On November 11, 2025, the Sun produced an X5-class flare that triggered an exceptionally rare event — a powerful Ground Level Enhancement (GLE). A stream of high-energy protons reached Earth and was detected even at ground level. New radiation sensors developed by the University of Surrey (UK), launched for the first time on weather balloons, recorded at aircraft cruising altitudes (around 12 km) almost a tenfold increase in radiation levels — the strongest reading since December 2006.

What Happened and Why It Matters

The X5 flare became the catalyst for a GLE — an event in which solar protons are accelerated to energies of hundreds of MeV and penetrate the atmosphere all the way to the ground. Such events occur only a few times per solar cycle and pose a real threat to aviation: at altitudes of 10–12 km, radiation levels can briefly exceed normal values by tens of times.

According to the British and Dutch meteorological agencies, just one hour after the event began, weather balloons equipped with Surrey’s new detectors were launched into the stratosphere. The instruments ascended to 30 km and transmitted the first three-dimensional data in history on radiation distribution at aviation altitudes.

“This is the strongest GLE surge since December 2006,” noted Professor Clive Dyer, the project lead. “Our new detectors showed how rapidly conditions can change at aviation altitudes. History tells us that much larger events are possible — and we must be prepared for them.”

Consequences for Aviation and Electronics

At the peak of the storm, the rate of single event upsets (bit flips) in onboard electronics may have reached 60 errors per hour per gigabyte of memory — a critical level for flight control systems. For passengers and crew, there was no real danger (the dose remained within annual limits), but during a more powerful event (such as the one in 1956) radiation could exceed normal levels by hundreds of times.

“These events are unpredictable, and it is important to collect as much data as possible when they occur,” emphasized Professor Keith Ryden, director of the Space Research Centre. “These measurements gave us the first three-dimensional view of radiation distribution in airspace. This is a significant step forward for flight safety.”

New Sensors: A Breakthrough in Space Weather Monitoring

The instruments developed at Surrey operate at –70°C and in thin atmosphere, transmitting data in real time. They are already integrated into the UK Met Office system and will help refine models predicting the effects of solar storms on aviation, satellites, and power grids.

Regular launches are planned in the coming years — especially during the peak of Solar Cycle 25 (2025–2027), when the probability of strong GLEs rises sharply.

In Short

On November 11, 2025, an X5 flare triggered the most powerful GLE surge in 20 years. New sensors from the University of Surrey recorded a tenfold increase in radiation at aircraft altitudes — the strongest since 2006. The collected three-dimensional data will help develop accurate space weather models and improve aviation safety. The solar maximum is only beginning — stronger events may still be ahead.