Technology & Science

X1.9 Solar Flare’s Full-Halo CME Spurs G4 Aurora Alert Across Lower 48

NOAA upgraded its geomagnetic storm watch to “severe” (G4) on 19 Jan 2026 after an X1.9-class flare a day earlier hurled a full-halo coronal mass ejection toward Earth, putting auroras within reach of Alabama and Northern California for the first time in decades.

By Priya Castellano

Focusing Facts

  1. The flare erupted from Active Region 4341 at 11:09 a.m. EST on 18 Jan 2026 and launched a CME calculated at >1,500 km/s, arriving at Earth roughly 30 hours later.
  2. NOAA confirmed S4 solar radiation levels on 20 Jan 2026—the first S4 event since 2003—while geomagnetic readings briefly hit G4, expanding the auroral oval over more than 25 U.S. states.
  3. The storm coincided with a new-moon window (18 Jan), giving exceptionally dark skies that boosted naked-eye aurora visibility well beyond typical high-latitude zones.

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