New findings from the European Space Agency’s Solar Orbiter spacecraft reveal that even the tiniest bursts of activity from the Sun may behave like their larger counterparts.
The Sun constantly produces tiny flashes of extreme ultraviolet (EUV) emission in its outer atmosphere, known as the corona. These flashes, called EUV brightenings, are small, short-lived bursts of energy that appear all over the Sun. Scientists are particularly interested in these events because the corona is mysteriously much hotter than the Sun’s surface, and these tiny brightenings might be key contributors to that heating. They may in fact be miniature versions of solar flares which are sudden, powerful releases of energy from the Sun’s atmosphere. Understanding whether EUV brightenings are truly small-scale flares, sharing the same physical mechanisms as larger flares, is therefore essential to solving the long-standing puzzle of coronal heating.
Now, researchers from KU Leuven and the Royal Observatory of Belgium (ROB), using high-resolution data from Extreme Ultraviolet Imager (EUI) operated from the ROB onboard the satellite Solar Orbiter, have found that these small brightenings can exhibit quasi-periodic pulsations (QPPs)—rhythmic fluctuations in brightness. This behavior has previously been observed in large solar and stellar flares, but it was unclear whether such patterns could occur in events as small as EUV brightenings.
Dr. Daye Lim, the lead author, explains: “We found that these small-scale events—likely 10 billion times smaller than typical solar flares—still exhibit the same kind of QPPs. This strongly suggests that similar physical mechanisms may drive both large and small-scale solar activity.”
This discovery supports the idea that EUV brightenings are miniature versions of flares, offering scientists a new, abundant way to study how energy is released and transported in the Sun’s atmosphere. Since these events occur far more frequently than larger flares, they open new opportunities for probing solar dynamics with greater statistical power. The results are published in the Astronomy & Astrophysics journal.
(Top) Full-Sun image taken on 12 October 2022 by the EUI’s Full Sun Imager telescope, with a zoom-in on the solar disk center captured by the High Resolution Imager. The Earth is shown for scale. A small-scale EUV brightening is highlighted by the red box, with an overlapping zoomed-in view shown above. The rightmost panel shows the light curve corresponding to this event (Courtesy: Lim et al. 2025 and Collier et al. 2024). A video of this small-scale event is also available.
(Bottom) Full-Sun image taken on 30 March 2022 by the Solar Dynamics Observatory’s Atmospheric Imaging Assembly. The region of a very bright X1.3-class flare is marked by a red box. The right panel displays the light curve from this flare event. A video of this flare is also available.
The pulsations are evident in both light curves.
