to study the most energetic solar flares — but the “lost” information may actually be recoverable. When light from an intense flare enters SDO’s instruments, not all of it pools in the saturated region of the detector: some of the light is diffracted by the optics, and by mathematically inverting this pattern of diffracted light, researchers can attempt to extract the encoded information about the saturated region. Researchers have used this technique for more than a decade, but options for validating the results were limited until now.

Solar Orbiter Lends a Hand

Launched almost 10 years to the day after SDO, the Solar Orbiter spacecraft provides an excellent opportunity to test inversion techniques for recovering information from saturated solar images. Solar Orbiter’s Extreme Ultraviolet Imager snaps brief photos of the Sun at a rapid cadence, and its images remain unsaturated even when faced with energetic solar flares.

As described in a recent research article by Sabrina Guastavino (University of Genoa; Italian National Institute for Astrophysics) and collaborators, the ideal setup for testing the inversion technique arose on 19 March 2024, when SDO and Solar Orbiter both viewed a solar flare while separated by just 1 degree in longitude.

Guastavino’s team aligned and reprojected the data, accounting for the slightly different viewing angles of the two spacecraft, then applied an algorithm called Adaptive SE-DESAT to reconstruct the flux within the saturated portion of the SDO image. The team compared the desaturated SDO images to the unsaturated Solar Orbiter images over the course of the flare, finding the same flare morphology and similar time evolution between the two data sets.

A Treasure Trove of Desaturated Data

Overall, these results demonstrate the effectiveness of the inversion technique, though Guastavino and coauthors noted that improvements could be made during the impulsive phase of the flare, when the emission is increasing. The team identified several reasons why the results may not match during this phase, including rapid evolution of the flare during individual exposures.

Despite these areas that require further attention, the validation of this technique unlocks 16 years of solar flare observations from SDO. This especially enhances our sample of powerful solar flares, increasing the available records of the most energetic solar flares by orders of magnitude.

Citation

“Validation of an Extreme-Ultraviolet Desaturation Technique for the Atmospheric Imaging Assembly on Board the Solar Dynamics Observatory Using Observations from the Extreme Ultraviolet Imager on Board Solar Orbiter,” Sabrina Guastavino et al 2026 ApJL 1005 L50. doi:10.3847/2041-8213/ae7d2e

The post When the Spacecraft Align: Rescuing Saturated Images of Solar Flares appeared first on AAS Nova.

Forecasting solar flares is one of the major challenges facing solar physicists today. New research finds that non-thermal emission can precede a solar flare by more than an hour, and this early emission may signal whether the flare will be accompanied by an explosion of plasma.

Flare Flavors

Solar flares come in two basic flavors: eruptive and confined. Eruptive flares are accompanied by the launch of tangled clouds of plasma and magnetic fields called coronal mass ejections. Confined flares, so called because the solar plasma remains confined to the Sun, feature only a brief blast of high-energy radiation.

Both solar flares and coronal mass ejections can disrupt everyday life on Earth, with flares knocking out radio communications and coronal mass ejections threatening spacecraft electronics and power grids. Given these real-life risks, as well as the potential for probing the physics behind the activity on the Sun and other stars, it’s critical to be able to identify signs of upcoming flares.

Looking at the Lead-Up

Luckily, there’s growing evidence that the Sun sends out subtle signals that a flare is soon to happen. One early sign of an impending flare is an increase in the non-thermal velocity of the plasma at the flare’s location. This phenomenon has been spotted in individual flares, but it hasn’t been studied and characterized for a large sample of flares — until now.

A recent research article led by Andy S. H. To (European Space Agency) takes the first systematic, large-scale approach to studying the non-thermal velocity changes that precede solar flares. The team amassed a sample of 1,449 solar flares that were seen by the Hinode spacecraft, the Geostationary Operational Environmental Satellite (GOES), and the Solar Dynamics Observatory (SDO). Hinode provided the spectral information needed to identify increases in the non-thermal velocity, GOES provided the flare start times, and SDO provided detailed information on the location and appearance of each flare.

Of the flares in the sample, 83% were moderately powerful C-class flares, 18% were stronger M-class flares, and 1% were the most powerful X-class flares. To’s team identified a clear trend across all types of flares: the non-thermal velocity increases 4–25 minutes before the flare’s X-ray emission begins to rise, peaks when the X-ray emission peaks, and decays as the flare decays. The team found some evidence that for smaller flares, the velocity increase begins in spectral lines that trace cooler plasma before spreading to lines probing hotter plasma, but more work is needed to confirm this trend.

More Details

Certain flares give even earlier hints of upcoming activity. M-class flares and some C-class flares exhibit what To’s team calls “precursor emission,” which emerges roughly 30–60 minutes before the flare’s X-ray emission peaks. The team also identified differences in precursor emission between confined and eruptive flares: eruptive flares display precursor emission over a broad range of spectral lines starting 45–74 minutes before the flare peaks, while confined flares show precursor emission later (31–54 minutes before peak) and in only a few spectral lines.

These results suggest that changes in the non-thermal velocity of solar plasma can not only signal when and where a flare is likely to arise, but also whether the flare will be accompanied by a potentially destructive coronal mass ejection. Upcoming missions like the Multi-slit Solar Explorer and SOLAR-C will give an even better view of the early stages of solar flares, helping to illuminate the physics behind them and enhancing our ability to forecast them.

Citation

“Systematic Nonthermal Velocity Increase Preceding Soft X-Ray Flare Onset: A Large-Scale Hinode/EIS Study,” Andy S. H. To et al 2025 ApJ 993 102. doi:10.3847/1538-4357/ae07de

The post How Solar Flares Hint That They’re About to Happen appeared first on AAS Nova.

Around Mother’s Day (12 May) last year, the Sun put on a spectacular display of solar activity. A clash between solar active regions incited 14 coronal mass ejections, launched multiple high-energy X-class solar flares, and sent shimmering aurorae as far south as Florida. The images above and to the right show the source of all this excitement: the active regions AR 13664 and AR 13668. In a recent research article, Mausumi Dikpati (High Altitude Observatory) and coauthors examined the origins of this cluster of active regions and why they were such a powerful source of solar storms. Their investigation showed that there are certain regions on the Sun where solar storms are more likely to arise. These regions occur where the Sun’s undulating bands of magnetic activity draw farthest apart, preventing oppositely directed magnetic fields from canceling one another out. In the case of the Mother’s Day superstorms, active regions 13664 and 13668 developed on the heels of a decaying active region, further contributing to their magnetic complexity. Ultimately, this analysis suggested that it may be possible to forecast damaging solar activity weeks in advance by predicting the locations of magnetically complex active regions and following their evolution. To learn more about the active regions that gave rise to the Mother’s Day superstorms, be sure to check out the full article linked below.

Citation

“Mother’s Day Superstorms: Pre- and Post-Storm Evolutionary Patterns of ARs 13664/8,” Mausumi Dikpati et al 2025 ApJ 988 108. doi:10.3847/1538-4357/addd09

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