Very rare S4 – Severe solar radiation storm in progress, G4 – Severe geomagnetic storm forecast
A G4 – Severe solar radiation storm is in progress after ≥10 MeV proton flux exceeded 10 000 pfu at 18:10 UTC on January 19, 2026, following the X1.9 solar flare on January 18. As the associated full-halo coronal mass ejection approaches Earth, forecasters warn that a G4 – Severe geomagnetic storm is likely early on January 20.
