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Rare S4 Radiation Storm, G4 Geomagnetic Surge Paint Skies Across US and Europe

NOAA says this is the strongest solar radiation event since 2003.

Overview

  • An X1.9 flare from Active Region 4341 launched a full‑halo CME that reached Earth in roughly 25 hours on Jan. 19, immediately driving G4 geomagnetic conditions.
  • NOAA’s Space Weather Prediction Center confirms an S4 radiation storm in progress, with elevated particle levels persisting into Jan. 20.
  • Auroras were widely observed across the continental United States, the UK and Europe, with reports as far south as Alabama, northern California and northern Italy.
  • Officials notified FEMA, power‑grid operators and aviation interests, and consulted NASA regarding astronaut exposure on the International Space Station.
  • Forecasters warn of potential impacts to satellites, HF radio and GNSS and possible grid voltage issues, with activity expected to gradually wane depending on solar‑wind conditions.