The Sun unleashed two powerful X-class solar flares in rapid succession on the night of April 23 and early morning of April 24, 2026, wiping out high-frequency radio communications across broad swaths of Earth’s sunlit hemisphere. Pilots flying transatlantic routes, ships navigating open ocean, and emergency responders relying on HF radio bands all faced back-to-back blackout windows with barely enough time between them to restore normal contact.
The first flare, classified as X2.4, peaked at 9:07 p.m. ET on April 23. Roughly seven hours later, a slightly stronger X2.5 flare peaked at 4:13 a.m. ET on April 24. NASA confirmed both events through its Solar Cycle 25 blog, and NOAA’s Space Weather Prediction Center independently corroborated the classifications using real-time data from its GOES X-ray Flux sensor aboard geostationary satellites.
Why these flares knocked out radio signals
X-class flares sit at the top of the five-tier scale used by space weather agencies, and an X2-level event is strong enough to trigger what NOAA classifies as an R3, or “Strong,” radio blackout on its Space Weather Scales. That means wide-area HF radio degradation lasting roughly an hour on the side of Earth facing the Sun.
The physics behind the disruption is straightforward but punishing. When an intense burst of X-rays from a flare reaches Earth, it floods a layer of the upper atmosphere called the D-region, which sits between about 50 and 90 kilometers altitude. Under normal conditions, HF radio waves pass through this layer and bounce off higher ionospheric layers to reach distant receivers. During a strong flare, the D-region becomes so energized that it absorbs those radio waves instead of letting them through. The entire HF band, from 3 to 30 MHz, goes dark across the affected hemisphere.
NOAA’s D-Region Absorption Predictions (D-RAP) model uses one-minute GOES X-ray flux readings to generate real-time maps of where and how severely HF radio is being absorbed. During both flares, the model would have shown deep absorption zones across the sunlit hemisphere. Low-frequency navigation systems were also degraded, according to NOAA’s product documentation for D-RAP.
Who felt it and when
The timing of each flare determined which parts of the world took the hit. The X2.4 peaked at 9:07 p.m. ET, which translates to 01:07 UTC on April 24, placing the sunlit hemisphere over Europe, Africa, the Middle East, and western Asia. HF-dependent operations in those regions, including transatlantic aviation routes over the eastern Atlantic, would have experienced the worst disruption.
By the time the X2.5 arrived at 4:13 a.m. ET (08:13 UTC), Earth had rotated enough to shift the sunlit footprint westward. The eastern Americas, the full Atlantic basin, and parts of western Europe were now in daylight and exposed. That second blackout window caught a different set of operators off guard, compounding the cumulative disruption for anyone working across time zones.
Specific incident reports from aviation authorities or maritime agencies have not yet been published, so the practical severity for individual flights or shipping routes remains undocumented. But the physics leaves little ambiguity: any HF radio link passing through the sunlit D-region during either peak would have experienced significant signal loss.
The CME question
Not every powerful flare launches a coronal mass ejection, but when one does, the consequences escalate sharply. A CME is a massive cloud of magnetized plasma that, if aimed at Earth, can trigger geomagnetic storms capable of disrupting power grids, degrading GPS accuracy, pushing auroras to unusually low latitudes, and stressing satellite electronics.
As of late April 2026, neither NASA nor NOAA has published an event-specific report confirming or ruling out CMEs associated with these two flares. Coronagraph imagery from spacecraft like SOHO and STEREO typically takes hours to days to fully analyze, and solar wind measurements from the DSCOVR satellite at the L1 point between Earth and the Sun would be the first to detect an incoming CME. Until that analysis is complete, the geomagnetic storm risk from these flares remains an open question. NOAA’s Space Weather Prediction Center posts three-day geomagnetic forecasts and storm watches on its main site as data becomes available.
Also unresolved is which active sunspot region produced the flares. That detail carries forecasting weight: a single hyperactive region firing repeatedly suggests more eruptions could follow, while two separate regions erupting by coincidence is a different risk profile. Solar observers are likely tracking the source region already, but no official identification has appeared in NASA’s or NOAA’s published materials.
Where Solar Cycle 25 stands now
These back-to-back X-class flares land during a period of intense solar activity. Solar Cycle 25, which began in December 2019, has been running hotter than many early predictions suggested. NOAA’s Space Weather Prediction Center originally projected a relatively modest cycle, but actual activity has exceeded those initial estimates. The cycle’s maximum phase, when flares and CMEs are most frequent, has been underway since 2024, and events like the April 23-24 double flare suggest the Sun is not winding down yet.
Monitoring steps for HF-dependent operators
For anyone whose work or safety depends on stable HF radio propagation, the current stretch of the solar cycle demands active monitoring. Aviation operators should watch for NOTAMs related to space weather. Amateur radio operators can consult D-RAP’s downloadable numerical outputs to plan around absorption windows. And anyone curious about whether a geomagnetic storm or aurora display might follow these flares should keep an eye on NOAA’s forecast dashboards over the coming 48 to 72 hours, the typical travel time for a CME to reach Earth.
More from Morning Overview
*This article was researched with the help of AI, with human editors creating the final content.
