X2.7 solar flare blacks out high-frequency comms, giving satellite and grid designs a live stress test

Not all solar flares are created equal. On one end of the spectrum are A-class solar flares, which are near background levels. And then there is the X-class, where an X1 event is 10,000 times more powerful in X-ray output than an A1 event. Early Wednesday, there was an X2.7 flare, the ‘2.7’ indicating it’s 2.7 times stronger than a baseline X1.0, landed firmly in this top tier.

The X2.7 flare had a corresponding burst of X-rays that abruptly ionized the D-layer, the lowest part of Earth’s charged upper atmosphere (ionosphere), so intensely that it temporarily wiped out high-frequency (HF) radio (3–30 MHz) on the Sun-lit side of Earth. HF is still the backbone for many aviation, maritime, military, and amateur/short-wave communications.

The X2.7 fare was the largest of the year so far.

To see why a single blackout still matters in 2025, consider how the toolbox for watching, and designing around, solar tantrums has evolved since Solar and Heliospheric Observatory (SOHO) first took station almost three decades ago.

Three decades of solar tech

From an R&D perspective, the study of the the sun has evolved considerably over the past three decades. One milestone was the 1995 debut of Solar and Heliospheric Observatory (SOHO), which provides continuous views of the sun and its outer atmosphere. NASA’s Solar Dynamics Observatory (SDO) followed in 2010. It now delivers around 70,000 high-resolution solar images per day, according to spacenews.com. It thus enables detailed observation of flares and eruptions. Complementing these space-based assets, ground facilities like the new 4-meter Daniel K. Inouye Solar Telescope (DKIST) provide ultra-high-resolution views of sunspots and flare source regions. The telescope can resolve features only tens of kilometers across.

The R&D push has also taken us physically closer to the sun, and thus providing novel opportunities for observe flares. NASA’s Parker Solar Probe, for instance, is making flybys through the Sun’s outer atmosphere. Similarly, the ESA/NASA Solar Orbiter is equipped with high-resolution imagers and an X-ray spectrometer telescope (STIX) to catch flares from new angles, including the sun’s poles. Then there’s international collaboration, which further broadens our observational capabilities, with India’s Aditya-L1 at the L1 point and China’s ASO-S (Kuafu-1) mission adding continuous data streams.

Several next-generation observatories and mission concepts are also in the works that could transform flare studies. NASA’s Multi-slit Solar Explorer (MUSE) aims to achieve the super-high resolution images of the Sun’s corona, while the HelioSwarm mission plans to deploy a constellation of nine small satellites to provide 3D snapshots of solar wind disturbances. For operational space weather forecasting, NOAA is preparing the SWFO-L1 satellite. In addition, the SunRISE array of six CubeSats will detect low-frequency radio bursts often associated with flare precursors, and ESA’s Vigil mission plans to monitor the Sun from the L5 point, offering a side view to detect flares before they rotate back to the earth.