CNN
• Ashley Strickland
X1.9 flare's CME sparks S4 radiation event and G4 geomagnetic storm — strongest since 2003
On Jan. 19, an X1.9 solar flare's coronal mass ejection struck Earth, producing an S4 radiation event — the most intense since 2003 — and triggering G4 geomagnetic storms that lit auroras into mid-latitudes while degrading GPS, satellite and HF communications and risking power‑grid and polar‑flight impacts.
