S3 – Strong Solar Radiation Storm Alert issued on November 12

An S3 – Strong Solar Radiation Storm Alert was issued on November 12, 2025 after the 10MeV integral proton flux exceeded the 1,000 pfu threshold at 01:45 UTC. The alert was officially released by NOAA SWPC at 01:55 UTC.

Potential impacts from this event include elevated radiation exposure for passengers and crew on high latitude, high altitude flights, as well as increased risk to astronauts conducting extra-vehicular activities. Spacecraft may experience single-event upsets to satellite operations, increased noise in imaging instruments, and a slight reduction in the efficiency of solar panels. Degraded or episodically blacked-out polar high frequency (HF) radio propagation is also likely.

The alert was triggered following heightened solar activity, specifically an impulsive X5.1/3B class flare originating from Region 4274, which peaked at 10:04 UTC on November 11, 2025. This event was associated with a type-II radio sweep, a significant radio burst, and an asymmetric halo coronal mass ejection (CME), with model forecasts indicating its arrival mid to late on November 12.