S4 – Severe Solar Radiation Storm Alert issued on January 19

An S4 – Severe Solar Radiation Storm Alert was issued on January 19, 2026. The alert was prompted when the 10 MeV integral proton flux exceeded 10,000 pfu, beginning at 18:10 UTC. This level of radiation storm is classified as severe according to the NOAA Space Weather Scale.

Potential impacts from an event of this severity include significant radiation exposures for passengers and crew in high latitude, high altitude flights. Astronauts performing extra-vehicular activities face unavoidable radiation hazard. Satellites may experience memory device problems, noise on imaging systems, and possible orientation issues due to star-tracker effects, along with degradation in solar panel efficiency. Widespread blackout of polar high frequency (HF) radio communications is likely.

The S4 – Severe Solar Radiation Storm was triggered by a long-duration X1.9 flare that peaked at 18:09 UTC from Region 4341 (S11E11, Dkc/beta-gamma). This flare was also associated with Type II and Type IV radio emissions, as well as a full halo coronal mass ejection (CME) first observed at approximately 18:30 UTC. Analysis suggests the associated CME may reach Earth early on January 20, potentially sustaining elevated radiation levels.